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This mechanism i nvolved releases from the legacy piping that conveyed contaminated water from the fPI-SFDS to the "E"-series sto rrnwater piping that runs beneath the access road on the South side of the Protected Area and discharges storm water to the cooling water Discharge Canal. While evaluating this hypothesis , we found evidence, as discussed in Section 6.62, that at certa in tidal cycles , water from the Discharge Canal and the Hudson River may back flow iDlO the se groundwater monitoring wells. To help identifY the source of Trit ium in these two wells , we developed a focused water quality probrram specific to the se wells. Generally , the water quality program involved analyzing select aqueou s geochemica l parameter s in groundwater and surface water samples. Evaluation of these data can allow conclusions to be drawn regarding the so urce of the sampled water. Both data s ets (elevatio n and water chemistry) indicate th at water co llected from th ese wells may contain river or cooling water from the Discharge Canal. Based on these finding s. we recommend that groundwater samp l e l aboratory results from th ese well locations n01 be used to evaluate the extent of groundwater contamination or contaminant 44 RelAtiv ely lar ge of water are required to overcome the:: Ihennal mass of the s ub surface deposits surrounding the well bore. Therefore.
This mechanism i nvolved releases from the legacy piping that conveyed contaminated water from the fPI-SFDS to the "E"-series sto rrnwater piping that runs beneath the access road on the South side of the Protected Area and discharges storm water to the cooling water Discharge Canal. While evaluating this hypothesis , we found evidence, as discussed in Section 6.62, that at certa in tidal cycles , water from the Discharge Canal and the Hudson River may back flow iDlO the se groundwater monitoring wells. To help identifY the source of Trit ium in these two wells , we developed a focused water quality probrram specific to the se wells. Generally , the water quality program involved analyzing select aqueou s geochemica l parameter s in groundwater and surface water samples. Evaluation of these data can allow conclusions to be drawn regarding the so urce of the sampled water. Both data s ets (elevatio n and water chemistry) indicate th at water co llected from th ese wells may contain river or cooling water from the Discharge Canal. Based on these finding s. we recommend that groundwater samp l e l aboratory results from th ese well locations n01 be used to evaluate the extent of groundwater contamination or contaminant 44 RelAtiv ely lar ge of water are required to overcome the:: Ihennal mass of the s ub surface deposits surrounding the well bore. Therefore.
whi Ie smaller exchan ges of g r OUndwa t e r/riv e r water may go undetected via temperature change. they may st ill be large enou g h to adversely impact I'cldiologieal water quality. panicuJarly in consideration of the data from t he:: proximate well screens. Also see:: discu ssio n in Stction 6.6.3. 70 flux to the Hudson River and that these wells not be incorporated into the Long Term Monitoring P l an as Boundary Well s. 6.6.3.1 Sampling Groundwater samples were co ll ected from monitoring well s MW -38 , MW-48-23 , and MW-48-38 and from the Discharge Canal and Hudson River on January 19 , 2007. These samp les were analyzed for bicarbonate alkalinity (as CaCO,), magnesium , sodium, calcium, s u l fate, and chloride.
whi Ie smaller exchan ges of g r OUndwa t e r/riv e r water may go undetected via temperature change. they may st ill be large enou g h to adversely impact I'cldiologieal water quality. panicuJarly in consideration of the data from t he:: proximate well screens. Also see:: discu ssio n in Stction 6.6.3. 70 flux to the Hudson River and that these wells not be incorporated into the Long Term Monitoring P l an as Boundary Well s. 6.6.3.1 Sampling Groundwater samples were co ll ected from monitoring well s MW -38 , MW-48-23 , and MW-48-38 and from the Discharge Canal and Hudson River on January 19 , 2007. These samp les were analyzed for bicarbonate alkalinity (as CaCO,), magnesium , sodium, calcium, s u l fate, and chloride.
The data was graphed on Stiff diagram s and is shown on Figure 6.16. 6.6.3.2 Water Quality Evaluation GZA used the six water quality indicators (bi carbonate alkalinity  
The data was graphed on Stiff diagram s and is shown on Figure 6.16. 6.6.3.2 Water Quality Evaluation GZA used the six water quality indicators (bi carbonate alkalinity
[as CaCO)], magnesium, sodium, calcium, s ulfate , and chloride) to assess whether or not Discharge Cana l and/or river water was present or mixed with gro undwater at the two location s of interest (note that the MW-48 monitoring well location contains a s hallow and a de e p well). A s ummary of our finding s follow s.
[as CaCO)], magnesium, sodium, calcium, s ulfate , and chloride) to assess whether or not Discharge Cana l and/or river water was present or mixed with gro undwater at the two location s of interest (note that the MW-48 monitoring well location contains a s hallow and a de e p well). A s ummary of our finding s follow s.
* The river and canal samples are c h emically s imilar and a re dominated b y sod ium and chloride.
* The river and canal samples are c h emically s imilar and a re dominated b y sod ium and chloride.
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FLOW PATTERNS A major purpose of this groundwater investigation was to identify the fate and level of groundwater contami nant migration.
FLOW PATTERNS A major purpose of this groundwater investigation was to identify the fate and level of groundwater contami nant migration.
The contaminants of potential concern are so luble in groundwater, and at somewhat varying rates, move with it. This section provides a description of ident ified groundwater  
The contaminants of potential concern are so luble in groundwater, and at somewhat varying rates, move with it. This section provides a description of ident ified groundwater
[low patterns in and downgradient of identified contaminant release areas. The piezometric data , shown in Table 6.1 , whic h form the basis of this evaluation are ind ependen t of chemical data collec t ed a t the same monitoring locati ons. Conseq uentl y. our evaluation of piezometric data provides an assessment of where contaminants are expected to migrate in various time frames. Refer to Section 9.0 for information on the observed distribution of contaminants and a discussion on disc re pancies between anticipated and observed conditions.
[low patterns in and downgradient of identified contaminant release areas. The piezometric data , shown in Table 6.1 , whic h form the basis of this evaluation are ind ependen t of chemical data collec t ed a t the same monitoring locati ons. Conseq uentl y. our evaluation of piezometric data provides an assessment of where contaminants are expected to migrate in various time frames. Refer to Section 9.0 for information on the observed distribution of contaminants and a discussion on disc re pancies between anticipated and observed conditions.
Testing has indicated that the bedrock is sufficie ntl y fractured to , on the scale of the Site , behave as a non-homogeneous , anisotropic , vertically porous media. This finding indicates that groundwater flow is perpendicular to lines of equal h eads. T hi s assessment appears particularly va lid in horizontal (East-West  
Testing has indicated that the bedrock is sufficie ntl y fractured to , on the scale of the Site , behave as a non-homogeneous , anisotropic , vertically porous media. This finding indicates that groundwater flow is perpendicular to lines of equal h eads. T hi s assessment appears particularly va lid in horizontal (East-West  
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Subsequent monitoring through 2006 and into 2007 has indicated that the leakage rate had fallen off rap i dly and become intermittent with an average flow rate of a pproximately 0.0 2 I/day , when flowing (s ee figure below presenting shrinkage crack flow rate and Tritium concentration over time). This small amount of leakage is pennanently being contained and it therefore i s not impacting the groundwater.
Subsequent monitoring through 2006 and into 2007 has indicated that the leakage rate had fallen off rap i dly and become intermittent with an average flow rate of a pproximately 0.0 2 I/day , when flowing (s ee figure below presenting shrinkage crack flow rate and Tritium concentration over time). This small amount of leakage is pennanently being contained and it therefore i s not impacting the groundwater.
Lrak collrction flow mle and Tritium coocrntmllon " 20,000,000 I.!. 15,000,000
Lrak collrction flow mle and Tritium coocrntmllon " 20,000,000 I.!. 15,000,000
* 10,000.000  
* 10,000.000
:; : i ____ __ * '.000,000 .
:; : i ____ __ * '.000,000 .
* 1 1 1 8107 4128107 &/&07 UNIT 2 2005 SHRINKAGE CRACK LEAK RATE AND TRITIUM LEVELS Based upon two years of flow and radiological and chemical sample data, it appears that excavation o f the backfill from behind the pool wall cau s ed the s hrinkage crack s to 95 begin releasing water trapped in the interstitial space dating back to 1992. This release mechanism i s hypothesized to have developed as follows:
* 1 1 1 8107 4128107 &/&07 UNIT 2 2005 SHRINKAGE CRACK LEAK RATE AND TRITIUM LEVELS Based upon two years of flow and radiological and chemical sample data, it appears that excavation o f the backfill from behind the pool wall cau s ed the s hrinkage crack s to 95 begin releasing water trapped in the interstitial space dating back to 1992. This release mechanism i s hypothesized to have developed as follows:
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In reviewing these figures, note that Strontium was not found below a depth of 105 feet in MW-67. We attribute the low concentrations of Trit ium below a depth of 200 feet at this location , at least in part, to t he downward migration of Tritium during our investigations.
In reviewing these figures, note that Strontium was not found below a depth of 105 feet in MW-67. We attribute the low concentrations of Trit ium below a depth of 200 feet at this location , at least in part, to t he downward migration of Tritium during our investigations.
For examp le, by necessity, well RW-J was an open wellbore for a period of time l16 which allowed vertical groundwater migration , along an artificial preferred pathway, deeper than would occur a long ambient flow paths. 9.3 UNIT 2 TRITIUM PLUME BERA VIOR As shown on Figures 8.1 and 9.3, the Unit 2 plume exhibits Tritium concentrations originating at (he IP2-SFP. The higher concentration isopleths are shown around the entire 11 6 RW-1 is located immediately below the 2005 shrinkage crack leak (high Tritium concentrations in shallow g r oundwater).
For examp le, by necessity, well RW-J was an open wellbore for a period of time l16 which allowed vertical groundwater migration , along an artificial preferred pathway, deeper than would occur a long ambient flow paths. 9.3 UNIT 2 TRITIUM PLUME BERA VIOR As shown on Figures 8.1 and 9.3, the Unit 2 plume exhibits Tritium concentrations originating at (he IP2-SFP. The higher concentration isopleths are shown around the entire 11 6 RW-1 is located immediately below the 2005 shrinkage crack leak (high Tritium concentrations in shallow g r oundwater).
This wcll had remained as an open wcllbore for periods of timc in prcparation for and during: 1) the drilling of the wellbore;  
This wcll had remained as an open wcllbore for periods of timc in prcparation for and during: 1) the drilling of the wellbore;
: 2) the packer testing: 3) the geophysical log ging: and, 4) the Pumping Test. Du ri ng these times. vertically downward grad i ents li kely movcd some Tritium to levels deeper than it would otherwise exist. When possible.
: 2) the packer testing: 3) the geophysical log ging: and, 4) the Pumping Test. Du ri ng these times. vertically downward grad i ents li kely movcd some Tritium to levels deeper than it would otherwise exist. When possible.
this welloorc has been sea l ed ove r its cntire length using a Flute Liner Sy s tem. liS pool area so as to include the location of the shrinkage crack leak in the S o ut h pool wall , the loca tion of th e 1992 l eak on the Eas t wall, and the l ocation of the weld imperfection in the No rth wall of the LP2 Transfe r C an al. We believe the core of th e plume , as shown , is relative l y narrow where Tritium flows downgradient (weste rly) t o MW and MW -Ill in the Transformer yard ll7 , Th i s delineation i s based on: 1) the degree of connection ll8 observed from MW-30 to MW-33 (as compared with that from MW-30 to MW-3 l and/or MW-32) as being indicative of a zone of hi gher hydraulic conductivity limiting lateral dispersion; and 2) the l ocalized increased thickness of the saturated soil in the vicinity of MW-lll (see Figure 1.3) which likely behaves as a local groundwater sink/source for wes te rly bedrock groundwater flow, pri or to en t e ring the associated backfill of the D i scharge Canal. .-.---. . !. . -.. -. -: . -. "
this welloorc has been sea l ed ove r its cntire length using a Flute Liner Sy s tem. liS pool area so as to include the location of the shrinkage crack leak in the S o ut h pool wall , the loca tion of th e 1992 l eak on the Eas t wall, and the l ocation of the weld imperfection in the No rth wall of the LP2 Transfe r C an al. We believe the core of th e plume , as shown , is relative l y narrow where Tritium flows downgradient (weste rly) t o MW and MW -Ill in the Transformer yard ll7 , Th i s delineation i s based on: 1) the degree of connection ll8 observed from MW-30 to MW-33 (as compared with that from MW-30 to MW-3 l and/or MW-32) as being indicative of a zone of hi gher hydraulic conductivity limiting lateral dispersion; and 2) the l ocalized increased thickness of the saturated soil in the vicinity of MW-lll (see Figure 1.3) which likely behaves as a local groundwater sink/source for wes te rly bedrock groundwater flow, pri or to en t e ring the associated backfill of the D i scharge Canal. .-.---. . !. . -.. -. -: . -. "
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Once on the western side of the Discharge Canal, as evidenced by groundwater elevations and Tritium concentrations in MW-37 , -49 , and 117   
Once on the western side of the Discharge Canal, as evidenced by groundwater elevations and Tritium concentrations in MW-37 , -49 , and 117   
-67, groundwater flow and Tritium migration is to the Hudson River, via both bedrock and unconsolidated material along the riverfront.
-67, groundwater flow and Tritium migration is to the Hudson River, via both bedrock and unconsolidated material along the riverfront.
The specific flow path for the Tritium detected in MW-37-22 (located in the fill on the West side of the canal) is not certain. It is however associated with either: 1) upward groundwater flow into the backfill from th e bedrock beneath the canal, as supported by the upward vertical hydraulic gradients;  
The specific flow path for the Tritium detected in MW-37-22 (located in the fill on the West side of the canal) is not certain. It is however associated with either: 1) upward groundwater flow into the backfill from th e bedrock beneath the canal, as supported by the upward vertical hydraulic gradients;
: 2) groundwater flow into the blast rock fill on the West side of the canal, with northerly flow in the fill to, and around the North end of the canal and then southerly along the East side of the canal to MW-37; andlor 3) exfiltration from the s torm water piping between MH-4 and MH-4A into the fill on the western side of the canal, with a similar flow path as described in 2). See Section 7.5 for additional information.
: 2) groundwater flow into the blast rock fill on the West side of the canal, with northerly flow in the fill to, and around the North end of the canal and then southerly along the East side of the canal to MW-37; andlor 3) exfiltration from the s torm water piping between MH-4 and MH-4A into the fill on the western side of the canal, with a similar flow path as described in 2). See Section 7.5 for additional information.
Regardless of the upstream flow path to MW-37-22, the groundwater flow direction from this location is westerly toward the Hudson River. Also note that the exact pathway to this location does not change the results of the groundwater flux calculations to be used in radiologic dose impact assessments.
Regardless of the upstream flow path to MW-37-22, the groundwater flow direction from this location is westerly toward the Hudson River. Also note that the exact pathway to this location does not change the results of the groundwater flux calculations to be used in radiologic dose impact assessments.
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... I I , 1" I .. * --, J L-.-, I H udson R iv er CURRENT UNIT I PLUME However, because of the timing of the interdictions and, we believe, the slower groundwater transport rates for Strontium, overa ll the Unit I plume has not decayed to the extent the Unit 2 plume has decayed (see Section 9.4.1). Tn fact, due to what we attribute to short tenn Strontium fluctuation s , at six of the well locations within the Unit I plume, the highest Strontium groundwater concentrations were observed during the last project samp lin g event (see the following table for additional deta il). In reviewing both figures, note th at they show what we believe are conservative estimates of the lateral distribution of the higher (25 pCi/L) Strontium g roundwat er concentrations.
... I I , 1" I .. * --, J L-.-, I H udson R iv er CURRENT UNIT I PLUME However, because of the timing of the interdictions and, we believe, the slower groundwater transport rates for Strontium, overa ll the Unit I plume has not decayed to the extent the Unit 2 plume has decayed (see Section 9.4.1). Tn fact, due to what we attribute to short tenn Strontium fluctuation s , at six of the well locations within the Unit I plume, the highest Strontium groundwater concentrations were observed during the last project samp lin g event (see the following table for additional deta il). In reviewing both figures, note th at they show what we believe are conservative estimates of the lateral distribution of the higher (25 pCi/L) Strontium g roundwat er concentrations.
125 ANALYSIS OF STRONTIUM CONCENTRATIONS OVER TIME Max. Monitoring Current ( ) Elapsed Time Current Observed II) Well Strontium between Max. Cone. As Strontium Concentration and Current Percent of Concentration (pCi/L) Concentrations Maximum -""CUL) (days) 110 MW-42 20.1 490 lS( I 37 MW*53* 37 0 100 ---3.6 MW-47* 3.6 0 100 2.7 MW-56 2.4 332 89 26.8 Ul-CSS* 26.8 0 100 21.9 MW-54 19.2 88 88 40.4 MW-55 34.0 263 84 45.5 MW-57 37.9 44 83 -----5.0 MW-36 2.3 483 46 29.8 MW*37 23.3 40 78 31 MW-50* 3 1 0 100 ------_.-25.6 MW-49* 25.6 0 100 \9.1 MW-67** 19.1 0 100" 6.2 MW_66n: 6.2 0 100
125 ANALYSIS OF STRONTIUM CONCENTRATIONS OVER TIME Max. Monitoring Current ( ) Elapsed Time Current Observed II) Well Strontium between Max. Cone. As Strontium Concentration and Current Percent of Concentration (pCi/L) Concentrations Maximum -""CUL) (days) 110 MW-42 20.1 490 lS( I 37 MW*53* 37 0 100 ---3.6 MW-47* 3.6 0 100 2.7 MW-56 2.4 332 89 26.8 Ul-CSS* 26.8 0 100 21.9 MW-54 19.2 88 88 40.4 MW-55 34.0 263 84 45.5 MW-57 37.9 44 83 -----5.0 MW-36 2.3 483 46 29.8 MW*37 23.3 40 78 31 MW-50* 3 1 0 100 ------_.-25.6 MW-49* 25.6 0 100 \9.1 MW-67** 19.1 0 100" 6.2 MW_66n: 6.2 0 100
* Cu rrent concentration is the maximum concentration ofsampJe s analyzed at this monitoring well . .. Only one sample analyzed.  
* Cu rrent concentration is the maximum concentration ofsampJe s analyzed at this monitoring well . .. Only one sample analyzed.
(1) Any depth, a ny event. at the indicated location.  
(1) Any depth, a ny event. at the indicated location.
(2) Any depth, on the date of the la s t project sampli ng event, at the indicated location (3) It should be noted that the latest data just recently receiv ed (well after the report data-cut-otf-date of August 31, 2007) for MW-42 shows an increase to 46 pCilL. 126 10.0 FINDINGS AND CONCLUSIONS At no time have analyses of existing Site conditions yielded any indication of potential adverse environmental or health risk , as assessed by Entergy as well as the principal regulatory aut h orities. In fact , radiological assessments have consistently shown that the releases to the environment are a s mall perce nt age of regulatory limits , and no threat to public health or safety. In this regard , it is also important to note that the groundwater i s not used as a s ource of drinking water on or near the Site. Consistent with the purpose of the inve s tigation s, we have developed six major su pporting conclusions which are described in the following subsections.
(2) Any depth, on the date of the la s t project sampli ng event, at the indicated location (3) It should be noted that the latest data just recently receiv ed (well after the report data-cut-otf-date of August 31, 2007) for MW-42 shows an increase to 46 pCilL. 126 10.0 FINDINGS AND CONCLUSIONS At no time have analyses of existing Site conditions yielded any indication of potential adverse environmental or health risk , as assessed by Entergy as well as the principal regulatory aut h orities. In fact , radiological assessments have consistently shown that the releases to the environment are a s mall perce nt age of regulatory limits , and no threat to public health or safety. In this regard , it is also important to note that the groundwater i s not used as a s ource of drinking water on or near the Site. Consistent with the purpose of the inve s tigation s, we have developed six major su pporting conclusions which are described in the following subsections.
Based on our findings and conclusions, we are recommending completion of source interdiction measures with Monitored Natural Attenuation as the preferred remedial measure. Refer to Section 11.0 for more information, including our reasons for making this recommendation.
Based on our findings and conclusions, we are recommending completion of source interdiction measures with Monitored Natural Attenuation as the preferred remedial measure. Refer to Section 11.0 for more information, including our reasons for making this recommendation.
10.1 NATURE AND EXTENT OF CONTAMINANT MIGRA nON The primary groundwater radiological contaminant s of interest are Tritium and Strontium.
10.1 NATURE AND EXTENT OF CONTAMINANT MIGRA nON The primary groundwater radiological contaminant s of interest are Tritium and Strontium.
Other contaminants (Cesium-13?, N i ckel-63 and Cobalt-60) have been detected , but are limited to areas that have groundwater pathways dominated by Tritium andlor Strontium, and are accounted for in Entergy's dose calcu J ations. Groundwater contamination i s limited to Indian Point's property and i s not migrating off-property to the North, East or South. The contamination migrates with the Site groundwater from areas of higher heads to areas of l ower heads along paths of le ast resistance , and ultimately discharges to the Hudson River to the West. This is supported by the bedrock geo l ogy, multi-level groundwater elevation data and the radiological re s ults from analytical testing. The nearest drinking water reservoirs are located at distance s and elevations which preclude impact s from contaminated groundwater from the Site and there is no nearby use of groundwater.  
Other contaminants (Cesium-13?, N i ckel-63 and Cobalt-60) have been detected , but are limited to areas that have groundwater pathways dominated by Tritium andlor Strontium, and are accounted for in Entergy's dose calcu J ations. Groundwater contamination i s limited to Indian Point's property and i s not migrating off-property to the North, East or South. The contamination migrates with the Site groundwater from areas of higher heads to areas of l ower heads along paths of le ast resistance , and ultimately discharges to the Hudson River to the West. This is supported by the bedrock geo l ogy, multi-level groundwater elevation data and the radiological re s ults from analytical testing. The nearest drinking water reservoirs are located at distance s and elevations which preclude impact s from contaminated groundwater from the Site and there is no nearby use of groundwater.
: a. The Site is located over a portion of the aquifer ba s in where Site-wide ambient groundwater flow patterns , both shallow and deep. have been defined. These flow s are toward s the Site from higher elevations to the North , East and South. Groundwater flow on Site enters the Hudson River through: footing drains (which di sc harge to the Di s charge Canal); the Discharge Cana l; the storm drain system; or direct discharge.
: a. The Site is located over a portion of the aquifer ba s in where Site-wide ambient groundwater flow patterns , both shallow and deep. have been defined. These flow s are toward s the Site from higher elevations to the North , East and South. Groundwater flow on Site enters the Hudson River through: footing drains (which di sc harge to the Di s charge Canal); the Discharge Cana l; the storm drain system; or direct discharge.
The result s of over two years of investigations demonstrate that the off-Site groundwater migration to the South , as originally hypothe s iz ed by others prior to the se investigations, i s not occurring.  
The result s of over two years of investigations demonstrate that the off-Site groundwater migration to the South , as originally hypothe s iz ed by others prior to the se investigations, i s not occurring.
: b. S u rface water samples collected from the Algonquin Creek , the T rap Rock Quarry and from the drinking water reservoirs do not exhibit impacts from the Site. c. The Hudson River i s the regional groundwater s ink for the area. We found no S i te data , published inf onnation , or other reasons s ugge st in g that g roundwater would migrate beneath the river. To the contrary , based on the a re a's hydrogeologic se tting and all available infonnalion , we are confident that groundwater beneath the Site discharges to the river. 127
: b. S u rface water samples collected from the Algonquin Creek , the T rap Rock Quarry and from the drinking water reservoirs do not exhibit impacts from the Site. c. The Hudson River i s the regional groundwater s ink for the area. We found no S i te data , published inf onnation , or other reasons s ugge st in g that g roundwater would migrate beneath the river. To the contrary , based on the a re a's hydrogeologic se tting and all available infonnalion , we are confident that groundwater beneath the Site discharges to the river. 127
: d. Because of the hydraulic properties of the bedrock, the bedrock aquifer on-Site will not support large yields, o r accept input of large volumes of water. e. There are no identified off-Site uses of groundwater (extrac tion or injection) proximate to the Site that influence groundwater flow patterns on the Site. Furthennore, we have no reason to believe that potable or irrigation wells will be installed on or near the Site in the reasonably foreseeable future, in part because municipal water i s available in the area. f. Groundwate r flow at the Site occurs in two distinct hydraulic regimes that are vertically connected, bedrock and overburden soils. Most of the groundwater flow and contaminants are found in the bedrock fractures.
: d. Because of the hydraulic properties of the bedrock, the bedrock aquifer on-Site will not support large yields, o r accept input of large volumes of water. e. There are no identified off-Site uses of groundwater (extrac tion or injection) proximate to the Site that influence groundwater flow patterns on the Site. Furthennore, we have no reason to believe that potable or irrigation wells will be installed on or near the Site in the reasonably foreseeable future, in part because municipal water i s available in the area. f. Groundwate r flow at the Site occurs in two distinct hydraulic regimes that are vertically connected, bedrock and overburden soils. Most of the groundwater flow and contaminants are found in the bedrock fractures.
No evidence of large scale solut i o n features exist in t he rock cores obtained from any of the bedrock borings advanced at the Site; i.e., no ope n vo ids such as runnels, caverns, caves, etc., sometimes referred to as "u nderground rivers," were found. Our on-Site investigatory findings are consistent with that expected for the Inwood Marble. The refore, this work eliminates from concern solution feature flow associated with karst systems. The second regime i s groundwater flow in the unconsolidated soil deposits.
No evidence of large scale solut i o n features exist in t he rock cores obtained from any of the bedrock borings advanced at the Site; i.e., no ope n vo ids such as runnels, caverns, caves, etc., sometimes referred to as "u nderground rivers," were found. Our on-Site investigatory findings are consistent with that expected for the Inwood Marble. The refore, this work eliminates from concern solution feature flow associated with karst systems. The second regime i s groundwater flow in the unconsolidated soil deposits.
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129 10.3 GROUNDWATER CONTAMINANT TRANSPORT Based on our assessment of the bedrock's hydraulic properties , the area's hydrogeologic se tting, the properties of the contaminants, the age of the releases, interdictions made to eliminate or reduce release rates, and the distances between the source areas and the Hudson River, we believe the groundwater contaminant plumes have expanded to their maximum extent and are now decreasing in size. tn this regard , the Unit 2 Tritium plume is decreasing faster than the Unit I Strontium plume, as anticipated.
129 10.3 GROUNDWATER CONTAMINANT TRANSPORT Based on our assessment of the bedrock's hydraulic properties , the area's hydrogeologic se tting, the properties of the contaminants, the age of the releases, interdictions made to eliminate or reduce release rates, and the distances between the source areas and the Hudson River, we believe the groundwater contaminant plumes have expanded to their maximum extent and are now decreasing in size. tn this regard , the Unit 2 Tritium plume is decreasing faster than the Unit I Strontium plume, as anticipated.
These conclusions are based on the data available which, given the aggressiveness with which Entergy implemented the investigations, is compressed in duration l JO , Therefore, ultimate confirmation of these conclusions will require monitoring over a number of years to allow ranges in seasonal variation to be adequately reflected in the monitoring data. During long term monitoring, GZA further anticipates that contaminant concentrations in individual monitoring wells will fluctuate over time (increasing at times as well as decreasing, as potentially related to precipitation events), and that a future short term increase in concentrations does not , in and of itself, indicate a new leak. In addition, it is also expected that some areas within the plumes will ex hibit faster decay rates than others. Both behaviors are commonly observed throughout the industry with groundwater contamination sam pling and analyses, and therefore, conclusions pursuant to plume behavior must be evaluated in the context of all of the Site-wide monitoring data. Overall , however, aZA believes that the continuing monitoring will demonstrate decreasing long term trends in groundwater contaminant concentrations over time given the source interdictions completed by Entergy. It is also further emphasized that even the upper bound Tritium and Strontium groundwater concentration isopleths presented on Figures 8.1 and 8.2 result in releases to the river which are only a small percentage of the regulatory limits , which are of no threat to public health. a. T he major groundwater tran sport mechanism is advection.
These conclusions are based on the data available which, given the aggressiveness with which Entergy implemented the investigations, is compressed in duration l JO , Therefore, ultimate confirmation of these conclusions will require monitoring over a number of years to allow ranges in seasonal variation to be adequately reflected in the monitoring data. During long term monitoring, GZA further anticipates that contaminant concentrations in individual monitoring wells will fluctuate over time (increasing at times as well as decreasing, as potentially related to precipitation events), and that a future short term increase in concentrations does not , in and of itself, indicate a new leak. In addition, it is also expected that some areas within the plumes will ex hibit faster decay rates than others. Both behaviors are commonly observed throughout the industry with groundwater contamination sam pling and analyses, and therefore, conclusions pursuant to plume behavior must be evaluated in the context of all of the Site-wide monitoring data. Overall , however, aZA believes that the continuing monitoring will demonstrate decreasing long term trends in groundwater contaminant concentrations over time given the source interdictions completed by Entergy. It is also further emphasized that even the upper bound Tritium and Strontium groundwater concentration isopleths presented on Figures 8.1 and 8.2 result in releases to the river which are only a small percentage of the regulatory limits , which are of no threat to public health. a. T he major groundwater tran sport mechanism is advection.
Sorption retards the migration of radiological contaminants other than Tritium relative to groundwater advection rates, while Tritium, within hydraulically interconnected fractures, can migrate at rates that approach the groundwater se epage velocity.  
Sorption retards the migration of radiological contaminants other than Tritium relative to groundwater advection rates, while Tritium, within hydraulically interconnected fractures, can migrate at rates that approach the groundwater se epage velocity.
: b. The Unit 2 contaminant plume is characterized by Tritium in the groundwater.
: b. The Unit 2 contaminant plume is characterized by Tritium in the groundwater.
Over the last two years, the highest Tritium concentrations in the Unit 2 plume have decreased (see Table 5.1 and Figures 8.1 and 9.3). However, the center of mass of the Unit 2 plume i s not rapidly migrating downgradient , and remains in proximity to the IP2-SFP. While a small active leak can not be ruled out completely, this behavior is also consistent with the identified role of unsaturated zone (above the water table) storage of historic releases, with precipitation
Over the last two years, the highest Tritium concentrations in the Unit 2 plume have decreased (see Table 5.1 and Figures 8.1 and 9.3). However, the center of mass of the Unit 2 plume i s not rapidly migrating downgradient , and remains in proximity to the IP2-SFP. While a small active leak can not be ruled out completely, this behavior is also consistent with the identified role of unsaturated zone (above the water table) storage of historic releases, with precipitation
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round s sp ann i n g multiple seaso n s are not yet availab l e. 130 10.4 concentrations in the Unit I West Fuel Pool via pool water recirculation through demineralization beds. While the physical l eak(s) in this fuel pool still exist, the source tenn to the groundwater has been reduced through reduction in the contaminant concentrations in the leak water. It is noted , however , the U nit 1 Strontium decreases are more modest and are generally more limited to the immediate source area than that observed for Tri tiu m at Unit 2. The slower rate of plume decay is not unanticipated give the adsorption properties of Strontium, Further planned interdictions include removal of the fuel rods and draining of the pool water, which will pennanently eliminate the West Fuel Pool as well as the entire IPI-SFP complex as a source of contamination to the groundwater.
round s sp ann i n g multiple seaso n s are not yet availab l e. 130 10.4 concentrations in the Unit I West Fuel Pool via pool water recirculation through demineralization beds. While the physical l eak(s) in this fuel pool still exist, the source tenn to the groundwater has been reduced through reduction in the contaminant concentrations in the leak water. It is noted , however , the U nit 1 Strontium decreases are more modest and are generally more limited to the immediate source area than that observed for Tri tiu m at Unit 2. The slower rate of plume decay is not unanticipated give the adsorption properties of Strontium, Further planned interdictions include removal of the fuel rods and draining of the pool water, which will pennanently eliminate the West Fuel Pool as well as the entire IPI-SFP complex as a source of contamination to the groundwater.
With elimination of this source , natural attenuation will reduce Strontium concentrations in the Unit 1 plume over time. GROUNDWATER MASS FLUX CALCULATIONS Dur ing the project (over the past two years), as testing progressed and more information became avai lable , we refined methods to calculate the groundwater flux and associated radiological activity to the Hudson River, As described below , we have developed a procedure which i s scien tifi ca lly sound , re lativ ely straight-forward, and appropriately conservative.
With elimination of this source , natural attenuation will reduce Strontium concentrations in the Unit 1 plume over time. GROUNDWATER MASS FLUX CALCULATIONS Dur ing the project (over the past two years), as testing progressed and more information became avai lable , we refined methods to calculate the groundwater flux and associated radiological activity to the Hudson River, As described below , we have developed a procedure which i s scien tifi ca lly sound , re lativ ely straight-forward, and appropriately conservative.
G roundwater flow rates are provided to Entergy , who computes the radiological dose impact. a. Migration of radionuclides to the river is computed based on groundwater flow r ates, in combination with contaminant concentrations within the flow regime. Th is information is then used in surface water models to compute radiological contaminant concentrations in the river and thus potential dose to receptors.  
G roundwater flow rates are provided to Entergy , who computes the radiological dose impact. a. Migration of radionuclides to the river is computed based on groundwater flow r ates, in combination with contaminant concentrations within the flow regime. Th is information is then used in surface water models to compute radiological contaminant concentrations in the river and thus potential dose to receptors.
: b. To assess the validity of the precipitation mass balance method used to date for computing groundwater flux ac r oss the Site , aZA also performed groundwater flux computations using an independent method based on Darcy's La w. Thus, the results from two widely accepted groundwater flow calculation methods were compared against each other. The fir st, the precipitation mass balance method, is a " top-d own" procedure based on precipitation-driven water balance analyses.
: b. To assess the validity of the precipitation mass balance method used to date for computing groundwater flux ac r oss the Site , aZA also performed groundwater flux computations using an independent method based on Darcy's La w. Thus, the results from two widely accepted groundwater flow calculation methods were compared against each other. The fir st, the precipitation mass balance method, is a " top-d own" procedure based on precipitation-driven water balance analyses.
The second , based on Darcy's Law, is a "bottom-up" method using hydraulic conductivity and flow gradient measurements.
The second , based on Darcy's Law, is a "bottom-up" method using hydraulic conductivity and flow gradient measurements.
These two methods resulted in estimated groundwater flow values which were in agreement , providing a high degree of confidence in the values obtained relative to their impact on subsequent dose computations and risk analyses.  
These two methods resulted in estimated groundwater flow values which were in agreement , providing a high degree of confidence in the values obtained relative to their impact on subsequent dose computations and risk analyses.
: c. The original groundwater flux computations were developed for two separate areas of the Site. The northernmost area included both the Unit 2 and Unit 1 plumes. The southernmost area encompassed Unit 3, This bifurcation of the Site was established given: 1) the co-location of the Uni t 2 plume and the Unit 1 plume near the western boundary of the Site just upgradient of the river; 2) the much lower contaminant concentrations in the Unit 3 area; and 3) the amount of data available at that time. Current data, derived from a greater number of groundwater e levation and samp ling points than reflected in ear li er data, show the Site can be divided into six separate areas, The computations were further separated into sha llow and deep flow regimes given: 1) the generally higher hydraulic conductivity in the shallow 131 portion of the bedrock, and 2) the general l y more elevated contaminant concentrations in the shal10w flow regime. d. The groundwater contaminant concentrations used for the radiological dose computations were obtained primarily from the ana l ysis of samples taken from the recently completed multi-level wells specifically installed for this p'ffi'0se.
: c. The original groundwater flux computations were developed for two separate areas of the Site. The northernmost area included both the Unit 2 and Unit 1 plumes. The southernmost area encompassed Unit 3, This bifurcation of the Site was established given: 1) the co-location of the Uni t 2 plume and the Unit 1 plume near the western boundary of the Site just upgradient of the river; 2) the much lower contaminant concentrations in the Unit 3 area; and 3) the amount of data available at that time. Current data, derived from a greater number of groundwater e levation and samp ling points than reflected in ear li er data, show the Site can be divided into six separate areas, The computations were further separated into sha llow and deep flow regimes given: 1) the generally higher hydraulic conductivity in the shallow 131 portion of the bedrock, and 2) the general l y more elevated contaminant concentrations in the shal10w flow regime. d. The groundwater contaminant concentrations used for the radiological dose computations were obtained primarily from the ana l ysis of samples taken from the recently completed multi-level wells specifically installed for this p'ffi'0se.
These wells are located downgradient of the Unit 2 and Unit 1 infrastructure!)
These wells are located downgradient of the Unit 2 and Unit 1 infrastructure!)
and are positioned within the plumes and just upgrad i ent of where the groundwater discharges to the river and Discharge Canal. The multi-level nature of these wells allows the groundwater to be sampled over at least five separate elevations in the bedrock, in addition to the overburden l ayer above. Sampling zones specifically targeted the most pervious depths within the bedrock borehole s. As s uch, the groundwater samples encompass the full depth of the contaminant plume, from the upper soil zones to depths where the contaminant concentrations have fallen off to insignificant levels. The high number of samples over the depth of the plume provide s a higher degree of confidence that the significant flow zones are accounted for. The high number of vertical sampling zones also provides a higher level of redundancy relat i ve to the longevity and efficacy of the monitoring network over time. 10,5 GROUNDWATER MONITORING The current groundwater well and footing drain monitoring network is consistent with the obj e ctives of the NEI Groundwater Protection Initiative l 32. Wells have been installed and are currently being monitored to both detect and characterize current and potential future groundwater contaminant migration to the river, as well as , in concert with specific footing dra in monitoring, provide earlier detection of potential future leaks associated with the existing infrastructure.  
and are positioned within the plumes and just upgrad i ent of where the groundwater discharges to the river and Discharge Canal. The multi-level nature of these wells allows the groundwater to be sampled over at least five separate elevations in the bedrock, in addition to the overburden l ayer above. Sampling zones specifically targeted the most pervious depths within the bedrock borehole s. As s uch, the groundwater samples encompass the full depth of the contaminant plume, from the upper soil zones to depths where the contaminant concentrations have fallen off to insignificant levels. The high number of samples over the depth of the plume provide s a higher degree of confidence that the significant flow zones are accounted for. The high number of vertical sampling zones also provides a higher level of redundancy relat i ve to the longevity and efficacy of the monitoring network over time. 10,5 GROUNDWATER MONITORING The current groundwater well and footing drain monitoring network is consistent with the obj e ctives of the NEI Groundwater Protection Initiative l 32. Wells have been installed and are currently being monitored to both detect and characterize current and potential future groundwater contaminant migration to the river, as well as , in concert with specific footing dra in monitoring, provide earlier detection of potential future leaks associated with the existing infrastructure.
: a. The network of 59 mon i toring well locations and over 140 sampling intervalsllocations, has allowed us to identify groundwater flow patterns.
: a. The network of 59 mon i toring well locations and over 140 sampling intervalsllocations, has allowed us to identify groundwater flow patterns.
A subset of this network will provide an adequate long tenn monitoring system. b. Existing and potential sources have been identified, and monitoring is in place to both evaluate current conditions and identify future releases, should they occur. c. The nature and extent of cornamination is known and reporting requi r ements are in place. 10.6 COMPLETENESS Inv es tigations at the Site have been broad, comprehensive, and rigorous.
A subset of this network will provide an adequate long tenn monitoring system. b. Existing and potential sources have been identified, and monitoring is in place to both evaluate current conditions and identify future releases, should they occur. c. The nature and extent of cornamination is known and reporting requi r ements are in place. 10.6 COMPLETENESS Inv es tigations at the Site have been broad, comprehensive, and rigorous.
Ma j or components of the field studies include: detailed acquisition of geologic infonnation; automated long duration collection of piezometric data; vigorous source area \3 1 The multi-level sampling network is concentra ted in the Unit 2 and Unit I areas given that this is wh e r e co ntaminant conc e ntrations are by far the highest. The individual monitoring well s located downgradient of Unit 3 are judged suffic ient for computations in this area given the low contaminant concentra ti o n s measured, even in the typically more contaminated s hallow flow regime. 1)2 NEI developed a set of procedures/goals for nuclear plants to assess the potential for releases of radionuclides to pote n tially migrate off-Si te. 132 identification; comprehensive aquifer property testing, including perfonnance of a full scale Pumping Test; and large*scale confirmatory contaminant transport testing, in the form of an extensive tracer test. The results of this systematic testing program are in agreement with conditions anticipated by our Conceptual Site Model. Based on our review of findings, we have concluded that the field studies conducted at the Site have addressed the study objectives.  
Ma j or components of the field studies include: detailed acquisition of geologic infonnation; automated long duration collection of piezometric data; vigorous source area \3 1 The multi-level sampling network is concentra ted in the Unit 2 and Unit I areas given that this is wh e r e co ntaminant conc e ntrations are by far the highest. The individual monitoring well s located downgradient of Unit 3 are judged suffic ient for computations in this area given the low contaminant concentra ti o n s measured, even in the typically more contaminated s hallow flow regime. 1)2 NEI developed a set of procedures/goals for nuclear plants to assess the potential for releases of radionuclides to pote n tially migrate off-Si te. 132 identification; comprehensive aquifer property testing, including perfonnance of a full scale Pumping Test; and large*scale confirmatory contaminant transport testing, in the form of an extensive tracer test. The results of this systematic testing program are in agreement with conditions anticipated by our Conceptual Site Model. Based on our review of findings, we have concluded that the field studies conducted at the Site have addressed the study objectives.
: a. There is no need t o monitor groundwater at off*Site locations.
: a. There is no need t o monitor groundwater at off*Site locations.
The density and spacing of on*Site monitoring wells i s adequate to: 1) demonstrate that contaminated groundwater is migrating to the Hudson River to the West , and not migrating off of the property to the Nonh , East or South; 2) monitor the anticipated attenuation of co ntam i n ant conce ntrati ons; 3) identify future releases , should they occur; and 4) provide the data required to compute radiological dose impact. h. Hydrau lic conductivity is the most important aquifer property.
The density and spacing of on*Site monitoring wells i s adequate to: 1) demonstrate that contaminated groundwater is migrating to the Hudson River to the West , and not migrating off of the property to the Nonh , East or South; 2) monitor the anticipated attenuation of co ntam i n ant conce ntrati ons; 3) identify future releases , should they occur; and 4) provide the data required to compute radiological dose impact. h. Hydrau lic conductivity is the most important aquifer property.
We have completed more than 245 hydraulic conductivity tests, including a full*scale Pumping Test. Therefore, we believe no future aquifer testing is required.
We have completed more than 245 hydraulic conductivity tests, including a full*scale Pumping Test. Therefore, we believe no future aquifer testing is required.
In addition , the contaminant plumes have reached their maximum spatial extent. Therefore, there is no need for contaminant transport modeling.  
In addition , the contaminant plumes have reached their maximum spatial extent. Therefore, there is no need for contaminant transport modeling.
: c. The sources of re l eases to the groundwater h ave been identified.
: c. The sources of re l eases to the groundwater h ave been identified.
In additio n to monitoring, act i ons have been taken to reduce or eliminate these releases.
In additio n to monitoring, act i ons have been taken to reduce or eliminate these releases.
Therefore, we believe no future source characterization is required.  
Therefore, we believe no future source characterization is required.
: d. All infonnation indicates Monitored Natural Attenuation is the appropriate remedial response and i s GZA's reco mmended app r oach (see Section 11.0). The existing monitoring network wi ll serve this remedial approach.
: d. All infonnation indicates Monitored Natural Attenuation is the appropriate remedial response and i s GZA's reco mmended app r oach (see Section 11.0). The existing monitoring network wi ll serve this remedial approach.
Therefore, no design phase studies are required.
Therefore, no design phase studies are required.
133 11.0 RECOMMENDATIONS Based upon the comprehensive groundwater investigation and other work perfonned by Entergy, aZA recommends the following:  
133 11.0 RECOMMENDATIONS Based upon the comprehensive groundwater investigation and other work perfonned by Entergy, aZA recommends the following:
: 1. Repair the identified Unit 2 Transfer Canal liner weld imperfection (completed mid December 2007); 2. Continue source term reduction in the Unit 1 pool via the installed demineralization system; 3. Remove the remaining Unit I fuel and drain the pool s; and 4. Implement long term monitoring consistent with monitored natural attenuation , property boundary monitoring , future potentia l leak identification , and support of ongoing dose assessment.
: 1. Repair the identified Unit 2 Transfer Canal liner weld imperfection (completed mid December 2007); 2. Continue source term reduction in the Unit 1 pool via the installed demineralization system; 3. Remove the remaining Unit I fuel and drain the pool s; and 4. Implement long term monitoring consistent with monitored natural attenuation , property boundary monitoring , future potentia l leak identification , and support of ongoing dose assessment.
It is GZA's opinion that our investigations have characterized the hydrogeology and radiochemistry of the groundwater regime at the Site. Therefore, we are not recommending further subsurface investigations (see Section 10.0). Based upon the findings and conclusions from these investigations , as well as other salient Site operational infonnation. we recommend the completion of s ource interdiction measures with Monitored Natural Attenuation (MNA) as the remediation teclmology at the Site. In no small part , this recommendation is made because of the low potentia l for ri s k associated with groundwater plume discharge to the Hudson River. Monitored Natural Attenuation is defined by the United States Environmental Protection Agency as the reliance on natural attenuation processes (within the context of a carefuUy controlled and monitored clean up approach) to achieve Site-s pecific remedial objectives within a time frame that is re asona b l e compared to other methods. The "na tural attenuation processes" that are at work in the remed i ation approach at this Site include a variety of phy s ical, chemical and radiological processes that act without human intervention to reduce the activity, toxicity, mobility , volume, or concentration of contaminants in soil and groundwater.
It is GZA's opinion that our investigations have characterized the hydrogeology and radiochemistry of the groundwater regime at the Site. Therefore, we are not recommending further subsurface investigations (see Section 10.0). Based upon the findings and conclusions from these investigations , as well as other salient Site operational infonnation. we recommend the completion of s ource interdiction measures with Monitored Natural Attenuation (MNA) as the remediation teclmology at the Site. In no small part , this recommendation is made because of the low potentia l for ri s k associated with groundwater plume discharge to the Hudson River. Monitored Natural Attenuation is defined by the United States Environmental Protection Agency as the reliance on natural attenuation processes (within the context of a carefuUy controlled and monitored clean up approach) to achieve Site-s pecific remedial objectives within a time frame that is re asona b l e compared to other methods. The "na tural attenuation processes" that are at work in the remed i ation approach at this Site include a variety of phy s ical, chemical and radiological processes that act without human intervention to reduce the activity, toxicity, mobility , volume, or concentration of contaminants in soil and groundwater.
These primarily include radiological decay. dispersion.
These primarily include radiological decay. dispersion.
and sorption.
and sorption.
MNA is typ ically used in conjunc t ion with active rem e diation measures (e.g., source control), or as a follow-up to active remediation measures that have already been i mplemented. At IPEC , active remedia1 measure s already implemented include e l imination (e.g., repair of the Unit 21990 liner leak and repair of Transfer Canal weld imperfection in mid-December 2007) and/or control (e.g., installation of a collection box to capture moistufe from the IP2 shrinkage cracks) of active leaks , and reduction of the source term in t he Unit 1 fuel s torage pool through with subsequent planned removal of the source term (fuel rods) followed by complete draining of the LPI*SFPs. Remediation  
MNA is typ ically used in conjunc t ion with active rem e diation measures (e.g., source control), or as a follow-up to active remediation measures that have already been i mplemented. At IPEC , active remedia1 measure s already implemented include e l imination (e.g., repair of the Unit 21990 liner leak and repair of Transfer Canal weld imperfection in mid-December 2007) and/or control (e.g., installation of a collection box to capture moistufe from the IP2 shrinkage cracks) of active leaks , and reduction of the source term in t he Unit 1 fuel s torage pool through with subsequent planned removal of the source term (fuel rods) followed by complete draining of the LPI*SFPs. Remediation
: 1. OUf recommendation of MNA principles include s source term contaminant reduction as an integral pan of this remediation strategy.
: 1. OUf recommendation of MNA principles include s source term contaminant reduction as an integral pan of this remediation strategy.
Data demonstrating plume concentration reduction s over time , as considered along with other salient 134 Site infonnation, are consistent with a conclusion that the interdiction efforts to date (both current and in the past) h ave resulted in: 1) tennination of the identified Tritium leaks in the IP2-SFP; 2) identification of an imperfection in a Unit 2 Transfer Canal weld which h as been repaired;  
Data demonstrating plume concentration reduction s over time , as considered along with other salient 134 Site infonnation, are consistent with a conclusion that the interdiction efforts to date (both current and in the past) h ave resulted in: 1) tennination of the identified Tritium leaks in the IP2-SFP; 2) identification of an imperfection in a Unit 2 Transfer Canal weld which h as been repaired;
: 3) reduction in IPl*SFP contaminant concentrations; and 4) elimination of Sphere Foundation Drain Sump discharges to the storm drain piping East of Unit 3. As such, these interdictions have resul ted in the elimination andlor control of identified sources of contamination to the groundwate
: 3) reduction in IPl*SFP contaminant concentrations; and 4) elimination of Sphere Foundation Drain Sump discharges to the storm drain piping East of Unit 3. As such, these interdictions have resul ted in the elimination andlor control of identified sources of contamination to the groundwate
: r. as required:  
: r. as required:
: a. Over the last two years, the highest Tritium concentrations in the Unit 2 plume have decreased.
: a. Over the last two years, the highest Tritium concentrations in the Unit 2 plume have decreased.
These data are consistent with a conclusion that the leaks responsible for the currently monitored Tritium plume are related primarily to the previously r epa ired 1992 l egacy liner leak and the imperfection in the Transfer Cana l weld. With the implemented physical containment of the associated 2005 "concrete wall crack leaks" and the repair of the Transfer Cana l liner, the source of contamination to the groundwater has been reduced and controlled.  
These data are consistent with a conclusion that the leaks responsible for the currently monitored Tritium plume are related primarily to the previously r epa ired 1992 l egacy liner leak and the imperfection in the Transfer Cana l weld. With the implemented physical containment of the associated 2005 "concrete wall crack leaks" and the repair of the Transfer Cana l liner, the source of contamination to the groundwater has been reduced and controlled.
: b. Over the last two years, the highest radionuclide concentrations in the Uni t 1 plume have decreased.
: b. Over the last two years, the highest radionuclide concentrations in the Uni t 1 plume have decreased.
These decreases are consistent with a reducti on in the concentrations in the Unit I West Fuel Pool via pool water recirculation through demineralization beds. While the physical leak(s) in thi s fuel pool still ex i st, the source tenn to the groundwater has been reduced due to treatment of the source water. Further planned interdictions include removal of the fuel rod s and draining of the pool water , which will permanently eliminate the West Fuel Pool as a source of contamination to the groundwater.  
These decreases are consistent with a reducti on in the concentrations in the Unit I West Fuel Pool via pool water recirculation through demineralization beds. While the physical leak(s) in thi s fuel pool still ex i st, the source tenn to the groundwater has been reduced due to treatment of the source water. Further planned interdictions include removal of the fuel rod s and draining of the pool water , which will permanently eliminate the West Fuel Pool as a source of contamination to the groundwater.
: c. The Unit 1 plume in the Unit 3 area has been attributed to a historic legacy discharge from the Sphere Foundation Drain Sump (SFDS) through the stonn drain system which traverses along the southeastern portion of the Site. Leaks from this s t onn drain system have. in turn , resulted in past contamination of the groundwater along the storm drains, with subsequent groundwater migration westward , through Unit 3 toward the river. The SFDS no longer discharges to the stonn drain and the Strontium concentrations in the Unit 3 groundwater have decreased to low levels, consistent with natural attenuation processes.  
: c. The Unit 1 plume in the Unit 3 area has been attributed to a historic legacy discharge from the Sphere Foundation Drain Sump (SFDS) through the stonn drain system which traverses along the southeastern portion of the Site. Leaks from this s t onn drain system have. in turn , resulted in past contamination of the groundwater along the storm drains, with subsequent groundwater migration westward , through Unit 3 toward the river. The SFDS no longer discharges to the stonn drain and the Strontium concentrations in the Unit 3 groundwater have decreased to low levels, consistent with natural attenuation processes.
: 2. GZA se l ected Monitored Natural Attenuation as the remediation strategy because: a. Interdiction measures undertaken and planned (0 date have, or are expected to, eliminate/control active sou rce s of groundwater contamination.  
: 2. GZA se l ected Monitored Natural Attenuation as the remediation strategy because: a. Interdiction measures undertaken and planned (0 date have, or are expected to, eliminate/control active sou rce s of groundwater contamination.
: h. Groundwater flow at the Site precludes off-Site migration of contaminated groundwater to the North, South or East. c. Consis tent with the Conceptua1 Site Model, no contaminants have been detected above regional background in any of the off-Site monitoring locations or drinking water supp l y systems in the region. d. The only on-Site exposure route for the documented contamination is through direct expo sure. Because the majority of the Site is capped by 135 impenneable surfaces, there is no uncontrolled direct contact with contaminants.  
: h. Groundwater flow at the Site precludes off-Site migration of contaminated groundwater to the North, South or East. c. Consis tent with the Conceptua1 Site Model, no contaminants have been detected above regional background in any of the off-Site monitoring locations or drinking water supp l y systems in the region. d. The only on-Site exposure route for the documented contamination is through direct expo sure. Because the majority of the Site is capped by 135 impenneable surfaces, there is no uncontrolled direct contact with contaminants.
: e. Our studies indicate that under existing conditions, the spatial extent of the groundwater plume will decrease with time. f. Groundwater is not used as a source of drinking water on the Site or in the immediate vicinity of the Site , and there is no reason to believe that this practice will change in the foreseeable future. g. Groundwater associated with the Unit 1 foundation drainage systems is captured and treated to reduce contaminants prior to discharge to the Discharge Canal , consistent with ALARA principles.  
: e. Our studies indicate that under existing conditions, the spatial extent of the groundwater plume will decrease with time. f. Groundwater is not used as a source of drinking water on the Site or in the immediate vicinity of the Site , and there is no reason to believe that this practice will change in the foreseeable future. g. Groundwater associated with the Unit 1 foundation drainage systems is captured and treated to reduce contaminants prior to discharge to the Discharge Canal , consistent with ALARA principles.
: h. At the location s where contaminated groundwater discharges to the Hudson River, the concentrations have been, and will continue to be, reduced by sorption , hydrodynamic dispersion and radiological decay. No detections of contaminants associated with plant operations have been found in the Hudson River or biota sampled as part of the required routine envirorunental sampling.
: h. At the location s where contaminated groundwater discharges to the Hudson River, the concentrations have been, and will continue to be, reduced by sorption , hydrodynamic dispersion and radiological decay. No detections of contaminants associated with plant operations have been found in the Hudson River or biota sampled as part of the required routine envirorunental sampling.
I. More aggressive technologies would alter groundwater flow pattern s and , therefore , in our opinion, offer no clear advantages.
I. More aggressive technologies would alter groundwater flow pattern s and , therefore , in our opinion, offer no clear advantages.
Long Term Monitoring  
Long Term Monitoring
: 1. The second primary requirement for implementation of MNA is a demonstration that contaminant migration is consistent with the Conceptual Site Model. In particular , rigorous monitoring is required to demonstrate reductions in source area contamination, reductions in plume contaminant concentrations, and reduction in contaminant discharge to the river over time. The initial implementation stages of this monitoring process were begun nearly two years ago as part of the investigations summarized herein. A s outlined above, reductions in maximum groundwater plume contaminant concentrations have already been documented.
: 1. The second primary requirement for implementation of MNA is a demonstration that contaminant migration is consistent with the Conceptual Site Model. In particular , rigorous monitoring is required to demonstrate reductions in source area contamination, reductions in plume contaminant concentrations, and reduction in contaminant discharge to the river over time. The initial implementation stages of this monitoring process were begun nearly two years ago as part of the investigations summarized herein. A s outlined above, reductions in maximum groundwater plume contaminant concentrations have already been documented.
T he elements for long term monitoring , consi s tent with the objectives of the NEl Groundwater Protection Initiative , are in place. We further note: a. Groundwater wells have specifically been installed , and are currently being monitored , to both detect and characterize current and potential future off-Site groundwater contaminant migration to the river. Additional wells have also been installed for monitoring of other Site property boundaries.  
T he elements for long term monitoring , consi s tent with the objectives of the NEl Groundwater Protection Initiative , are in place. We further note: a. Groundwater wells have specifically been installed , and are currently being monitored , to both detect and characterize current and potential future off-Site groundwater contaminant migration to the river. Additional wells have also been installed for monitoring of other Site property boundaries.
: b. Monitoring well s have also been installed just downgradient of identified critical Structures, Systems and Components (SSCs). These wells, in concert with specific footing drain monitoring , provide earlier detection of potential future leaks associated with the power generating units than would be po s sible with boundary well s alone. c. Monitoring wells have been strategically placed to monitor the behavior of the plumes identified on the Site. d. MW-38 and MW-48 should be excluded from the monitoring plan as samples from these wells are generally indicative of a mixed groundwater 136 and Discharge CanaUriver water condition and, therefore, are not completely groundwater specifi c lJ3. e. The long term monitoring plan should include action levels, which if exceeded, trigger further analysis and/or investigations, potentially leading to implementation of an interdiction plan, if required.  
: b. Monitoring well s have also been installed just downgradient of identified critical Structures, Systems and Components (SSCs). These wells, in concert with specific footing drain monitoring , provide earlier detection of potential future leaks associated with the power generating units than would be po s sible with boundary well s alone. c. Monitoring wells have been strategically placed to monitor the behavior of the plumes identified on the Site. d. MW-38 and MW-48 should be excluded from the monitoring plan as samples from these wells are generally indicative of a mixed groundwater 136 and Discharge CanaUriver water condition and, therefore, are not completely groundwater specifi c lJ3. e. The long term monitoring plan should include action levels, which if exceeded, trigger further analysis and/or investigations, potentially leading to implementation of an interdiction plan, if required.
: f. A number of individual vertical sampling zones were included in nearly all the monitoring well installations, particularly within the contaminant plumes and at the location of plume discharge to the river. These individual vertical monitoring zones provide a significant level of vertical resolution and also provide a substantial degree of redundancy relative to the longevity and efficacy of the monitoring network ove r time 134. g. While previous and current dose calculations are both reasonable and conservative, we recommend that, with the accumulation of additional Site-specific hydrogeologic information , the calculations be modified to incorporate Site-specific transmi ss ivities and groundwater gradients.
: f. A number of individual vertical sampling zones were included in nearly all the monitoring well installations, particularly within the contaminant plumes and at the location of plume discharge to the river. These individual vertical monitoring zones provide a significant level of vertical resolution and also provide a substantial degree of redundancy relative to the longevity and efficacy of the monitoring network ove r time 134. g. While previous and current dose calculations are both reasonable and conservative, we recommend that, with the accumulation of additional Site-specific hydrogeologic information , the calculations be modified to incorporate Site-specific transmi ss ivities and groundwater gradients.
Entergy has agreed that Site-specific model information will be utilized in the next NRC required annual assessment of dose from this pathway. Our specific recommendations (which will include additional trend information in early 2008) will be provided under separate cover for Entergy's incorporation to sup port the annual report. III Sce Section 6.6.3 for funher discussion pursuant to this conclusion.
Entergy has agreed that Site-specific model information will be utilized in the next NRC required annual assessment of dose from this pathway. Our specific recommendations (which will include additional trend information in early 2008) will be provided under separate cover for Entergy's incorporation to sup port the annual report. III Sce Section 6.6.3 for funher discussion pursuant to this conclusion.
1 14The l evel of redundancy designed into the long term monitoring network anticipates and allows for the loss of a number of monitoring zones without significant impact to the adequacy of the monitOring system. 137}}
1 14The l evel of redundancy designed into the long term monitoring network anticipates and allows for the loss of a number of monitoring zones without significant impact to the adequacy of the monitOring system. 137}}

Revision as of 02:03, 29 April 2019

Official Exhibit - ENT00331B-00-BD01 - Hydrogeologic Site Investigation Report for the Indian Point Energy Center, Page 64 Through Page 137
ML12338A616
Person / Time
Site: Indian Point  Entergy icon.png
Issue date: 01/07/2008
From: Barvenik M J, Powers M, Winslow D M
GZA GeoEnvironmental
To: Evers R
Enercon Services, Atomic Safety and Licensing Board Panel
SECY RAS
References
RAS 22125, 50-247-LR, 50-286-LR, ASLBP 07-858-03-LR-BD01
Download: ML12338A616 (74)
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Text

ENT00331B Submitted: March 29, 2012 United States Nuclear Regulatory Commission Official Hearing Exhibit In the Matter of

Entergy Nuclear Operations, Inc. (Indian Point Nuclear Generating Units 2 and 3)

ASLBP #:07-858-03-LR-BD01 Docket #:05000247 l 05000286 Exhibit #:

Identified:

Admitted: Withdrawn:

Rejected: Stricken: Other: ENT00331B-00-BD01 10/15/2012 10/15/2012* 0 " : .... ,,1-0 .... ? ****il 1.£+0 1 Analytical olution of tidal re pon e Amplitude:

  • P eak de l ay: * * * * .. *
  • Average measured amplitude

--T heoretica solution with OOOf e/d Y=Aex{-xmJ dist a nc e fr o m lhe booodary (ft) A i dal amp lit ude (ft) 1 0 i dal cyc le (day)

  • 1.£-02 o 10 0 200 300 400 500 600 700 Distance from the river, x (ft) TIDAL RESPONSE VS DISTANCE FROM THE HUDSON RIVER 00 Fetter 3 8 provides an analytical solu t i on for the theoretica l piezometric response of an aquifer adjacent to a t i dal boundary (see above grapb). T he assumptions upon which this solution is based are quite re t ricli e. In addi t ion to the normal difficult i es aquifer heterogeneities anisotropic profert i es e t c.) which limit the practical use of the solution in estim a ting aquifer properties J it i not clear if water levels at the Site are responding to changes in the river level changes in the Discharge Canal levels or perhaps a combination o f both. F urther complicating this issue , the concrete canal walls , and at some locations (no t a ll) the concrete canal bottom, should clearly affect propagation oftidal fluctuations in the canal. With these limitations noted our review of data indicates that the hydraulic diffu s ivity 40 transmi s sivity T div i d e d by s torativity ) of the rock as es ti mated b y the tidal respon es , is on the order o f 80 000 ttl/day. See the above graph and information in Appendix K. As presented i n Section 6.S, we believe the average transmissivity o f the bedrock a q uifer is typically in th e range of 30 to 5 0 if/da y. Using a transmissiv i ty o f 40 ft 2/day and a d i ffusivity of 80 , 0 0 0 if/day , it fo ll ows the storativity of the bedrock aquifer is on the order of 5 10-4. This value is in g ood agreement with the values we computed from an evaluatio n of th e Pumping T est data and from the cubic equation (see Section 6.S.1). 38 C.W. Fe t te r. Ap p lied H yd rol ogy, econd E dition. M e rrill 1 988. 39 Pa tr ick Pow e r , Co n s tru c tion D ew at e rin g e c ond E dition. 40 Free z e & h e rry , G roundwa t e r Prenti c c-I lall 1979. 64 Another effect of river tidal changes i s manifested in monitoring wells in close proximity to the river or Discharge Canal as follows. As the river approaches high tide , the groundwater gradients in proximity to the river become flatter, and a t certain locations and tides , are reversed; that is, on a temporary bas i s , groundwater discharge to the river is generally s lowed , and in at least s ome location s, groundwater flow nonnally to the river is reversed to then be from the river into the aquifer. 6.6.2 Groundwater Temperature The cooling water intake structure is located North (up s tream) o f the cooling water discharge structure (see Figure 1.3). When the river is near high tide, the cooling water intake draw s river water that contains di s charge water 4! (i.e., river flow rever s es and water begins to tlow away from the ocean). At periods near low tide, the current in the river reduce s or eliminates thi s circulation (within the river) of cooling water. A consequence of this tidal influence is that the temperature of water in the Discharge C anal, in addition to always being warmer than the river water , varies with tidal cycles. This i s illu s trated on Figure 6.15 as well as the graph below , a double-axis graph to show the water level and temperature data collected in January 2007 from two s tilling wells: Out-I , loc a ted at the southern end of the Discharge Canal , and HR-!, located in the cooling water intake structure of Unit 1 4 2. 7 Out-! and HR-! 6 5 '" 4 3 2 -I 3 L __ 1/14/07 1/1 5/07 1/16107 )( O ut*! w:l t e r lev e l -HR*! " a t e r l e v e! 1117/07 '" 65* i 60 = .. -II Co o
  • lO E-4l 40 3l 1/19/0 7 111 81 07 WATER LEVEL AND TEMPERATURE RELATIONSHIPS FOR DISCHARGE CANAL AND HUDSON R I VER (JAN. 07) The d i r e ct i on of the now i n the ri v er i s t i dall y influ e n ce d. whi c h at periods near high tid e , is to th e N orth , away fro m th e ocean. 42 Unit I is i n act i ve an d thi s s tillin g w ell s hould pro v id e a g ood m eas ure o f th e riv er e l e v ations with tim e. 65 Based on this information and water quality variatio n s (see Section 6.6.3). we evaluated the potential for the Discharge Canal water to influence water quality at two locations originally proposed for southern property boundary monitoring 43 , MW-38 and MW-48 (located adjacent to the canal and river respectively; see Figure 1.3). 6.6.2.1 Monitoring Well MW*38 Groundwater response to tidal influence of the coo lin g water Discharge Canal (at thi s location) is strong and appears to vary between tidal cycles. We note , however , that we observed responses from approx imat e l y 60% to at least 86% w ith an average of approximately 70%. , 1/14107 " Out-l water level -M Out-\ terrperaturt 1115 1 07 1116107 MW-38 water level MW-38 tefT1>crature 1/17/07 1118107 40 30 2IJ 111 91 07 WATER LEVEL AND TEMPERATURE RELATIONSHIPS FOR DISCHARGE CANAL AND MW*38 (JAN. 07) Additionally.

at high tide the canal leve l is above the water level in MW-38 and at low tide the water level in MW-38 is above the level of the canal (see above graph). These data demonstrate the potential for water in the canal to migrate to the proximity of MW*38 during periods of high tide. Groundwater temperature data collected from MW-38 indicate that canal water does in fact, at times , migrate to we ll MW-38. This is shown on the above graph 4) Th e re s ul ts of o ur ana l y se s demonstrate that monitorin g well s MW-38 and MW-48 arc impacted hy Di sc har ge C anal water at v ariou s time s. Therefore.

these wells arc not s uitabl e for measuring southern boundary groundwater mdiolo g ical condition s. 66

7 -1"'\ 7. 6 69 * --M W 4&.23 wat e r l eve l .... l

  • 68 ., -HR* I water lev el * "
  • 67 j 4 , . M W 41\.23 tCrf1)crature

'" 3 66 ...

  • f\!-6l 0 " oS , .--* -,
  • I , * *
  • 64 *
  • i -* -*
  • 63 E * -I 62 ... -2 61 -3 60 1 114/07 1/15107 111&07 1 117/07 1/1 8107 1/1 9/07 " j '" * " .;: , * -*
  • WATER LEVEL AND TEMPERATURE RELATIONSHIPS FOR HUDSON RIVER AND MW-48*23 (JAN. 07) 7 6 l 4 3 , 1 -* -I -, -3 7 1 22106 7/23/06 7124106 7/25 1 06 >( O ut-I willer level 7 126/06 7127106 7/28106 90 85 '80" x 0 " "' f "'I 75 ! f , I 70 65 60 7/29/06 WATER LEVEL AND TEMPERATURE RELATIONSHIPS FOR DISCHARGE CANAL AND MW*48*23 (JULY 06) 68

.. 7 6 l .. 4 J "' 3 * " .. 2 * " * * -M W 3 8 level -HR-I w!l t cr l eve l o M W 38 temp e rature 0 -Ff-----"'----\+----"'---4

f. --\-"'1-+=#--

I 3 1114/0 7 1115/07 1/16/()7 1/17/01 1/18 107 10 (/I 68 67 , 66 , 65 J i , 64, ----+ 63 62 6 1 60 1119107 WATER LEVEL AND TEMPERATURE RELATIONSHIPS FOR HUDSON RIVER AND MW-48-38 (JAN. 07) 7 66 6 l 6l --MW-48-38 water level 4 J 3 o MW-48-38temperulurc 64 /' !\ !\ !\f\I\f\t\f\ .. * " .. * " * * " 2 0 !\ \/\1:1\1\1\1\:

Ii **ll/r.J t : V V , V V,V \J *1 6 1 *2 _3"--7n2J06 7 123/06 7124106 7/2 5/06 7 12 6!06 712_ WATER LEVEL AND TEMPERATURE RELATlONSfnPS FOR MW-48-38 (JULY 06) At high tide, the level of water in both of these wells is very close to the river level , while at low tide , it is s lightly above the river level and approximately 2 feet below the level of the Discharge Canal. The vertical gradient at this location is upward , with a st ronger gradient at low tide. These data are consistent with anticipated trends, indicating groundwater discharge to th e river occurs predominantly at low tide. Note that the river water temperatures shown on graphs in thi s report are not representative of the temperature of the water in the river adjacent to monitoring wells MW-48. This i s due to the location of river transducer HR-I , and tidal induced flows in the river. However, the elevated (above ambient) temperature of the groundwater at the se locations (65 to 69' F) indicates it has been warmed by the Site's cooling water discharge.

69 The temperature of water in monitoring well MW-48-23 varies with some tide cycles, with the coolest temperature being near high tide in the winter, and the warmest temperature being near high tide i n the summer. This pattern of temperature change is consistent with this monitoring well receiving r iver water at times of high tide. The temperature of water in monitoring we ll MW-48-38 does not appear t o vary with tidal cycles. We i nt erpret these data to mean that physical water quality in monitoring we ll MW-48-38 is not typicall y influenced by large exchanges of river water 44. The elevated groundwater temperature at this l ocation, and the piezometric data, suggest, however, that flows created by purging of the well prior to sampli ng , at times of high tide, could induce river water flow to this l ocation. 6.6.3 Aqueous Geochemistry Routine groundwater monitoring indicated t he presence of Tritium in a limited number of samples collected from monitoring wells MW-38 and MW-48. MW-38 was originally installed under the first phase of in vestigation to bound the southern extent of Tritium co nt ami n ation at the Site along the cooling water Discharge Canal. However , subsequent sampling events indicated the presence of Trit iwn in groundwater at this l ocation. The presence of Tritium in this well did not fit our CSM or what we knew of groundwater flow at the Site. A seco nd well , MW-48 , was insta ll ed at the southern Site boundary along the Hudson River to establish i f any Tritium would potentially migrate off-Site.

Triti um was detected interminent l y in groundwa t e r samples collected at this loca t i on as well. As neith er of these locations was hydraulically downgradient of identified rele ase areas, another mechanism othe r than groundwater migration from the r elease area was postulated.

This mechanism i nvolved releases from the legacy piping that conveyed contaminated water from the fPI-SFDS to the "E"-series sto rrnwater piping that runs beneath the access road on the South side of the Protected Area and discharges storm water to the cooling water Discharge Canal. While evaluating this hypothesis , we found evidence, as discussed in Section 6.62, that at certa in tidal cycles , water from the Discharge Canal and the Hudson River may back flow iDlO the se groundwater monitoring wells. To help identifY the source of Trit ium in these two wells , we developed a focused water quality probrram specific to the se wells. Generally , the water quality program involved analyzing select aqueou s geochemica l parameter s in groundwater and surface water samples. Evaluation of these data can allow conclusions to be drawn regarding the so urce of the sampled water. Both data s ets (elevatio n and water chemistry) indicate th at water co llected from th ese wells may contain river or cooling water from the Discharge Canal. Based on these finding s. we recommend that groundwater samp l e l aboratory results from th ese well locations n01 be used to evaluate the extent of groundwater contamination or contaminant 44 RelAtiv ely lar ge of water are required to overcome the:: Ihennal mass of the s ub surface deposits surrounding the well bore. Therefore.

whi Ie smaller exchan ges of g r OUndwa t e r/riv e r water may go undetected via temperature change. they may st ill be large enou g h to adversely impact I'cldiologieal water quality. panicuJarly in consideration of the data from t he:: proximate well screens. Also see:: discu ssio n in Stction 6.6.3. 70 flux to the Hudson River and that these wells not be incorporated into the Long Term Monitoring P l an as Boundary Well s. 6.6.3.1 Sampling Groundwater samples were co ll ected from monitoring well s MW -38 , MW-48-23 , and MW-48-38 and from the Discharge Canal and Hudson River on January 19 , 2007. These samp les were analyzed for bicarbonate alkalinity (as CaCO,), magnesium , sodium, calcium, s u l fate, and chloride.

The data was graphed on Stiff diagram s and is shown on Figure 6.16. 6.6.3.2 Water Quality Evaluation GZA used the six water quality indicators (bi carbonate alkalinity

[as CaCO)], magnesium, sodium, calcium, s ulfate , and chloride) to assess whether or not Discharge Cana l and/or river water was present or mixed with gro undwater at the two location s of interest (note that the MW-48 monitoring well location contains a s hallow and a de e p well). A s ummary of our finding s follow s.

  • The river and canal samples are c h emically s imilar and a re dominated b y sod ium and chloride.

The sodium and chloride contents are highest at the mid tide sam pling event. T hese data indicate that at mid tide there was a greater vertical mixing of river water which caused the water to contain more sodium and chloride 45.

  • The MW 23 sample s collected at low, mid and high tide are all geochemically s imilar and are dominated by the sod ium and chloride ions. However. th e electrolyte conce n tration of these two ions is approximatel y h alf af th at measured in the river or canal samp l es. Additionally , at low tide , there is slightly le ss sodi um chloride and slightly more bicarbonate anion t h an at mid or high tide. We believe thi s indicates that at low tide, thi s location receives relative l y more groundwater.
  • Samples collected from MW-48-38 at low , mid , and high tide were generally all dominated by calcium and magnesium cations and chloride and bicarbonate anions. These samp le s also contained s imilar so dium , chlo r ide, calcium, bicarbonate. magne sium, and sulfate electrolyte concentrations.

H ow ever , at mid and high tide, there was so mewhat more ca l cium , magnesium , and bicarbonate measured in the se samples. It is further noted that the cation/anion imbalance for the MW-48-38 samples (excep t MW-48-38-L1) was greater than 5%. T hi s indicates a lack of accuracy or the presence of unanalyzed ion s in the groundwater samples. While sa mples from MW-48-38 currently appear more representative of groundwater than those from wells MW-38 and MW-48-23, it is not certain that they are a l ways fully representative of groundwater only46. We the riv er and canal samples arc simi lar (in pan) b<<ause the river sample location was situaled immediatel y down-river of the Discharge Canal outfll il. In additi on, the river samp l i n g location vi si bly appears to remain w ithin t he discharge water heat plume. Therefore.

the river samples are likely Di scharge Canal water or at least mixed with what is being discharged f r om the canaL 46 For example. 573 pCiIL of Tritium was detected in this interval on September 5.2006. Tritium had n ever previously been detected and has since nOI been detected i n this intervaL It may be: that s ample was mi siden tifi ed in the field and the sample was actually obtai ned from the upper interval of this well where Tritium rout inel y detected. I l owe vcr. 71

  • The samples collected from MW-38 at low, mid and high t ide are all geochemically s imilar and are dominated by the sodium and chloride ions. How ever, the electro lyte concentration of the se two ions is less than half of that measured in the river or canal samples. Additionally, at low tide , there is sl ightly less sodium and chloride than at mid or hi gh tide. We believe this likely indicates that at low tide, this l ocation se es relatively more groundwater.

These data indicate that water samples collected from MW-38 and MW-48-23 are lar gely representative of the proximate surf ace water bodies at the Site. Recognizing the SOU Tce of water in these we ll s, the other chem ist ry data (e.g., Trit ium and Stronti um) are suspect and should not be used for evaluation of groundwater contaminant migration o r flux. Base d on the available data , MW-48-38 may provide samples more repre sentative of Site groundwater than MW-38 and MW-48-23.

However, further analysis would be necessary to allow this well to be recommended as a southern boundary monitoring location, particularly in light of the above analysis pursuant to th e proximate well sc reens and the potential for false positives.

Given the demonstrated grou ndwater flow directions in thi s area 47 , it is GZA's opinion that an additional southern boundary monitoring loc at i on (in addition to MW-S\ and MW-40) is not required proximate to MW-48-38.

6.7 GROUNDWATER

FLOW PATTERNS A major purpose of this groundwater investigation was to identify the fate and level of groundwater contami nant migration.

The contaminants of potential concern are so luble in groundwater, and at somewhat varying rates, move with it. This section provides a description of ident ified groundwater

[low patterns in and downgradient of identified contaminant release areas. The piezometric data , shown in Table 6.1 , whic h form the basis of this evaluation are ind ependen t of chemical data collec t ed a t the same monitoring locati ons. Conseq uentl y. our evaluation of piezometric data provides an assessment of where contaminants are expected to migrate in various time frames. Refer to Section 9.0 for information on the observed distribution of contaminants and a discussion on disc re pancies between anticipated and observed conditions.

Testing has indicated that the bedrock is sufficie ntl y fractured to , on the scale of the Site , behave as a non-homogeneous , anisotropic , vertically porous media. This finding indicates that groundwater flow is perpendicular to lines of equal h eads. T hi s assessment appears particularly va lid in horizontal (East-West

& North-South) directions.

The nature of bedrock fracturing suggests the hydraulic conductivity is higher in the horizontal than in the vertical direction.

Furthermore it appears the upper portion s of the rock are more conductive than the deep rock except within the zone of higher h ydraulic conductivity between U nit s I and 2. These fmdings suggest that the bulk of the it al so is po ss i ble that this sample: is reflecti ve ofr i vcr water induced into th e well through sampling and/or th e specific conditions existing at the lim e the sample was taken. 47 Whil e the representativeness of thc chemistry data in these! wells (MW-38. MW-48*23 and MW-48*38) is not certain. the groundwater elevation dMa is reliable for establi s hin g flow direction. 72 groundwater moves at shallower depth, with small masses being reflected deeper into the rock mass than wou ld be seen in anisotropic aquifer. 6.7.1 Groundwate r Flow Direction Groundwater elevations from pressure transd u cers at a representative low tide have been used to construct a potentiometric surface map of the aqu i fer beneath the Site (see Figure 6.17). We chose this data set after evaluating a number of piezometric data sets. More spec ificall y we have mapped s i x groundwater conditions:

  • Low tide during the drier portion of the year (2/12/07)
  • High tide during the wetter portion of the year (3/28/07)
  • Low tide during the wetter portion of the year (3/28/07)
  • High tide during the drier portion of the year (2/12/07)
  • Groundwater elevations at sample locations with the greatest Tritium impact during wet season
  • Groundwater elevations at sample locations with the greates t Tritium impact during the dry season Based on this evaluation , it appears that there is not a great deal of change i n groundwater flow patterns over time (see Appendix S). However, as groundwater elevat i o n s have a smalle r tidal response (amp lit ude) than the fluctuations of the river, low tide is a time with a relatively high degree of groundwater flux from the Site. Furthermore, low tide during the drier portion of the year li kely represents a period of highest groundwater flux. Groundwater flow is in three dimensions.

A representative set of groundwater elevations was used to construct a cross-sectional groundwater contour map as shown on Figure 6.18. This figure is based on a 1:1 horizontal to vert ic al hydraulic conductivity.

Because horizontal fractures transmit flow in only a horizontal direction, and vertical fractures transmit flow in both a horizontal and vertical d ir ection, the aquifer is vertically anisotropic with a preference for horizontal flow. Converse l y, if the vertical hydraulic conductivity decreases with depth , the groundwater flow should be driven deeper than shown on the figure, but would still ultimately discharge to the Hudson River. Based on the observed vertical distribution of piezometric heads , the deepest flow paths of potential interest for this investigation originate near Unit 2. Based on the observed vertical distribution of contaminants (see Section 9.2), these flow paths are limited to depths of between 200 and 300 reet below ground surface. As discussed previously , groundwater flow panerns are also influ enced by anthropogenic sources and sinks. The groundwater source s/sinks are shown on Figure 1.3 and are summarized below:

  • Un i t 1 Chem i cal Systems Building (lPl-CSB) Foundation Drain: This drain discharges into the Sphere Foundation Drain Sump (SFDS) and is designed to ma in tain groundwate r elevations beneath TP-I-CSB subbasement to an elevation of approxima tel y 1 2 feet NOVD 29. The reported groundwater extraction rate from this drain is approximately 10 ga li ons per minute (gpm). 73
  • lP I-NeD: This drain is designed to maintain groundwater elevations beneath the Uni t I containment building (IPI-CB) and the Uni t I Fuel Handling Building FHB) at an elevation ranging from 33 to 42 feet NGVD 29. The reported groundwater extraction rate from this drain is approximately 5 gpm.
  • Unit 2 Footing Drain: This drain is designed to maintain groundwater elevations beneath the Unit 2 Vapor Containment (IP2-VC) at an elevation ranging from approximately 13 to 42 feet NGVD 29. The long tenn flow rate from this drain is not known , but short tenn measurements made prio r to and during the Pumping Test indicate it i s likely on the order of5 gpm.
  • Uni t 3 Foot ing Drain: fP3-VC is known to have a Curtai n Drain. However , specifics of it s construction were not available.

It is known that a pipe that connects to the Unit 3 Curtai n Drain is currently under water in a manhole Northeast of U nit 3. Due to this condition , it is unknown how much or whether or not this drain is removing groundwater.

  • Unit I , 2 , and 3 stann drains: The storm drains surrounding Units I, 2, and 3 were constructed of corrugated metal piping. These pipes and associated utility trenches have been shown to allow at least some infiltrationlexfiltration.

That is, depending on rainfall and location, these struct ure s may either receive groundwater or rech arge the aquifer. 6.7.2 Groundwater Flow Rates In the interest of evaluating conditions when a relatively large amount of groundwater (and associated constituents) flux to the Hudson River occurs, our discussion of lateral groundwater flow direction focuses on the low tide potentiometric surface contours as shown on Figures 6.19 and 6.20. These groundwater contours show that groundwater generally flow s toward the Site from the North, East and South, with a generally westerly flow direction ac ro ss the Site with a gradient averaging about 0.06 feet per feet. 6.7.2.1 Seepage Velocities We used Darcy's Law to est imate the average groundwater seepage velocity across the Site: Where: dh I V=K*-*dl n" v = average linear groundwater velocity K = hydraulic conductivity (0.27 feet/day [see Section 6.50]) dh -= groundwater gradient (0.06) dl n , = effec ti ve porosity (assu m ed to be 0.0003 based on spec ific yie ld measured during Pumping Tes t) 74 Based on this equation and Site data, we computed the average groundwater seepage veloc i ty to be on the order of 55 fl/day. This i s an upper end estimate in that i t does not accoun t for the effect of dead-end fractures and irregularities in fracture apertures.

That i s , we believe the effective porosity is lar ge r than that indicated by hydraulic testing. Also note that this is an average velocity with flow rate in individual fractures being controlled by the local gradient and hydraulic aperture of the fracture.

Based on the tracer test (see Section 7.3.2), actual measured ave r age seepage rates were substantially less than 55 ftlday. 6.7.2.2 Groundwater flux To estimate groundwater flows (Le., groundwater mass flux) beneath the fPEC , a calibrated analytical groundwater flow model was constructed.

This model was based on two independent equations, both of which provide grou ndwater flow estimates.

The first of these equations i s based on a ma ss balance. That is, on a long term average, the groundwater discharging from the aquifer is equal to the aquifer recharge.

The second equation is " Darcy's Law" , which states the flow per unit width of aquifer i s equa l to the transmissivity of the aquifer multiplied by the hydraulic gradient.

As discussed in the followi ng su b sectio n s using S i te-specific data for the governing parameters, both of these i ndepend ent methods provided similar results. Because we were conservative (that is, we chose values for both equations that we believe may somewhat overestimate flows), we believe the model is approp riate for it s intended use for estimating the mass of groundwater discharging to the Hudson River as part of dose impact computations

48. Please note, this model is not, therefore, conservative for all purposes.

For example , we believe it would likely ove re stimate th e yield of extraction wells shou ld they be developed at the facility. While the calculated groundwater flux from the Site directly to the river (approximately 1 3 gpm) may intuitively seem small , it is consistent with our Conceptua l Site Model and the identified hydrogeological sett ing. Mass Balance The mass balance approach r ecognizes that the on l y substantial s ource of recharge to aqu i fer is areal recharge derived from precipita t ion. Precipitation in the area reported l y varies from 49 inches per year (3D-year average) to 36 inches per year (IO-year average) at the IPEC Meteorological Station. Areal rechar ge is that portion of precipitation that reaches the water table (total precipitation minus run-off, evaporation and transpirati on). The average areal recharge is dependent on total precipitation, the nature and timing of individual stonn events , soi l types, topography , plant cover, the percentage of imperviou s cover (roads , buildings, etc.) and precipitation recharge through ex filtrating 43 It is noted that the dose impact computations reponed for 2006 were based on the mass balance model only. These analyses were completed prior to obtaining s ufficient data to implement the Darcy's Law model. It is recommended that future dose impact computations also be based on the mass balance model , but with upgrades based on Darcy's Law analyses.

75 Cin stormwater management systems. Based on our re vi ew o f avai l able information , we bel ieve that the areal recharge at the IPEe i s greater than 6 in ches per year and l ess than 12 inche s per year. For the purpo s e s of this s tudy, an average of 10 inches per year was used (see Appendix S for infonnation on how we arrived at thi s average).

To pographic divide s were used to defined the recharge area (see Figure 3.1). This provides a recharge area of approximately 4,000 , 000 squar e feet (92 acres) and a calculated recharge r a te of 38 gpm. Fro m this va lu e, the 20 gpm extracted by pumpin g fr o m foundation drain s was s ubtracted (see Section 8.0). This approach. therefore, i ndi ca t es that the grou nd wate r di s charge to the coo lin g wate r Di scharge Cana l and the Hudson River is app r oxima t ely 18 g pm. Darcv's Law Dar cy's Law i s presented below: Where: Q = vo lum e tric flow (ft') T = transmissivity (1l2/day)

W = width of the s treamtube dh d h Q= K*A*-=T*W*

-dl dl To e s timat e tran s ml ss l vltJes , the a qui fer was divided i nto two layers o r zo n es: the upper forty feet; and be tween depths o f 40 reet and 185 reet, the identifi ed bottom of the sig nificant groundwater flow field. In each of th e zo n es , tran s mi ssiv iti es were calculated using the geom e tric mean of hydraulic conductivity testing. The facility was further divided into 6 flow zo ne s repre se nting a rea s beneath pertinent Site fe at ure s; and data Eas t (upgrad ient) of the Discharge Canal was reviewed independently of that West (dow n g radien t) of the Discharge Canal. This proce ss, s h own o n the following f our table s, prov id es an estimate of th e grou nd water flux passing be n eath s tructure s of in te re st that d i sc har ge t o the coo li ng water Discharge Cana l and the H u dson River. In reviewing the se ca l c ul a t ions, note the re s ultin g t o tal groundwater flo w East of t he canal i s approximately 18 gpm, which i ndic a t es that the long t enn areaJ recharge to the aquifer is 10 inches per year, o r 28% of the I O-y ear average precipitation rec or d ed at the IPEC. 76 Unit Transmissivity Width (ft) Hydraulic Volumetric (friday) Gradient Flow Rate (ftlft) (gpm) Northern Clean A r ea 0.36 209 0.600 0.23 Unit 2 North 1.59 294 0.014 0.03 Unit 1 12 31.97 215 0.007 0.26 Unit 3 North 29.87 324 0.054 2.74 Unit 3 South 16.02 3 3 8 O.oJ8 1.07 Southern Clean Zone 24.34 879 0.037 4.12 Total'" 8.45 SHALLOW ZONE BEFORE CANAL (OVERBURDEN AND TOP 40 FEET OF BEDROCK) Unit Transmissivity Width (ft) Hydraulic Volumetric (friday) Gradient Flow Rate (ftlft) (gpm) Northern Clean A r ea 0.36 209 0.600 0.23 Uni t 2 North 1.59 2 2 1 0.038 0.Q7 Uni t 1 12 31.97 146 0.022 0.52 U nit 3 North 29.87 3 16 0.013 0.61 Unit 3 South 16.02 248 0.011 0.24 Southern Clean Zone 24.34 879 0.037 4.12 Total'" 5.79 SHALLOW ZONE AFTER CANAL (OVERBURDEN AND TOP 40 FEET OF BEDROCK) Unit Transmissivity Width (ft) Hydraulic Volumetric (friday) G radient Flow Rate (ftlft)

Northern Clean Area 10.77 209 0.068 0.80 Un i t2 North 1 0.77 294 0.030 0.49 U nit 1 12 62.15 2 1 5 0.023 1.61 U nit 3 North 37.65 324 0.022 1.41 U nit 3 South 22.02 338 0.040 1.55 Southern Clean Zoo< 1 9.66 879 0.043 3.83 Total'" 9.69 DEEP ZONE BEFORE CANAL (FROM 40 TO 18 S FEET BELOW TOP OF BEDROCK) 77 U.it Transmissiv i ty Width (ft) Hydraulic Volumetric (ft'lday)

Gradient Flow Rate (flirt) (2pm) N onhern Cl e an Mea 10.77 209 0.068 0.80 Unit 2 NOI1h 10.77 294 0.023 0.29 Unit 112 62.15 215 0.018 0.8 3 Unit 3 North 37.65 324 0.QI8 1.09 Unit 3 South 22.02 338 0.016 0.4 5 Southern Clean Zo ne 19.66 879 0.04 3 3.8 3 Total" 7.25 DEEP ZONE AFTER CANAL (FROM 40 TO 18 5 FEET BELOW TOP OF BEDROCK) GZA's groundwater flux calculations are used b y Entergy to calculate rad i olog i cal dose impact. Entergy currently estimates this do s e based upon the precipitation mass balance approach alone. Refinements to this dose model are feasible utilizing the hydrogeo l ogic data presented above. These refinements will improve the overall data fit of the flow model in concert with the long term monitoring program being implemented by Entergy. The resultant dose assessments are expected to remain close to , or be somewhat lower than, what has alre a dy been estimated.

It is recommended that Entergy evaluate the refinements to the existing model for inclusion in the next annual effluent assessment report. 78

7.0 GROUNDWATER

TRACER TEST RESULTS A tracer test was conducted to help assess g roundwater migration pathways from IP2-SFP. As discussed in the following s ections, the test al so helped to confinn migration pathways from Uni t I. The test was des i gne d to simula t e a l eak from rP2-SFP , i n that the trace r (Fl uore scein) was released directl y to th e bedrock a t the base of the struct ure , immediate l y below the shrinkage c r acks associated with the 2005 release. The bedrock surface at this location is approximate l y eleva ti on 5 1 feet, a n d thu s app ro ximate l y 40 feet above the water table (as measured in the i mmediately adjacent MW-30 -see Figu re 7.1). This app r oach was taken (recogniz i ng it wo uld comp li cate tracer fl ow pat h s relative to injection directly into the groundwater) to pro vide better understanding of the role of un saturated bedrock in storing and tran sport ing Tritium. A major difference in the test , as compared to possib l e releases at LP2-SFP , i s the rate of the injection.

The 2005 Triti u m release was measured at a peak rate of app r ox.im ately 2 liters per day (0.005 gpm), as opposed t o th e tracer inj ectio n that occurred rela t ively instan t aneously (as co mp ared to the T ri t ium release) at a r ate of a pproximatel y 3.5 gpm over approximately an h our. T hi s higher injection r ate w as used to insure that a s u , fficient ma ss of F lu oresce in was released at a known time. As ant i cipa te d, and discussed in s u bsequent sectio n s, thi s practice ap p ears t o have enhanced the lateral spreading of the tracer in the unsaturated zone. 7.1 TRACER INJECTION Preparat i on for the injection began on January 29, 200 7 with the injection of potable water to test the ability of the injection poi nt 49 , T I-U2-1 , to ac cept water and to pre-wet fractu r es. The first potable wa t e r injection was cond u cted on January 29, 2007. Five hundred gallo n s of water (measured using an inline totaling wa t e r meter) was i ntroduced as fast as the water so urce wou ld penni! (app r oximately 8.5 gpm). The water level i n the well did not rise s i gnificantly.

T he s ec ond potable water injection was conducted on January 30, 2007. A total of 1 ,0 1 2 gallons of tap water was introduced at a mean rate of approximate l y 8.3 gpm. The piezometr i c data co ll ected during t hat period from wells MW-30 , MW*31 , MW*33 , MW-34 and MW-35 were r eviewed for ev iden ce of groundwater mounding. (Note: transducers were not installed in RW-I and MW-32 on that date.) Mounding , on the order of 0.5 to 1 foo t , was recorded at MW-31. No response was noted at the other four nearby monitored locations.

Note that MW-3 1 is located upgradie nt of the i njection point fTom a sa turated zone groundwater flow perspective , and unsaturated zone flow i n this di r ection is The injection point as s hown on Fig ure 7.2 is constructed from tw o-inch st eel pipe t hat en d s in a tee and pcrfonlted pip in g running directl y on the bed rock s urface. we ll abovc t h e water !ab le. *'11i 5 perforated piping was covered with approximately 0.5 feet of crush e d Slone extending from the bedrock excavation face to the South face of the S FP. over a l e n gt h of approximately 8 feet. The crushed S t one was covered with filler fabric pri o r to placing the con c rete mud-mat for gantry crane foundation constructio n: th e mud-mat covers the en t ire bedrock exc avation **f1oor** adjacent 1 0 the South s ide of the SPP. 79 c,i\) consistent with the bedrock strike/dip directions.

Based on the shape of the time response curve at MW-3I, GZA believes that: I. 2. 44 43 42 41 40 39 The center of the release to the water table was at some distance from MW-31 (see time lag), and; Injected water was released to the water table over a longer duration tban tbe two hour injectio n test. This opinion i s based on tb e relatively s l ow decay ofthe mound at MW-3 1. This response is shown on the figure below: 1/29/07 injection 1/30 injection

  • I I , , , , J ;F -* t I * * ---* t I .. .:'"'" ,
  • 1 128107 1129/07 1/30/07 1/31/07 PIEZOMETRIC GROUNDWATER RESPONSE TO WATER INJECTION We have insufficient infonnation to render an opinion on the shape or height of the tracer injection-i nduced groundwater mound. We note, bowever, because of tbe lower rate of the tracer injection , the short duration of the injection (see below), and the groundwater flow velocities, as derived from the tracer test, alA believes mounding had relatively little effect (compared to unsaturated flow) on the lateral s preading of the tracer. That is , the life of the mound was not of sufficient duration to cause long tenn, widespread lateral migration in the groundwater.

The tracer injection was perfonned on February 8 , 2007. It consisted of the release of 7.S pounds of Fluorescein with 210 gallons of wate r. Mo re specifically, prior to Fl uore sce in injection, 30 gallons of potable water was released to the well , this was followed by 10 gallons of a Fluore sce in-water mi x ture , followed by 170 gallons of potable water (to flush the Fluo r escein out of the well). This procedure re sulted in a minimum initial average tracer concentration of 4,300 , 000 ppb. 80

7.2 TRACER

CONCENTRATION MEASUREMENTS The concentrations of Fluorescein in groundwater were routinely measured between February 8 , 2007 and August 21 , 2007" at 63 locations.

This resulted in the collection analysis of 4 , 488 samples, including background samples, charcoal samplers and water samples. These data are tabu lat ed and presented on time-concentration graphs in Appendix N. Measurements of Fluorescein concentrations were made by two methods. The first is through aqueous sample analysis (1 , 969 individual samples).

These water sample analyses provide direct concentrat i on measurements, at the time of sampling, with a detection limit ofless than 1 ppb. A second method entailed desorbtion of Fluorescein from packets of activated carbon (carbon samplers) suspended in the groundwater flow path at multi-l evel sampling locations.

This method provides a measure of the mass of Fluorescein moving through a monitoring well s creen over the period the act iv ated carbon is in the welL However , the actual concentration of Fluorescein in the groundwater i s not detenninable from this test. Among other things , carbon sample analyses are useful in establishing that the F luorescein mass being transported by groundwater did not pass samp lin g locations between discrete sampling events. This was important for this study because of the potential for high transport rates (see Section 6.0). 7.3 SPATIAL DISTRIBUTION AND EXTENT OF FLUORESCEIN IN GROUNDWATER The groundwat er tracer test was developed primarily to identify groundwater migration pathways.

We have divided our discussion on observed pathway s into three subsections:

unsaturated zone migration , the lateral distribution of Fluorescein , and the vertical distribution of Fluo r escein. Unsaturated Zone Transport By design, F luore scein was released atop the bedrock, in the unsaturated zone. The bedrock s tructure (s trike and dip direction of bedrock fractures) therefore played a dominant role in controlling tracer migration to the water table. This is witnessed by the s ign ificant F luorescein concentrations observed in the upgradient monitorin g well MW-31 and MW-32 (see below) and at lower concentrations in the more distant and upgradient Unit 1 monitoring well MW-42. The observed unsaturated zone migration to the South and Eas t is consistent with the observed bedrock fracturing (see Section 6.0). Th i s mechanism i s also evidenced by data showing the highest Fluorescein concentration (49,000 pico-curies per liter _ pC i lL)51 S<) In addition to th e routine sampling , s pecific well s wcre s amplcd for II longer period of time as part of short term variability testing (scc Section 9.0). 5! pCiIL is a standard unit of radiation measurement.

81 being found in well MW-32, located 60 feet to the South of the injection location , and not in MW-30 , located immediately be l ow th e injecti on l ocat ion. In reviewing tracer test results, it should be recognized that the F lu orescein released at a s in gle location on the bedrock was not released to the water table at a single l ocation , rather, it reached th e water table over an undefined area that likely extends to the East of MW-31, to the South to MW-42, and lik ely not far to the North of the injection well. As discussed in Section 7.5, this limits our ability to evaluate migration r ates, but increases our ab ili ty to understand likely Tritium migration pathways from LP2-SFP. The sp re ading of Fluorescein i n the unsaturated zone was li kely more pronounced than the spreading of Tritium because of the higher re l ease rate. The tracer test , however , supports data that shows the Unit 2 plume to extend upgradient of the source area and laterally to Unit I to the South of ll'2-SFB. Lateral Distribution Two co n d i t i ons were se lected to show the lateral distribution of Fluorescein in a manner illustrating cond i tions influencing the migration of groundwater in the vicinity of [P 2-SFB. These are: 1. The maximum observed concentrations; and , 2. Cond ition s just prior to, and including, June 14 , 2007. While the maximum observed concentrations do not illustrate an actual condition, the resulting figure is useful in high l ighting migration pathways.

We chose June 1 4th because i t represents conditions approximately 4 months after the inj ection. With estima t ed F luo resce i n transport rates on the order of 4 to 9 feet pe r day (see Section 7.4), co nd itions proximate to that date clearly illustrate the effects of subsurface sto r age on both Fluorescein and TritiumS2.

Lateral Distribution

-Maximum Observed Concentrations The distribution of the observed maximum concentrations of Florescein, at any depth , in groundwate r is shown on Fig ure 7.2. This figure was developed based on both the observed concentrations and OUf understanding of groundwater flow direct i o n s (inferr ed from groundwater contours).

This figure does not s how conditions at any s ingle time; rather it represents our interpretation of the highest tr acer concentratio n , at any time during the test , at a location.

In reviewing that figure please note:

  • The maximum observed tracer concentration was 49 , 000 ppb; approximately I % of the calc uJ ated average injection concentration.

We interpret these data to mean that there i s considerable spreading and mixing of the tracer in the unsaturated and s h allow saturate d zones. 5: Lat e r dal es not se lected because of th e assoc iated reduction in the samplin g frequ e nc y and/or number of samp lin g location s. 82

  • The 50 ppb contour represents approximately 1/100,000 the concentration of the injected tracer. Because Tritium concentrations in are approximately 20 ,0 00 , 000 pCilL this contour (50 ppb Fluorescein) represents the detection limit of a release ofTririum from IP2-SFP (at the injection well).
  • The general shape of the resulting plume is s triking l y similar to the observed Unit 2 plume, see Figure 8.1. This supports our interpretation of contaminant migration from [P2-SFP.
  • Because tracer was detected in MW-42 and MW-S3 , the test can be used to he l p assess migration pathways from Unit I. The observed distribution of Fluorescein in the vicinity of Unit 1 supports our interpretation of the migration of Strontium , with a westward migration toward s the Hud so n River in a fairly narrow zone (see Figure 7.2).
  • The low concentrations to the West (downgradient) of the cooling water Discharge Canal (as compared to East of the canal) indicate the canal received a significant mass of the tracer, as opposed to direct discharge to the river.
  • Concentrations found in Manhole Five indicate the IP-2 Curtain Drain received tracer (see Section 7.5). Lateral Distribution

-June 14,2007 aZA's interpretation of the distribution of Fluorescein in groundwater proximate to June 14,2007 is s hown on Figure 7.3. Again , concentrations are the highest measured at any depth. While not ideal for the observed concentrations, the contour interval was se lected to match the contour intervals s hown on Figure 7.2. In reviewing that figure, please note:

  • The shape of the plume is more representative of an ongoing release than of a month-old instantaneous release in a strong groundwater flow field. This supports other data which indicate water is stored in the unsaturated bedrock (and potentially within the upper water bearing zone) and is released to the groundwater flow field over time.
  • The center of the Fluorescien mass in groundwater , in the release area, shifted to the North. (See data for wells MW-30 and MW-32 on Figures 7.2 and 7.3). GlA interprets these data to mean:
  • There is more storage in the un sa turated z one in proximity to IP2-FSB , than to the South or West; and The relatively high injection rate re su lted in more lateral spreading of the tracer than would have resulted from a slow, long duration release. Vertical Distribution The tab l e provided below presents data on the vertical distribution of Fluorescein along the center line of the tracer plume (see Figure 7.2 for well locations).

It presents the maximum observed concentration at each depth and the approximate concentration B proximate to June 14, 2007. 'J Duta es timated for the June 14th dille are based on time conecntrution grap h s (see Appendix N). 83 Gn FLUORESCEIN CONCENTRATIONS I\tW-JI MW-J 2 I\IW-3O I b C ODe. D<" Co ne. De th Co n e. H 1 6001 62 49 ,000 12 74 5690 0.5 2600 6' 1 2}00 I 92 24.300 1 88 167/110 200 500 89 1 8 1 01 ] 14 0 15JOO/6 lO S 4 160 116 19' 621156 1600 I 0.5

  • Max. cone. I COI1C. p roxi mat e t o 61 14/07 in Ilgil De pth -&l ow Gro und Surface (Fee t) NO -Not Detected MW-JJ MW-III ch Co ne. I)c th Cone.. 1 18 6.6 1 1 6 2.' 1 1 2.' MW-J7 Dc th Cooe. 22 4 7/1 0 32 1.3 1 NO T he available data indicate the bulk of the Fluorescein was migrating at fairly shallow depths, although not always at the water table. As a nticipated (consistent with the Conceptual Site Model), it also suggests the pathway becomes somewhat deeper downgradient of the injection point , likely being below the well screens at MW-33 and MW-lii. T he comparatively low concentrations at MW-l11. as compared to Tritium conce n trations , likely highlights the importance of unsaturated zone migration in groundwater contaminant distributions.

7.4 TEMPORAL

DISTRIBUTION OF FLUORESCEIN IN GROUNDWATER Groundwater samples were co ll ected at re g ul a r intervals between February 8 and Augu s t 21, 2007 54. These data are shown on g r aphs provided in Appendix N with selected information s h own below. In t erp r etation of these graph s is complicated, beyond the nonnal difficulties associated with interpreting tracer te s t data in fractured rock. This i s because the tracer was not injected directly t o the water tab l e, as would be more typical. Rather , the tracer was released at the top of the bedrock , in the unsaturated zone , so as to better mimic the behavior of the Tritium release from the cracks in the fuel poo l wall; as was the primary objective of the tracer test. Therefore , the tracer then entered the groundwater regime at numerous l ocations due to unsaturated zone spread i ng from the rele ase point. In add ition , the se numerous r e l ea s e points remained active over an extended period of time (months) due to sto rage in the unsaturated zone; see the previous subsection and Section 8.1.2 for further di s cussion. With the s e li mi t ations noted , the following observa tion s/interpre t ations a re provided:

  • At some locations , the re l ease to the water table was rapid. Fo r examp l e, at monitoring we ll MW-32-62. located approximate ly 60 feet to th e South of the i n ject i o n point, the tr ace r arrival time SS was app r ox imately o n e day. Conversely, at MW-30-74. located adjacent to the injection well , the arrival t i me was approx i mately 25 days. See the following figures. 54 In addition to the routi ne sampling, s pecific wcll s wcre sa mpl e d f or a l o n ge r period of time as part of s hort tenn variability t es tin g (se c Section 9.0). 5 5 Arr i val tim es are generally established as the cente r of mas s (oft en the p ea k) of the concentration

'I s. time graph. 84

  • "' * , .. i-Cl 30000 i . 'i .. 2 0000 "
  • I 1/28/0 7 3(29/07 j 4r.!8107 MW-32-62 I sl28m D a t e 6/2 7 10 7 7mm ""M MW-32-62 FLOURESCEIN AND PRECIPITATION VS TIM E a e * * * " ."" * 'i ". " ,"" 1 .. ,"" i 1 r.!81(l7 MW-30-69 '!l a m """ bl27107 1fl110 7 1lIl6lO 7 MW-30-69 FLO U RESCEIN AND PRECIPITATION VS TIME 85 , , 9 12310 7 * " ,
  • i
  • on)
  • In mid-J une 2007, there was sti ll an ongoing source of Fluo r escein to the water table in the vicinity of f P2-FSP. This is ev i denced by the time-concentration graphs for MW-30 -74 (see previous figure) and MW-30 -88. presented below: ,., 0 .. , .. .. , " . .. ; '00 a I .. * "' * ". 0-o \0 * ** ** ** r .. f-, 0 " 0 .. 0 " ox , , , ,,.,., !J1.1 10 7 MW-30-88 0 o o
  • 0 J A 1\ 000 jJ. .1 7 127 10 7 J * , MW-30-88 FLOURESCEIN AND PRECIPITATION VS TIME
  • Because the l ocations and times of rele ases from the unsatu r ated zone to the water table are not known, it is difficult , at best, to estimate tracer transport velocities.

However , as shown below , the ave ra ge value appears to be on the order of 4 to 9 feet/day.

Well Location Time or Time Distance (feet) Velocity (fUOay) Arrival Date (Days) MW-33 3-5-0 7 25 110 4.4 MW-111 3-14.{)7 34 145 4.3 MW-37-22 4-1 0-07 61 3 00 4.9 MW-55 3-28-07 48 240 5 to 9 FLOURESCEIN ARRIVAL TIMES AND TRANSPORT VELOCITIES 56 The souree or the Flu orescei n observed in MW 37-22 is uncenain.

11 may be entire l y rrom m igration i n the bedrock s lightl y to t he North orthat location.

or may be d u e, in part or in whole. t o transport via s torm drains and in the backfill around the Discharge Cana l walls. See Section 4.5. n The calcu lat e d velocity depends on which flow path is selec ted. Using a flow path rrom MW-32 (day or rel ease) t o MW-55. the calculated velocity i s approximately 5 feet/day. Us in g a fl o w path between MW-53 and MW-55 (t he Strontium flow path) th e calculated v e locity i s 9 feet/day.

86 Also note, the carbon sampler data supports these estimates to the extent that no evidence of significant F luore s cein migration between aqueous s ampling events w as found. T he ob s erved tracer migration rates are approximately liS to 1110 the calculated groundwater velocity of SS ftlday , see Section 6.7.2. GZA attributes the difference between the " observed" and the "computed" transport velocities primarily to the effective porosity of the bedrock. That is, we believe the actual effective porosity is considerably larger (more on the order of 0.003) than that computed from our analyses of the Pumping Test (see Section 6.5.1); the aquifer response testing (s ee Section 6.6.1); or the hydraulic aperture of the bedrock (see Section 6.5.2). T his slower transport velocity helps to explain the observed lon g term temporal variations in both tracer a nd Tritium groundw a ter concentrations, and supports the use of a porous media flow model. As a practical matter, this s lower transport velocity encourages the use of convention a l groundwater monitoring frequencies (quarterly or longer); and reduces concerns over the possibility of high concentration s of contaminant s migratin g by a monitorin g location between s ampling events. 7.5 FLUORESCEIN IN DRAINS, SUMPS AND THE DISCHARGE CANAL Fluorescein was al s o detected within s torm drain catch basin s, foundation drain sumps , and the D ischarge Canal. Fluorescein was detected in manhole s MH-4, M H-S and MH-6. In reviewing the s e data , note:

  • MH-S receive s di s charge from the IP2-V C C urtain Dr a in s ystem. The pres e nce of tracer in this manhole indicates that tracer entered the Curtain Drain system due to lateral spreading at the rele as e point during injection.

Once in the C urtain Drain system, the tracer migrated to MH-S.

  • Wat e r in MH-S flow s toward s the cooling water Discharge C anal pas s ing through MH-4 , discharging at MH-4A.
  • T h e concentrations detected in MH-4 are very s imilar to the Fluorescein concentrations detected in samples collected from MH-S, while Fluorescein wa s not detected in s amples collected from the downstream manhole M H-4A. T his s uggests that either dilution in MH-4A reduced Fluorescein to below method detection limits, and/or the tracer is lost via exfiltration from piping between M H-4 and MH-4A. This los s (if it occurs) in conjunction with flow in the canal backfill , could explain the Fluorescein observed in MW-37. Available data are not adequate to fully address thi s i s sue. In any event , the test further demon s trate s the need to account for the Tritium being transported in the IP2-VC Curtain Drain (see Section 7.6).
  • In reviewing data, note that the tracer concentrations in M H-6 are lower than the concentration s observed in MH-S (peak. in MH-6 of 14.4 ppb as opposed to a peak. in MH-S of 43.1 ppb). We attribute the concentrations in MH-6 to groundwater infiltration in the area o f the identitied tracer plume. Also note the flow from MH-6 is to MH-S. Fluo r escein wa s al s o detected in the IPI-N C D , the IPI-SFDS , and the C ontainment Spray Sump (CSS). We have attributed the presence of tracer at these locations to unsaturated zone mi g ration to the vicinity and We s t of MW-42. The concentration a nd arrival times at 87 these three locations are not easily explained but , taken as a whole, are consistent with the observed migration of Tritium. Fluorescein was detected at low co n centrations, a t various time s, in carbon samp l es co ll ected from the cooling wa t e r Discharge Cana l. Because of the s u bstantial di l ution in the canal , the extended release of tracer to the canal and the low concentrations of tracer found i n the samples , we believe these data represent background conditions)8 , and cannot be used to evaluate the tracer test. 7.6 MAJOR FINDINGS As an overview, the tracer test, s upports our CSM and the observed distribution of contaminated groundwater.

GZA also concludes that:

  • U n sa turated zone flow is important to the migration of contaminants released above the water table in the vicinity of Unit 2. Bedrock fractures induce this flow to the South and East of the release.
  • There is significant storage of contaminated groundwater above the water table or in zo nes of low hydraulic conductivity (homogeneities) in the sa turated zone. These features allow a long-lived release of contaminants to the Site groundwater fl ow field.
  • Observed tracer migra t ion rates are l ower than calculated theoretical migration rates. As a practical matter, thi s "migra tion" indicates that the use of the estimated average hydraulic conductivity (0.27 fi/day or lxlO-4 cm/sec) will overestimate the volume of groundwater migrating through a given area. That is, we attribute the lower transport ve locity to be due , in part, to a lower average hydrau li c conductivity.
  • In o ur opinion. the tracer test , in conjunction with the T ritium release, indicate s that the existing network of monitoring wells can be u se d to monitor groundwater at IP EC. " It i s noted that Fluoresccin i s the primary coloran t in automobile coo lant anti-freeze. Thcrerore , leaks from cars to parking lot/road s urfaces can impact surface water bodic s via s tonn drain sys tems and/or direct runoff. Fluorescein was detect e d in the Discharge Ca n a l prior to initiation of the tracer injec tion. further indicatin g its presence as background.

88

8.0 CONTAMINANT

SOURCES AND RELEASE MECHANISMS GZA conduc t ed a review of availab le co n st ructio n drawings , aer i a l photographs, prior reports, and d oc umented releases, a nd int erv iewed Enterb'Y personnel to assess potential contaminant so urce s. T he primary S9 r ad iolo g ical so urce s identified were the Uni t 2 Spent Fue l Poo l (JP2-SFP) located in the U nit 2 Fuel Storage Building (JP2-FSB) and th e Unit 1 Fuel Pool Com ple x (JP I-S FPs)'" in the U nit I Fuel Handling Bui l ding (IP I-FHB. These two di s tinct so ur ces are responsible fo r th e Uni t 2 plume and the U nit 1 p l ume. respec ti v el y. No release was iden tifi ed in the Uni t 3 area. The absence ofU oit 3 sou rc es is attribu ted to the design up grades incorporated in the more rec ently con s tructed {P3*S FP. These upgrade s in clude a stainless steel liner (cons istent with Un it 2 but not included in the U ni t 1 design) a nd an additional, seco ndary l eak. detection drain system not included in th e U ni t 2 design. The identified speci fic s ource mechanisms assoc iat ed with the IP 2-SFP and the [P I-S FPs are discussed in the foUowing sect ion s. We have segrega t ed this so urce discussion base d o n primary contaminant type; those cl assi fied as primarily Tritium sources, as associated with the U nit 2 plume, and th ose cl ass ified as primaril y Strontium sources, as associa t ed with th e Unit 1 plume. While the g roun dwate r plumes emanat in g from th e ir respective source areas can clearly be characterized using each plume's primary constituent, r adionuclides other than T ritium and Strontium also exist to a limit ed ext ent and are fu ll y addressed within the context of the Un.it 2 and U nit I plum e discussions 61* D isc u ssio n of th e two primary sou rce types will be p arse d further as f o llo ws:

  • The Uni t 2 (T ri tium) plume sou r ce analyses will be split i nto: 1) "d irect sources" defined as releases to the exterior of Systems Structures and Componen t s (SSCs); an d 2) "in direct s tora g e sources" related to natural hydrogeologic mechanisms in the unsaturated zo ne (suc h as adsorption and dead-end fractures) and potential anthropogenic contaminant retention mechanisms (s u ch as certain s ub surface foundation construc t ion details);
  • The Unit 1 (Strontium) plume source analyses w ill be s plit int o the mechanism s spec ifi c to the indi v idua l p l unle flow paths identified.

S' In addi tion t o sou rc es that directl y impac t groundwa t er. atmospheric deposition from pt:nnilled air discharges was also identified as 0. potentia l source of diffuse. low l evel Tritium impact to t h e groundwate

r. 60 All of the pool s in th e IPI-SFPs co n tained radionudides in t h e past. Ho ..... ev er. onl y t he West pool currently contain s any remaining fue l rods and a ll of the other IPI poo l s have been drained o f water. 11 is also noted th a t the Unit 1 Wes t pool has been undergoing inc reased proce ssi n g to sig nificantly reduce the amou nt of radioactive mate ri al i n th e pools. Once fuel is removed. the IP1-SF P s will no longer con5litu t e an active source of g ro undwater c ontam ination. 'I Contaminants associated w ith the Uni t 2 leak we r e found t o be essentially comprised of T r itium. 'In c Uni t I plume i s comprised primari l y of Strontium, but also includes T ritium and sporadic observa tion of Cesi u m-137. Nickc:1-63 and Coba lt-60 at low levels in so me well s downgrodicnt of the IPI-SFP (see Figure 8.3). Ente r gy accoun t s for all rod i onuelidc s that can be to r eac h the river in their requi r e d regu l atory repon i ng of eS t imaK-d dose impact. 89 8.1 UNIT 2 SOURCE AREA The majority of the Tritium detected i n the g roundwat e r at t h e Site was traced to IP2-S F P. This poo l contains water with maximwn Tritium concentrations of up to 40 ,000,000 pCi/L", The highest Tritium level s measured in groun dw a ter (up to 60 1 ,0 00 pCi1L 63) were detected ear l y in the inve st igation a t MW-30. This lo ca tion is immedia t ely adjacent to IP2-S FP and directly be l ow the 2005 s hrinkage cracks, As s h own on Fig ure 8.1 , the Tritium con tam ination ( .. the plum e 64 ,,) then t r ac k s with downg rad i ent groundwater fl ow 6 S through the Uni t 2 Transformer Yard , u nder the Discharge Canal and discharges t o th e ri v er 66 between the Unit 2 and Unit 1 i n take struc tur es. Dur i n g r ev i ew of the foll o wing sections, it is important to recognize that on l y s mall quantitie s of pool leakage (on the order of liters/day) will res ult in the Tr itium groundwater plume observed on the Site. to! In contrast.

the levels of Tritium in the Unit I West poo l arc cnl)' on the order of 250.000 pCiIL. Stron t iu m concentratiOn!>

in IP2*SFP lITe on the order o f 500 pCilL. 6) The 60 1.000 pCil L Tritium concentration was measured during packer testing of the open borehole prior to multi*level completion. This valuc i s therefore actually n lower bOl/lld estimate for depth*spec ific Tritium concentration s at that time. If the multi*level samp lin g instrumentation cou ld have be en completcU pri or to ob taining these data (not po ss ibl e bccaus<: the packer testing was required to design the multi-l e vel i n sta ll ation), sa mple s would have yhddcd eq ual or higher concentrations.

This conclusion reflec t s the limited s tandard l ength and temporary emplacement of the packers used during the packer t esting, and th us th e grea t er poten tial for mixing and dilution between zones. as compared to th..: numerou s packers pcnnanentl y installed in the multi-level comple ti ons. 60 It is that Fig ure 8.1 does nOl show an actual Triti um plume: the i so plcth s presented conto u r upper bou nd co n centra t io n s for sam ple s taken at ony lime an d any deplh at a particular location. ratht.'f than a 3-dimensiona l s nap s hot of concentra t io n s lit a si ngle time. As s uch , this " plume" i s an overstatement of the contaminant levels exi s t in g a t any time. [I s hould also be noted t hallhe lightest colored con tour interval begin s at one-quarter the USEPA drink i ng water standard.

While drinking water standards do not apply to the Site (there are no drinking wat e r wel1s on o r p r oximate to the Site), th ey do provide a r ecogni7.c d, and highly conserva tive. bench m ark for comparison purposes).

Lower. but positiv..:

detection s ou t si de the colored contours nr c show n as col ored dal a blocks. Se..: figure for additional notes. 65 It i s recognized that low co nc entratio n s of Tritium likely extend to the Sout h. all the way 1 0 Uni t I. This co n c l u s ion i s su pported by: I) the low Tritiu m concentrations remaining i n IPI*SFPs (250,OOOpCil L): 2) the data from MW-42 and MW-53: and 3) the Tritium balance between that released by the I PI*SFP s leak and th at collected by the NC O. The t ransport mec hani s m i s thro u gh unsaturated zone flow which follows bedrock frac l ure s trik e/dip direction s rather than gro u ndwater 110w direction (see sc h ematic of unsat u rated zone now mechanism incl uded below). The levels of Tritium d etected upgraditnt of IP 2*S FP i n monitoring wells MW*31 and MW-32 arc also duc to un saturated zone tran s port from IP 2-SFP a l ong the genemlly sou th erly siri k ing and eas t erly dippi n g bedrock fractures (sec structural goo l ogy analy s i s in Stttio n 6.0 and trattr test di scussions in Section 7.0). 06 As the Tritium moves under the Discharge CanaL a sign ificant amount discharges di r ec tl y to the canal before the plum e r eac h es the I ludson River. 90 I' * * * .I -:J " ._. .; .. : . .. -. ..... ; _ .. , -. I:J l UNI T l .-' . -.-I:. ... -. * * . -' -. * * * . -' *

  • 1 I I .
  • Hudson River UNIT 2 BOUNDING ACTIVITY ISOPLETHS 1!!Ia_" __ .'_ .............. --------_ ... ___ ...,10 ... _ __ n.) __ ....

BAC KF IL L BeDROC K I P 1-CB IP 2*SFP UNSATURATED ZONE FLOW MECHANISM 91 The U'2-SFP contains both the fuel pool itself as well as its integral Transfer Cana l. IP2-SFP is founded directly on bedrock which was excavated to elevation 51.6 feet for construction of this structure.

As such, this pool's concrete bonom slab is located approximately 40 feet above the groundwater (as measured directly below th e pool in MW_30 67). During construction , a gri d of steel "T-beam s" was embedded in the interior s urface of the 4-to 6-foot-thick concrete pool walls. These T-beams provided linear weld points for the 6 by 20 foot stainless s teel liner plates. Given this construction method, an interstitial space exists between lhe back of the lh-inch-thick stainless steel pool liner and the concrete wa lls. The s pace is expected to be irregular 68 and its exact width is unknown, but nominal estimates of a I/S to Y. inch are not unreasonable for assessing potential interstitial volume. Usi ng the se estimates, the volu m e of the s pac e behind th e liner could be on the order of 1500 gallons. In ad dition , the degree of interconnection between the spaces behind the individual liner plates i s also expected to be highly variable given the likely variability of weld penetration into the "T beams." Therefore, the travel path for pool water that may penetrate through a leak in the liner is likely to be highly circuitous. 8.1.1 Direct Tritium Sources Two confirmed leaks in the lP2-SFP liner h ave been documented.

as well as the 2005 shrinkage crack leak through the IP2-SFP concrete wall". The first liner leak dates back to the 1990 time frame, under prior ownership.

This legacy leak was discovered and repaired in 1992. With the more recent discovery of the concrete shrinkage cracks in September 2005, E ntergy undertook an extensive investigation of the IP2*SFP liner integrity.

Within areas accessible to inve s tigation , no additional leaks were found in the liner of the pool itself. However , after draining of the lP2-SFP Transfer Canal in 2007 for further liner investigations specific to the T ran sfer Canal, a si n gle smal l weld imperfectio n was detected in one of these Liner plate welds. Thi s was the only leak identified in the Transfer Canal where the entire su rface and all the welds could be and were inspected.

This second liner leak is expected to have released tritiated pool water into the interstitial space behind this area of the liner plates whenever the Transfer Canal was filled above the depth of the imperfection (the Transfer Ca nal is currently drained and this imperfection will be welded leak-tight prior to refilling the Transfer Cana l). All identified leak s h ave therefore been terminated.

While additiona l active leaks can not be completely ruled out, if they exist, the data 7 0 indicate they mu st be very small and of little impact to the groundwater

11. 61 While s imilar and lower g r oundwater elevations persist downgradientto the We s t. the s hall ow groundwater are much higher (up to approximately elev. 45 feet) within on l y 50 feet to \he East (MW-3 I) and Southeas t (MW-32) of the pool. 611 The interstitial space width and uniformity will be related to the degree to which the concrete wall s urface falls wi th in II single plane. Because of the praclic:llities of forming and pouring concrete walls. we believe the surface is unlik ely to be planer. 69 While the 2005 leak from the shrinkage cracks not appear to be related to a spe cific leak in the pool liner. it is considered a " direct sou ree'* because it still resulted in a release to the exterior of o ne of the p l ant's SSCs. 10 Th ese data include: m onit ored water levels in th e SFP, with variations acco u n t ed fo r based on refitling and evapora tion volumes: the mass of Tritium migratin g w i th groundwate r is small: and the age of th e waler in the interstitial s pace. 71 For examp l e. the 2005 s hrinkage cracks s till intermittently release small amou n ts of water: on the order of 10 to 20 ml/d a y. This water could represent II tran sient active leak. or it may just be due t o re s idual water trapped behind the l iner plates above the 2005 crack elevation s till working i ts way slowly to th e cracks. While this water i s contained and prevented from rcaching the groundwater, other s uch s mal11eaks may exist which do reach the groundwater. 92 The three identified direct sources are discussed indiv idually In the following paragraphs and shown on the figure below. FSB loading b'f ... Full SIorIgtl eundlng ..... _. ",o.t UNIT 2 FUEL POOL DIRECT SOURCE LOCATIONS IP2-SFP \990-\992 Legacy Liner Leak -This leak was first documented o n May 7, 1992 when a small area of white radioactive precipitate was discovered above the ground s urface on the outside of the rP 2*SFP East concrete wall. Thls boron deposit exhibited radiological characteristics consistent with a potential leak from the pool. A camera survey was then conducted within the IP2*SFP to identify the locati on of the associated leak (s) in the liner. The survey initially revealed no damage to the liner. However, t o further investigatory efforts, di ve r s were utili zed to visually in spec t accessible portions of the liner. The divers found indication s that the liner had been gouged when an intemaJ ra ck had been removed on October I , 1990. Two hundr e d and forty linear feet of the North and West lP2-SFP wa1l welds were then inspected and vacuum-tested to ve ri fy that the identified damage wa s isolated to this one case. No other leaks were identified, and on June 9, 1992 , the leak was repaired.

Subsequent analyses conducted by the previous plant owne r indicate that approximately 50 gallons per day could have leaked through the liner. This leak rate and the t ime scale of the relea se even t would be expected to fill all the accessib l e interstitia l space behind the l in er 72. Once the space behind the liner was fi l l e d to elevation 85 feet (the elevation of the 1990 cracks), water then began to l eak ou t of the cracks in the concrete wall, with a maximum total release volume of up to 50,000 gallons. Given the very slow release rate (0.035 gaUmin), the porous, hydrophilic nature of concrete, and the location of the leak at approximately five feet above the ground surface, a significant portion of the released water likely evaporated prior to entering the soils. However, given that the soils 11 Whil e th e in t erstitial space was fillin g up t o elevation 85 feet. any other crac k s or joints in the concrete wall bel ow this elevation.

s uch as those identified in 2005, l ikely released contaminated water to the environment.

As discussed below. il is hypothes i zed thai with time , these subs u rface cracksljoinlS may have become se aled due 1 0 precipiwtion of dissolved compounds.

cit h cr carried with the pool water o r derived from the concrete pool wall. Thi s would have been required 10 allow rlo':tention of pool water in the inllo': Th'titia l s pace below elevation 85 fecI allcr th e liner l eak was repaired in 1 992, and thus su b se quent I cakage of the 2005 s hrinkage cracks. 93 below the leak we r e found to be contaminated 73 , it is clear that some portion of this release ente r ed the subsu r face. While Strontium and Ces ium could have l argely partitioned out of the pool water to the shallow so il s, tritiated water would be expected to have continued to migrate downward to the groundwater.

IP2-SFP 2007 Transfer Canal Liner Weld Imperfection

-As part of the recently completed lin e r in spections initiated by Entergy in 2005 , the IP2-SFP Transfer Canal was drained in 2007 to facilitate further leak-detection efforts including vacuum box testing of the welds. These inspections discovered a single small imperfection in one of the liner plate welds on the North wall of the Transfer Canal at a depth of about 25 which is approximate l y 15 feet above the bottom of the pool. All of the welds and the entire liner surface area of the Transfer Canal have been i nspected by one or more techniques and no other leaks were found. Engineering assessments indicate this wall imperfection is likely from the original construction activity s ince there is no evidence of an ongoing degradation mechanism.

Given that the Transfer Canal is now drained, this we l d imperfe c t ion is no longe r an active leak site. However, the historic practice of maintaining water in the Transfer Canal likel y re sulted in a generally continuous release of pool water into the interstitial space behind the liner over time , and then potentially through the concrete pool walls and into the groundwater.

JP2-SFP 2005 Concrete Shrinkage Crack Leak -During construct i on excavation in September 2005 for the dry cask storage project , the South wall of the IP2-SFP was exposed and two horizontal "hairline" shrinkage cracks were discovered (see schemat ic below). These cracks exhibited signs of moisture , though fluid flow was not observed emanating from the cracks. To promote collection of adequate liquid volumes for sampling and analysis.

the crack s were subseque ntl y covered with a plastic membrane to retard moisture evaporation and enhance water vapo r condensation. The trapped fluid was drained to a samp l e collection container.

This temporruy collection effort not only provided leak rate measurement capability and suffic ient water for analysis , it also prevented further r elease to the groundwater.

n Approximately 30 c ubic yards of radio nuclide contaminated so ils were excavated from the area in 1992. 94 UNIT 2 SFP 2005 SHRINKAGE CRACKS IDENTIFIED IN SEPTEMBER 2005 In i tially , the two cracks were found to be leaking at a combined average rate typically as high as 1.5 Vday (peak of about 2 J/day) from the time of crack discovery/initial containment through the tall of 2005. In early 2006 , a pennanent stainless steel leak containment and co ll ect i on device was in s talled. This containment was al s o piped to a permanent collection po i nt such that any future leakag e from the crack could be monitored and prevented from reaching the groundwater.

Subsequent monitoring through 2006 and into 2007 has indicated that the leakage rate had fallen off rap i dly and become intermittent with an average flow rate of a pproximately 0.0 2 I/day , when flowing (s ee figure below presenting shrinkage crack flow rate and Tritium concentration over time). This small amount of leakage is pennanently being contained and it therefore i s not impacting the groundwater.

Lrak collrction flow mle and Tritium coocrntmllon " 20,000,000 I.!. 15,000,000

  • 10,000.000
i ____ __ * '.000,000 .
  • 1 1 1 8107 4128107 &/&07 UNIT 2 2005 SHRINKAGE CRACK LEAK RATE AND TRITIUM LEVELS Based upon two years of flow and radiological and chemical sample data, it appears that excavation o f the backfill from behind the pool wall cau s ed the s hrinkage crack s to 95 begin releasing water trapped in the interstitial space dating back to 1992. This release mechanism i s hypothesized to have developed as follows:
  • During the original construction, the fuel pool walls developed shrinkage cracks in the concrete upon curing, as is not atypical for concrete.
  • When the pool walls were backfilled with soil, they flexed inward slightly in response to the soil pressures developed during backfill placement and . 74 compactIon .
  • The pool was then filled with water which exerts an outward pressure against the walls. However, little outward flexure would be expected given the stiffness of the compacted soil backfill , which assists the concrete walls in re sist ing outward bending motion due to the water pressure.
  • The stainless steel pool liner was punctured in 1990 and began leakin g. Over time , this leak filled the interstitial space between the liner and the concrete walls. tritiated pool water then likely first leaked out of the lower-most cracks/joints , s uch as those responsible for the 2005 leak (elevation 62 to 64 feet), and successively leaked out of higher imperfections until it reached the cracks at elevation 85 feet. At this point , leakage was detected and the leak was fixed in 1992.
  • At some point during the leakage , the subsurface cracks apparently became plugged with precipitate which stopped the leakage. This allowed pool water to remain trapped behind the liner at an elevation above the 2005 shrinkage cracks, potentially as high as elevation 85 feet. To the extent that the subsurface cracks/joints in the concrete did not all become completely leak-tight, the interstitial space behind the liner wa s likely recharged by leakage from the Transfer Canal weld imperfecti on (up until Transfer Canal drainage in July 2007) and/or other small leak sites in the liner.
  • With excavation of the soil backfill from behind the southern pool wall , the pressure exerted by the backfill material was sequentially removed from the top to the base of the concrete wall. The elimination of this inwardly focused backfill pressure allowed the outwardly directed water pressure in the pool to flex the wall outward. It is hypothesized that this motion, while limited , was sufficient to initiate leak age from the 2005 shr inkage cracks at a rate of approximately 1.5 Vday during the fall/winter of2005.
  • The released water is believed to be primarily residual water derived from the 1990-1992 liner leak. However , laboratory r esu lt s for water samp les initially collec ted from the crack in the September 2005 time frame yielded Cesium-137 to Cesium-134 ratios indic a tin g that the age of the water wa s approximately 4 to 9 years old. This age does not directly correlate with the 1990-1992 release timeframe.

Co nver se ly , the water clearly had exited the pool many years ago. A potential explanation for this intennediate age water is the mixing of water from a then-current small leak in the liner with 1992 age water.

  • Over time, the shrinkage crack leak reduced the elevation of the residual water trapped behind the liner to the elevation of the cracks. Beginning in 2006 and through 2007 , the leak rate was observed to have quickly become intennittent with typical leak rates, when leaking , of only approximately 0.02 l/day. These 7. While the 4*10 6*fool-lhick concrelc wall s are s liff. so me ncxure is r e quired for the walls 10 deve l op bendi n g s tre sses. 96 subsequent water samples did not contain Cesium-134, indicating that this more recent crack water could, in fact. be old enough to be from the 1990-1992 leak 75.
  • As a corollary to the above conceptual model , the intennediate-aged crack water may be partially comprised of leakage from the Transfer Cana l weld imperfection. This release pathway could potentially explain the measured intermittent and variable leakage collected in the permanent containment system after 2005. The variations in water elevation and temperature in the Transfer Canal are consistent with this hypothesis.

While the Transfer Canal leak water would be recent, it is likely that it would take a substantial amount of time to flow from the North wall of the Transfer Canal to the South wall of the IP2-S Fp 76. This hypothesis is therefore consistent with the lack of short-lived isotopes (as associated with SFP water) currently being found in the water from the shrinkage crack. A more significant leak rate with shorter transit times (e.g., the magnitude of the 1990-92 leak) would be expected to, and did previously show, short-lived radionuclide sig nature s.

  • Although several additional theories have also been postulated and investigated , a definitive explanation of the apparent discrepancy in Cesium age ratios could not be definitively determined.

This discrepancy from the early sample data when the crack location was first investigated was an important factor in Entergy's decision to perform intensive pool and ongoing Transfer Canal liner inspections.

  • It can also be concluded from the above data and analysis that any ongoing active leak in the pool liner , if one exists , must be quite small. Otherwise, the limited volume of the interstitial space between the liner and the concrete wall would transport a more s ubstantial leak to the shrinkage cracks in a s hort time and the water would thus show a young age 77. 8.1.2 Indirect Storage Sources of Tritium The extensive testing of the IP2-SFP liners to date by Entergy provides evidence that all direct sources (Le., releases from SSCs) of Tritium have been identified and are currently no longer contributing radionuclides to the groundwater
78. However , the Unit 2 plume, while decreased in concentration relative to the samples taken just after 7S Cesi um-137 was present at sufficient concentrations that if the water was "youn g", Ces ium-134 would have also been present a1 concentrat ion s above method detection limits. [\ i s further noted thaI Ihe IWO isotopes of Cesium s hould partition to solids at the same ratios. Ther e for e, preferential removal of the Cesium-134 due t o partitioning t o the concrete i s not an explanation for the lack of thi s isotope in the more recent crack water samples. 76 [t is noted that the seepagt! path(s) from Ihe liner leak on the North wall of the Transfer Canal 10 the s hrinkage cracks on the southern pool wall is likely to be particularly circuitous.

The interstitial space between these two liners can only be co nn ected (if t hey are connected at all) at the gale from the Tran s f er Canal t o the fuel pool and/or through imperfections in the concrete walVfloor waterstops or in the co ncrete itself (given the five-foot-thick co ncrete wall se paratin g th e Transfer Cana l from the $FP itself). 71 As a benchmark.

p ool water from a one-tenth of a gallon per minute l eak would be expec ted to rea ch the sh rink age crack in less than two weeks given the estimated volume of the interstitial space. n H owever, some amoun t of leakage eou ld still be ongo in g from other p o tential imperfections in th e lin e r and/or concrete poo l wall: large o ngoin g leak s would result in conditions inconsistent with the measurements of both leak rate and water age collected from the 2005 s hrinka ge crack. A large leak would also be inconsistent with the reductions observed in the Tritium concen trati ons in the groundwater.

97 identification of the 2005 shrinkage crack leak 79 , still exhibits elevated concentrations.

If all of the releases to the groundwater were tenninated, it would be expected that the Unit 2 plume would attenuate more quickly than observed 8o. As such, a subsurface mechanism appears to exist in the unsaturated zone under the IP2 w FSP that can retain substantial volumes of pool water for substantial amounts of time. The existence of such a "retention mechanism" is also supported by both the results of the tracer test and the recent evaluation of contaminant concentration variability trends over short timeframes and precipitation events. The tracer test results, discussed more fully in Section 7.0, indicate that:

  • Tracer injection directly to the top of bedrock below the IP2-S FP above MW-30 did not result in arrivals at MW w 3 0 in time frames expected for vertical transport through the fractured bedrock vadose (i.e., unsaturated) zone. In fact, the earliest arrivals a nd maximum tracer concentrations were detected in MW w 3\ and MW-32 at distances of greater than 50 feet from the injection location;
  • Tracer concentrations in MW w 30 took longer than expected to reach peak concentrations from the time of first arrival;
  • The tracer concentration vs. time curves exhibit a " long tail;" and
  • The tracer concentrations exhibit significant variation over short periods of time, which may be related to precipitation events moving tracer out of storage. It is, therefore, apparent that once tracer, and thus tritiated water , is released from directly below the rp2-SFP. it does not flow directly down to the groundwater but can be "trapped" (held in storage) for substantial periods of time. The Tritium concentrations in MW w 30 were measured on a weekly basis between August 8 and August 30, 2007 (see Section 9,3,1). These data show significant var ia bility in concentrations over these short timeframes.

This variability appears to far exceed that which can be attributed to variation inherent in groundwater sampling or radionuclide analyses.

Aliquots submitted for tracer concentration testing also showed similar trends. It appears that the se variations may be the result of the displacement of water, as evidenced by both tracer and Tritium, from this storage mechanism by infiltration such as associated with precipitation events. Based on the above summarized infonnation, two indirect storage mechanisms are postu l ated to explain the persi s tence of the Unit 2 plume. The fir st i s the s torage of tritiated water in dead-end fractures in the unsaturated zone. The second is the potential for tritiated water from the S FP to be trapped in the blast-rock backfill above the "m ud-mat 81 .. 79 The ear lie st samples tak en from d irect ly below the SF P in MW*30 (open borehole and packer testing samples) yielded Tritium concentrations over 600,000 pC i/L. More currently, maximum concentrations detected havc been below one* halfoft ho sc initial concentrations.

so Rapid attenuation of the Tritium plume would be expected based on 1) Tritium's lack of partitioning to so lid materials in the subs urface; and 2) (he crys tallin e nature. low storat ivity and high gro und water gradients associated with the bedrock on Ihe Si le. g , Prior 10 constructing a strU(.'!u ral base slab (typically 2 10 5 feet th i ck) for the fuel pool. a 6-10 8-ineh-lhiek, lean concrete "mud-mat" is typically co n structe d over blasted bed rock to even o ut the irre gu lar r ock surface and provide a 98 which was placed prior to construction of the SFP structural base slab. A combination of these two indirect storage mechanisms , as discussed separately below, is a conceptual model that explains the observed Unit 2 plume behavior in the context of the termination of the identified direct release mechanisms

82. Dead-Ended Bedrock Fracture Storage -Naturally occurring bedrock fractures, as discussed in Section 6.0, are seldom long , continuous linear features.

Rather, they are more typically networks of interconnected, discontinuous fractures.

These networks often contain many dead-ended fractures.

While dead-ended fractures are not subject to advective groundwater flow, they still can contain high contaminant concentrations. Contaminants enter these fractures through osmotic pressures set up i n the subsurface by concentration gradients (initially high concentrations at the fracture "mouth" and low concentrations within the fracture).

Over time , the se concentration s equilibrate through liquid-phase diffusion.

Therefore, under conditions of high Tritium groundwater concentrations , such as likely occurred during the two year timeframe of the 1990-1992 liner leak, the dead-ended fractures would be expected to end up containing high Tritium concentrations.

Once the liner leak was repaired, the input of Tritium to the groundwater would subs i de and the concentrations i n the advective fractures would start to decrease.

However, the high Tritium concentrations within the dead-ended fractures would then start to diffuse back out of the dead-ended fractures into the groundwater flowing past them, thus maintaining higher than otherwise expected Tritiwn concentrations in the groundwater.

Our computation of the volume of the naturally occurring dead-ended fractures in the unsaturated zone below the IP2-SFP yields fracture volwnes which are unlikely to s upport the observed Unit 2 plume for the required time frames (years). However, two add i tional considerations substantially increase the dead-ended fracture volume: 1) the observed un sat urated flow to the East and Southeast (this migration pathway exposes many more fractures to the Tritium due to the bigger area involved); and 2) construction blasting (which creates more fractures in the bedrock remaining below the s tructure).

As demonstrated vividly during the tracer test, contaminants released to the bedrock at the bottom of the SFP travel at least 50 to 75 feet to the Eas t and Southeast as evidenced by the high tracer concentrations quickly detected in the upgradient monitoring wells hard, fl at surface upon which to se t the r einforeing rod *'chllirs** (these chairs elevate the lowest luyer of rods to provide sutlicicnt concrete corrosion prevention cover). 82 It i s not ed that we origina l l y believed that the gro undwat cr in the Unit 2 Transfonner Yard was uncontaminated with Tritiu m pr ior to February of 2000. I f true , this finding would be inconsistent with the storage mechanisms proposed.

Our original co nclu s ion was based on the sampling results at that time from MW-Ill: this well was s ampled as part of the due diligence for property transfer to Entergy lind found not to contain Tritium above detection limit s (900 peill.). However, interviews with faciJity personnel revealed that the sample was collected from the upper s urface of the water table with a bai l e r. Ther e was no attempt t o pur ge the well to obtai n samp l es representative of deeper aquifer water because th e samples were taken primar i l y to look for floating oil i n the well. Because this sample was collec ted from th e upper groun dwater surface (w hich will be most subject to infiltration by rain water) without adequate well purging. it is l ikely Ihal this sample result was biased low. I\s discussed in Section 9.0. Ihis well is s ub ject to wide variations in Tritium concentrations due t o rainfall events. Therefore, it is entirely plausible that no Tritium was detected above labor atory method detection lim it s even i f Tritium were present at much hi gher concentrations deeper in the aquifer. I\s s uch. this February 2000 ground wat er sample result should not be used to assess T r il ium g roundwater i;o nditiO Il S at {hal time. See support ing da ta in Section 9.3.1. 99 MW-31 and MW_32 83; th e same b e havior would be expected for Tritium. This wide areal distribution would substantially increase the volume of dead-ended fractures available for storage of contam i nants. In add i tion to naturally occurring fractures, the founding elevation of the SFP was achieved through construction blasting of the bedrock. While the bulk of the blasted rock was removed to allow construction, a zone of much more highly fractured bedrock typically remains after the founding e l evation is reached. While these blast-induced fractures may be interconnected, they may not be fully connected to tectonic fractu r es that intersec t the groundwater, and thus would be dead-ended. Therefore, contaminated water may be stored in these fractures and pe r iodically escape in response to precipitation events. Blast-Rock Backfill Sto r age -Following blasting of the bedrock to accommodate the [P2-SFP foundat i on, standard construction practice would have been to pour a mud_mat S4* Based on construction photographs.

it appears that the areal extent of the blasting was not much bigger than the dimensions of the structura l slab for the SFP; this would be typical given standard contracting specifications and the cost of blasting.

Therefore , it would be expected that the mud-mat was poured d i rectly against the face of the bedrock excavation, without the use of forms. This hypothesis was confirmed visually during the 2005 excavation alongside the IP2-SFP for dry cask gantry crane foundation construction.

The concrete for a mud-mat is typical l y placed in a relatively fluid state to enhance self-leve li ng properties.

As this fluid concrete is placed , it is typically pushed up against the per i meter forms, or in this case the bedrock face. Th is p l acement procedure would be expected to coat and seal off the fractures in the lower portion of the bedrock sidewalls.

While the height above the surface of the mud-mat to which th i s seal would be fonned is highly variable and occurrence-specific, it would not be unreasonable to find a 2-to 6-inch high "lip" of concrete against the bedrock. The net effect would have been to create sto rage volume above the mud-mat , between the sides of the subsequently constructed structural floor slab and the bedrock sidewa ll s directly at the base of the SFP. While this space was likely filled w i th blast-rock fill , the pore volume of this material available for pool water storage could easily be over 30 percent of the total volume. T hi s result s in a substantial storage volume when compared to that required to "feed" and maintain the U nit 2 plume over time. During the 1990-1992 liner leak, a large volume of highly tritiated water appears to have been released from the pool, the r eafter traveling down the exterior of the SFP concrete wall. This travel path wou l d place the pool water directly into the hypothesized storage containment.

Once full, additional pool water would overtop the containment , migrate into fractures that were not sea led off by concrete, and then travel through the unsaturated zone. Once i n the unsaturated bedrock , some tritiated water would quickly 8l Tracer reached MW-3J and MW-32 in less t han four hours (time of first sample). thus supporting the conclusion of unsaturated zone transport to these locations.

8 4 A 6-to 8-inch, lean conc re te **mud-maC is typically constructed over blasted bedrock to even out the irregular surface and provide a hard flat surface upon which to set the reinforcing rod **chai r s" (these cha i rs elevate the lowe s t layer of rods to provide sufficie nt co ncr e te cover for corrosion prevention).

1 00 reach the groundwater and some would be retained in dead-ended fractures, as discussed above. Over time , rainfall events would be expected to repeatedly displace pool water out of the containment and into the bedrock fractures.

Contaminated water would therefore continue to impact the groundwater even if all active leak s from the pool were tennin a ted. We believe this process could continue over substantial periods oftime 85. 8.2 UNIT I SOURCE AREA The Un it 1 contamination , as shown on Figure 8.2 and the figure included below, i s often referred to as the Strontium

" plume"s 6. This is because the other radionuclides detected, including Tritium, Ces ium-137, Nickel-63 and Cobalt-60, have a smaller radiological impact when compared to Strontium-90 and the Strontium is found in the entirety of the plume's areal while the other contaminants are found only sporad ically and in smaller subsets of the plume's area. The Tritium data for the Unit 1 plume is included on Figure 8.1 and the Cesi um-137, Nickel-63 and Co balt-60 data are presented on Figure 8.3. r. -'r:;c;;. ..... .... . -..-:-. L [tiii! 2 ... --. .-* * .' , * ., -.-... .. ' * -.-.--' . h 1 ,; ....... ..... ... -! .' . _., .----.; ,--,---.... . -. _.L .... h;"n * ---' ..... : .... [1 , _1, * --, '--l \: I . * .

  • R i ver H udson ____ .... UNIT I BO UNDING ACTIVITY ISOPLETHS 1 5 See footnote No. S8 above relative to the reported T rit ium results for MW-Ill as sa mpled i n May of 2000. 1!6 It is noted that Figure 8.2 does ruu show an actual Strontium plume: the isopleths presented contour upper bound concentrations for sam ple s takcn at allY lime and allY depth at a particular location.

rather than a 3*dimo::n sional snapshot of concentrations at a single time. such, this "plume" i s an overstatement of the contami nant !evels existing at an y time. It should also be not ed that the lightest co l ored contour intcrvall>egins at one-quarte r the USEPA drinking water standard.

While drinking water standards do not apply to the Site (there arc no drinking water wells on or proximate to t h e Site). (hey do provide a recognized.

and highly conservative benc hmark for comparison purposes).

Lower , but positive detl.'Ctions outside the co l o red contours are shown as co lor e d data blocks. Sec figure for add ition al notes. IOI The highest l evels of Strontiwn (up to 110 pCi/L) were originally found adjacent to the North side of IPI*SFPs in MW-4i:l7. However , since Entergy began processing the poo l water to remove the Strontium , the leve l s of Strontium (and other radionuclides) i n this well have decreased.

From MW-42. the Unit 1 :'p l ume" tracks downgradient with the groundwa t er along the North s ide of the Unit I Superheater and Turbine BUildings 8!. As thi s plume app r oaches and moves under the Discharge Canal, it comming les with the U ni t 2 plume , and discharges to the river 89 between the Units I and 2 intake structures , as does the Unit 2 plume. As discussed in Section 6.0, the plume track appears to follow a more fractured, higher conductiv i ty preferentia l flow path in this area. The sou rc e of all the Strontium contamination detected in groundwater beneath the Site has heen established as the IPI-S FPs. The !P1-SFPs were identified by the prior owner as leaking in the mid-1990's, and are estimated to currently be le aking at a rate of up to 70 gallons/day.

A schematic of this pool complex is included below. '/Wt.tPOOI , e .. !POoi . . UNIT I FUEL POOL COMPLEX The IPt-SFP s were constructed of reinforced concrete with an internal low permeability coating 90; stain l ess steel liners were not included in the design of these early fuel pools. The pool wa ll thickness range s from 3 to 5.5 feet thick. The bonom of the !P I-SFP s is IT The highes t concentrations orlhc other co ntam inants associated with thc U nit I pl u me. including Cesiu m-I 37. Nickel-63 and Co balt-60 were also found in ..... ell MW-42. Thi s location is very close to the IP1*SFPs and il is therefore not unexpected 10 find these high e r concentrations of less mobile radionuclide s near the source. U This gcncrn l introductory discussion of the Unit I plume i s focused specifica ll y on th e "primary Unit I plum e:' Furthe r more detailed discussion of the other "secondary Uni t I plumes.-which all originate from the IPI-SF P s. is p, r ovide d in s ubsequent subsections.

9 I\s is the case with the Tritium from the Unit 2 plume. some S trontium discharges directly to the Discharge Canal before the plume reaches the Hudson River. 90 The originnl coati n g failed and was subseque ntly removed. 102 founded directly on bedrock, generally at elevation 30 feet". As such, there is no significant unsaturated zone below the IPl-SFPs. While all of the pools have been drained except the West Pool, the other pools have all contained radionuclide at various times in the past. The West pool. which is approximately 15 feet by 40 feet in area, currently contains the last 160 Unit 1 fuel assemblies remaining from prior plant operations.

This plant was retired from service in 1974. The IPI-SFPs are contained within the lPI-FHB. The foundation system of the FHB and rP l-CB complex contains three levels of subsurface footing drains (see figure included below). The design objective of these drains, with the potential exception of the Sphere Foundation Drain (SFD)92 , appears to be permanent depression of groundwater elevations to below the bottom of the structures

93. North and South Curtain Drains -The uppermost IPI-FHB drain encircles the Unit 1 FHB and IP I-CB. This footing drain, typically referred to as the Curtain Drain, is divided into two sections, the North Curtain Drain (NCD) and the South Curtain Drain (SCD). Each of these drains starts at a common high point (elevation of 44 feet) located along the center of the eastern wall of the FHB. These drains then run to the North and South , respectively , and wrap around the Unit I FHB and CB. The NCD then discharges to the spray annulus in the IP l_C8 94 at an elevation of 33 feet. From the annulus, the water is pumped for treatment and then discharged.

The NCD flows at a yearly average of about 5 gpm carrying a Strontium concentration of 50 to 200 pCilL (concentrations measured prior to reductions in Unit I pool water radionuclides via accelerated demineralization).

The SCD pipe remains as originally designed with discharge to the Discharge Canal; however, the SCD is typically dry95. Chemical Systems Building Drain -The lowest level of the [PI-CSB (contained within the FHB) is also encompassed by a footing drain. The eastern portion of this drain begins at a high point elevation of 22 feet at its northernmost extent, located proximate to the IP I-C8, and then slopes to elevation 11.5 feet at its low point on the southern side of the IPI-CSB. The western portion of this drain begins at a high point elevation of 12.5 feet at its northernmost extent, again located proximate to the IP I-CB, and then slopes to elevation 11.5 feet at its low point on the southern side of the IPI-CSB. Both portions of the drain join at the southern side of the IPI-CSB where the common drain line runs below the floor slab and drains into the [PI-SFDS (bottom elevation of 6.5 feet). This drain typically Hows 91 The bottom elevation ofthe individual pools range from a high elevation of36 feet for the Water Storage Poo l to II low of 22 feet for the Tran s fer Pool. <n The SFD is con s tructed at an elevation of 16.5 feet. It is abovc the bottom of the Sphere (elevation -I I feet) and comp l etely encapsulated in either concrete or grout. OJ The elimination of hydro s tatic uplifi pre ss ures Illlow s a "relieved de s ign" to be u s ed for the bottom concrete s lab s of the structures.

The alternative to a relieved slab design is a ""boat slab design:' In this case. the slab is heavily reinforced 10 re s ist hydrostatic uplift pre ss ure s. Boat s lab s are more expen s iv e to con s truct than relieved s lab s. and thu s arc typically only used when it is not feasible to relieve the hydrostlltic uplift pr e ssures. Thi s design modification within the lPl-CB. to allow storage of the footing drain water prior to treatment..

was implemented by the fonner owner onc e the water was found to contain radionuclid es. The initial Unit I de s ign connected the two 12-fool perfomted footing drain lines into a common 15-inch tce and drain pipe at the entrance to the Nuclear S ervice Building. Thi s IS-inch footing drain pipe collocated in the bedr o ck trench containing t he s pra y annulus to CSS drain linc. 95 The lack ofwaler in the SeD is consistent with the expected impact of the CS8 drain given its proximity and lower elevation. 103 at a yearly average of 10 gpm carrying a Strontium concentration of not detected (NO) to 30 pCilL. DRAlN (SCD) 'FO' FOUN D ATION DRAlN NOT TO SCALE,/ ,/ '-CHEM. SYS. BUILDING (CSB) DRAIN

  • UNIT 1 FOOTING DRAINS AND DISCHARGE SUMP Sphere Foundation Drain* The third foundarion drain below the IPI*FHB a nd lPI*CB complex is the SFD. This drain is located directly around the bottom portion of the Sphere and co n sists of: 1) nine perforated pipe risers spaced around the sphere and tied int o a circumferential drain line at elevation 13.75 feet; 2) each vertical riser is surrounded by a graded crushed stone filter; and 3) al l of which are within a clean washed sand whic h encompasses the Sphere from elev ation 25 to 16.5 fee t (t he " sand cushion).

The sand cushion is "sandwiched" between the concrete foundation wall , the Sphere and the grout below the Sp here; it i s open at the top, proximate to the annulus. As s uch , it appears that this drain does not interface with the groundwate r , except to the extent that some leakage may occur through imperfections in joint seals. This drain is also connected to the SFDS through a valve. During the development of the initi a l Co nceptual Site Model, it was understood tbat th e IPI-SFP s were currently l eaki n g, but it was conc l uded t h at the footing drainage systems would contain any releases from the [PI-SFPs.

This was also the conclusion ofa previous analysis perfonned for th e prior owner in 1994 96. This conclusion was based on:

  • The proximity of the drains to lP I*SFPs; in fact , the NCD runs a lon g the Nort h and East walls, and in conjunction with the SCD, completely encompasses the lPl*SFPs;
  • The generally downgradient location of the drains relative to the WI-SFPSi
  • The elevation of the drains r elat i ve t o the bonom of the lPI-SFPs; 96 Assessment of Groundwater

/lIigration from (jnit I Spellf Fuel P ools at Indian P oi nt P o wer Plant. Bu c hanan. NY; The Whitman Companies , luly 1994 104

  • * *
  • The elevation of the drains relative to the surrounding groundwater elevations 97; The continuous flow of the drains, even during dry periods; therefore, the groundwa t er surface does not drop below, and thus bypass , the drains; The reported predominant southerly strike and easterly dip of the bedrock fractures relative to the southerly location of the CSB footing drain; this expected anisotropy should extend the capture zone of this drain preferentially to the North towards the !PI-SFPs; and The existence of IPl-SFPs pool water constituents in the drain discharge 98. In February 2006, Strontium was detected in the downgradient, westerly portion of the IP2-TY (downgradient of IP2-SF?).

Given that Strontium could not reasonably be associated with a release from the Unit 2 SFP, the most plausible source remaining was the retired Uni t 1 plant where: I) the SFPs historically contained Strontium at approximately 200 , 000 pCi/L (prior to enhanced demineralization 99); and 2) legacy leakage was known to be occurring. Based on this finding, we concluded that either: I) an unidentified mechanism(s) must be transport i ng JPI-SFPs leakage beyond the capture zone of the footing drains L oo; or 2) other sources of Strontium existed on the Site. A number of plausible hypotheses potentially explaining each of these two scenarios were therefore developed, and then each was investigated further. During these investigations, additional detections of Strontium were also identified , including some relatively low concentrations in the area of Unit 3. However, with completion of the investigations and associated data analyses, it was concluded that all of th e Strontium deteclions could be traced back to leakage from the IP /-SFPs. These Strontium detections can be grouped into five localized flow paths , each associated with a d ifferent LPI-SFPs release area. Collectively.

these flow paths define the overall Unit I "piume JOJ" as listed below:

  • The primary !PI flow path;
  • The eastern IP I-CB_flow path;
  • The southwestern IPI-CB_flow path;
  • The IP I -CSS trench flow path; and
  • The legacy IPI stonn drain flow path. q, Thi s line of evidencc remained sup portiv c of t he initial co nclu sion until the installation of MW-53. which occurred during the third phase of borings (after the discovery of Strontium in the groundwater).

q l Drain watcr i s treated prior t o discharge as permitted monitored effluent.

9'1 Strontium levels in IPJ-SFP s have been more recently reduced to approximately 3.000 pCi/1. under acc::elerated liltering through demincralization beds. Tritium concentrations in IP I-SFPs !lJ" e on the order 01'250,000 pCi/L. 1 00 Onc::e Stro ntium-contaminated pool leakagc enters the groundwater, it is transponed in the dircc::tion of groundwater flow: Strontium.

as well as the other potcntial radionuclides, do not migrate in directions opposing gro undwater flow (w ith th e exc::ept ion of diffusive flow which i s insignificant as com pared to adveetivc flow under these hydrological c::onditions).

Therefore leakage entering the groundwater within the c::aplUfe zone of the footing drains is c::aptun:-u by those: d rain s. 1 0 1 The grouping of Strontium detections into co ntiguous "plumcs" may be an ovcr-simplilkation.

and the dc::tcctions may. i n reality be duc to s mall , isolated individual groundwater entry points and flow paths from the IPl*SFP s. This is lik e ly to bc particularly truc pursuant to the [PI Lcgacy Piping "flow path:' 105

_., --.-... --." * . -' -. '--"'--.-' * * . ' EASTERN 1P1-CB FLO I WJ;A T H .. LEGACY IP1 STORwiI'DRAIN' FL.OWPArH* . ..::,. .. ,-: . ." . *** .-1m I T ll SOUTH WESTERN : IP1-CB FLOW PATH : .-I I , I I 1

  • rI., * * .--* I I I I -I I \
  • l _ .
  • I , , " I ,
  • Hudson River INDIVIDUAL UNIT 1 STRONTIUM FLOW PATH LOCATIONS The discussions below are focused on the discovery and characterization of these individual flow paths, and the final mechanisms that best explain their existence.

Other initially plausible mechanisms were also investigated as part of the Observational Method approach employed l0 2 , but they did not remain plausible in light of the subsequently developed data and analyses , and are therefore not discussed herein. In addition , portions of the discussions below also relate to the conc u rrent investigation of other potential source areas across the Site. During review of the following sections , it is important to recognize that only small quantities of leakage are required to resul t in the groundwater plumes observed on the Site. Primary [Pt Flow Path -Monitoring well MW-42 was initially installed to investigate the premise that contaminants may be leaking into the subsurface from the IP2-Reactor Water Storage Tank (RWST). However , the sample analysis made it clear that IPI-SFPs water was present in the groundwater at MW -42; the radiological profile was consistent with 1 0 2 As indicated above, multiple initially plausible hypothesL"S potentially explaining the genesis of these flow paths were developed and investigated. These investigation s proceeded in a s tep*wi s e. iterative manner con s i s tent with the Observational Method. whereby variou s aspects of the Conceptual Site Model (CSM) were modified to develop an overall CSM that better fit all of the data. Not all mechanisms investigated remained plausible in li g ht of all the data and analyse s developed as part of thi s hypothe s i s-te s ting. 106 Unit I fuel pool water (low Tritium, high Strontium and Cesium). While IPI-SFPs leakage was known to be ongoing, this conclusion was not consistent with the CSM at the time which was predicated, in part, on containment of IP l-S FPs leakage by the footing drains (North and South curtain Drains, and the Chern. Sys. Building Drain). An additional monitoring well, MW -53 , was subsequently installed downgradient of MW-42 (on the Northwest side of the IPI-CB). Groundwater in this well was also apparently impacted by IPl-SFP water, thus resulting in the initial steps in the identification of the Unit I primary Strontium flow path. The groundwater elevations measured in MW-53 proved even more enlightening than the radiological profile. In the case of a continuollsly flowing footing drain such as the NCO , groundwater would generally be expected to be flowing into the drain over the entire length of the drain; the corollary to this conclusion is that the groundwater elevation would be above the drain invert along its entire extent. Otherwise, water flowing into the drain along its eastern, upgradient extent would exfiltrate the drain along its western, downgradient extent and thus , water would no longer discharge out of the end of the dra in into the rP I-CB Spray Annulus; it would therefore not typically be continuously flowing. However, the groundwater elevation in MW -5 3 was measured at approximately elevation 9 t o 10 feet , substantially lower than the water table elevation in MW-42 (35 feet) and the elevation of the N e D invert (33 feet). Therefore , it was found that only a portion of the groundwater which infiltrated the drain to the East was observed as continuous flow at the Spray Annulus collection point. The remainder of the water was ex filtrating along the drain further to the West 103 , where groundwater elevations were below the drain invert and thus outside the capture zone of the drain. Therefore , leakage from the IP I-SFPs was initially being captured by the NCD , but then during transport to the Annu lu s for collection and treatment , a portion of this leakage was discharging to the groundwater outside the capture zone of the drain. T his leakage then migrates downgradient to the West with the groundwater and establishes the Unit 1 primary Strontium flow path. Eastern IPI-CB Flow Path -A Strontium plume is shown on Figure 8.2 as existing be l ow the entire IPl-SFPs. W i th the exception of MW-42, there are no monitoring wells in tills area to verifY that this plume actually exists. However, it is known that the IP1-SFPs have and continue to leak , and the NCO and CSB footing drains have been shown to contain radionuclides consistent with that expected from IPl*SFPs' leakage. The locations of the specific release point s are not known , but could be anywhere along the wall s and bottom of the IPI-SFPs.

Once leakage from any of the above postulated points enters the groundwater , it will migrate either to the NCO or the CSB drain, depending on where the specific release point is located relative to these drains. Leakage located along the northeastern portions of the IPI*S F Ps is likely to migrate to the NCO (elevation 33 feet), whereas leakage located more to the South and West is more likely to migrate to the lower CSB drain (elevation 22 to IOJ [t is hypothesized that, i n the past, the drain lik e ly did not now continuously.

However. over time. the exfiltration ratc h as been r e duced through siltation s ueh that the drain can no lon g er release water ov c r it s wc s tern extent a s fast as it infiltrat es into th e drain furth e r to the East. 107 11.5 feet). These scenarios, when considered for multiple potential release points, should result in Strontium flow paths that are all contained within the plume boundaries shown on the figure. Southwestern

'P]-CB Flow Path -As part of the investigations to identify other potential releases to the groundwater across the Site, low levels of Strontium (less than 3 pCilL) were detected in monitoring wells MW-47 and MW-56. Groundwater contamination in this area was inconsistent with the known sources and the groundwater flow paths induced by the IPI-CSB footing drains. A summary of the investigations and analyses undertaken to identify the release mechanism responsible for this Strontium flow path follows. Construction drawings indicate that the lPl-CB and the IPI-FHB were constructed with an inter-building seismic gap and stainless stee l plate between the two s tructures.

T his construction detail creates a preferential flow path for any pool leakage through the western walls of the IP I-SFPs, as well as leakage from othe r locations which migrates to the w estern side of the IPI_SFPS 104. While thi s "p late/gap" separates the structures all the way down through the structural foundat i on slabs, it likely would not have penetrated the mud_mat tOs. In addition , it would not be uncommon for the surface of the mud-mat to not be completely cleaned prior to pouring of the structural s l ab. Even small amounts of soil, mud , dust, etc. between the mud-mat and the structura l slab above would result in a preferential flow path along the top of the mud-mat. Therefore, it is expected that pool leakage in this zone (between the structural slab and the mud-mat) could flow laterally and would still be isolated from the fractured bedrock below. It would then, in tum, also be isolated from the influ ence of the footing drains (both the NCD and the lPl-CSB drain). To the extent that the above hypotheses are correct, this leakage could then build up and flow a l ong the plate and above the top of the mud-mat. With s ufficient input of leakage from the pool, the elevation of this flowing water could also rise above the top of the IPI-CB footing 1 06. With the above hypothesized conditions, pool l eakage may migrate along the plate all the way around the IPI-CB to the South and West until it reaches the end of the plate (at the intersection of the perimeter of the lPI-CB with the [PI-FHB). At that location, the water wou ld follow the top of the mud-mat (and/or top offooting) a lon g the [PI-CB bottom s l ab further to the West 1 07* This leakage flow path is highlight ed on Figure 8.2. The leakage water would not be constrained to flow into the SCD given that thi s footing drain is dry. Once past the end of the plate, the pool leakage could enter the bedrock at multiple points, wherever it encounters bedrock fractures.

Thereafter, the leakage would enter the groundwater and thus be constrained to migrate in the direction of groundwater flow. 104 This hypothesis is funher supponed by the prescnce of weep s of contaminated water (SFP leakage) in the ca."tcrn wall oflhc IP l*eB at the footing w a ll j o int. IO! Wh ile not sh own on th e constructions drawin gs reviewed "as required", construction photo s sho w that a mud*mat was p lac ed prior \0 rcbar cage construction (also sec discussion of rationale under Tritium sou rce areas above). Given th e cons i stent bottom e l eva tion s of both the VC and t he SFPs s tru ct ural concrete s lab s. a s ingle mud-mat was likely con s tructed. 106 Leakage now above the top o f the footing (elevation 33 fect) to the East and Southeas t of the VC would not be captu r ed by the SeD given that this dra i n is dry. 101 See discu ssio n of likely mud-m atlbedrock excavation wall configuration and the impact of precipitation events in the section above under Tri tium so urce areas. 108 As shown on the figure , pool le akage entering the groundwater along the South side of the IPI-CB would be expected to mound the groundwater somewhat.

This is particularly true in this case given the leakage entry point within the "fla t zone" encompassing the groundwater divide between flow to the river to the West and flow to the East to the CSB footing drain 108. The portion of the pool leakage which flows West would form the southwestern lPl-CB Strontium flow path and thus exp l ain the l ow leve l s of Strontium found in MW-47 and MW-5 6. From this point, the "plume" continues to flow West and joins the primary Strontium flow path. IPI-CSS Trench Flow Path -During the course of the inve s ti gat ion for potential sou rce s, MW-57 exhibited significant Strontium concentrations.

Strontium was also detected in the upgradient IP I-CSS, located in the Unit I Superheater Building.

This s ump was investigated to evaluate the extent to which it may be associated with the contamination identified to the West, near the Discharge Ca nal. A retired subsurface pipe, designed to drain water from the Unit 1 Spray Annulus to the CSS, was determined to be the input source path for water observed within the sump. During Unit I construction, this pipe was installed within a 3-foot-wide trench cut up to 20 feet into bedrock , which slopes downward from the Spray Annulus to the CSS!09. Construction drawings further indicate that this trench was backfilled with soil. This pipe had been temporarily plugged in the mid-1990's when contaminated water from the NCD was routed to the Spray Annulus. However, the temporary inflatable plug was later found to be leaking and the pipe was then permanently sealed with grout. As part of our in vestigations, a monitoring well (U l-CS8) was installed horizontally through the East wall of the CSS at an approximated elevation of 4 feet. This horizontal well is connected to a vert ic al riser which extends to above the top of the CSS. Water level s in this well typically range from elevation 12 to 18 feet and re spond rapidly to precipitat ion events. Based upon avai l able data, we believe the IPI-CSS is not a source of contamination to the groundwater.

Inspec t ions of the sump indicate the likely entry point for water periodically found in the sump is the pipe from the IP! Spray Annulus, the joint between the concrete sump wall and the sump ceiling (the floor of the Superheater Building), and/or tbe joint in the s ump wall where the pipe penetrates from the rock trench into the sump. These conclusions are based on:

  • The groundwater elevations measured in UI-CSS are above the bottom oftbe CSS which is generally nearly empty (bottom elevation of 1.0 feet);
  • The results of the tracer test confirmed that contaminated groundwater can enter the CSS when it is empty; and
  • Visual inspections of the interior of the sump and associated piping. lOS While a groundwater divide must exist between the C53 footing drain and rive r to the WeSt, the exaet l ocation of the divide is unknown. 1 1)1) The tre nch bottom starts at elevat ion 22.75 feet at the Spray Annulus and slopes gradually to elevatio n 21.75 feet at a point 9 fect from the CSS. From this point, the trench s lop cs s t eeply to elevation 1 3 feeet at the css. 1 09 This sump is no longer in service as the system it supported is retired. While the ess itself does not appear to be a release point, we believe the associated bedrock trench between the Spray Annulus and the C SS is a sourc e of contamination to the groundwater.

As indicated above , the Spray Annulus is used to store releases collected from the IP I-SFPs by the NeD , which contains contaminants.

The Annulus water has been historically documented as leaking into the pipe and surveys indicate that the pipe itself likely leaks into the trench. While the leak into the pipe from the Spray Annulus was s ealed , other leakage inputs to the trench also likely exi s t. One s uch likel y leakage path is for water to flow directly from the NCD through the drain backfill and abandoned piping'lO to the pipe trench. This flow path is s upported by the trends in V I-e SS water elevation variation as compared to the NCD discharge rate (see figure included below). J * '=' " = ,: ' , 0 flow m. 1 " Ul*('SS 2122106 4f]]J06 612106 7f22.oti 9!11W6 10!3Ml6 1 ll19J06 211107 3f29/o7 S/18J07 7n/07 8f2M17 1 0/15107 UNIT I NCD FLOW, VI-CSS GROUNDWATER ELEVATION AND PRECIPITATION RELATIONSHIPS " " " " ; " * " * , These hypothesized leakage paths are highlighted on Figure 8.2. Once leakage enters the trench , it should flow along the sloped bottom until it finds bedrock fractures through which to exfiltrate.

This leakage will then flow through the unsaturated zo ne along the strike/dip of the fractures until it encounters the saturated zone, and thereafter will follow groundwater flow. Because of these hypothesized, but probable conditions, we concluded that leakage has exited the trench and impacted groundwater.

Impacts directly to the groundwater below the pipe trench are characterized by Strontium concentrations in monitoring well V I-ess. In addition , source inputs to the groundwater from the trench are also envisioned to h ave occurred farther to the South, where the groundwater flow would then carry contamination t o MW-57, thus explaining the Strontium concentrations found in that well ili. While southerly flow in this area is inconsistent with groundwater flow direction , source inputs can migrate from the bedrock trench to the South in the unsaturated zone near th e 11 0 A s n o t e d above. th e NCD di sc har ge wa s re routed into the S pmy Annulu s when the NC D was found to contain contaminants by the previous owner. Prior to this modificmion , the footing drain was routed to a IS-inch drain line collocated i n the CSS pipe trench. The abandoned pipin g and permeable backfill s till exist and lik e l y act as an anthropogenic preferential flow path. 111 Monitoring wells UI*CSS and MW-S7 do not appear to be i n the grou ndwater flow path of the primary Unit I "plum e:* 110 CSS, where the unsaturated zone is relatively deept t2, This hypothesized unsaturated zone flow path is shown on Figure 8.2 , as well as the sc hematic included below. _____ .0 -_ ...... _ ... --_._ ..... -....-..-_

... _...,h .. __. __ 'I --... IPI-CSS TRENCH UNSATURATED ZONE FLOW MECHANISM In addition, the construction detail s of the Superheater East wall m ay a l so channel sat urated flow to the South , depending on variation in groundwater elevations.

These le ss direct le akage inputs then es tabli s h the so uthern portion of the so urc e area fo r the CSS trench flow path s uch that the groundwater flow cames the "p lum e" through monitorin g well MW-57, thu s explaining the Strontium found in sa mples collected from this well ll3. Legacy IPt Storm Drain Flow Path -As s ummarized above, the C SB footing drain collect s groundwater from the vicinity of the rP I-SF Ps; thi s water ha s been documented to contain radionuclides.

The contaminated water is then conveyed to the SFDS, located at the so uthern end of the CSB. In additi on , hi s tori ca l events , including CSB s ump tank overflows in U nit 1, have impacted the S F DS. Prior t o construction of Uni t 3, water collected in the SFDS was pumped up to elevation 65 fe e l and discharged to the sto rm water sys t e m on the South si de of the Un it I C SB. The discharge was conveyed b y these drain s to the South toward s catch basin Ut-CB-9 (c urrenlly und er the access ramp 10 U nil 3), and Ihen Wesl (U I CB-IO) under whal i s n ow the rP3-VC toward the Di s charge Canal. Thi s pathwa y was re-routed during con s truction of U nil 3 in the early 1970 s 10 flow S o uth from ealeh basin U I-C B-9 , I hen further Soulh lowards caleh basin U 3-CB-A4 and s ub seq uentl y 1 0 Ihe Di sc harge Canal throu g h Ihe 1 12 The hypothesized so utherl y no w of a portio n of the tre n ch l eakage to the So uth through th e unsaturated zone i s consisten t with: I) t he st ri ke/dip direction of major joint set s found on S it e: and 2) the groundwa ter flow path from the re su ltin g unsaturated lone i nput to the well s which i denti fi e d thi s St r on tium flow path. IIJ Th is well a ppears to be located outside. and up gradient oC , t he primary U nit 1 S tront ium flow path to th e North. II I E-Series s torm drains. (See figure included below and Figure 8.2 where these p athways are al so hi g hli g hted.) '-. -. .,-.-.-... ... --. legend -" 1""--/c-.-' I -' . , -. ' .. \..; ", -..... ..., .. -.-.-w-I ' . I . II II I I " __ + . . Hud son River DIFFERING SPHERE FOUNDATION DRAIN SUMP DISCHARGE PATHWAYS OVERTIME A recent in spe cti o n of the s t o rm d ra in syste m , including smo k e te sts a nd water flu s hin g, has revealed th a t a number of pipes along these sections h ave been co mpromised a nd are leakin g. Strontium found in groundwater on the South s ide of the U nit 1 F SB , an d upgradient of U nit 3 , i s coincident w ith the location s of the s e s tormwater pipe s. Theref o re , we concluded that so me of th e contaminated water di sc har ged into these pipe s ex filtrated , and th en mi g rated downward throu g h the un sa turated zo ne and contaminated th e gro u ndw a ter , thus r es ulting in th e " l egacy" s torm drain flow pathl1 4s hown on Figure 8.2. I n 1994, thi s discharge rout e was changed again , wh en contamination was detected in the effluent from the Un it 1 SFDS. The pipe l eading from the SFDS t owar d s Un it 3 was capped , and di s charges were thereafter routed directly to the Discharge Cana l through a series of interior pipe s as well as a radiation monitor. As s u c h, the s torm dr a in line s t o th e 1 1 4 Three discre t e i sopleths h ave been drawn around MW*39. MW-41 and M W-43 given the measured concen t ra t ion s grea t er t han 2 pC il L. H owever. it is expected t ha I si milar co n centrations ex i s t al other locat i on s a l ong the le gacy pipi n g alignm ent in addition to those s ho wn on thc figure. During the historic active di scharge t o the stonn drain s, i t is expected th at the individual leak a<<:as would have resulted in comming lin g of the groundwate r contam in ation into a single " pl ume" area. Thi s "p lume-wou l d have then migrated do .... ngradicnt across the U nit] area. With the cessation of discharge to the sto nn drains. the "pl u mc" atte nuat ed over ti me. leaving downgradienl remnants which arc s till d e t ectable as low l evel S trontium contamination in U nit 3 monitorin g wells suc h as MW.44. 4 5 & 46 , U3*TI & 2, and U3*2. 11 2 South of Unit 1 no longer carry this contaminated water and they are therefore no longer an active source of contamination to the groundwater.

However , from a contaminant plume perspective , these historic releases still represent an ongoing legacy source of Strontium in the groundwater to the South side of Unit 1. This is because Strontium partitions from the water phase and adsorbs to solid materials, including subsurface so il and bedrock. The Strontium previously adsorbed to these subsurface materials then partitions back to, and con tinue s to contaminate, the groundwater over time , even after the storm drain releases have been terminated.

As shown on Figure 8.2 , low level residual evidence of this legacy pathway was identified in monitoring wells installed to South of Unit 1 during the course of the investigations proximate to potential sources associated with Unit 3. Stront ium , Ces ium and Tritium were detected in these wells at levels below the EPA drinking water standard.

Three monitoring wells to the South of Unit I show "Lega cy Storm Drain flow paths" drawn around them. These wells have yielded samples at one time/depth with Strontium concentrations greater than 2 pCilL , or oneMquarter of the Strontium-90 drinking water standard.

While the actual extent of these Strontium concentrations is not known given that each has been drawn around a single point, they appear to be limited in extent (base d on the data from the surrounding monitoring wells). It is also important to recognize that the specific l ocations of the historic releases from the storm drain lines are not known. In addition , once water has exfiltrated from the drain line, it moves generally downward in the unsaturated zone as controlled by the strike/dip direction of the specific bedrock fractures encountered.

Therefore , legacy groundwater contamination does not have to be located immediately downgradient of the storm drain system (as exemplified by the Strontium found in MW M 39 and tracer in MW-42). While three i sop leths are shown on Figure 8.2, we believe it is possible that other areas in the general vicinity of thjs piping may exhibit similar groundwater concentrations.

We have also concluded that the lower concentrations of Strontium detected in monitoring wells further dO\VJ1gradient , in the Unit 3 area, are also due to these historic , l egacy storm drain releases.

113

9.0 GROUNDWATER

CONTAMINATION FATE AND TRANSPORT Strontium (the U nit 1 plume) and Trit ium (the Unit 2 plume) are the radionuclides we used to map the groundwater contamination.

The investigation focused on these two contaminants because they describe the relevant plume migration pathways , and the other Site groundwater contaminants are encompassed within these plumes. While radionuclide contaminants have been detected at various locations on the Site, both the on-Site and off-Site analytical testing, as well as the groundwater elevation data, demonstrate that groundwater contaminants are not flowing off-Site and do not flow to the North, East or South. Groundwater flow and thus contaminant transport is West to the Hudson River via: 1) groundwater discharge directly to the river; 2) groundwater discharge to the cooling water canal, and 3) groundwater infiltration into stonn dra i ns, and then to the canal. The primary source of groundwater T ritium contamination is the JP2-SFP. The resulting Unit 2 plume extends to the West , towards the river , as described in subsequent sections.

T he source of the Strontium contamination is the IP l-SFPs. Previous conceptual models , based on infonnation presented in prior reports, indicated that releases from the IP I-SFPs were likely captured through collection of groundwater from the Uni t 1 foundation drain systems. However, based upon groundwater sampling and tracer tes t data, we now know that the Unit 1 foundation drain system , particularly the NCO, i s not hydraulically containing all groundwater contamination in this area (see Section 8.0). GZA's understanding of the Tritium source and Strontium source are discussed in more detail in Section 8.0. T he plumes described on the figures in the following subsect ion s are based on: 1) the isopleths bounding the maximum concentrations , as representative of "wors t case conditions

.. IIS (Figures 8.1 and 8.2); and 2) the most recent l aboratory data collected through August 2007 , as representative of current conditions (Figures 9.1, 9.2, 9.3 and 9.4). While the figures showing upper bound isopleth concentrations do not show actual conditions, we believe these graphics are useful in developing an understanding of groundwater and radionuclide migration pathways.

In reviewing this section please note the plumes show our current understanding of how anthropogenic features influence groundwater flow patterns, in particular the various footing drains and backfill types used during construction.

Also note that flow in the IU It is noted that these ligures (F igures 8.1 and 8.2) do nO! show actual plume s: the isopleths pre scnt contoured upper bound concentrat ion s for samples taken at any time and any depth at a particular location. rather than a J-dimcnsional snapshot of concentrations at a s ingle tim e. As such. these "plumcs" are an overstatement of the conta minant levels existing at any time. It s hould also be noted that the lightest co l ored contour interval begin s a t one-quarter the USF, PA drinking water standard. While drinkin g water standa rds do not apply to the Site (there are no drinking water well s on or proximate t o the Site). they do provide a recognized.

and highly c onservative benchmark for compari so n p u rposes). Lower. but positive.

detections outside the co l ored conto u rs arc s hown as colored data blocks. See figure for additional notes. 114 unsaturated zone plays an important role in both the timing of releases to the water table and in the spread in g of contam in ants. Based upon the results of GZA's geostructural analysis, the extent of contaminated groundwater, the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Pumping Test, the tracer test and tidal response tests, we believe that the bedrock underneath the Site is sufficient ly fractured and interconnected to a llow the Site to be viewed as a non-homogenous and anisotropic porous media. Based on this finding, and because advection is the controlling transport mechanism, groundwater flow, and consequently contaminant migration in the saturated zone, is nearly perpendicular to groundwater contours on the scale of the Site. 9.1 AREAL EXTENT OF GROUNDWATER CONT AM1NA nON Based on measured tracer velocities (4 to 9 feet per day; see Section 7.4), the limited distances between release areas and the river (typically les s than 400 feet), the age of the plumes (years), and recent interdictions, we believe contaminant plumes have reached their maximum size and are currently decreasing in s iz e_ Consequently, our reporting in this section focuses on observed, "current" conditions (the s ummer of 2007). That is, we saw no need to mathematically predict future conditions.

9.2 DEPTH

OF GROUNDWATER CONTAMINATION Because of the location of Indian Point on the edge of the Hudson River, the width of the river, and the nature of contaminants of potential concern , groundwater flow patterns (and , consequently, contaminant pathways) are relatively shallow. Furthennore, as discussed in Section 6.0, the upper portion of the aquifer (typica lly , the upper 40 feet of the bedrock) has a higher average hydraulic conductivity than the deeper portions of the bedrock. Consequently, the center of mass of the contaminated groundwater is sha llow. Figures 9.1 and 9.2 are cross sections which show the approximate vertical distribution of Trit ium and Strontium, near the center lines of the Un it 1 and Unit 2 plumes, in the summer of 2007 ("current conditions").

In reviewing these figures, note that Strontium was not found below a depth of 105 feet in MW-67. We attribute the low concentrations of Trit ium below a depth of 200 feet at this location , at least in part, to t he downward migration of Tritium during our investigations.

For examp le, by necessity, well RW-J was an open wellbore for a period of time l16 which allowed vertical groundwater migration , along an artificial preferred pathway, deeper than would occur a long ambient flow paths. 9.3 UNIT 2 TRITIUM PLUME BERA VIOR As shown on Figures 8.1 and 9.3, the Unit 2 plume exhibits Tritium concentrations originating at (he IP2-SFP. The higher concentration isopleths are shown around the entire 11 6 RW-1 is located immediately below the 2005 shrinkage crack leak (high Tritium concentrations in shallow g r oundwater).

This wcll had remained as an open wcllbore for periods of timc in prcparation for and during: 1) the drilling of the wellbore;

2) the packer testing: 3) the geophysical log ging: and, 4) the Pumping Test. Du ri ng these times. vertically downward grad i ents li kely movcd some Tritium to levels deeper than it would otherwise exist. When possible.

this welloorc has been sea l ed ove r its cntire length using a Flute Liner Sy s tem. liS pool area so as to include the location of the shrinkage crack leak in the S o ut h pool wall , the loca tion of th e 1992 l eak on the Eas t wall, and the l ocation of the weld imperfection in the No rth wall of the LP2 Transfe r C an al. We believe the core of th e plume , as shown , is relative l y narrow where Tritium flows downgradient (weste rly) t o MW and MW -Ill in the Transformer yard ll7 , Th i s delineation i s based on: 1) the degree of connection ll8 observed from MW-30 to MW-33 (as compared with that from MW-30 to MW-3 l and/or MW-32) as being indicative of a zone of hi gher hydraulic conductivity limiting lateral dispersion; and 2) the l ocalized increased thickness of the saturated soil in the vicinity of MW-lll (see Figure 1.3) which likely behaves as a local groundwater sink/source for wes te rly bedrock groundwater flow, pri or to en t e ring the associated backfill of the D i scharge Canal. .-.---. . !. . -.. -. -: . -. "

  • Hudson Il.
  • 1.-.. "" , .---'"',. " _ ,.cl ___ ':-i 1 . ..* .', . -. "', .. ; .. .. _ .. "'-, r , I -=1 R i ver BOUNDING UNIT 2 ACTIVITY ISOPLETHS

.-T ritium has been detected in MW-31 and MW-32, both of which are upgradient of th e IP2-SFP. As evidenced by the tracer test (see Sect i on 7,0) and hydraulic heads , this 111 The bedrock in th is a r ea was exca v ated via blas tin g \0 allow foundation constructio

n. As s uch. Ihe upper portion s of the bedrock are likel y highly fractured in this area. I n addition , the pr e-construc t ion bedrock contours (see Figure 1.3) indicate that the particularly deep depression in the bedrock in the Transf orme r y ard in the vicin i ty of MW-I II (filled with so il down to elevation 0 fcet) was l ikely excavated to s erve as u dewatering s ump. The assoc i a t ed deeper blastinginduced fracturing and the saturated soil backfill are also likely to furt her inc r ease th e transmissivity in this area \\1 The degree of c onnecti on i s infem..'<.i based o n both the s imilar s tatic water l eve l s in MW-30 and -33 (separated by ov e r 1 00 fcct), as contrasted to the much higher water levels in MW-3 1 and -32 located about 65 fect from MW-30, and the rapid change in water elevat ion in MW-30 in res p onse to water level perturbations in MW-33 (e.g .. during drillin g/sa mpling), with little o r no r esponse in MW-3 I and -3 2. 116 occurrence involves gravity flow along bedrock fractures in the unsaturated portion of the bedrock beneath the IP2-SFP. This unsaturated flow direction is consistent with the dominant foliations (which strike to the Northeast and dip to the Northwest).

T hi s behavior is shown on the figure by dashed arrows and the isometric insert (see Section 8.1). This mechanism also accounts for some of the Tritium found near Unit 1 and is also supported by the results of the tracer test (see Section 7.3). However, once the contaminated water enters the local groundwater flow field , it migrates via advection in a direction generally perpendicular to the groundwater contours (Le., with the groundwater flow). In the IP2-TY, the plume i s drawn as more dispersive in response to the concentrations measured in MW-34 and -35 as well as the high degree of connection observed between MW-33, -34 and -35 along an orientation transverse to the general groundwater flow direction.

See the figure below for a schematic of the three dimensional fracture orientations in this area that account for the observed lateral di spersion. In thi s general area, the Unit 2 plume is bounded to the South by MW-54 and to the North by MW-52. 33 34 35 Tran.ml ** lve Fraetu .... In MW*34 e nd MW*35 at Approximately Elevation 3 3 -DIMENSIONAL BEDROCK FRACTURE ORIENTATIONS At the western boundary of IP2-TY, Tritium flow s into the highly conductive soil backfill found along the eastern wall of the Discharge Canal (see Figure 1.3). This conclusion is s upported by both the groundwater elevations and Trit ium concentrations in MW-36. The groundwater elevations with depth in MW-36 indicate that once in the Discharge Canal backfill, the groundwater flows downward below the canal wall and, subsequently , into both the Discharge Canal (lower water elevation in the canal) as well as under the canal through the bedrock fractures (see Section 6.7.2.2 for an estimate of the relative flows to these two discharge locations).

Once on the western side of the Discharge Canal, as evidenced by groundwater elevations and Tritium concentrations in MW-37 , -49 , and 117

-67, groundwater flow and Tritium migration is to the Hudson River, via both bedrock and unconsolidated material along the riverfront.

The specific flow path for the Tritium detected in MW-37-22 (located in the fill on the West side of the canal) is not certain. It is however associated with either: 1) upward groundwater flow into the backfill from th e bedrock beneath the canal, as supported by the upward vertical hydraulic gradients;

2) groundwater flow into the blast rock fill on the West side of the canal, with northerly flow in the fill to, and around the North end of the canal and then southerly along the East side of the canal to MW-37; andlor 3) exfiltration from the s torm water piping between MH-4 and MH-4A into the fill on the western side of the canal, with a similar flow path as described in 2). See Section 7.5 for additional information.

Regardless of the upstream flow path to MW-37-22, the groundwater flow direction from this location is westerly toward the Hudson River. Also note that the exact pathway to this location does not change the results of the groundwater flux calculations to be used in radiologic dose impact assessments.

Both Figures 8.1 and 9.3 show a southern component of flow as the Trit ium migrates West towards the riv er. This pathway corresponds with the location of severa l East-West trending fractures zones and a fault zone. It is likely th at this area is characterized by a zone of higher transmissivity that induces th e contaminated groundwate r to migrate as shown on these figures. We also note that it appears groundwater flow from higher e l evations to the Nort h also impedes a more northerly contaminant migration pattern. 9.3.1 Short Term Tritium Fluctuations During our investigation , we observed short term fluctuating Tritium concentrations that we cannot reasonably attribute to a continuous release 1l9 (see Table 5.1). These fluctuations make drawing an accurate representation of a plume, on any single date, difficult because any single sample may not be repre sentat ive of the overall water quality in proximity to the samp ling location.

In the case of T ritium associated with the IP2-FSB, we believe the fluctuations are assoc iated with temporal variations in the release of contaminated groundwater from the un sa tura ted zone to the water table. T hat is, we believe the unsaturated zo ne acts as an intermittent , ongoing source to the groundwater flow regime (see Section 8.0). The following graph shows the results of Tritium vs. time in samp l es collected from MW-30 , located adjacent to the IP 2-SFP. 119 In addition, our r eview of sampling procedure s and laboratory methods did not explain the variations obscrv(.od in sam pl cs collected from monitoring well MW-30. 118 700.000 * -

__ ... 'JIeTIOO ...,., 600.000 , , low*fbw/pKU, obaIow 0 __ *fbw","l>>, deep 500.000 0 0

  • wO/C,locIdeep

.; 0 pm"" .. !"",

  • S , 400.000 , 1i * , 0 300.000 , ., 0 *C , 1 " 2(4),000 0 8 0 '-....,""-..// . Loo,OOO , 0 TRITIUM CONCENTRATIONS AND PRECIPITATION VS TIME FOR MW-30 Similar temporal vanatlOns in Tritium concentrations are observed in data generated by te s ting of samples downgradient of IP2-SF P at MW-33-34-35 and -Ill; see the fo ll owing figure: :i u E " .. 3SO,C(K) ,. 3OO,(XX) j 2lQOO)1 lOI),00) ISO ,C(K) 1 00,00) J Sll,00) , 0 1 MW-3J, -34, -35,*1 11 T ri Lilim + + + + + + + + ++ __ MW.3) ___ MW.).( _MW.3$ 91510S l Ql'2S/OS 12JI4IOS '1J2JrfJ 3124106 .5113106 7f2J06 8121!(x) 10l1Ml6 TRITIUM CONCENTRATIONS VS TIME FOR MW -33, -34, -35 AND -III MW-lI1 is a shallow overburden well completed to a depth of 19 feet below ground s urface (bg s), This well i s located in a soil-filled bowl-shaped depression within the Transfonne r yard (see Figure t.3), Consequently, the concentrations of Tritium in samples collected from MW-lll are more sensitive to precipitation (and the l ikely associated exfiltratio n from the proximate stonn drain) than samples collected from other wells in this area (see above). In particular, note the substantial decrease in Tritium concentration as shown on the following graph , in samples collected after significant precipitation events in October 2005 and May 2006. 119 JSO.ooo
  • MW*33 300 , 000 ** Tritium o MW.J 4 0 a M W*H I. * :z.so,ooo t* .M W.]l1 sl F O ol << 'i. "",000 .. .. 0
  • E o * ,. 1 50,000 ** * *C 0 * ... 0
  • 1 00 , 000 1 0 so.ooo 0 3 a 0 0 0 , 6 to 12 Pruipil il ion 10lal lOr 7 days prior 10 sampling , In. TRITIUM CONCENTRA nONS VS PRECIPTIATION 9.3.2 Long Term Variations in Tritium Concentrations Recognizing the limitations posed b y short tenn fluctuation s, we constructed Figure 9.3 , which s hows the l atera l extent of T ritium co ntaminati on i n th e late s umm er of 2007 ("c urr en t co nditions"), . -. -.r-. * -.. -. * -'. . -. .-.. * * ,,-. Hudson _. ,,-. .-. '. .... II " " .. , : ._, -.; M' * ..., *** ::.J L I I R i ver CURRENT U NIT 2 PLUME 120 .--.

Our review of this figure , in conjunction with Figure 8.1 1 20 and Table 5.1, reveals the following:

  • Despite interdictions , the lateral extent of the two plumes (i.e., the Tritium plume vs. the bounding isopleths) is similar. This indicates storage in the unsaturated zone remains important, and that previous releases did not generate significant groundwater mounding.
  • The highest concentrations remain in the area of IP2-SFP. This is consistent with the observed relatively high (4 to 9 feet pe r day) groundwater transport veloc i t ies and an ongoing but s maller release from the un saturated zone.
  • Interdictions made at the lP2-SFP appear to have resulted in measurable reductions in Tritium groundwater concentrations over the entire Unit 2 plume lengthl2l.

The larger reductions in Tritium concentrations are mo s t evident in the source area , closer to the IP2-SFP (see table below). ANALYSIS OF TRITIUM CONCENTRATIONS OVER TIME Well **b Tritium Concentrations (pCVL) 601 , 000 MW-RW-Wo MW-36 44 ,800 3.9 80 13,200 1,100 1,800 ',100 1 , 860

  • Sample obtained during Pumping Tesl. .. Only one samp le analyzed.

! ,<, Tritium Concentrations (pCUL) 92,000 5,950 12 , 500 6,680 1 , 600 8 , 050 9 ,9 10 4 , 500 9.100 4,860 (1) Any depth, any date at the indicated location. n;;;;-between Max. and Current Concentrations (days) 65i 6: *

  • 400 49 34 26 .. 0 0 (2) Maximum concentration , at any depth , report e d during the last project sampling event at the indicated location s. ,Cone. As Percent of Maximum 15 l3 48 40 61 76 42 100 100 120 Wh e n co mparing lhe Uni t 2 (Tritium) plum e shO",l1 on Fie ur e 9.3 wilh the bounding iso pleths presented on Figure 8.1. the analy sesl m e ihod s u se d to d e velop the bounding isop l e ih s need to be fully conside red -please refer to S<<tion 8.0. m As based on monitoring

..... ell data over the plume length down to and across the Discharge Canal to MW*37, as well as the apparent migration velocity of Tritium in lhe groundwater observed on-Site. Data from monitoring well s downgradiem of MW*37 have not been sampled ov er a s uffiCiently long period of tim e to confi rm thi s co n clus i on. Further analysis of the plume behavior will be conducted as the Long Term Mon i torin g Plan data is developed over time. 121 9.4 UNIT I STRONTIUM PLUME RERA VIOR Figures 8.2 and 9.4 illu s trate the migration paths for Strontium.

These flow paths represent Strontium originating from an ongo i ng legacy leak(s) in the IPl*FHB (see Section 8.0). This leak explains the Strontium levels detected in MW-42. This well is located in close proximity to the NCD!21, with the upper sc reen spanning the elevation of the drain (e le vation 33 feet) and the l ower s creen located approximately 35 feet below the drain elevation , Thi s well exhibits upward vertica l gradients from the bedrock into the overburden and the NCO. Therefore, a release through a crack in the Water Storage Pool wall (a l so fonns the wa ll of the FHB), for example, would flow down through the backfill and into t h e drain where it would enter groundwater near monitoring well MW-42. However, as described in Section 8.0 , the NCD is not 100% effective in bydraulically containing leaks from the IP I-S FPs. Contaminated pool water collected along the eastern portion of th e NCD is rele ased from the NCD via exfiltration as the groundwater elevations drop below elevation 33 feet towards the West; this is one so urce mechanism responsib l e for the U nit I Plume. _. ..... .. .. .. .--. . --_o r * . < Hudson -. -" " J River .; ******** * ** h* ** " .. .;.-: --, -.; -. r=_'l , . . J .-.-' BOUNDING UNIT 1 ACTIVITY ISOPLETHS III It i s no t ed that MW-42 is sc reened in the bedrock s l igh tl y No rth of the drain. As s uch. it i s located hydraulically upgradient o f thc drain. Th e drain s hould therefore form a sink between the pote nt ial leaks and the we ll. t hu s cap turi ng conlami n ant s from th e HIB furt h er South. with the well only enco u n t ering groundwuter flowing from the Nonh to the South towards the drain (Le., the well should not sample groundwater in communication with IPl*FI1B leaks). H owevcr. during rain events. it appears that th e groundwater elevations at the drain ean increase to a point where th e groundwater flow d irection is temporarily reversed (fl ows from the NCD nonhward pasl MW-42) due to the high inflows associated with storm drain leak s (storm drains being repaired.

and/or taken o ut of service).

This flow reversal can deposit Strontium on fracture su rfac es aroun d MW-42. which later c nter s the well during pur g ing. 122 The easternmost portion of t h e overall U nit 1 plum e is s h own t o exis t below th e en tire lPI-SFP s. OZA termed this the easte rn U nit 1 C B Flow P a th. Stront i um-contaminated groundwater in thi s area will migrate eith er t o the NCD or the CS B drain, depending on where the specific release point is l ocate d relative to these drains. As discussed in Section 8.0 , th e overa ll Unit I plume also extends to the West towards MW-47 and MW-56. OZA termed this the sou th western U nit I CB F l ow Path. O n ce the contaminated water enters the groundwater on the S ou th side of U nit 1. i t flows e ith er Eas t to the CS8 foo tin g drain or to the No rthwe st t owards Hudson Ri ver. depending o n the hydraulic gradient at the l oca tion where th e release r eaches th e water table. I n addition, we be liev e the bed r ock tren ch that co nt ained the Unit I Annulus*to*CSS drain creates a preferential pathway (through the backfill within the bedrock trench), further aiding th e transport of Strontium*contaminated groundwater to the We st. aZA tenned thi s the Unit 1 C SS Trench F l ow Path. Once leaka ge enters the trench , it should flow along the s l oped bottom until it finds bedmck fractures through whic h it will exfiltrate.

T hi s leakage will then fl ow t hrough the unsaturated zone along the strike/dip of the fracture s until i t encounters th e satura ted zone, and the r eafter will fo ll ow groundwater fl ow. Thi s pattern i s illu stra ted on Figure 9.4 by dashed arr ows to the We st of U nit I. h results in a s preading of Strontium*contaminated groundwate r , whi ch then fl ows with gro undwater to the Hudson River. Figures 8.2 and 9.4 also s h ow th e Strontium contamination related t o releases from l egacy pipi ng. These historic releases from the drain pipes are c urrentl y mani fest ed as sporadic. low level de t ec ti ons of Strontium in g r ou ndw ate r wells (M W-39, 41 a nd 43) along the le gacy piping. No te , as s h ow n , thi s spa t ia l di st ribut ion of contamination is not a result of groundwater cont am inant transport to t h e South; rather it i s a resul t of multiple release points a l o n g the piping. In s umm ary, thi s contamination repre sents res idual co n tami n atio n w hich has attenuated and decayed ove r time. and will n ot result i n further sign i ficant mi gra ti on. Once outside th e drain captu re zone, th e Str o ntium migrates West towards the l ower groWldwater elevations m easu red in the LP2* TY and along th e wa ll s of the Discharge Cana l along the so uthern end of the 1P2-TB (MW-36 , -55 , -37 , -49, -50 and -67) (see Figures 8.2 and 9.4). A m o re so utherl y track is nOl an ticipat ed because: I) th e higher groundwater elevat i o n s measured in MW-58 and -59 j u st to the South of the IP I TOB; a nd 2) the likely ex i ste nc e of l ow conductivity conc r e t e backfill along the in side of th e IPl*TB walls. it s subbasement, discharge piping and eastern Discharge Canal wa ll (as contraste d with the much higher conduc tivity blast-rock backfill likely u sed in the IP2-TY and along the ou t side of the IPI-TOB walls as well as adjacent to the upgradientlPI slTUct ure s). In add iti o n , as discussed in Section 6.0 and s hown o n Figure 6.2 , there are North-So uth tren din g fau l ts in th e vic i nity of MW49. MW-6 1 , and MW-66 , which are characterized by 123 clay-rich fault gouge.

In aZA's opmlOn (see Section 6.4.5), these zones of low hydraulic conductivity limit the southerly extent of contaminated groundwater.

In addition, this area is characterized by the two discrete plumes (Tritium and Strontium) commingling and following the same flow path West towards the Hudson River. We attribute this flow pattern to a zone of higher transmissivity located between Units I and 2. Also note this area of higher flow is accounted for in our groundwater flux calculations.

T he Unit 1 plume in the Transformer yard area is shown as widening due to Strontium concentrations detected in MW-ll1 and MW-36. This widening may reflect the increased thickness of the saturated zone soi l deposits around MW-Ill, or the presence of high conductivity backfill around the Discharge CanaL This conclusion is supported by the hydraulic heads that indicate groundwater flow to the North along the canal as discussed above pursuant to the Unit 2 plwne and the tracer test. West of the Discharge Canal, the Strontium pathways correspond to those described for the Unit 2 plume in Section 9.3. 9.4. t Short Term Strontium Concentrations As observed with Tritium, it appears that Strontium groundwater concentrations fluctuate, over short durations, more than can be reasonably exp lained l 24 (see Table 5.1)by a continuous release at generally constant concentration.

We attribute these fluctuations to variations in flows in the IPI*NCD, which are directly influenced by precipitation events (see Section 8.2). That is, we postulate that as flows in the drain vary, so do the concentrations and/or volumes of Strontium contaminated water being released.

9.4.2 Long Term Variations in Strontium Groundwater Variations We used the results of the last sampling event to construct the current Unit 1 plume (see Figure 9.4 and Table 5.1). In reviewing that figure (see below), note the overall configuration i s similar to that of the bounded Unit 1 plume (see Figure 8.2 125). The major difference between these flumes is the decrease in concentrations shown in the immediate vicinity of the IPI-SFp I2 . We attribute this decrease in Strontium concentrations to the increased rate of demineralization of the I P l*S FPs water (overall source of the plwne). I:):) 'I bis conclusion has been verified in the areas where the gouge was confirmed with split spoon sampling. See individual boring logs in Appendix B for funher. more detailed.

information. I l4 For example. our review of samp lin g procedures and laboratory methods did not explain the variations observed in samples collected from monitoring well MW-42. I l S When comparing the Unit I (Strontium) plume s hown on Figure 9.4 with the bounding i so pleths pre s ented on Figure 8.2, the analyses/methods used to develop the bounding isopleths need to be fully considered

-please refer to Section 8.0. 126 It should be noted that the latest data just recently received (well after the repon data-cut-off-date of August 3 1 , 2007) for MW-42 shows an increase to 46 pei/1.. This in crease, however. st ill remains within kvels consistent with an overall reduction in concentration s in this area. as attributed to accelerated demineralization orthe IP I-SFP s. 124

. -. .-,-, .. . -. . -.-' --. -. * -. __ + .--* * .; ... _.-. " '. -... ! \ \ ...... * ** , ... "

  • _ . _ .. " ". ;, .. a £... .. * ..!. . -' . -.... : c'J 1.--I....., ----_ *
  • I * ....... I. J 1 k l _': "' u * -* rw ,; -' .. ,.

... I I , 1" I .. * --, J L-.-, I H udson R iv er CURRENT UNIT I PLUME However, because of the timing of the interdictions and, we believe, the slower groundwater transport rates for Strontium, overa ll the Unit I plume has not decayed to the extent the Unit 2 plume has decayed (see Section 9.4.1). Tn fact, due to what we attribute to short tenn Strontium fluctuation s , at six of the well locations within the Unit I plume, the highest Strontium groundwater concentrations were observed during the last project samp lin g event (see the following table for additional deta il). In reviewing both figures, note th at they show what we believe are conservative estimates of the lateral distribution of the higher (25 pCi/L) Strontium g roundwat er concentrations.

125 ANALYSIS OF STRONTIUM CONCENTRATIONS OVER TIME Max. Monitoring Current ( ) Elapsed Time Current Observed II) Well Strontium between Max. Cone. As Strontium Concentration and Current Percent of Concentration (pCi/L) Concentrations Maximum -""CUL) (days) 110 MW-42 20.1 490 lS( I 37 MW*53* 37 0 100 ---3.6 MW-47* 3.6 0 100 2.7 MW-56 2.4 332 89 26.8 Ul-CSS* 26.8 0 100 21.9 MW-54 19.2 88 88 40.4 MW-55 34.0 263 84 45.5 MW-57 37.9 44 83 -----5.0 MW-36 2.3 483 46 29.8 MW*37 23.3 40 78 31 MW-50* 3 1 0 100 ------_.-25.6 MW-49* 25.6 0 100 \9.1 MW-67** 19.1 0 100" 6.2 MW_66n: 6.2 0 100

  • Cu rrent concentration is the maximum concentration ofsampJe s analyzed at this monitoring well . .. Only one sample analyzed.

(1) Any depth, a ny event. at the indicated location.

(2) Any depth, on the date of the la s t project sampli ng event, at the indicated location (3) It should be noted that the latest data just recently receiv ed (well after the report data-cut-otf-date of August 31, 2007) for MW-42 shows an increase to 46 pCilL. 126 10.0 FINDINGS AND CONCLUSIONS At no time have analyses of existing Site conditions yielded any indication of potential adverse environmental or health risk , as assessed by Entergy as well as the principal regulatory aut h orities. In fact , radiological assessments have consistently shown that the releases to the environment are a s mall perce nt age of regulatory limits , and no threat to public health or safety. In this regard , it is also important to note that the groundwater i s not used as a s ource of drinking water on or near the Site. Consistent with the purpose of the inve s tigation s, we have developed six major su pporting conclusions which are described in the following subsections.

Based on our findings and conclusions, we are recommending completion of source interdiction measures with Monitored Natural Attenuation as the preferred remedial measure. Refer to Section 11.0 for more information, including our reasons for making this recommendation.

10.1 NATURE AND EXTENT OF CONTAMINANT MIGRA nON The primary groundwater radiological contaminant s of interest are Tritium and Strontium.

Other contaminants (Cesium-13?, N i ckel-63 and Cobalt-60) have been detected , but are limited to areas that have groundwater pathways dominated by Tritium andlor Strontium, and are accounted for in Entergy's dose calcu J ations. Groundwater contamination i s limited to Indian Point's property and i s not migrating off-property to the North, East or South. The contamination migrates with the Site groundwater from areas of higher heads to areas of l ower heads along paths of le ast resistance , and ultimately discharges to the Hudson River to the West. This is supported by the bedrock geo l ogy, multi-level groundwater elevation data and the radiological re s ults from analytical testing. The nearest drinking water reservoirs are located at distance s and elevations which preclude impact s from contaminated groundwater from the Site and there is no nearby use of groundwater.

a. The Site is located over a portion of the aquifer ba s in where Site-wide ambient groundwater flow patterns , both shallow and deep. have been defined. These flow s are toward s the Site from higher elevations to the North , East and South. Groundwater flow on Site enters the Hudson River through: footing drains (which di sc harge to the Di s charge Canal); the Discharge Cana l; the storm drain system; or direct discharge.

The result s of over two years of investigations demonstrate that the off-Site groundwater migration to the South , as originally hypothe s iz ed by others prior to the se investigations, i s not occurring.

b. S u rface water samples collected from the Algonquin Creek , the T rap Rock Quarry and from the drinking water reservoirs do not exhibit impacts from the Site. c. The Hudson River i s the regional groundwater s ink for the area. We found no S i te data , published inf onnation , or other reasons s ugge st in g that g roundwater would migrate beneath the river. To the contrary , based on the a re a's hydrogeologic se tting and all available infonnalion , we are confident that groundwater beneath the Site discharges to the river. 127
d. Because of the hydraulic properties of the bedrock, the bedrock aquifer on-Site will not support large yields, o r accept input of large volumes of water. e. There are no identified off-Site uses of groundwater (extrac tion or injection) proximate to the Site that influence groundwater flow patterns on the Site. Furthennore, we have no reason to believe that potable or irrigation wells will be installed on or near the Site in the reasonably foreseeable future, in part because municipal water i s available in the area. f. Groundwate r flow at the Site occurs in two distinct hydraulic regimes that are vertically connected, bedrock and overburden soils. Most of the groundwater flow and contaminants are found in the bedrock fractures.

No evidence of large scale solut i o n features exist in t he rock cores obtained from any of the bedrock borings advanced at the Site; i.e., no ope n vo ids such as runnels, caverns, caves, etc., sometimes referred to as "u nderground rivers," were found. Our on-Site investigatory findings are consistent with that expected for the Inwood Marble. The refore, this work eliminates from concern solution feature flow associated with karst systems. The second regime i s groundwater flow in the unconsolidated soil deposits.

This includes groundwater found in native g l acial and alluvial deposits , as well as groundwater flow in anthropogenic structures such as blast rock fill and utility trenches.

These flow paths, while potentially complicating migration patterns , all terminate at th e Hudson River. g. While groundwater movement in the bedrock is controlled by fracture patterns, the high degree of fracturing allows g roundwater flow to be effect ivel y repre sented and modeled on a Site-wide scale using the well developed techniques derived for porous media l27. 10.2 SOURCES OF CONT AMlNA nON The i nvestigations identified two sources of radiological contamination.

The IPI-SFPs and the IP2-SFPrrransfer Canal. The IPJ-SFPs are the primary source of Strontium groundwater contamination, while the IP2-SFP is the primary source of Tritium groundwater contamination.

No evidence of releases from Unit 3 have been identified during this investigation.

During the course ofGZA's and Entergy's investigations, we have identified the sources of leakage associated with the IP2-SFP and Transfer Canal. These sources ha ve been eliminated and/or controlled by Entergy. Specifically, Entergy has: 1) confinned that the damage to the liner associated with the 1992 release was repaired by the prior owner and is no longer leaking; 2) installed a containment system (collection box) at the site of the leak age discovered in 2005, which precludes further release to the groundwater; and 3) identified a weld imperfection in the Transfer Canal liner that, once identified , was prevented from leaking further by draining the Transfer Canal. This weld imperfection was then subsequently repaired by Entergy (comp leted in mid December 07). Therefore , all identified leak s have been addressed.

Water likely remains between the IP2-SFP stainless 127 Wh i le fracture-specific numerical models exist, th ey are less well developed and less flexible than porous media-based models. The use ora porous media representation requires some level or approximation , particularly on small scales of tens of feet. How eve r , the fracture flow models also require substantial approximations based on fracture statis tic s and are thus , more prob l ematic a t this Site than a porous model. 128 steel liner and the concrete walls, and thus additional active leaks can not be completely ruled out. However, if they exist at ali, the data l28 indicate they must be very sma ll and of little impact to the groundwater.

Our investigations also identified the source of all the Strontium contamination detected in groundwater beneath the Site as coming from the Unit 1 Fuel Pool Complex (IP1-SFPs).

The IPl-SFPs were identified by the prior owner as leaking in the mid-1990's.

All of the pools have been drained by Entergy except the West Pool, which currently contains the last 160 Unit I fuel assemblies remaining from prior plant operations.

This plant was retired from serv ice in 1974. Following detection of radionuclides associated with IPl-S FPs in the groundwater, Entergy, as part of their already planned fuel rod removal and complete pool drainage program, accelerated efforts to further reduce activity in the IP I-SFPs through demineralization

.. T he on-Site tracer test demonstrated that aqueous releases in the vicinity of fP2-SFP are stored above the waler table in either: 1) unsaturated zone dead-end fractures; and/or 2) anthropogenic foundation details such as blast-rock backfill over a mud-mat (see Section 8.1.2). Thi s impacted unsaturated zone water is then periodically released to the groundwater ove r time as driven, for example, by infiltration of precipitation.

Consequent ly , subse quent releases 10 the groundwa t er can continue for significant durations after the initial leak has been terminated.

In addition, the tracer studies further demonstrate that the migration rates fo r the Tritium plume in the groundwa t er can be slowed down as compared to the groundwater itself. This reduction in Trit ium plume migration velocity occurs when impacted groundwate r encounters, and becomes "entrapped" by dead-end fractures, both naturally occurring fractures and those created by excavation blasting during Site const ru ction l29. The radionuclides identified in the Unit 3 area are related to historic legacy leak age f r om IP I , and reflect what remains of the plume that has been naturally attenuat ing since approximately 1 994. The pathway to the Unit 3 area was via the lPl-SFDS and then to the stonn drain system which transverses along the southeastern portion of the Site; not via groundwater flow to the South (see Section 8.2). Exfiltration from this stonn drain system had , in tum, resulted in contamination of the groundwater along the stonn drain pip in g. The Sphere Foundat ion Drain Sump no longer discharges to the stonn drain system and this legacy release pathway had therefore been tenninated because the associated piping was capped in 1994. 128 These data include: monitored water levels in the SFP. with variat i ons accounted for based on refilling and evaporation volumes: th e mass of Tritium migrating with gr oundwatcr i s sm all: and the age of the water i n the interstitial sp,ace. 1.9 Once co ntaminant s enter dead*end fractures , they no longer migrate w ith th e groundwatcr flow. H o wever, this **entrapped contamination*'

does re*enter the flow regime over time due to turbulent flow mixing at the fracture opening as well as diffusion.

129 10.3 GROUNDWATER CONTAMINANT TRANSPORT Based on our assessment of the bedrock's hydraulic properties , the area's hydrogeologic se tting, the properties of the contaminants, the age of the releases, interdictions made to eliminate or reduce release rates, and the distances between the source areas and the Hudson River, we believe the groundwater contaminant plumes have expanded to their maximum extent and are now decreasing in size. tn this regard , the Unit 2 Tritium plume is decreasing faster than the Unit I Strontium plume, as anticipated.

These conclusions are based on the data available which, given the aggressiveness with which Entergy implemented the investigations, is compressed in duration l JO , Therefore, ultimate confirmation of these conclusions will require monitoring over a number of years to allow ranges in seasonal variation to be adequately reflected in the monitoring data. During long term monitoring, GZA further anticipates that contaminant concentrations in individual monitoring wells will fluctuate over time (increasing at times as well as decreasing, as potentially related to precipitation events), and that a future short term increase in concentrations does not , in and of itself, indicate a new leak. In addition, it is also expected that some areas within the plumes will ex hibit faster decay rates than others. Both behaviors are commonly observed throughout the industry with groundwater contamination sam pling and analyses, and therefore, conclusions pursuant to plume behavior must be evaluated in the context of all of the Site-wide monitoring data. Overall , however, aZA believes that the continuing monitoring will demonstrate decreasing long term trends in groundwater contaminant concentrations over time given the source interdictions completed by Entergy. It is also further emphasized that even the upper bound Tritium and Strontium groundwater concentration isopleths presented on Figures 8.1 and 8.2 result in releases to the river which are only a small percentage of the regulatory limits , which are of no threat to public health. a. T he major groundwater tran sport mechanism is advection.

Sorption retards the migration of radiological contaminants other than Tritium relative to groundwater advection rates, while Tritium, within hydraulically interconnected fractures, can migrate at rates that approach the groundwater se epage velocity.

b. The Unit 2 contaminant plume is characterized by Tritium in the groundwater.

Over the last two years, the highest Tritium concentrations in the Unit 2 plume have decreased (see Table 5.1 and Figures 8.1 and 9.3). However, the center of mass of the Unit 2 plume i s not rapidly migrating downgradient , and remains in proximity to the IP2-SFP. While a small active leak can not be ruled out completely, this behavior is also consistent with the identified role of unsaturated zone (above the water table) storage of historic releases, with precipitation

-induced infusion of this entrapped water into the groundwater regime over time. c. The Unit I contaminant plume is primarily characterized by Strontium concentrations in the groundwater, though near the physical pool area o ther isotopes are present as expected due to proximity.

Over the last two years, the highest Strontium concentrations in the Unit I plume have decreased (Tab le 5.1). These decreases in concentration are consistent with a reduction in Strontium IJQ It is noted that a number of key monitoring installation s have only recently been comp let e d. and monitoring.

round s sp ann i n g multiple seaso n s are not yet availab l e. 130 10.4 concentrations in the Unit I West Fuel Pool via pool water recirculation through demineralization beds. While the physical l eak(s) in this fuel pool still exist, the source tenn to the groundwater has been reduced through reduction in the contaminant concentrations in the leak water. It is noted , however , the U nit 1 Strontium decreases are more modest and are generally more limited to the immediate source area than that observed for Tri tiu m at Unit 2. The slower rate of plume decay is not unanticipated give the adsorption properties of Strontium, Further planned interdictions include removal of the fuel rods and draining of the pool water, which will pennanently eliminate the West Fuel Pool as well as the entire IPI-SFP complex as a source of contamination to the groundwater.

With elimination of this source , natural attenuation will reduce Strontium concentrations in the Unit 1 plume over time. GROUNDWATER MASS FLUX CALCULATIONS Dur ing the project (over the past two years), as testing progressed and more information became avai lable , we refined methods to calculate the groundwater flux and associated radiological activity to the Hudson River, As described below , we have developed a procedure which i s scien tifi ca lly sound , re lativ ely straight-forward, and appropriately conservative.

G roundwater flow rates are provided to Entergy , who computes the radiological dose impact. a. Migration of radionuclides to the river is computed based on groundwater flow r ates, in combination with contaminant concentrations within the flow regime. Th is information is then used in surface water models to compute radiological contaminant concentrations in the river and thus potential dose to receptors.

b. To assess the validity of the precipitation mass balance method used to date for computing groundwater flux ac r oss the Site , aZA also performed groundwater flux computations using an independent method based on Darcy's La w. Thus, the results from two widely accepted groundwater flow calculation methods were compared against each other. The fir st, the precipitation mass balance method, is a " top-d own" procedure based on precipitation-driven water balance analyses.

The second , based on Darcy's Law, is a "bottom-up" method using hydraulic conductivity and flow gradient measurements.

These two methods resulted in estimated groundwater flow values which were in agreement , providing a high degree of confidence in the values obtained relative to their impact on subsequent dose computations and risk analyses.

c. The original groundwater flux computations were developed for two separate areas of the Site. The northernmost area included both the Unit 2 and Unit 1 plumes. The southernmost area encompassed Unit 3, This bifurcation of the Site was established given: 1) the co-location of the Uni t 2 plume and the Unit 1 plume near the western boundary of the Site just upgradient of the river; 2) the much lower contaminant concentrations in the Unit 3 area; and 3) the amount of data available at that time. Current data, derived from a greater number of groundwater e levation and samp ling points than reflected in ear li er data, show the Site can be divided into six separate areas, The computations were further separated into sha llow and deep flow regimes given: 1) the generally higher hydraulic conductivity in the shallow 131 portion of the bedrock, and 2) the general l y more elevated contaminant concentrations in the shal10w flow regime. d. The groundwater contaminant concentrations used for the radiological dose computations were obtained primarily from the ana l ysis of samples taken from the recently completed multi-level wells specifically installed for this p'ffi'0se.

These wells are located downgradient of the Unit 2 and Unit 1 infrastructure!)

and are positioned within the plumes and just upgrad i ent of where the groundwater discharges to the river and Discharge Canal. The multi-level nature of these wells allows the groundwater to be sampled over at least five separate elevations in the bedrock, in addition to the overburden l ayer above. Sampling zones specifically targeted the most pervious depths within the bedrock borehole s. As s uch, the groundwater samples encompass the full depth of the contaminant plume, from the upper soil zones to depths where the contaminant concentrations have fallen off to insignificant levels. The high number of samples over the depth of the plume provide s a higher degree of confidence that the significant flow zones are accounted for. The high number of vertical sampling zones also provides a higher level of redundancy relat i ve to the longevity and efficacy of the monitoring network over time. 10,5 GROUNDWATER MONITORING The current groundwater well and footing drain monitoring network is consistent with the obj e ctives of the NEI Groundwater Protection Initiative l 32. Wells have been installed and are currently being monitored to both detect and characterize current and potential future groundwater contaminant migration to the river, as well as , in concert with specific footing dra in monitoring, provide earlier detection of potential future leaks associated with the existing infrastructure.

a. The network of 59 mon i toring well locations and over 140 sampling intervalsllocations, has allowed us to identify groundwater flow patterns.

A subset of this network will provide an adequate long tenn monitoring system. b. Existing and potential sources have been identified, and monitoring is in place to both evaluate current conditions and identify future releases, should they occur. c. The nature and extent of cornamination is known and reporting requi r ements are in place. 10.6 COMPLETENESS Inv es tigations at the Site have been broad, comprehensive, and rigorous.

Ma j or components of the field studies include: detailed acquisition of geologic infonnation; automated long duration collection of piezometric data; vigorous source area \3 1 The multi-level sampling network is concentra ted in the Unit 2 and Unit I areas given that this is wh e r e co ntaminant conc e ntrations are by far the highest. The individual monitoring well s located downgradient of Unit 3 are judged suffic ient for computations in this area given the low contaminant concentra ti o n s measured, even in the typically more contaminated s hallow flow regime. 1)2 NEI developed a set of procedures/goals for nuclear plants to assess the potential for releases of radionuclides to pote n tially migrate off-Si te. 132 identification; comprehensive aquifer property testing, including perfonnance of a full scale Pumping Test; and large*scale confirmatory contaminant transport testing, in the form of an extensive tracer test. The results of this systematic testing program are in agreement with conditions anticipated by our Conceptual Site Model. Based on our review of findings, we have concluded that the field studies conducted at the Site have addressed the study objectives.

a. There is no need t o monitor groundwater at off*Site locations.

The density and spacing of on*Site monitoring wells i s adequate to: 1) demonstrate that contaminated groundwater is migrating to the Hudson River to the West , and not migrating off of the property to the Nonh , East or South; 2) monitor the anticipated attenuation of co ntam i n ant conce ntrati ons; 3) identify future releases , should they occur; and 4) provide the data required to compute radiological dose impact. h. Hydrau lic conductivity is the most important aquifer property.

We have completed more than 245 hydraulic conductivity tests, including a full*scale Pumping Test. Therefore, we believe no future aquifer testing is required.

In addition , the contaminant plumes have reached their maximum spatial extent. Therefore, there is no need for contaminant transport modeling.

c. The sources of re l eases to the groundwater h ave been identified.

In additio n to monitoring, act i ons have been taken to reduce or eliminate these releases.

Therefore, we believe no future source characterization is required.

d. All infonnation indicates Monitored Natural Attenuation is the appropriate remedial response and i s GZA's reco mmended app r oach (see Section 11.0). The existing monitoring network wi ll serve this remedial approach.

Therefore, no design phase studies are required.

133 11.0 RECOMMENDATIONS Based upon the comprehensive groundwater investigation and other work perfonned by Entergy, aZA recommends the following:

1. Repair the identified Unit 2 Transfer Canal liner weld imperfection (completed mid December 2007); 2. Continue source term reduction in the Unit 1 pool via the installed demineralization system; 3. Remove the remaining Unit I fuel and drain the pool s; and 4. Implement long term monitoring consistent with monitored natural attenuation , property boundary monitoring , future potentia l leak identification , and support of ongoing dose assessment.

It is GZA's opinion that our investigations have characterized the hydrogeology and radiochemistry of the groundwater regime at the Site. Therefore, we are not recommending further subsurface investigations (see Section 10.0). Based upon the findings and conclusions from these investigations , as well as other salient Site operational infonnation. we recommend the completion of s ource interdiction measures with Monitored Natural Attenuation (MNA) as the remediation teclmology at the Site. In no small part , this recommendation is made because of the low potentia l for ri s k associated with groundwater plume discharge to the Hudson River. Monitored Natural Attenuation is defined by the United States Environmental Protection Agency as the reliance on natural attenuation processes (within the context of a carefuUy controlled and monitored clean up approach) to achieve Site-s pecific remedial objectives within a time frame that is re asona b l e compared to other methods. The "na tural attenuation processes" that are at work in the remed i ation approach at this Site include a variety of phy s ical, chemical and radiological processes that act without human intervention to reduce the activity, toxicity, mobility , volume, or concentration of contaminants in soil and groundwater.

These primarily include radiological decay. dispersion.

and sorption.

MNA is typ ically used in conjunc t ion with active rem e diation measures (e.g., source control), or as a follow-up to active remediation measures that have already been i mplemented. At IPEC , active remedia1 measure s already implemented include e l imination (e.g., repair of the Unit 21990 liner leak and repair of Transfer Canal weld imperfection in mid-December 2007) and/or control (e.g., installation of a collection box to capture moistufe from the IP2 shrinkage cracks) of active leaks , and reduction of the source term in t he Unit 1 fuel s torage pool through with subsequent planned removal of the source term (fuel rods) followed by complete draining of the LPI*SFPs. Remediation

1. OUf recommendation of MNA principles include s source term contaminant reduction as an integral pan of this remediation strategy.

Data demonstrating plume concentration reduction s over time , as considered along with other salient 134 Site infonnation, are consistent with a conclusion that the interdiction efforts to date (both current and in the past) h ave resulted in: 1) tennination of the identified Tritium leaks in the IP2-SFP; 2) identification of an imperfection in a Unit 2 Transfer Canal weld which h as been repaired;

3) reduction in IPl*SFP contaminant concentrations; and 4) elimination of Sphere Foundation Drain Sump discharges to the storm drain piping East of Unit 3. As such, these interdictions have resul ted in the elimination andlor control of identified sources of contamination to the groundwate
r. as required:
a. Over the last two years, the highest Tritium concentrations in the Unit 2 plume have decreased.

These data are consistent with a conclusion that the leaks responsible for the currently monitored Tritium plume are related primarily to the previously r epa ired 1992 l egacy liner leak and the imperfection in the Transfer Cana l weld. With the implemented physical containment of the associated 2005 "concrete wall crack leaks" and the repair of the Transfer Cana l liner, the source of contamination to the groundwater has been reduced and controlled.

b. Over the last two years, the highest radionuclide concentrations in the Uni t 1 plume have decreased.

These decreases are consistent with a reducti on in the concentrations in the Unit I West Fuel Pool via pool water recirculation through demineralization beds. While the physical leak(s) in thi s fuel pool still ex i st, the source tenn to the groundwater has been reduced due to treatment of the source water. Further planned interdictions include removal of the fuel rod s and draining of the pool water , which will permanently eliminate the West Fuel Pool as a source of contamination to the groundwater.

c. The Unit 1 plume in the Unit 3 area has been attributed to a historic legacy discharge from the Sphere Foundation Drain Sump (SFDS) through the stonn drain system which traverses along the southeastern portion of the Site. Leaks from this s t onn drain system have. in turn , resulted in past contamination of the groundwater along the storm drains, with subsequent groundwater migration westward , through Unit 3 toward the river. The SFDS no longer discharges to the stonn drain and the Strontium concentrations in the Unit 3 groundwater have decreased to low levels, consistent with natural attenuation processes.
2. GZA se l ected Monitored Natural Attenuation as the remediation strategy because: a. Interdiction measures undertaken and planned (0 date have, or are expected to, eliminate/control active sou rce s of groundwater contamination.
h. Groundwater flow at the Site precludes off-Site migration of contaminated groundwater to the North, South or East. c. Consis tent with the Conceptua1 Site Model, no contaminants have been detected above regional background in any of the off-Site monitoring locations or drinking water supp l y systems in the region. d. The only on-Site exposure route for the documented contamination is through direct expo sure. Because the majority of the Site is capped by 135 impenneable surfaces, there is no uncontrolled direct contact with contaminants.
e. Our studies indicate that under existing conditions, the spatial extent of the groundwater plume will decrease with time. f. Groundwater is not used as a source of drinking water on the Site or in the immediate vicinity of the Site , and there is no reason to believe that this practice will change in the foreseeable future. g. Groundwater associated with the Unit 1 foundation drainage systems is captured and treated to reduce contaminants prior to discharge to the Discharge Canal , consistent with ALARA principles.
h. At the location s where contaminated groundwater discharges to the Hudson River, the concentrations have been, and will continue to be, reduced by sorption , hydrodynamic dispersion and radiological decay. No detections of contaminants associated with plant operations have been found in the Hudson River or biota sampled as part of the required routine envirorunental sampling.

I. More aggressive technologies would alter groundwater flow pattern s and , therefore , in our opinion, offer no clear advantages.

Long Term Monitoring

1. The second primary requirement for implementation of MNA is a demonstration that contaminant migration is consistent with the Conceptual Site Model. In particular , rigorous monitoring is required to demonstrate reductions in source area contamination, reductions in plume contaminant concentrations, and reduction in contaminant discharge to the river over time. The initial implementation stages of this monitoring process were begun nearly two years ago as part of the investigations summarized herein. A s outlined above, reductions in maximum groundwater plume contaminant concentrations have already been documented.

T he elements for long term monitoring , consi s tent with the objectives of the NEl Groundwater Protection Initiative , are in place. We further note: a. Groundwater wells have specifically been installed , and are currently being monitored , to both detect and characterize current and potential future off-Site groundwater contaminant migration to the river. Additional wells have also been installed for monitoring of other Site property boundaries.

b. Monitoring well s have also been installed just downgradient of identified critical Structures, Systems and Components (SSCs). These wells, in concert with specific footing drain monitoring , provide earlier detection of potential future leaks associated with the power generating units than would be po s sible with boundary well s alone. c. Monitoring wells have been strategically placed to monitor the behavior of the plumes identified on the Site. d. MW-38 and MW-48 should be excluded from the monitoring plan as samples from these wells are generally indicative of a mixed groundwater 136 and Discharge CanaUriver water condition and, therefore, are not completely groundwater specifi c lJ3. e. The long term monitoring plan should include action levels, which if exceeded, trigger further analysis and/or investigations, potentially leading to implementation of an interdiction plan, if required.
f. A number of individual vertical sampling zones were included in nearly all the monitoring well installations, particularly within the contaminant plumes and at the location of plume discharge to the river. These individual vertical monitoring zones provide a significant level of vertical resolution and also provide a substantial degree of redundancy relative to the longevity and efficacy of the monitoring network ove r time 134. g. While previous and current dose calculations are both reasonable and conservative, we recommend that, with the accumulation of additional Site-specific hydrogeologic information , the calculations be modified to incorporate Site-specific transmi ss ivities and groundwater gradients.

Entergy has agreed that Site-specific model information will be utilized in the next NRC required annual assessment of dose from this pathway. Our specific recommendations (which will include additional trend information in early 2008) will be provided under separate cover for Entergy's incorporation to sup port the annual report. III Sce Section 6.6.3 for funher discussion pursuant to this conclusion.

1 14The l evel of redundancy designed into the long term monitoring network anticipates and allows for the loss of a number of monitoring zones without significant impact to the adequacy of the monitOring system. 137

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