ML17138B031
| ML17138B031 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 01/02/1980 |
| From: | Bivins W NRC OFFICE OF STANDARDS DEVELOPMENT |
| To: | Sells D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8001230189 | |
| Download: ML17138B031 (24) | |
Text
Docket Nos.60-387
'nd 50 388 JAN 0 8 1980 t/IElIRANDtJN FOR:
Donald E, Se'(is, Act)ng Chief Environmental Projects Branch No. 2, DSE THRU:
FR$2r SUBJECT<
L. G, Hulman, Chief Hydrology-Meteorology Branch, DSE H
S Bivins Leader llydrologic. Engineering Section,
- Hb18, DSE HYDROLOGIC EHGINEERING INPUT TO THE DRAFT ENVIRONMENTAL STATEMENT SUPPLEf~)EHT - POND HILL RESERVOIR EVALUATION PLANT HAt2E; Susquehanna StearmElectric Statidn, Units 2 and 2 LICENSING STAGE:
OL RESPOi<SIBLE BRANCH:
EPB102; S. Baj<<aEPH Enclosed
)n the hydrologic engineering input to the Draft Environmental Statement.
TAis input contains hydrologic engineering descriptions and evaluations related to the augmentation reservoir the applicant is pro posing to build on Pond Hill Creetc.
Due to insuffMient information from the applicant <<e are unable to reach conclusions with respect to the siting of the pumping plant in the floodplain consistent <<ith the guidance of'.O.
3.2988 << Floodplain Management, In addition, our analysis indicates that the hydrologic design of the dam pr'obably does not meet the criteria <<e use for {radiologically) safety~related dR~s which is similar to the criteria used by other Federal agencies that de-sign, construct, operate and regulate dams.-
If you have any quesCions regarding this matter, please contact ll; Fliegel on extension 28028.
Or<.I",<.'-'-"-i
>>"-P>>11"< >7>>
Z02'ry I Jo>we on ll., S, Bivins, Leadei Hydrologic Engineering Section Hydrology>>fleteorology Branch Division of Site Safety and Environmental Analysis SURNAME~
c DATE~
See attach E closure DPPIcE3PA QSE J3HB+
.dNHEj ieg.ej mg 1Z/ /'79...--
.L.GUS.man
...I,RJggZ79 NRC FORM 318 (9-76) NRI 0240 4 V, 6, OOVERNMENT PRINTINS COPPICE<
ISTS d2d d24 Olgap
C
/
4 h
il t
l> g h
k'
V
~
kW w Jgn 02 1980 Donald E. Sells 2
can s>/enclosure
- 0. Muller M. Kregev L. Hulman G. Lear B, 9>.Youngblood H. Bivins N. Fliegel S.. Bagwa NRC PDR LPOR aCRS (lS)
'OFF IC SURNAM 2)ATE'$
NRC FORM 318 (9 76) N RGB'24 ll.S GOYEIIN'iENTPRINTING OFFICEI l979.269.369 p
~
t 4
~ C
Dock t Nos; 50-387 and 50>>388 gag 02 1980 MEMORANDUM FORr Qooald E. Sells, Acting Chief En, ironmental Projects Branl.h No, 2, DSE THRU:
SUBOECTi L, G". Hulman; Chief Hydrol y~Neteorology Branch, DSE FRoN;
'h sh Biv:qs, Leader, Hydrologic E gineer ing Section, HNB, DSE HYDROLOGIC ENG NEERING INPUT TO THE DRAFT ENVIRONMENTAL STATEMENT SUPPL8(ENT 'OND HILL RESERVOIR EVALUATION v
PLANT NAMEB Susquehanna Steam Electr
, Station, Units 1 and 2
LICENSING STAGE!
OL RESPONSIBLE BRANCH!
EPB82; Sh Bajwa, EPN Enclosed )s the hydrologic engineer ing input 'ho the Draft Environmental Statement; This input contains hydrologic engineering descyipt)ons and evaluations related to the augmentation r'eservoir the applicant is pi'omposing to build on Pen'd! Hill Creek.
Due to insufficient information from the ap~licant we are unabTe to reach conclusions with 'respect to the siting of the',pumping plant in the flood-p'lain consistent with the guidance of E.O>>
11988 ~ Ffoodplain Management.
In addition, our analysis indicates that the hydrologic dhgign of the dam may not meet the criteria used for (radiologica'liy) safety-relathgdams; If you have any questions regarding this matter, gtleasei,gontqct fifi. Fliege'l on extension 28028.
Enclosure!
As Stated cc!
See attached page I
t3".'., S,'IBivins, Leader Hydrologic Engineering Section Hydrology>>tfeteorology Branch Division of Site Safety and Environmental Analysis ajar (Ffi.'filgr MHFliegel:km 12J19 j'79 OFFICE)
SURNAME D.ATE/
NRC FORM 318 (9.76) NRCM 0240 DR:H B
'HSBivins an
,.12/P
/79
+U S ~ GOVERNMENT PAIN NG OFFICEs 1979.289 369
lV
~v
~
~
I 7
t p1
I'k
/1
Docket Nos.
6 307 and
~0-308 02 1980 ffEMORAHDI) FOR:
Donald E. Sells, Acting Chief Environmental Projects Branch No. 2, DSE FROID:
SUBJECT:
L. G. Hulman, Chief Hydrology~~feteoro Togy Branch, DSE M. S.. Bivins, Leader, Hydrologic Engineering Section, HNB, DSE HYDROLOGIC ENGINEERING INPUT TO TflE DRAFT ENVIRONMENTAL STATEMENT SUPPLEMENT POND HILL RESERVOIR EVALUATION PLANT NAKE:
Susquehanna Steer Electr ic StationUnits I and 2 LICENSING STAGE:
OL RESPONSIBLE BRANCH:
EP882; S, Bajtsa, EPt4 W
Enclosed is 'the hydrologic engineering input to the Draft Environmental Statement.
This input contains hydroIogic engineering descriptions and evaluations related to the augmentation reservoir the applicant is proposing to build on.Pond;Hill Creek.
Due to insufficient information from the applicant'e are unable to reach conclusions
<arith respect to the siting of the pumping plant in the flood-plain consistent trith the guidance of E 0 1'l988 Floodplain Management.
In addition, our analysis indicates that tl>e hydj ologic design of'he dam may not meet the criteria used for. (radiologically) safety-related dams.
If you have any questions regarding this matter, please!contact tf, Fliegel on extension 28028,.
Enclosur e:.
As Stated cc:
See attached page
. Or~S~nG~ 33QneQ f3/'Ter~5.
Johnson (f> S.', Bivins, Leader Hydr'ologic Engineering Section
'ydrology-~feteorology Branch Division of Site Safety and Environmental Analysis DSE:HMB,
....DSZ:eB......... USE;;HIfB....
"HHFliege1.:k... MSE)vi.ns...
".12/19/29..........12/..... /79 OFFICE P
.LGHulman
...1,2/..../.79......
SURNAME DATE$
NRC FORM 3j8 (9 78) NRCM 0240
- U.S. GOVERNMENT PRINTING OFFICE: 1979 289 389
0 1
r ~
E C
4 1
~
(
n t
Q lh
~
r fl g
III o
E 1
I I
'l t
I C
Donald E. Sells cc:
M!enclosure D.
Nu)1'.
Kreger L. Humean G. Lear 8, 0.Youngb)ood tt, Bfvins N. F>fege't S~ BB)L'la HRC PDR LPOR ass (18)
OFFICE)
SURNAME DATE/,
NRC FORM 318 t9.78) NRCM 0240 kU.S. GOVERNMENT PRINTING OFFICE: 1979 289.389
0 4
C P
~
N L>>
b I
,HYDROLOGIC ENGINEERING INPUT TO THE DRAFT ENVIRONMENTAL STATEMENT SUPPLEMENT POND HILL RESERVOIR EVALUATION SUS(UEHANNA:;STEAM, EEECTRIC STATION UNITS I AND 2.
DOCKET-'NUMBERS 50-38?"AND 50-388 2.3.2 2.3.2.3 Hydrology Pond Hill Reservoir Pond Hill Creek is located in a small valley on the east bank of the Susquehanna River about 3.7 kilometers (2.'.3 miles) upstream from the Susquehanna Steam El'ectric Station.
The stream;flows generally west to its confluence with the Susquehanna River;
.The north stream valley slope is steep,, with a. ridge line 215 to 245 meters (700"to 800 feet) above the valley floor.
The valley side on the south is flatt'er with a ridge line about 60 to 90 meters.
(200 to 300 feet) above the -stream bed.
The stream is. steep, dropping about 150 meters (500 feet) between its upstream end near Lily Lake (which does not drain to Pond Hill Creek) and the Susquehanna,.
a distance of just over three kilometers (two miles).
The drainage area of the stream above the proposed site of the dam is 329 hectares (1.2T square. miles).
This upper section of'he stream, which would be inundated by the proposed reservoir, has an average gradient of about 11 meters per kilometer (57 feet per mile).
The stream bed is mostly silt,. mud, and gravel.
The stream width ranges from 0.8 to 3.7 meters (2.5 to 12 feet) with an average of about'.2 meters (7.1 feet), Oepths. range.
from 3'o 40 centimeters (0.1 to 1.3 feet).
The lower portion of the. stream is much steeper than the upper, the average gradient being about 71 meters per kilometer (375 feet per mile).
The width ranges from 0.9 to 4.3 meters (3 to 14 feet), with an average of about 2.6 meters. (8.6 feet).
Oepths range from 3 to 40 centimeters (0.1 to 1.3 feet).
The stream, substrate is mostly bedrock and boulders with some rubble and isolated patches of gravel.
There are several small and one relatively large, waterfalls in. this section of the stream.
.Because there is no gaging station on the stream, no information on historic flows was, obtained.
The applicant did, however, estimate flood flows using. standard hydrologic methods.
The estimated 4 percent chance (25-year recurrence) flood flow is 39.3 cubic meters per second (1387 cubic feet per second),, the I percent chance (100-year) flood flow is 49.7 cubic meters per second (1756 cubic feet per second),
and the estimated probable maximum flood flow is 202 cubic meters per second (7120 cubic feet per second).
In addition,. the methodology utilized by the Pennsylvania Oepartment of Environmental Resources to estimate the seven-day ten-year low flow results in a flow of 0.005 cubic meters per second (0.02 cubic feet per second).
It is. probable, however, that the stream does not flow at all during drought periods..
The floodplain of Pond Hill=Creek below the proposed site of the dam is very narrow and is shown in figure (Plate 17 of Nov. 13, 1979 submittal).
The floodplain of the Susquehanna River in the vicinity of the proposed location of the pumping station is shown in figure (Exhibit 3 of Nov 13, 1979 submittal as revised in response to Nov. 30,. 1979 HES question 8).
Data from borings and wells indicate that the. groundwater contours in the vicinity of the proposed reservoir generally follow the surface contours.
On the ridges north and south of the stream channel, ground-water was: usually encountered between 4 and 15 meters (13 and 49 feet) below the surface The stream valley contains several marshes and springs, i.e., groundwater sinks:
Water Sources The applicant's investigations have revealed no users of Pond Hill Creek at present.
Host. of the nearby residences obtain water from individual wells.
There are no wells within the proposed. project boundary.
H drolo ic Im acts of Construction Various, aspects of the construction of the project will increase the erosion potential'ithin the Pond Hill Creek watershed.
This can result in increased turbidity and sedimentation in the stream.
The applicant has stated that construction practices to minimize erosion and control sedimentation will be employed.
This will include the use of diversion
- ditches, hay bale check dams, and sediment traps.
The applicant has
4 stated that the.'contractor will be required'to submit a plan for erosion control that is consistent with the approach that will be developed in cooperation with reviewing agencies including the Pennsylvania Department of Environmental Resources.
The applicant has also committed to storing topsoil stripped from work areas for use in re-landscaping of exposed areas following construction.
If properly implemented,, the erosion control program can minmize the potential impacts of construction.
Stripping. of vegetation from the area to be inundated and from other P
areas will increase the runoff coefficient, resulting in higher peak.
flows. in Pond Hill Creek.
However, since this effect will be temporary (the dam when complete, will'rovide:flood control for the remaining section of the-stream) and since there are. no residences that can be affected by the higher, stream flows,we conclude that the impact is minimal..
The major hydrologic impact of the construction of the dam is to convert
,a natural
- stream, Pond HilT Creek, into a reservoir and a stream whose maximum and minimum flows will be controlled.
The hydrologic aspects of.
the stream before construction are discussed in Section 2.3.2.3.
The upper portion of that stream will be replaced by a, reservoir with a normal or full pool elevation of 981 ft. MSL.
This reservoir would cover 127 hectares (315 acres) and contain approximately 29.7 x 10 cubic meters (24,100 acre-feet) of water..
The maximum depth during normal pool elevation would be about 67 meters (220 feet) and the average depth would be 23.3 meters (76.5 feet).
The applicant ased the HEC Mater guality Yodel to simulate the thermal behavoir of the reservoir.
The model results are sensitive to calibration constants-which can only be determined by field measurements.
For the Pond. Hill thermal simulation, the vertical eddy diffusion coefficients were estimated by comparison with similar lakes and reservoirs.
In addition,. the analysis was performed for the smaller reservoir originally proposed by the applicant.
- Regardless
. the results, are useful in that they provide a general description that should be representative of the proposed reservoir.'.s, thermal characteristics.
The HEC model predicted that the proposed reservoir would be thermally stratified during the summer with turnovers and mixing in early spring and late fall.
A relatively stable thermocline was predicted to form in late April and remain throughout the rest of the spring, summer and early fall through October; The model predicted an epilimnion (upper layer) approximately 4.6 to 6'.1 meters (15 to 20 feet) thick with summer temperatures between 20 and 25 C..
Temperatures in the hypolimnion (lower layer) were predicted to range-from 5
to 10 C.
Water will be conveyed between the inlet-outlet structure in the reservoir and the pumping plant at the Susquehanna River,. via pipeline.
Portions of the pipeline will be buried,, including the section under the dam, but a large section of the pipeline will be within an unlined tunnel.
Just below the dam an offshoot of the main pipeline will run to the stream.
This will be used to divert natural streamf low during the construction of the dam and later, as described. in section 4.3.2, to supply conservation flow to the stream.
The proposed'ocation of the pumping station is in the floodplain of the Susquehanna River.
The hydrologic effect of the;"pumping plant's location is to reduce the cross-sectional area available for flood waters resulting in higher water levels upstream.
The maximum increase in upstream flood, I
- levels, based on a conservative computation, during the one percent chance flood (100 year flood) could not be greater than 19 cm (7.5 inches).
A more realistic (and complex) analysis-would show the effect-to be smaller.
The maximum increase in water level would be immediately upstream of the pumping station, with the effect rapidly I
~
~
decreasing further upstream.'
H drolo ic Im acts of 0 eration Mater Su The Pond Hill Reservoir is proposed to provide replacement for Susquehanna River water consumed by the Susquehanna
'Steam Electric Station during periods of low flow as defined in 18 CFR Part 803.
The low flow criteria is the seven-year,,
ten-day (g7-10) low flow of the Su'squehanna River plus the consumptive water use= of the power plant.
At Wilkes-Barre, the g7-10 is estimated to be 22.7 cubic meters per second (800 cfs).
Thus, the requirement for replacement of consumed water becomes effective. whenever the river flow at Wilkes-Barre is. below 22.7 cubic meters per second (800 cfs) plus the plant's actual measured consumptive use.
Average-plant consumptive use is estimated to be 1.4=cubic meters per second (50 cfs) with the maximum estimated to be 1.8 cubic meters per second (64 cfs).. Therefore, water replacement may be required when flow at Wilkes-Barre is below 24.5 cubic meters per second (864 cfs).
The reservoir was designed to be able to supply the required replacement water to the Susquehanna River during a recurrence of the drought of record (August to November, 1964).
Ouring that drought there were 106 days (including one period of 85 continuous days) when the flow at Wilkes-Barre was below 24.1 cubic meters per second (850 cfs).
(There was only one additional day when the flow was below 24.5 cubic meters per second
(864 cfs). If it were assumed that the maximum consumptive use occurred on that day,. the conclusions would not change significantly. At normal full. pool; the reservoir contains approximately 29.7 x 10 cubic meters (24,100 acre-feet) of water. with approximately 27.1 x 10 cubic meters I
(22,000 acre-feet) available for release. If released at an average rate of 1.4= cubic meters, per second (50 cfs) the estimated average plant consumptive use,. there-is enough water for over 220 days without.refilling:
the reservoir.
The applicant has assumed a higher release rate of about 2.9 cubic meters per second (104 cfs).
At this rate,'the reservoir's available storage would be used up on about.106'days, which is the number of days that replacement water would be required during a repeat. of the drought. of record.
b At the assumed average release rate of 2.9 cubic meters per second (104 cfs),
an average of 1.4 cubic meters per second (50 cfs) would be needed for replacement of plant water consumption and 1.5 cubic meters per second (54 cfs) would be avai lable for other uses.
During times of greater plant water consumption the water available for other purposes would be reduced.
At the maximum estimated plant consumption rate of 1.8 cubic meters per second (64 cfs), approximately 1.1 cubic meters per second (40 cfs) would be available-for other uses.
The applicant states that the reservoir could be refilled with water from the Susquehanna River at a rate of 3.7 cubic meters per second (132 cfs).
I~
At this rate it would take approximately 84 days to refill the reservoir.
However, the applicant has stated that refilling will riot occur at times when the flow in the Susquehanna River is below 85.0 cubic meters per second (3000 cfs).
Even w'ith this;restriction, 'it is almost:certain
~J r
that 'the reservoi'r wouTd. be refHied prior.", to the:. next 'low. flow,
=
Pond Hill Creek The. operation of the Pond Hill Reservoir will change the character of the remaining portion of Pond Hill Creek, primarily during periods of high and low flow.
Most of the time, with the reservoir full, surface flow intoor rainfall onto, the reservoir will be. released through the spillway.
This fl'ow will be directed to the remaining lower portion of Pond Hill Creek..
The repl'acement-of approximate'Iy 39 percent of the upper drainage area of the stream with a reservoir will increase the flow at the spill-way during moderate storms.
However, during severe storms, the discharge will be limited; by the cross-sectional area-of the spillway.
The excess inflow to. the'eservoir will be accomodated by a rise in water-level.
The applicant analyzed. the system response during a 1 percent chance flood (100 year recurrence flood).
The analysis indicated that under natural conditions, the peak stream discharge would be about 49.7 cubic meters per second (1760 cfs).
The calculated peak inflow (overland flow into and rain-
\\
fall onto) to the reservoir was estimated to be about 60.8 cubic meters per second (2150 cfs).
However, the peak discharge through the spillway was calculated to be only 0.84 cubic meters per second (30. cfs).
The reservoir, therefore, serves to consideraly attenuate the effects of the flood on the downstream portion of the stream.
~s I
Normally, with the reservoir at full pool elevation of 981 feet MSL, all inflow to the upper'portion of the watershed will pass to the lower portion of the stream via the spillway.
'fhe applicant has stated,
- however, that a minimum flow of 0.005 cubic meters per second (Oe2 cfs) will be.
maintained.
A section of pipeline, connected to the reservoir-to-pumping plant pipeline immediately downstream of, the dam will be used for'his purpose.
The release point will be between the toe of the dam and the spillway discharge location.
The choice of 0.005 cubic meters per second (0.2 cfs) for the minimum flow is based upon the 'methodology used by the Pennsylvania Department of Environmental Resources to estimate the seven-day ten-year 4ow'.fl'ow on ungaged streams..
Since the natural streamf low probably ceases during drought periods, the proposed conservation release represents a change in the hydrology of the downstream portion of the stream.
H drolo ic Desi n of Dam Since-failure of the dam would not result, in radioactive releases.
nor effect
/
the: reactor.
s~se we have oot. performed at"deta11ed evaToatfoh of 1ts hy'dro-"
logic design..
We: have',. however,. reviewed th'e hydrologic criteria used and com-pared it with*criteria we use for (radiologically) safety.-related dams.
The applicant routed a flood series consisting of the Probable Maximum Flood, followed 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> later by what is labeled as the "Recurrent Flood", through the reservoir.
The maximum reservoir level calculated was 984.89 feet MSL, more than 5 feet below the crest of the dam.
This would provide adequate
freeboard to prevent overtopping of the dam by coincident wind waves.
Our criteria, however, is somewhat different.
He would require that the dam be designed to handle the Probable Maximum Flood (PNF) preceded
.3. to 5 days. by 40.percent of the PMF.
I The value chosen by the applicant for the depth of the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Probable Maximum Precipitation,. using "Technical Paper No. 40", U. S. Heather Bureau (1961),. and reduced 20 percent (because the drainage area is less
~
~
than 26 km ),. was 508.mm (20.0 inches).
Our criteria require using the more recent "HydrometeoroTogical Report No. 51", National Heather Service (1978) with no reduction from the 26 km2 (10 mi
) value.
This results. in a value of 673;.
mm (26.5 inches) for the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> PNP, which=-
is more than 30 percent greater than the applicants'NP Additionally, because the spillway is small, it will not be able to pass the PMF.
- Instead, most of the inflow will be held in storage in the reservoir, raising its.water. level until the outflow through the spillway can "catch up" to the inflow,. near-the. end of the flood..
Because of this characteristic.
of the reservoir's flood routing, a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> PMF may not be appropriate.
Here this a 'safety-related..'dam we. would eval'uate PNF's of longer duration to determine the maximum water level in the reservoir.
Our criteria also require that the PMF be preceeded by a flood whose magnitude is 40 percent that of the PMF.
The applicant's "Recurrent Flood" precipitation, based on the record rainfall in the region, is 231.
mm (9.1 inches) in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
40 percent of our estimate of the 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> PNP is 269.
mm (10.
6 inches).
However, if our evaluation indicated that the critical duration for the PMF was greater than 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, the duration (and depth) of the anticedent flood would also be increased..
In addition,'he applicant applied the "Recurrent Flood" 2 days after the PNF.
Since this procedure does. not ra~se the calculated maximum reservoir level, which is achieved during the PNF,'t is meaningless in terms of design criteria.
The more critical approach is to assume an antecedent flood which serves to raise the water level in the reservoir before the PMF and thus to increase the maximum level attained during the PNF.
Applying our criteria to this dam would raise the calculated maximum water level in the reservoir,. probably to the extent that the dam would be overtopped.
Since the criteria we use for safety-related dams is similar-to that used by other Federal agencies that design, construct operate and regulate
- dams, we conclude that this dam probably would not meet criteria used by other Feder al agencies.
Groundwater Effects Filling of the reservoir wi 11 alter the ground water conditions within the drainage area of the upper portion of Pond Hill Creek.
The groundwater level should rise to at least the level of the reservoir at its perimeter.
Since 'groundwater levels in the ridge north of the reservoir are. clear ly well above the reservoir level, there should be no. effect on the ground-water regime north of the Pond Hill Creek drainage area.
The limited infor-mation available on the groundwater conditions on the ridge south of the reservoir indicate that groundwater levels are also above the proposed water level in the reservoir.
In addition, the applicant has proposed a
saddle dam and an impervious cutoff section along the two lowest sections of that ridge.
We;therefore,conclude that groundwater levels south of the ridge should not be effected by the reservoir.