ML19269C501
| ML19269C501 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 01/31/1979 |
| From: | Werner R TEXAS UTILITIES SERVICES, INC. |
| To: | Naventi R Office of Nuclear Reactor Regulation |
| References | |
| TXX-2941, NUDOCS 7902050137 | |
| Download: ML19269C501 (41) | |
Text
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TEXAS UTILITIES SERVICES INC.
Ju>t 15t4YAN TO% Ett D 4112N. TEX Ah 75201 TXX-2941 January 31, 1979 Mr. R. Naventi Licensing Project Manager Light Water Reactors Branch No. 4 Division of Project Management Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D.C. 20555 COMANCHE PEAK STEAM ELECTRIC STATION NRC ROUND ONE HYROLOGY QUESTIONS DOCKET NOS. 50-445 & 50-446 FILE N0. 10010
Enclosed are our initial responses to your round one questions on hydrology (Q371.4-Q371.13). As agreed, these are being transmitted to you by letter to expedite response time. These responses will be retransmitted to the Commission in FSAR Amendment 4. Also enclosed in response to the above questions are three copies of drawing numbers FN-SCR-5, 9,11,14,17, 26 and 37.
If you have any questions about this matter, please contact this office.
Sincerely, j Lc l LvwD Richard Werner RAW:tls Enclosure cc: H. C. Schmidt Y(5 b s "N O
TA@'p 1902050137
CPSES/FSAR Q371.4 You have not demonstrated that the_ service spillway will not fail during the occurrence of a Probable Maximum Flood.
According, provide the following additional .information .
regarding the spillway and appurtenant structures.
(1) Provide the height of the spillway chute ides downstream of the crest in the chute. Document the freeboard provided and the basis for its selection.
Provide a drawing of the chute showing the height of the sides for the entire length together with a profile of water surface elevations for the Probable Maximum Flood. Provide the "n" values and velocity distribution coefficients that were used and the bases for their selection. .
(2) Provide more detailed and larger scale drawings in plan and profile of the approach channel, spillway and appurtenant structures.
(3) Provide a detailed plan view of the transition area between the stilling basin and the spillway discharge channel.
(4) Discuss the gradation limits of the 24 inches and the 48 inch riprap to be provided on the sides of the discharge channel. Provide the median rock size to be used.
(5) Provide the equations used to define the upstream and downstream quadrants of the ogee crest. Also, provide the radius of curvature of the transition between the downstream quadrant and the spillway and the coordinates of the points of tangency.
e 371-4
CPSES/FSAR (6) . Define the location and length of the hydraulic jump in the stilling basin.and assure that the side walls are of sufficient height to contain this jump. ,
(7) Provide a tailwater rating curve and a water surface profile in the s,nillway discharge channel. Discuss the computational technique used to derive this profile.
R371.4 (1) Drawing number Fil-SCR-14, transmitted to the commission by letter dated January 31, 1979, shows the water surface profile through the spillway during the probable maximum flood. The chute walls are 9 feet high and provide a minimum freeboard of 4.1 feet. The required freeboard was computed as 3.9 feet (reference: U.S. Bureau of Reclamation, Design of Small Dams, Second Edition, page 393). To determine the wall heights a velocity distribution coefficient of 1.0 and a !1anning's n of 0.018 were used for conservatism. ,
(2) Drawing numbers Ffi-SCR-11, Fft-SCR-14, Fft-SCR-26, and Fil-SCR-37, transmitted as above, give additional details of the approach channel, spillway end service outlet.
(3) Drawing number Fli-SCR-9, transmitted as above shows a detailed plan view of the transition area between the stilling basin and spillway discharge channel.
371-5
CPSES/FSAR (4) The riprap was graded within the following limits:
Percent Lighter Limits of Stone Weight (Lbs.)
By Weight 24-inch Riprap 48-inch Riprap 100 607 - 243 4859 - 1944 50 -
180 - 121 1440 - 972 15 90 - 38 720 - 304 The median rock size was 150 pounds for the 24-inch riprap and 1,200 pounds for the 48-inch riprap.
(5) Drawing number FN-SCR-17, transmitted as above, gives details of the spillway crest and transition curve.
(6) The location and length of the hydraulic jump during the probable maximum flood are snv.:n on drawing number FN-SCR-14. This location and length are for a Mantting's n of 0.008 and a velocity distribution coefficient of 1.0. The stilling basin walls are 35.5 feet high, and the jump height is 34.2 feet.
(7) The tailwater rating curve for the stilling basin design and the water surface profile in the spillway discharge channel during the probable maximum flood ;
are shown in Figure 371.4. The tailwater rating l
curve for the spillway was abtained from a backwater '
analysis of the flow in tha spillway discharge channel. The Corps of Engineers' HEC II computer program was used for the analysis. A Manning's n of 0.030 was used for the channel. The water surface elevation at the downstream end of the discharge ;
channel was obtained from a backwater analysis of the existing conditions on Squaw Creek. Studies showed '
371-6
a i CPSES/FSAR that the tailwater rating curve was not sensitive to water levels at the downstream end of the discharge channel.
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371-7
CPSES/FSAR Q371.5 You have not demonstrated that the auxiliary spillway is
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designed to safely discharge the Probable Maximum Flood without failure. Accordingly, provide the following .
additional information.
(1) Detailed drawings in plan and profile.
(2) Discuss velccities caused by the Probable Maximum Flood discharge over the spillway and demonstrate that these velocities are low enough to preclude failure of the unlined spillway.
(3) Describe the composition of the spillway crest.
(4) Provide the basis for design of any erosion control structures. ~
(5) Demonstrate that a Probable Maximum Flood discharge through the spillway will not endanger the Squaw Creek Dam embankment.
(6) Provide a tailwater rating curve.
R371.5 (1) Drawing number FN-SCR-5, transmitted to the commission by letter dated January 31, 1979, is a detailed drawing of the emergency spillway.
v a (283) The maximum velocity along the emergency spillway will be 10 feet per second during the probable maximum flood. Velocities at the downstream edge of the spillway will be higher. These velocities will cause some erosion damage. The erosion will not be severe, as the spillway cut is into limestone. In 371-8
CPSES/FSAR places, surface materials (up to 2 feet thick) overlying the limestone consist of softer materials, graded for drainage. The crest of the spillway has a ,
concrete wall at Elevation 783.0, anchored into the limestone. The frequency of operation of the emergency spillway is in excess of 100 years. The
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erosion damage will not endanger the dam or reduce its storage capacity.
(4) The only erosion control structure is the concrete wall on the spiilway crest. Its purpose is to maintain a uniform elevation for the entire length of the crest. ,
(5) The emergency spillway discharges into a tributary of Squaw Creek whose confluence with Squaw Creek is 7,000 feet downstream of the dam. A water surface profile in Squaw Creek showed that the water level at the toe of the dam will reach elevation 656 during the probable maximum flood. The tributary through which emergency spillway discharges will flow ir separated from the dam by a large hill composed of a thin overburden overlying limestone. The Squaw Creek Dam embankment will not be endangered by flows through the emergency spillway.
(6) A tailwater rating curve was not needed for design of
<.- the emergency spillway, since the flow will pass through critical depth at the downstream edge of the spillway.
, 371-9
. t CPSES/FSAR Q371.6 Provide the rip-rap gradation limits for the Safe Shutdown Impoundment Spillway. Provide the velocities through the spillwey. .
R371.6 There is no riprap in the SSI Dam spillway channel. The channel is excavated in'to limestone. The velocity through the spillway will reach 10.3 feet per second.
e e
e 371-10
CPSES/FSAR Q371.7 There are many discrepancies between various tables, figures and the text. Some of these are listed below.
These and others should be corrected. .
(1) Page 2.4-31 shows the storage of Squaw Creek Reservoir (SCR) at elevation 775 feet to be 151,953 acre-feet while Table 2.4-17 shows this as 150,953 acre-feet.
(2) Page 2.4-31 also shows the area of SCR at elevation 770 feet to be 3043 acres while Table 2.4-17 shows this as 3084 acres.
(3) Page 2.4-14 shows the area ~of SCR at elevation 775 feet to be 3,228 acres while Table 2.4-17 shows this as 3272 acres.-
(4) Page 2.4-31 shows the storage of SCR at levation 770 as 135,062 acre-feet while page 2.4-49 shows this as
. 135,360 acre-feet.
(5) Page 2.4-1 shows the elevation of the operating deck of the service water intake structure as 796 feet while page 2.4-15 states this 795 feet.
(6) Page 2.4-19 shows the maximum water surface in the Safe Shutdown Impoundment (SSI) to be 790.7 feet while Table 2.4-15 shows 791.8.
(7) Page 2.4-29 and Figure 2.4-14 show the effective fetch of the SCR as 1.28 miles while page 2.4-18 and page 2.4-32 show 1.56 miles.
371-11
CPSES/FSAR (8) Page 2.4-37 shows the effective fetch for the SSI as 0.42 mile while figure 2.4-15 shows 0.36 miles.
(9) Riprap thickness on page 2.4-37 should be 24 inches instead of 24 feet as shown.
(10) tiote on bottom of Table 2.4-24 makes reference to figure 2.4.13.2.1.2-1. Shouldn't this be figure 2.4-33?
(11) In section 2.5.4.6 you state, "As discussed in Section 2.5.4.5, groundwater was not encountered in the primary unweathered Glen Rose Limstone." Section 2.5.4.5 does not contain this description. Please correct this reference. - .
(12) Figure 2.5.5-77 shows the piezometric level of boring P-9 at a minimum elevation of 750 feet, but page 2.5-133 states that the piezometric level in boring P-10 is at elevation 670 feet. Furthermore, the logs of these two borings show the base of the Glen Rose formation at elevation 610. This means that the static water levels are- 60 feet and 140 feet above the base of the Glen Rose formation for borings P-9 and P-10, respectively. Explain then your statement in the previous question that groundwaer was not encountered in the Glen Rose Limestone.
(13) On page 2.5-133 you state that the static water level in the Twin Mountains formation was observed in boring P-10 at elevation 670 feet. As mentioned above, elevation 670 is in the Glen Rose formation.
371-12
CPSES/FSAR (14). On page 2.5-133 you state that groundwater observations for piezometers installed at the site are provided on fig. 2.5.5-5. This should be fig.
2.5.5-77.
R371.7 The following changes have been made to the FSAR as indicated:
(1) The Squaw Creek Reservoir storage at elevation 775, shown on page 2.4-31, should be 150,953 acre-feet.
(2) The. Squaw Creek Reservoir area at elevation 770, shown on page 2.4-31, should be 3,084 acres.
(3) The Squaw Creik Reservoir area at elevation 775, shown on page 2.4-14, should be 3,272 acres.
(4) The Squaw Creek Reservoir storage at elevation 770, shown on page 2.4-49, should be 135,062 acre-feet.
(5) The elevation of the Service Water Intake Structure operating deck, shown on page 2.4-19, should be 796 feet.
(6) The SSI maximum water surface elevation shown on page 2.4-19, should be 790.5. Table 2.4-15 has been revised and now shows the same maximum elevation.
(7) The effective fetch of SCR is 1.28 miles. Pages 2.4-18 and 2.4-32 have been corrected.
N (8) The effective fetch for the SSI is 0.36 miles. Page 2.4-37 has been corrected.
371-13
CPSES/FSAR (9) Page 2.4-37 has been corrected to show a riprap thickness of 24 inches.
(10) Table 2.4-24 has been changed to reference Figure 2.4-33.
(11) The reference by~Seciton 2.5.4.6 to Section 2.5.4.5 has been corrected.
(12&l3) The groundwater in the Twin Mountains formation is under artesian pressure. The piezometric level in the Twin Mountains as measured by Boring P-10 is at 670 feet. However, due to the imprevious Glen Rose overlying the Twin Mountains, a boring must penetrate into the Twin Mountains, to allow the water to rise to its piezometric level.
The piezometer in Boring P-9 was blocked, as shown on Figure 2.5.5-77, and no reading was possible. This piezometer was reinstalled, but only to Elevation 749.8, which is in the Glen Rose formation. The readings show that after a couple of months, the piezometer ws dry.
(14) The reference to Figure 2.5.5-5 on page 2.5-133 was to location of borings. In the same paragraph it does say that the observations are summarized in Figure 2.5.5-77.
371-14
CPSES/FSAR Q371.8 In developing hydrographs for flood analyses, you divided the SCR catchment into three areas, the upper and lower areas and the area within the reservoir. It appears that only the first two were considered in developing a Probale Maximum Flood. Provide additional information showing that the area within the reservoir was considered, or revise your computations by assuming that all of the Probable Maximum Precipitation which falls on the reservoir
. contributes to the-total Probable Maximum Flood.
R371.8 The flood routings for Squaw Creek Reservoir and the Safe Shutdown Impoundment did include allowance for rainfall on the surface of the reservoirs. Tables 2.4-11 and 2.4-15 have been expanded with additional columns"to show the rainfall volumes included.
C 371-15
CPSES/FSAR Q371.9 The.available storage in the SSI will be reduced by sediment depletion from 367. acre-feet to about 300 acre-feet during the life of the plant. Discuss ,
sedimentation effects on the service water intake structures. Provide assurance that the intake will not be clogged. Discuss your mon.oring and maintenance programs that will be implemented to detect and renove sediment.
R371.9 The SSI is a quiescent body of water. It receives silt form a small drainage area and, therefore, sedimentation buildup is expected to be slow and gradual. There is no formal program 't'o directly monitor sedimentation accumulation at the service water intake structure.
Itowever, if sedimentation begins to significantly accumulate at the service water intake structure, it would be indirectly detected during the Technical Specification required monthly service water pump surveillance tests performed in accordance with ASME,Section XI. Since significant sedimentation accumulation occurs over a long period of time, the monthly interval established by the Technical Specifications for the service water pump surviellance test is sufficient for detecting the gradual pump performance deterioration due to sedimentation. V'en significant service water pump ' performance deterioration is determined from the results of surveillance test trends and it is determined to be the result of sedimentation accumulation, then the sedimentation will be removed to astore pump performance.
c 371-16
CPSES/FSAR Q371.10 Provide the basis for your conclusion that water from the Service Water Discharge Struature enters the SSI at a point remote enough from the Service Water Intake Structure and ,
at a velcity high enough to ensure adequate mixing, dispersion and evaporative cooling of the effluent.
R371.10 The ser.vice water system effluent flows through an open channel type discharge canal prior to entering the 5SI.
Cooling occurs throughout the approximately 1300 ft. length of the discharge canal before the service water effluent mixes with the SSI bulk fluid. The discharge canal outlet enters the SSI in a direction away from the service water intake structure. Mixing and dispersion of the effluent occurs when the SSI fluid reverses direction in order to pass to vicinity of the intake structure. The minimum shore line distance between the discharge canal and intake structure is 1500 ft. Further cooling of the mixed fiaid occurs en route. Because the intake is submerged and the discharge is on the surface, there is vertical as well as horizontal separation. See Figure 9.2-2. ,
s 371-17
CPSES/FSAR Q371.11 Provide the basis for your statement that an effective porosity of 0.28 is conservative. (Section 2.4.13.3.3)
R371.11 Based upon a wet density of 135 pounds per cubic foot for the Twin Mountains formation, the porosity could vary between 0.28 and 0.36 for specific gravities of 2.65 and 2.8 respectively. However, the lower the porosity, the faster the seepage velocity and the greater the rate of dispersion. Therefore, since the lower bound of the porosity was used in the dispersion comp 0,tations, the results obtained are conservative.
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8 371-18
CPSES/FSAR ,
Q371.12 Explain your statement in section 3.8.5.1.5 that, " ground water is not expected to reach higher that 775 feet because of the impenneable nature of the rock," when in figure 2.5.5-77 you shaw piermetric water levels as high as 830 feet and the packer test results shown in tabla 2.5.6-1 indicate that the Glen Rose formation is not uniformly of low permeability but rather contains more permeable lenses.
R372.12 All peizometric levels recorded on Figure 2.5.5.77 are measures of pearched water in the upper zone of the Glen Rose Formation measured in the immediate area of each piezometer. These water levels resulted from surface run-off and are not a true measure of any permanent groundwater in the formation. These piezometers were installed during preliminary design work at the site and before the plant site was excavated to plant grade (elevation 810). In Table 2.5.6-1 only zones at a depth range of 194 feet to 214 feet -(elevation 649.04 to 629.04 feet) recorded any water loss during the Packer Test. By reviewing the Log of Boring for Boring P-10 it can be seen that zone of sandstone and sand lenses are the cause of the water losses recorded in the Packer Test. The remaining Glen Rose Formation is uniformly of low permeability in its in situ state. However, excavation and the subsequent backfilling with pervious naterial of the duct banks, piping etc. throughout the plant site has changed the rock formation from an impervious material to a factured and previous material. The horizontal and vertical extent of the fractures and backfilling varies over the site. A field monitoring program will be established, as soon as construction activities permit, to determine if groundwater conditions have changed at the site.
371-19
CPSES/ESAR Q371.13 You lave not demonstrated that your subsurface groundwater design level, which is normal maximum water level in Squaw Creek Reservoir, elevation -775 feet, is conse tative. We note that the water level in borehole P-4, which is located between the two reactor units, fluctuated between elevation 780 and 830 during the period when water level observations were made. (Figure 2.5.'S-77) You should therefore, substantiate and show by pertinent analyses that your design groundwater levels will never be exceeded.
Alternately, you should use a more conservative groundwater design level . ,
R371.13 See response to question 371.12. -
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371-20
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CPSES/FSAR These values are indicative of the magnitude of precipitation losses expected on the SCR catchment due to its similarity to the Paluxy watershed in regard to general topography, geology, soil types and land
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usage. The values require evaluation, however, in light of some differences between the two watersheds, including: 1) the SCR catchment is generally not as steep as the Paluxy watershed; 2) the SCR watershed is much smaller; and 3) much of the relatively level, low-lying portion of the SCR catchment will be inundated by the reservoir.
Although the first difference described above tends to increase the precipitation losses on the SCR catchment in relation to that of the Paluxy River, the other two differences indicate a decrease in losses.
Smaller drainage areas, such as the SCR catchment, generally have lower losses than larger areas, and submergence of much of the creek alluvium removes a section of the catchment which should have the most infiltration capacity. Thus, it is prudent to adopt lower estimates of losses on the SCR catchment. This conclusion is further supported by the relatively short duration of the available historical storms studied, in comparison to the 48-hour storm used in computing the PMF.
In view of these factors, an initial loss estimate of 0.5 inches and an infiltration rate of about 0.1 inch per hour is considered appropriate for the catchment.
2.4.3.3 Runoff Model 2.4.3.3.1 Description of Squaw Creek Reservoir Catchment
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Figure 2.4-1 illustrates the 64-square mile SCR catchment and the reservoir limits corresponding to a selected flood-stage at Elevation 780 feet.
The maximum normal operating reservoir level will be Elevation 775 feet. The higher level has been utilized as the pre-flood condition.
2.4-13 ,
JANUARY 31, 1979
CPSES/FSAR 4 During the PMF, pool level will rise from Elevation 775 feet (area Q371.7 3,272 acres) to Elevation 789.7 feet (area 3,863 acres).
2.4.3.3.2 Synthetic Hydrographs Synthetic methods for developing a runoff model have been undertaken.
Three methods of synthetic hydrograph development were considered:
- 1. Use of Snyder's Unit hydrograph relations presented by the U.S.
Army Corps of Engineers (USACE) [14].
- 2. Use of dimensionless hydrographs presented by the Soil Conservation Service (SCS) [14].
- 3. Use of triangular hydrograph techniques presented by the U.S.
Bureau of Reclanation [123 The empirical relations developed by Snyder have also been shown to be reliable through widespread usage. To eaploy this method, two coefficients which depend upon drainage basin characteristics are computed from hydrologic records for a representative portion of the drainage area under study, or for nearby catchment of similar characteristics [15]. Snyder's method was adopted for development of a runoff model for Squaw Creek.
2.4.3.3.3 Hydrograph Development For purposes of analyses, the SCR catchment has been divided into three areas, as shown on Figure 2.4-1 and described below:
- 1. The Upper Squaw Creek catchment, which consists of about 38 square miles of land located above the reservoir area.
AMENDMENT 4 2.4-14 JANUARY 31, 1979 .
4 4 CPSES/FSAR Except for a few. existing small farm ponds, there are no present or planned structures upstream of SCR; therefore, the effect of such structures was not considered in developing the PMF hydrograph. .
The PMF was routed through the SCR assuming the reservoir level at the beginning of the PMF was at elevation 775, the maximum operating level.
All discharge was assumed to occur over the uncontrolled spillways of Squaw Creek Dam.
All streams in the SCR basin empty directly into SCR; therefore no channel routing coefficients were required. The applicability of the stream course response nodel to handle the PMF is discussed in Section 2.4. 3. 3.4 . The ability of the SCR dem to withstand the PMF and coincident wave action is discussed in Section 2.4.3.6.
2.4 . 3. 5 Water Level Determinations The mass curve, the capacity-area-depth curves, and the spillway rating curves (Figure 2.4-9) are used in routing the PMF through the reservoir to evaluate water level. The resulting peak reservoir level is Elevation 789.7. ,
In routing, the reservoir water surface has been assaned to be nearly horizontal, and the volume of water in the reservoir has been assumed to be directly related to the reservoir elevation. These are reasonable assumptions in via1 of the shape and depth of the SCR.
These assumptions allow the principle of continuity expressed as a storage equation (It - s= t, where I and are the average rates of inflow and outflow for the time t, and s is the change in water volume during time t) to be applied directly to the routing problem [16].
2.4-17 JANUARY 31, 1979
CPSES/FSAR 2.4.3.6 Coincident Wind Wave Activity The magnitude of the wind tide and wave runup are dependent upon the ,
wind velocity, fetch and reservoir depth. The wind direction must coincide with the fetch direction. An overload wind velocity of 40 miles per hour has been approved by,the USACE for use in determining freeboard requirements in the Fort Worth District. This 40 mph wind velocity is the highest that may reasonably be assumed to occur coincidentally with the probable maximum flood [17].
The effective fetch length for wave generation was determined for the 4
Q371.7 center of Squaw Creek Dam (fetch of 1.28 miles) and for the exposed side of the CPSES plant location (fetch of 1.25 miles). It was also determined for the Safe Shutdown Impoundment Dam and the protected side of the CPSES plant location, but freeboard requirements were found to be less than two feet for these locations, so discussion is not included here. Computation of effective fetch considered radial lines at angles up to 42 degrees from the central or primary fetch line, as recommended by the USACE [10].
The average depth of the reservoir at PMF, Elevation 789.7 feet, is approximately 55 feet, and the longest theoretical deep-water wave length (for waves reaching the center of Squaw Creek Dam) is 46 feet, so the ratio of water depth to wave length is well over one-half, and the reservoir can be considered to have " deep water" [10].
Computation [10] utilizing data for wind velocity, fetch length, and reservoir depth yield the results shown in Table 2.4-14. The Table illustrates the maximun runup and setup of smooth and riprapped banks on the Squaw Creek Dam and at the exposed side of the CPSES plant area.
As can be seen from the Table, wave runup and wind tide at the dam and plant are about 4 and 5.0 feet and elevations reached are 793.7 feet and 794.7 feet, respectively. Due to the much shorter fetch available around the area, water level elevation reached at the SSI is about AMENDMENT 4 2.4-18 JANUliRY 31, 1979
CPSES/FSAR 791.3 feet. All plant facilities are above the maximun wave runup and setup elevation of 794.7 feet. The Service Water Intake Structure is the only safety-related structure subject to wave action. The 4-elevation at the operating deck is approximately 796, above'the maximum Q371.7 expected wave runup. Section 2.4.10 discusses the effect of wave runup and wind tide on all pertinent safety-related facilities.
2.4.3.7 Flood Evaluations for Safe Shutdown Impoundment A 40-ft wideopen channel with a crest at elevation 769.5 feet above mean sea level (0.5 fcet below minimum operating pool) and a channel slope of .003 has been cut through the peninsula that consitutes the south abutment of the Safe Shutdown Impoundment (SSI) Dam. Water can pass freely between the SSI and SCR, and the water surface in both water bodies normally will be at the same elevation. Figure 2.4-11 is a graph of the discharge characteristics of the SSI spillway. Table 2.4-15 outlines predicted performance of the SSI during occurrence of simultaneous Probable Maximum Floods on the over-all SCR watershed and the SSI watershed. The maximum level reached in the SSI during the PMF is computed to be 790.5 feet, leaving a freeboard in the SSI of 5.5 Q3fl.7 feet. Further details on the Safe Shutdown Impoundment Dam are given in Section 2.4.8.2.2. Table 2.4-16 gives the unit hydrograph parameters for the SSI watershed, and Figure 2.4-12 shows the unit hydrograph for the SSI watershed.
2.4.4 POTEiTIAL DAM FAILURES (SEISMICALLY INDUCED)
There are no impoundments other than small farm ponds on the SCR catchment; therefore, a postulated dam failure upstream on Squaw Creek is not appropriate for the CPSES facilities. The farm ponds on the catchment have a combined volune which is less than one percent of thc reservoir volume and are insignificant.
2.4-19 AMENDMENT 4 JANUARY 31, 1979
CPSES/FSAR Failure of Squaw Creek Dam itself presents no danger of flooding the CPSES, as the Station is above the PMF water level. The possibility of damage to Squaw Creek Dam by backwater due to flooding on the Brazos River in the event of a postulated domino-type failure of Morris -
Sheppard Dam and DeCordova Bend Dam is ruled out in Section 2.4.4.3.
2.4.4.1 Reservoir Description Present and possible future reservoirs which might be considered to have an influence on the site from a safety or water-supply standpoint are described in Tables 2.4-1 through 2.4-3, and their locations are shown in Figures 2.4-5 and 2.4-6.
2.4.4.2 Dam Failure Permutations Considering CPSES safety, the most severe dam failure permutation conceivable is the failure of Morris Sheppard Dam and the subsequent domino-type failure of DeCordova Bend Dam. The 25-year floods of both the Brazos and Paluxy rivers can be added into the effects of the combined dam breaks without significantly intensifying the results.
Failure of the Lake Whitney Dam, downstream, would not have an adverse effect on CFSES.
The detailed analysis of the most severe dam failure permutation is presented in Sections 2.4.4.3 and the effect of landslides into the reservoir is discussed in Section 2.4.2.2.
There will be no commercial water traffic on SCR, and no possible blockage of any water course in the site region could affect the plant.
2.4.4.3 Unsteady Flow Analysis of Potential Dam Failures The possibility of damage to Squaw Creek Dam due to failure of Morris Sheppard Dam and DeCordova Bend Dam was examined by initiating a number JANUARY 31, 1979 2.4-20
CPSES/FSAR ,
2.4 . 8 COOLING WATER CANALS AND RESERVOIRS ,
2.4 . 8.1 Canals .
No canals are involved. .
2.4 . 8.2 Reservoirs -
2 .4 . 8. 2.1 Squaw Creek Reservoir (SCR)
SCR is a cooling lake for CPSES. The location and configuration of the reservoir are shown in Figures 2.4-5 and 2.4-5. Table 2.4-17 gives the area and capacity characteristics of the SCR site, based on planimeter measurements from U.S. Geological Survey quadrangle maps entitled Hill City, Texas, and Ueno, Texas, scale 1:24,000. The volumes and areas indicated are those of the entire reservoir, including the reserve storage within the Safe Shutdown Impoundment (SSI) described in Section
'2.4.8.2.2 below. The performance capability of SCR as operational cooling pond was evaluated through mathenatical modeling as documented in Reference [40].
Under normal conditions, the reservoir will remain in the five-foot range between a normal minimum operating level at elevation 770.0 and the crest of the service spillway at elevation 775.0. At the lower drawdown limit, elevation 770.0, the over-all surface area will be 3,084 acres, and the content will be 135,062 acre-feet. When filled to 4 the top of conservation storage, at elevation 775.0, the area will be Q371.7 3 3,272 acres and the capacity 150,953 acre-feet.
- 1. Squaw Creek Dam The layout of Squaw Creek Dam is shown in Figure 2.4-16. A typical cross-section of the embankment is shown in Figure 2.4-17. The top of the dam is at elevation 796.0. The central section is constructed of 2.4-31 AMENDMENT 4 JANUARY 31, 1979
CPSES/FSAR select, impervious material, wetted and rolled, with a cutoff trench extending down t'o impervious foundation material. The outer zones of the embankment are of less select material. A filter system separates the impervious central zone from the less select outer zone on the downstream side and extends outward to the downstream toe to provide drainage and protection for the core.
The reservoir side of the dam is protected by rip-rap and gravel blanket from the top of the embankment to elevation 760.0, which is ten feet below the minimum operating level. The top width of the embankment is 20 feet, exclusive of the gravel blanket and rip-rap.
Design for the rip-rap was based on an average over-water wind of 95 mph (Probable maximum wind - 200 year frequency) over the effective fetch distance. The method of computing the effective fetch distance.
set forth in Department of the Army Office of the Chief of Engineers ETL 1110-2-8, 1 August 1968, was adopted. Mimimum layer thicknesses were determined using the requirements set forth in EM 1110-2-2300 (April 1959) and EM 1110-2-1601 (July 1970). The specific gravity of the rock was assumed to be 2.3. The result are as follows: ,
4 Q371.7 a. Effective Fetch - 1.28 miles '
- b. Significant Wave Hgt. - 5.0 ft.
- c. Layer Thickness - 33 Inches
- d. Average Rock Size - 22 Inches
- 2. Spillway's The service spillway is an uncontrolled structure (i.e., without gates),100 ft wide, with a standard ogee crest at elevation 775.0.
Additional discharge capacity for protection from extreme floods is provided by a broad-crest emergency spillway, 2,200 ft wide, excavated through the rock of the north abutment at elevation 783.0. A 12-inch diameter makeup water pipeline crosses the emergency spillway along its crest. This line is placed in a trench cut in limestone and is covered AMENDMENT 4 2.4-32 JANUARY 31, 1979
CPSES/FSAR 1110-2-2300 (April 1959) and EM 1110-2-1601 (July 1970). The specific gravity of the rock was assumed to be 2.3. The results are as follows:
4.
- a. Effective Fetch - 0.36 mi Q371.7
- b. Significant Wave Hgt. - 2.6 ft
- c. Layer Thickness - 24 in Q371.7
- d. Average Rock Size - -
15 in Estimated sediment production from the Panther Branch watershed above tiie SSI during the 30-yr projected service life of CPSES was der'ved based on analytical procedures for small watersheds as described in .
Ref erence [38]. The. anticipated reduction in storage capacity of the SSI during that period due to accumulati-on of sediment was found to be 69 ac-ft, of which 64 ac-ft would be below elevation 770.0 and the remaining 5 ac-ft above elevation 770.0. Comparative plots of area and capacity characteristics before and after sedimentation are shown in Figure 2.4-22. Table 2.4-19 outlines the predicted area and capacity values at the end of the 30-year period.
A detailed layout of the r3I design features is given in Figure 2.4-23.
Seismic Design Criteria for the SSI are discussed in Section 3.7.
The ability of the SSI to meet criteria of Regulatory Guide 1.27 is discussed in S,ection 9.2.5.
\_
2.4-37 AMENDMENT 4 JANUARY 31, 1979
CPSES/FSAR 2.4.9 CHANNEL DIVERSIONS The SCR catchnent has developed streams with distinct valleys and has sustained numerous farm ponds. Therefore, diversion of water from the catchment appears impossible. The reservoir is formed in the Glen Rose formation, a predominately limestone sequence. Information developed regarding this formation indicated it is relatively impermeable and free of sinkholes and solutioning. Thus, significant loss of water is improbabl e.
Lake Granbury, which is on the Brazos River, will be a major source of makeup cooling water. The loss of Lake Granbury makeup water due to the diversion of the Brazos River is highly improbable. Above Lake Granbury, the Brazos River channel is cut into bedrock which precludes any reasonable possibility of the river changing its channel significantly within the life of the CPSES and thus affecting the supply of water.
Extraction of groundwater, oil, and gas from the region is relatively nominal. It is concluded that subsidence sometimes associated with these extractions will not occur in the vicinity of the CPSES. The potential of subsidence at the site is discussed in detail in Section 2.5.1.2.6.
JANUARY 31, 1979 2.4-38
4 CPSES/FSAR s 2.4.12 DISPERSION, DILUTION, AND TRAVEL TIME OF ACCIDENTAL RELEASES OF LIQUID EFFLUENTS IN SURFAC.E WATERS 2.4.12.1 Introduction This section provides a conservative analysis of a postulated accidental release of radioactive material in surface waters adjacent to the site. The postulated release was assumed to occur due to an accidental rupture of the waste holdup tank which is located in the Auxiliary Building near the Containment Building.
The volume of the tank is 30,000 gallons and at the time of rupture it was assumed that the tank was 80 percent full. The assumed quantities of radionuclides in the tank at the time of rupture are given in Table 2.4-20. -
It was conservatively assumed that all the liquid radwaste (24,000 gallons, or 7.36 x 10-2 acre-feet) is spilled into squaw Creek Reservoir. Minimua dilution in Squaw Creek Reservoir would occur at minimum pool elevation 770.00 feet (msl), corresponding to a storage volume of 135,062 acre-feet. Assuming complete mixing, the minimum Q3 1.7 dilution factor is 135,360/ (7.36 x 10-2) or 1.84 x 106 ,
The instantaneous concentrations in Squaw Creek Reservoir are calculated by dividing the concentrations in the tank by the dilution factor. Due to the decay characteristics of the radionuclides, the concentrations will decrease with time. The equation used to define the concentration of any radionuclide for certain periods of time is:
3 C
t
= 2 b XC g WNQd where, 2.4-49 AMENDMENT 4 JANUARY 31, 1979
CPSES/FSAR ,
C o
= Concentration in time zero ,
t = Time interval considered t = Half life of radionuclide g
C t
= C ncentration at time t The concentration of each radionuclide in Squaw Creek Reservoir at the end of the first day and at the end of the first month is shown in Tabl e 2.4-21.
Under normal operating conditions, there will be no controlled release of water to Squaw Creek from the Squaw Creek Reservoir. Instead, an average of 52,60.0 acre-feet of water per year will be pumped to Squaw Creek Reservoir from Lake Granbury and 26,400 acre feet of water per year will be pumped back to Lake Granbury. The " Partially Mixed Model," described in the NRC Reg. Guide 1.113 (May,1976), was used to calcute radionuclide concentrations in Lake Granbury due to this pumpage.
The blowdown of Lake Granbury is conservatively assumed to be the 50-year low flow of the Brazos River at Granbury, which is 35 cfs (Figure 2.4-24). The spillway crest elevation of Lake Granbury is 658.0 feet and the corresponding reservoir capacity is 15,440 acre-feet. Water released from Lake Granbury will travel down the Brazos River and enter Whitney Reservoir approximately 75 miles downstream.
Given a low flow condition of 35 cfs and by assuming a roughness coefficient of 0.035, it is estimated that travel of the radionuclides will be 3 days, 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />. In the portion of the Brazos River between Lake Gralbury and Whitney Reservoir, there are no significant tributaries which might affect the radionuclide concentrations in the JANUARY 31, 1979 2.4-50
CPSES/FSAR TABLE 2.4-11 SQUAW CREEK RESERVOIR PROBABLE MAXIMUM FLOOD .
Hours Probable Maximum Losses Rainfall Probable Maximum Rainfall Cumulative Storm Rainfall Excess Flood Hydrograph on Reservoir Inflow (Inches) (Inches) (Inches) cfs) ac-ft) (ac-ft) (ac-ft) 3 .5 .5 .0 0 0 158 158 6 .5 .3 .2 951 118 158 434 9 .6 .3 .3 2,358 41 0 18" 1,033 12 .7 .3 .4 3,774 760 22i 2 ,014 15 .8 .3 .5 5,140 1,105 253 3,372 18 .8 .3 .5 6,002 1,382 253 5,007 21 .9 .3 .6 6,864 1,595 284 6,886 24 .9 .3 .6 7,473 1,778 284 8,948 27 2.3 .3 2.0 14,424 2,585 726 12,259 30 5.5 .3 5.2 34,370 5,665 1,737 19,661 33 20.0 .3 19.7 121,907 14,958 6,317 40,936 36 3.5 .3 3.2 142,576 33,962 1,105 76,003 39 .6 .3 .3 66,914 25,258 189 101,450 42 .5 .3 .2 21,545 10,402 158 112,010 45 .5 .3 .2 7,796 3,281 158 115,449 48 .5 .3 .2 4,079 1,389 158 116,996 51 2,118 768 . 117,764 54 907 375 118,139 57 329 153 118,292 60 115 55 118,347 63 40 19 118,366 66 15 7 118,373 69 4 2 118,375 72 2 1 118,376 Totals: 39.1 5.0 34.1 a
AMENDMENT 4 JANUARY 31, 1979
1
. 9 TABLE 2.4-15
. SAFE SHUTDOWN IMPOUNDMENT PROBABLE MAXIMUM FLOOD Time in Incremental Incremental PMF Hydrograph Rainfail on Cumulative SSI Surface SSI Spillway Hours Rainfall Rainfall Excess SSI Surface Inflow Elevation Flow (Inches) o (Inches) (cfs) (ac-ft) (ac-ft) (ac-ft) (cfs) 3 .5 .0 0 0 1 1 775.0 0 6 .5 .2 111 14 2 17 775.3 60 9 .6 .3 200 30 2 58 775.5 130.
12 .7 .4 285 60 3 121 775.7 200 15 .8 .5 354 79 3 203 776.0 270 18 . .8 .5 368 89 3 295 776.5 320 21 .9 .6 431 99 3 397 777.0 350 24 .9 .6 442 108 4 509 777.5 370 25 .6 .5 504 39 4 552 777.8 380 26 .8 .7 851 55 4 611 778.1 380 27 1.2 1.1 1 , 311 88 4 703 778.6 830 28 2.2 2.1 2,103 140 10 853 779.3 1,900 29 2.6 2.5 3,586 2 31 11 1,095 780.3 3,000 30 2.9 2.8 4,683 340 'l 1,446 781.5 4,200 2.35 5,151 203 10 1,659 782.1 4,600 30-1/2 2 '. 4 31 2.6 2.55 5,883 227 11 1,897 782.9 4,900 5.9 5.85 7,451 275 25 2,197 784.2 6,200 31-1/2 8,400 32 9.3 9.25 10,079 361 40 2,598 785.5 1.6 1.55 15,828 526 7 3,1 31 787.5 11,600 32-1/2 17,600 33 1.5 1.45 20,840 799 6 3,936 790.1 1.0 .95 1 7,31 - 798 4 4,738 790.5 18,400 33-1/2 15,400 34 .9 .85 13,321 633 4 5,375 789.8 7 .65 10,124 483 3 5,861 789.2 10,200 34-1/2 7,200 35 .+ .35 7,783 370 2 6,233 789.5
.3 .25 6,107 285 1 6,51 9 789.7 5,600 35-1/2 4,600 36 .2 .15 4,787 225 1 6,745 789.8 37 .2 .1 2,832 314 1 7,060 789.7 3,500 38 .2 .1 1,538 178 1 7,239 789.2 2,000 39 .2 .1 838 97 1 7,337 788.5 1,500 42 .5 .2 178 1 01 2 7,440 786.4 600 45 .5 .2 145 40 2 7,482 784.9 300 48 .5 .2 146 36 1 7,51 9 783.9 100 51 .0 .0 28 22 7,541 783.3 100 54 .0 .0 3 4 7,545 782.9 . 100 AMENDMENT 4 44.9 39.9 JANUARY 31, 1979
CPSES/FSAR TABLE 2.4-24 PUBLIC SUPPLY, INDUSTRIAL AND IRRIGATION WELLS, 0-20 MILES Piezometric b Well a Elevation (ft) Yield Drawdown c
Number and Date (gryn) (feet) Use 1 701 3/15/68 100 90 PS City of Walnut Springs 2 - --
135 90 PS City of Walnut Springs 3 628 8/24/66 -
110 Irr James Smith 4 890 10/14/65 69 0 Irr Lee Manning 5 974 3/27/69 150 0 Irr J. W. Waldie 6 992 10/14/65 150 0 Irr J. W. Waldie 7 - --
550 0 Irr Triangle Ranch 8 - -- -
0 Irr Triangle Ranch 9 845 10/26/65 120 0 Irr Stanley Allen '
10 834 3/27/69 46 0 Irr St'anley Allen 11 868 3/26/G9 -
30- Irr E. L. Huffman 12 855 10/15/65 - 30 Irr E. L. Huffman
. 13 615 9/13/60 - 40 Irr Roy Kenedy 14 620 1960 614 100 PS City of Glen Rose 15 6P7 9/21/60 250 100 PS City of Glen Rose 16 f '.0 6/19/30 50 100 PS Young Wo.nen's Christian As.
17 >ll 9/14/60 -
90 Irr Squaw Creek Cemetery As.
18 708 7/20/66 222 190 Ind Texas Line Company 19 L75 9/15/60 100 140 Ir.d
- Texas Cedar Oil Company 20 46! 6/06/68 -
210 FS U.S. Army Corps of Engrs.
21 - -- -
0 PS City of Tolar 22 - -- - 0 PS City of Tolar 23 - -- 65 0 PS City of Granbury (9 wells) 24 - -- - 25 Irr L. L. Williams 25 - -- -
100 PS Camp El Jesom
- Well locations are shown on Figure 2.4.33. Q3 1.7 Estimated drawdown, based on original static, piezometric level, before 1900, c
Use: Ind, Industrial; Irr, Irrigation; PS, Public Supply. AMENDMENT 4 JANUARY 31, 1979
Cl' Si~ S/ F SAR The compaction requiroaents on the bed ling naterial, placed in both the Class I Electrical Duct Banks and Service Water Pipe Trench, is a miniunn density of not less than 80% of the relative density as determined by AST:i Test Designation D2049, lotest revision effective prior to Septenber 4,1975. In-place density shall be detensined in accordance with ASTli D1556 (Sand Cone), ASTil D2167 (Balloon), of AST!!
D2922 (Nuclear). Figure 2.5.4-39 shows the gradatio_n requirements of the bedding material.
2.5.4.6 Groundwater Conditions A detailed description of groundwater is presented in Section 2.4.13.
4 No grounJuate was encountered during excavation for the plant Q371.7 foundations. ;roundwater observations from piezometers installed at the site are provided on Figure 2.5.5-77.
2.5.4.7 Response of Soil and Rock to Dynamic Loading During design, adopted values for the cyclic shear strength for Class 1 2 backfill and bedding material were based on the published data for granular soils. A discussion of the published data is presented in Section 2. 5. 6.4 . 3.4. Since the D f the bedding material was 50 approxinately the sane as for Filter "A" for the SSI Dam, the material was assuned to have essentially the same cyclic characteristics. Cl ass I backfill material has a D 50 of approximately 15mm and since this material is coarser than the published data utilized, the cyclic strength characteristics of this material .should be greater. For design, the cyclic strength criteria was assuned based on the data 4
l presented on Figure 2.5.6-48. The specific criteria as spelled out in Gibbs & Mill Specification 2323-SS-8, Section 10 was that the material with the gradation limits as shown on Figure 2.5.4-38 shall not allow 2 developnent of shear strain larger than 5% under specific corresponding stress conditions shown on Table No. 2.5.4-11.
AMENDMENT 4 2.5-124 JANUARY.31, 1979