ML17256A480

Deer Creek Overflow Flooding Study:Sep Topic II-3.B.

ML17256A480
Person / Time
Site:	Ginna
Issue date:	01/31/1983
From:	ROCHESTER GAS & ELECTRIC CORP.
To:
Shared Package
ML17256A479	List: ML17256A478 ML17256A480
References
TASK-02-03.B, TASK-2-3.B, TASK-RR NUDOCS 8302070275
Download: ML17256A480 (35)

Text

GINNA STATION DEER CREEK OVERFZON FIOODING STUDY SEP TOPIC II-3.B JANUARY 31, 1983 8302070275 83013i PDR ADOCK 05000244 P PDR

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GINNA STATION DEER CREEK OVZRFLON FLOODING STIJDY.

This report is derived from a recent NUS study, which supplements previous Deer Creek studies( 'erformed by NIIS for Rochester Gas and Electric Corporation. This report determines elevations in Deer Creek and at Ginna structures under conditions of flood flow. The August 1981 study discussed the elevations in Deer Creek for various precipitation events and estimated return periods for the events. It was shown that a storm of 12 inches in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (estimated return period much greater than 10 years) will result in,a Deer Creek flow (approximately 13,200 1

la cfs) which remains within'he creek 'channel, thereby not affecting Ginna Station operation. The Probable Maximum Flood (PMF),

approximately 32,500 cfs, was found to overflow the channel banks.

An analysis sponsored by the NRC determined that. the Standard Project Flood (SPF) for the Ginna site was 15,000 cfs and the PMF was 38,200 cfs. The June 1982 NIIS study, using different parameters than the NRC study, found an SPF of approximately 13,100 cfs. This flood, and any flow less than approximately 14,600 cfs, will result in the creek staying totally within its banks.

~td The present analysis is an extension of previous NIJS analyses, in that it considers water elevations at. Ginna Station for floods

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which overflow the Deer Creek Channel and breach plant grade elevation. Plant grade elevation is 270 feet to the west of the containment and 269 feet to the east of the containment,.

The equipment at the lower elevations of the plant is protected by means of curbs, or equipment elevation, to' height of approximately 255 feet. No specific flood barriers are available at the higher plant grade elevations, other than window sills and door steps. Floor elevation at the higher plant grade is at

.271 l 0".

This analysis presents water levels across the plant, from Deer Creek to the screen house, for flood flows up to 38,700 cfs, corresponding to the largest calculated PNF.

Deer Creek Channel As in the previous studies, the HEC-2 computer code was used to calculate water surface elevations within Deer Creek t P Channel at various cross-sections; and for vaiious flows. 'igure 1,

1 H 1 (taken from RGGE drawing SK447.-93) shows the locations of cross sections used to model Deer Creek elevations with the 270 foot contour darkened. A number of sections were added between sections 1420 and 2620 since the June 1982 study. These sections were surveyed for this study in order to give better definition to the flood elevations in the area of the Ginna Station. The use of the new surveyed sections lowered the SPF water elevations approximately 0.1 feet.

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Parameters used, such as Manning's, transition, and bridge loss coefficients, have been described previously. These Manning's coefficients are more conservative (higher elevation for a given flow) than those of the NRC-sponsored study except in the area between cross-sections 1670 and 2620 (see Figure 1),.

The overbank coefficient in this area (during the flood conditions considered here almost all of the flow is carried by the overbank) was taken as 0.03. This value corresponds to "Flood Plains-Pasture, no brush-short grass," the condition actually observed during of six inches for flows in the range of the

's multiple visits to the site. The difference in predicted elevations for the two sets of Manning's Coefficients SPF.

one the order Ginna Station Channels When the channel flood flow exceeds 14,600 cfs a portion of the flow will be directed through the plant site to the west of the containment, exiting the site via the discharge canal. When the total flood flow increases to approximately 18,000 cfs, Deer Creek will begin to overflow to the east, of the containment as well. The two flow channels will combine in the vicinity of the screen house before exiting the site. Figure 2 (based on RG&E drawing 33013-352 Rev. 5) shows the cross-sections used to model the flood elevations onsite. Sections 1 through ll define Ginna Station Channel West and Sections 101 through 106 define Ginna Station Channel East,. A single Nanning s coefficient of 0.030 (short-grass) was chosen.

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The HEC-2 computer code was used to calculate water surface elevations within the two Ginna Station Channels at various flows. Deer Creek flows and overflows were taken to synoptically correspond when elevations were eguivalent at. their flow splits, i.e., at Sections 11 and 2380 for the west channel and Sections 106 and 1475 (average of elevations at 1420 and 1530) for the east channel. Deer Creek Sections 1420, 1530, 2300, and 2380 are indicated on Figure 2 along with the Ginna Station Channels.

Flood Flow Elevations Between Ginna Station West Section 1 and East Section 101 water elevations will be determined by three hydraulic controls:

the spilling of water into the discharge canal, the flow out the discharge canal opening, and the breakwall separating the site from the Lake Ontario beach. For total Ginna Station flows up to 4340 cfs, the spilling of water into the discharge canal will control water elevations in the vicinity of the screen house according to the broad crested weir equation of Q = CLH where Q

= flow over weir, cfs L = length of weir crest, feet (296 feet )

H = height of water behind weir, feet, (measured from elevation 253.5 feet )

C = coefficient that depends on H and the breadth of the weir crest.

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The value of C was taken as a constant of 2.9, based on the design value of H (1.5 feet) and a weir breadth of 1.5 feet.

For total flows through the station between 4340 cfs (screen house water elevation = 256.4 feet) and the flow that results in the breakwall being overtopped (elevation 261 feet) the discharge canal opening controls water elevations at the screen house. The discharge opening approximates a trapezoid with a base 20 feet wide (at elevation 238 feet) and a top width of 51 feet (at elevation 253.5 feet). From elevation 253.5 feet to the top of the breakwall at elevation 261 feet the opening width remains constant at 51 feet. 'aking the discharge opening as a flow obstruction, or weir, and applying Bernoulli's equation results in the relationship LH3/2 + 3 (B g)H3/2 (2)

Q Q t 5 1 where length of weir at top of opening, feet (51 feet) height of water behind weir as measured from lake level, feet (lake level assumed at 247 feet.)

length of weir at lake level, feet (38 feet.)

height of top of trapezoid above lake level, feet (6.5 feet) coefficient taken as 3.2.(

At elevation 261 feet the flow calculated from equation 2 is 8,160 cfs.

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Total Ginna Station flows greater than 8,160 cfs will result in overtoppping of the breakwall, which acts as a broad crested weir. Accordingly, equation 1 is applied to the increment of flow above the 8,160 cfs going through the discharge opening with L = 761 feet, H measured from elevation 261 feet, and C =

2.7 (breadth of weir crest = 4 feet ). Figure 3 shows the total flow through the Ginna Station Channels as a function of water elevation at. the screen house (between Sections 1 and 101),

as calculated from the hydraulic control equations described previously. A flow of 1,580 cfs is seen to correspond to the design elevation of 255 feet.

The HEC-2 computer code was run for Ginna Station Channels West. and East with the elevations and flows of Figure 3 as boundary conditions. The results indicate that the screen house levels do not affect the levels at, sections ll and 106 because intermediate sections 8 and 105 act as hydraulic controls, i.e., critical flow sections. Figure 4 relates the total Deer Creek overflow into Ginna Staton to the total flood flow, calculated according to the previous descriptions. Also indicated on Figure 4 is the flow through Ginna Station Channel West, the difference between it and the total Ginna Station flow being the amount, flowing through Ginna Station Channel East. Figure 4 also shows that the east side overflow does not become significant until total flood flows exceed approximately 21,000 cfs. Even at the maximum calculated PNF of 38,700 cfs, 76 percent of the Ginna Station flow is through the west channel.

f Figure 5 shows water elevations at, the screen house as a function of total flood flow. Various flows of interest are indicated on Figure 5, including the Deer Creek capacity with no overflow (14,600 cfs - no water at the screen house), the largest calculated SPF (15,000 cfs screen house water elevation =

253.55 feet), the flow corresponding to the largest calculated SPF plus one foot, at Deer Creek Section 2380 (17,300 cfs - screen house water elevation = 254.0 feet), and the largest calculated PMF (38,700 cfs screen house water elevation = 262.3 feet).

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It should be noted that the (+1 foot) above SPF is being taken at the cross-section where the Deer Creek overflow occurs. This is the only logical place to add margin, since the SPF itself does not, overflow the Deer Creek channel. Taking an additional one foot margin at the buildings or equipment location, when no flooding occurs, would obviously be inappropriate.

Table 1 presents the information of Figures 3, 4, and 5 in tabular form.

Table 2 shows the channel invert and water elevation at the various Deer Creek Channel sections for the SPF and PNF indicated on Figure 5. It can be seen that the SPF elevation barely exceeds plant grade elevation of 270 feet west of the containment (section 2380) and is significantly less than plant grade elevation, 269 feet, east of the containment (section 1530). Table 3 shows the corresponding information for the Ginna Station Channels for SPF

+ 1 foot and PNF (flow is negligible for the SPF). Between sections 1 and 101, the flood water essentially forms a pond, the level of which is determined by the hydraulic controls described

previously. Although no flood water flows down the east channel for the SPF + 1 foot (indicated by dashes in Table 3), the water flowing down the west, channel will fill the screen house area to elevation 254 feet. Figure 6 depicts site topography for a general north-south cross section through the plant. This latter figure is included to illustrate the site in an unexaggerated, horizontal to vertical scale ratio of 1:1.

Conclusion RG6E believes that an appropriate Design Basis for Deer Creek flooding would be protection for the Standard Project Flood. The hydraulic analysis presented in this report demonstrates that. the safe operation of Ginna Station will not be affected by flood flows less than 17,300 cfs (SPF + 1 foot).

Cost Benefit Evaluation As requested in the NRC's SER, RG&E has made an estimate of the cost to provide protection for the PMF.. Based on extensive channel widening and improvement (excavating 106,000 yd of material, forming a channel with a bottom width of 116 ft., with 1:1 side slopes), construction of a new bridge, possible relocation of the training center, and installation of approximately 31 waterproof doors, the cost is estimated at more than $ 2 million.

Based on the fact that 1) the Ginna SPF has an expected recurrence interval of greater than 10 years, 2) an additional margin of 1 foot is available, 3) the cost in terms of money and manpower expenditures, which would have to be distracted from other ongoing

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regulatory review efforts, would be quite severe, and 4) the Ginna Station meets the requirements of General Design Criterion 2, "Design Basis for Protection Against Natural Phenomena," in that the SPF + 1 foot certainly reflects ". . . appropriate consideration of the most severe of the natural phenomena 'I'related to flooding] that have been historically reported for the site and surrounding area . . . with sufficient margin . . ." it is considered that no additional protection for Deer Creek flooding is warranted.

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• REFERENCES

1. NUS Corporation, Ginna Station Desi n Basis Floodin Stud For Rochester Gas and Electra.c Cor oratl.on, Rockvz.lie, MD, August 1981.

2. NUS Corporation, Ginna Station Standard Pro'ect Floodin Stud For Rochester Gas and Electric Cor oration, Gazthersburg, MD, June 1982.

3. J.S. Scherrer et al, H drolo ical Considerations Rochester

,Gas and Electric Co oration, R.E. Gonna Nuclear Power Plant, Technical Evaluation Report, Franklin Research Center, Philadelphia, PA, April 27, 1982.

Nuclear Regulatory Commission, Final Safet Evaluation Re ort For Ginna Station, Topic II-3.B, 1982.

Corps of Engineers, HEC-2 Water Surface Profiles Users Manual, Davis, CA, January 1981.

6. Ven Te Chow, 0 en-Channel H draulics, McGraw-Hill Book Co.,

New York, NY, 1959.

7. Rochester Gas and Electric Corporation, Drawing No. 33013-171F, R. E. Ginna Nuclear Power Station, 1973.

8. Rochester Gas and Electric Corporation, Drawing No. 33013-51E, R. E. Ginna Nuclear Power Station, 1973.

9. E. F. Brater and H. W. King, Handbook of H draulics, 6th Edition, McGraw-Hill Book Co., New York, NY, 1976.

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Table 1. Deer Creek Overflow Summary Table Total Flood Flow Through Flow Through Elevation at Elevation at Deer Flow (cfs) Ginna Station Ginna Station West Screen House =

Creek Section 2380 (cfs) Channel (cfs) (ft) (ft) 14,600 0 0 253.5 270.0 Channel Capacity 15,000 0 0 253.55 270.1 SPF 16,000 100 100 253.7 270.6 17,300 300 300 254.0 271.1 SPF + 1 foot 18,000 500 500 254.2 271.4 20,000 1,300 $ .,300 254.8 272.1 20,600 1, 580 1,.580 255.0 272 ~ 3.

22,000 2,300 2'50 255.4 272.8 24,000 3,350 3",200 256.0 273.3 26,000 4,400 4,150 256.6 273.8 28,000 5,400 4,900 257.8 274.2 30,000 6,400 5,6oo 259.0 274.5 35,000 9,150 7,400 261.6 275.1 38,700 11,400 8,700 262.3 275.7 PMF

TABLE 2 DEER CREEK CHANNEL FLOOD ELEVATIONS Water Surface Elevation For'Indicated Dischar e (ft.)

Cross Section Standard Project Probable Maxi-Number Channel Flood (SPF)* mum Flood (PMF)*

(Distance from Invert 15,000 cfs*

• 38,700 cfs**

mouth, ft) (ft) 100'00 246.0 257.4 260.6 247.0 260.0 263.7 470 247.4 263.7 267.4 580 247.0 267.2 271.2 680 248.3 267.1 271.0 780 248.7 267.3 271.5 860 246.0 267.4 271.6 880 247.0 267.4 271.5 900 (Lower 247.0 267.7 271.9 Bridge) 920 248.0 267.7 271 '

1120 249.6 267. 7 271.9 1420 251 ' 267.1 271.6 1530 249.7 268.0 272.9 1670 250.0 267.4 272.2 1740 249.1 266.8 273.5 1820 251 0

~ 267.1 272.4 1860 250.0 269.1 274.5 1920 250 ' 269.9 274.8 2150 250.2 269.9 274.8 2280 250 ' 269.9 274.8 2300 (Culvert 250.0 270.1 275.0 Bridge) 2320 249.0 270.1 275.2 2380 249.8 270.1 275.7 2500 248.5 270.1 276.1 2620 251.0 270.2 276.5

• Maximum calculated value

• • Downstream from Ginna Station (Section 1420), flows within Deer Creek Channel for SPF, and PMF are 15,000, and 27,300 cfs, respectively.

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Table 3 Ginna Station Channel Flood Elevations Water Surface Elevation (ft.)

For Indicated Dischar e*

Standard Project Probable Maxi-Channel Flood Plus mum Flood (PMF)**

Cross-Section Invert One Foot (SPF+1') 38,700 cfs***

Number (ft) 17,300 CPS***

West. Channel 1 253.5 254.1 262.4 2 253.8 254.5 262.4 3 254.0 254.9 262.3 254 ' 255.5 262.2 5 254.0 256.0 261.6 6 256 ' 258.0 264.6 7 260 ' 261.6 267.1 8 269.0 270.1 273.3 9 270.0 270 ' 274.5 10 270.0 270.9 275.0 270.0 271 F 1 275.7 East Channel 101 252.5 254 ~ 0 262.4 102 254.7 262.4 103 257.5 262.3 104 264.5 267.0 105 268.3 271.4 106 269.0 272.2

• flow in channels for Standard Project Flood.

• • Negligible Maximum calculated value.

• • • Flows within Ginna Station Channel West, for SPF +1'nd PMF are 300 and 8,700 cfs, respectively. Flows within Ginna Station Channel East for SPF +1'nd PMF are 0 and 2,700 cfs, respectively.

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Feet Location of Cross-Sections on Deer Creek 0 200 400 600 800 Scale Figure 1

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0 30 60 90 120 Meters r Location of Cross. Sections in Ginna Station I

0 100 200 300 400 Feet 2380. 2300, Figure 2

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SPILLING OF FLOOD WATER INTO 31 255 DISCHARGE CANAL CONTROLS 254

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2 4 6 8 10 12 14 16 TOTAL FLOW THROUGH GINNA STATION CHANNELS (1000 CFS)

Screen House Water Elevation vs.

Total Flow Through Ginna Station Figure 3 16 '-

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0 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 TOTAL FLOOD FLOW (1000 CFS)

Flow Through Ginna Station vs. Total Flood Flow Figure 4 17

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C ~ CHANNEL CAPACITY WITH NO OVERFLOW PMF 263 262 261 QJ z0 260 Fu 259 I

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255 1 FOOT SPF 254 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 TOTAL FLOOD FLOW (1000 CFS)

Screen House Water Elevation vs. Total Flood Flow Figure 5

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"LOW WATER DATUM EL.

243.0'IGH WATER DATUM EL.

247.0'REAKWALL EL.

261'ISCHARGE CANAL EL.

231.5'RADE 253'LANT INVERT OF EL.

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270'RADE EL. 270' DEER CREEK EL. 250',

.GUARDHOUSE SCREENHOUSE General North-South Cross Section Figure I6~

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