ML20041F578
| ML20041F578 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/15/1982 |
| From: | Krieger R SOUTHERN CALIFORNIA EDISON CO. |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-03.A, TASK-02-03.B, TASK-2-3.A, TASK-2-3.B, TASK-RR NUDOCS 8203170183 | |
| Download: ML20041F578 (7) | |
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Southern California Edison Company h5 PO box 800 2244 W ALNUT GROVE AVENUE ROSEME AD. C ALIFORNI A 917 70 March 15, 1982 Director, Office of Nuclear Reactor Regulation 8
Attention:
D. M. Crutchfield, Chief RECEfVED 9
Operating Reactors Branch No. 5 Division of Licensing MARI ~619825r 0
' umY7 U. S. Nuclear Regulatory Commission 7,
tam %
Washington, D.C.
20555
/
./7 Gentlemen:
b-e
Subject:
Dock et No. 50-206 SEP Topics II-3. A and II-3.B San Onofre Nuclear Generating Station Unit 1 As a result of discussions with the NRC Staff regarding the flood protection features at San Onofre Unit 1, SCE has prepared the enclosed i nforma tion. This information is provided for use by the NRC Staff and their consultants in the preparation of the assessments for SEP Topics II-3.A, Hydrologic Description, and II-3.B, Flooding Potential and Protection Requirement s.
If you have any questions on any of this information, please let me kn ow.
Very truly yours, b
R. W. Krie Supervising Engineer San Onofre Unit 1 Licensing Enclosure 6
8203170183 820315 PDR ADOCK 05000206 P
INFORMATION REGAPDING FLOOD PROTECTION FEATURES SAN ON0FRE UNIT 1 1.
Maximum Wave Run-up on Seawall Wave run-up on the seawall is based on the methods and procedures presented in the U.S. Army Coastal Engineering Research Center's Shore Protection Manual. The maxinum wave run-up on the seawall with the beach walkway in place was determined to be elevation 26.6 f t. MLLW. Since the top of the seawall is at elevation +28.2 ft. MLLW, no overtopping will occur. Specific parameters used to determine run-up are cescribed in the f ollowing paragraphs.
A.
Still Water Level The still water level with tsunami included is 15 6 ft. in accordance with SONGS 283 FSAR Sections 2.4.5.2.5 and 2.4.6.1.
B.
Critical Wave Based on a 1961 Marine Advisers report entitled "A Statistical Survey of Ocean Wave Characteristics in Southern California Waters,"
two graphs (attached) were plotted to show the percentage exceedance of various wave heights for expected wave periods at two stations.
The plots shw that for a 1% chance of exceedance per year, the longest period wave of 16.5 seconds has a corresponding unrefracted deep water wave height (Ho') of 4 feet.
This was selected for calculation of the maximum run-up.
C.
Depth of Water at Structure Toe SCE Dwg. #5180943 shms the top elevation of the newly constructed beach walkway to be +14.0 f t. MLLW, which gives a depth ds Of 15.6' - 14.0' = 1.6'.
D.
Critical Beach Elevation Testimony of Omar J. Lillevang, Consultant to SCE, on May 19, 1976 for the licensing of SONGS 2&3, indicated that the typical beach sand elevation at the base of the seawall would vary from approximately +10 to +14 f t. MLLW when the beach returns to its natural configuration after the construction of SONGS 283.
The maximum run-up is based on a beach elevation of +14 f t. MLLW.
2 E.
Critical Beach Slope The critical beach slope for run-up is estimated to be 1 vertical to 18 horizontal. This slope is based on an average of beach slope profiles taken from site hydrography drawing No. 8474 prepared by Pafford and Associates in December 1%3.
It is felt that this slope will be representative of the maximum summer beach slopes which may occur when the beach returns to its natural configuration.
It should be noted that the natural beach configuration was disturbed by SONGS ? construction, which began in May,1964. The beach was again disturbed by SONGS 283 construction starting in 1974 and continuing to the present. Beach profile surveys conducted from May,1964 to the present would not be representative of the natural beach configuration because of the large amounts of sand deposited on the beaches during construction, Therefore, the December,1963 survey conducted prior to construction of Unit 1 was selected for use in determining the beach slope. This will give a conservative estimate of the run-up.
I I.
Wave Impact Force on the Seawall The wave impact force on the seawall is based on the methods and procedures presented in the U.S. Army Coastal Engineering Research Center's Shore Protection Manual.
The maximum wave induced impact force with the beach walkway in place and during post-seismic conditions was calculated to be 3,200 pounds per f oot of wall length. Calculations indicate that this will not cause either a stability failure or material failure (stress beyond yield) of the sheetpile wall with the beach walkway in place.
The factor of safety against a stability failure is 5.3 versus 1.1 allowable, and the maximum bending stress with this loading is 6.8 ksi versus 40 ksi allcwable.
Specific paraneters used to determine the irpact force are described in the following paragraphs.
A.
Still Water Level The still water level is 15.6 feet as discussed in It'em I. A above.
B.
Critical Wave The maximum impact force generally occurs with the shorter period waves. Based on the 1961 Marine Advisers' Report referenced in I.B above, a conservative estimate of the shortest period for a wave of suf fir.ient buildup to inpact the seawall is 4 seconds.
C.
Depth of Water at st ructure The depth of water is 1.6' as discussed in iten I.C above.
. D.
Critical Beach Elevation The maximum impact force for t is type of structure generally occurs h
when the beach at the base of the structure is eroded to its lowest point.
The testimony of Omar J. Lillevang referenced in I.D above, indicated a typical minimum beach elevation of +10 f t. Pt.LW at the base of the seawall.
However, with the newly constructed beach walkway now providing protection for the seawall on the ocean side, a conservative beach elevation of +7 f t. MLLW was selected. This was used in conjunction with Figure 7-80 of Volume II of the Shore Protection Manual to determine the impact force.
E.
Critical Beach Slope Generally the lwer the eroded beach, the flatter the beach slope will be in front of the structure.
Since the eroded beach was taken as +7 f t. MLLW, a typical beach slope of 1 vertical to 40 horizontal was selected for calculation of the inpact force.
This slope was estimated f rom U.S. Army Corps of Engineers drawing No. D-726-72-3 dated Perch 1972.
III. Seismic Capability of Seawall The performance of the seawall during a DBE was examined as part of the Balance of Plant Structures Seismic Reevaluation Progr;m.
The criteria for reevaluation and the results thereof were submitted by letter dated December 8,1981. This evaluatinn concluded that the seawall will not fail during the DBE with the bear walkway in place.
The calculations b
indicate a factor of safety against a stability failure of 3.8 versus 1.1 allwable, and a maximum bending stress of 4.4 ksi versus 40 ksi allawable.
IV. Sliding of the North PMF Wall A calculation of the potential for sliding of the north PMF wall was performed for PMF conditions. This calculation concluded that the factor of safety against sliding is 1.63.
This calculation was based on the assunptions in the follwing paragraphs.
i A.
A coefficient of f riction of 0.59 was used to corpute wall sliding.
This coefficient is f rom Woodward-McNeill and Associates' Report
" Development of Soil - Structure Interaction Parameters, Proposed Units 283, San Onofre Generating Station, January 31, 1974".
I B.
The passive soil resistance f rom approximately 2'-6" of soil was conservatively not considered in the design of the north PMF wall.
.t.
V.
Silt Buildup in the North PMF Channel The area which drains to the north PMF channel is approximately 16.81 acres. Since the SONGS 1 site is a highly developed area, the rate of debris production will be low.
It is estimated that 20% of the area will produce debris. This debris volume is approxinetely 850 cubic yards.
This will not cause the channel to overflow as the maximum depth of debris buildup in the channel is determined to be about 2 feet based on an average channel width of 6 feet.
VI.
Sediment Removal in the PMF CMP Culverts Most of the sediment debris entering the PMF CMP culverts will range from fine sand to gravel (0.1mm to 50mm). During the PMF peak flow, the velocity through the culverts is calculated to be 10 fps based on their slope of 1.33%. According to the Corps of Engineers " Hydraulic Design of Flood Control Channe'ls Design Manual", a velocity of 10 fps will transport material as large as 200 mm.
Therefore, flow will scour the pipe bed leaving it free for full flow.
It should be noted, however, that it is unlikely that sediment will be deposited in the culverts because the top of the diversion basin wall is about 3 feet, 9 inches higher than the expected depth of sediment buildup in the channel for the PMF.
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