ML20039E064

Notifies of Planned Mods to Excavation for Facility Svc Water Intake Structure.Excavation Will Extend Deeper to Greenish Gray Vincentown Formation Between Elevation 23 & 29 Ft.Tremie Concrete Will Be Placed in Mar 1982

ML20039E064
Person / Time
Site:	Hope Creek, 05000355
Issue date:	12/22/1981
From:	Liden E Public Service Enterprise Group
To:	Schwencer A Office of Nuclear Reactor Regulation
References
NUDOCS 8201060485
Download: ML20039E064 (4)

Text

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• O PSEG Public Service Electric and Gas Company 80 Park P1aza Newark, N.J. 07101 Phone 201/430-7000 Mailing Address: P.O. Box 570, Newark, N.J. 07101 December 22, 1981 tD f

S RECEIVED Director of Nuclear Reactor Regulation ,,

U.S. Nuclear Regulatory Commission }"g '

S7 JAN5 Eggn.

7920 Norfolk Avenue Bethesda, MD 20014 _

q NuNnYm7EE Attention: Mr. Albert Schwencer, Chief f Licensing Branch 2 4 m Division of Licensing Gentlemen:

HOPE CREEK GENERATING STATION NO. 1 AND 2 UNITS DOCKET NOS. 50-354 AND 50-355 SERVICE WATER INTAKE STRUCTURE This letter is to advise you of planned modifications to the excavation for the Station Service Water Intake Structure at.

the Hope Creek Generating Station. These modifications, discussed herein, are required because of variations of actual subsurface ccnditions from those anticipated.

The construction plan for the Service Water Intake Structure was described in our letter of July 12, 1978 (R. L. Mittl, PSE&G to Director, NRR, NRC). In the letter, we committed to support the foundation on the greenish gray Vincentown formation which, based on previous explorations, was ex-pected to be at el. 35 ft. (average). In addition, we com-mitted to construct a shear key (minimum plan dimensions of bottom of key 20 ft by 35 ft) at the bottom of the excava-tion, extending to elevation 20 ft.

To date, the excavation for the structure has reached ap-proximately el. 31 and the shear key el. 20. During excava-tion, the greenish gray Vincentown formation was located at elevations lower than 30. To confirm these findings, addi-tional soils exploration was initiated. The top of the greenish gray Vincentown formation within the limits of the cofferdam, was confirmed with eight additional borings.

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In order to adhere to the original foundation criteria, the excavation will be extended deeper to the greenish gray Vincentown formation which we now anticipate will vary be-tween el.- 23 and 29 within the limits of the structure.

Modifications to the excavation support system are being im-plemented before deepening the excavation. In order to maintain confinement of the toes of the cofferdam sheet piles, a herm with a maximum width of 10 ft will be provided around the perimeter of the excavation. The shear key hav-

'ing bottom dimensions 20 ft by 35 ft in plan, will extend from the top of the -greenish gray Vincentown to el. 20.

Refer to the attached Figures 1 and 2 for the overall gen-eral arrangement.

Based on our analysis of the modified configuration, we have

. concluded that the design now being implemented satisfies our design criteria. In fact, the configuration changes en-hance the design margins for sliding and overturning under extreme loading conditions.

In response to recent on-site inquiries by NRC rep.*:esenta-tives, the ongoing, non-safety related excavation support activity which includes, for example, the driving of con-struction pin piles within the limits of the cofferdam, is only construction-related and is not seismically considered part of the permanent safety-related structure.

We are currently planning to place tremie concrete in March 1982.

Should you have any questions, do not hesitate to contact us.

Very truly yours, A. Liden

/E.Manager - Nuclear Licensing and Regulation

'BAP/CWC/MCR:ds Attachments CC: Dr. Robert A. Gilbert USNRC Licensing Project Manager Mr. W. H. Bateman USNRC Senior Resident Inspector

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