ML19207C413

Forwards Detailed Description of Reverse Fault in Soil Pit

ML19207C413
Person / Time
Site:	Phipps Bend
Issue date:	09/06/1979
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 7909110597
Download: ML19207C413 (5)

Text

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TENNESSEE VALLEY AUTHORITY CH ATTANLOGA. TENNESSEE 374o1 400 Chestnu. e Street Tower II September 6, 1979 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Mr. Denton:

In the Matter of the Application of ) Docket Nos. STN 50-553 Tennessee Valley Authority ) STN 50-554 In an August 16, 1979, telephone conversation, Jerry Wills of my staff notified Bob Benedict of your staff that an additional fault had been discovered at our Phipps Bend Nuclear Plant in a soil pit area north-east of the intake pumping station. A conference call was subsequently made to the NRC geologist, Sandra Wastler, on August 16, 1979, to discuss th.e fault. The enclosure provides a detailed description

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of this feature.

We do not consider this minor fault to be capable within the meaning of Appendix A to 10 CFR Part 100.

Very truly yours, TENNESSEE VALLEY AUTHORITY

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L. M. Mills, Manager Nuclear Regulation and Safety Enclosure s*\

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ENCLOSURE PHIPPS BEND NUCLEAR PLANT RTNERSE FAULT IN SOIL PIT A fault was uncovered in a soil pit excavated in an area northeast of the intake pumping station at apprcximate station S16+

24.4 and E10+72.6. (See attached map for location. )

This is a reverse fault, defined by a tight fracture, which strikes N.50*E. and dips 55*SE. (See attached photographs and sketch.) Cn the north side of the fault, bedding strikes N. 50 *E.

and dips 62*SE.; on the south side, adjacent to the fault, bedding is contorted, but farther to the south it strikes N.45*E. and dips 45*SE.

Above the fault, at the contact between top of rock and Quaternary terrace deposits, the gravel layer shows no offsets or disturbances. No evidence has been found which ;'ould indicate that this fault did not occur in the early tectonic de.siopment of th :

Paleozoic (250 million years before present) folding and faulting in this area. The fault site, having been stable for 250 million years, is not considered to be capable of producing ground offsets or generating earthquakes. Therefore, we do not classify it as a capable fault, within the meaning of Appendix A to 10 CFP Part 100.

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