ML19289E908

Suggests Subsurface Explorations in Bedrock & Soils to Reveal True Stratigraphic & Structural Conditions Prior to Const.(Author'S Name & Affiliation Deleted)

ML19289E908
Person / Time
Site:	FitzPatrick
Issue date:	05/07/1969
From:	AFFILIATION NOT ASSIGNED
To:	Hard J Advisory Committee on Reactor Safeguards
References
ACRS-CT-0162A, ACRS-CT-162A, NUDOCS 7905290424
Download: ML19289E908 (2)

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. . . a I Mr. James E. Hard Senior Staff Assistant Advisory Co=mittee on Reactor Safeguards b7 O/6 % b United States Ato ic Energy Cc==ission [pg Washington, D. C. 20545 y James A. Fitzpatrick Nuclear Power Plant Power AuG6FI'Ey'*oTThe State of New York

Dear Vr. Hard:

'Ihe steeply dipping fault diagonally crossing the turbine area foundation at the Fitzpatrick plant, was examined on the afternoon of May 6 in ec=pany with:

Representatives of PASHY, including Chief Engineer Asa George Representatives of S & W, including Consulting Engineer W. F. Swiger Mr. Tom Cardone, DRL AEC Mr. Howard H. Waldron, Engineering Geology Branch, U. S. Geological Survey.

The fault is exposed on the east and west sides of the excavation in the Oswego sandstone in the turbine area. It strikes about N 70 W, thereby It being about 20 degrees off of nor=al to the centerline of the building.

dips northward away from the reactor at about 70 to 75 degrees from'Ihe the horizontal, thereby being about 20 degrees flatter than vertical. It foundation of the reactor is about 100 feet to the south of the fault.

is underneath the fault in the foot vall in co=pletely undisturbed rock. The The north wall of the fault has a very few short vertical fractures.

underside *" north side (hanging wall) of the fault is stridted in the vertical, It shoving that the walls of the fault have moved in a vertical direction.

is not a lateral fault like the San Andreas. The gouge, or crushed =aterial between the walls of the fault, is a few inches thick and is aSome grayofsilcy these are

=aterial, containing about 30 to 407o fragments of sandstone.On the footwall, or south side platy and oriented parallel to the striae.

the fault, the laminae of the discontinuous, occasional layers of shale in But the the Oswego sandstone have been bent dotm next to the fault plane.

sandstone beds dip south, away from the fault at angle of about 15 degrees for a distance of about 20 feet. Thus the beds for a short distance on the underside of the fault have been tilted upward as if refusing to myefault downward. This tilting is the main reason for censidering that c 2 is a reverse fault (one in which the upper side = oves up) even though the dip is a great deal steeper than is usually found in the thrust faults in the flatlying rocks of the platform area of the northeastern part of the>

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Stone and Webster had directed the excavation of two pits over a hundred feet east and west respectively of the main excavation to expose the fault directly bereath the overlying glacial tin for the purpose of seeing whether the fault continued from the ordovician bedrock upward into the Pleistocene till. If the fault continued into the till and the till was offset or disturbed then it may be assumed that action on the fault has occurred in the past 13,000 years since the Wisconsin ice sheet left the site.

The till in the easterly pit was co= posed of boulders and coarse materials so oriented that it was not clear whether these materials were of natu-al origin or had been dumped there during this or an earlier construction episode when the area was part of an Ar=y installation during World Wars I and II. However, preliminary clean up of the easterly wall of the vesterly pit and exposure of the vertical gouce on the fault plane in its contact with the overlying till for a north-south discance of a foot or so, revealed a continuous dark organic layer which was not_ broken either directly above the fault er norch or south of the fault for several feet.

In my opinion from the data and conditions visible in the excavations on the site on the afternoon of May 6 the fault is old and not active within the age of the organic layer in the westerly pit. It may be considered as a horizontally restrained, nearly vertical, very thin, weak zone in a strong bedrock foundation and not an active fault.

l'ay I suggest that this fault might have been recognicable prior to construc-tion if the cores of the borings had been logged to define the stratigraphy and structure of the site as they would have been in a foundation study for a high concrete dam. There will be many other nuclear plants in stratified bedrock and soils and unless the subsurface e::plorations in the bedrock and in the soils are conducted in such a way as to reveal the true stratigraphic and structural subsurface conditions, such construction events will continue to disrupt the construction schedule.

Very truly yours, P .}

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