ML20148T670
| ML20148T670 | |
| Person / Time | |
|---|---|
| Site: | Vallecitos Nuclear Center |
| Issue date: | 10/24/1978 |
| From: | Thompson G AFFILIATION NOT ASSIGNED |
| To: | Okrent D Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-CT-1066, NUDOCS 7812060002 | |
| Download: ML20148T670 (2) | |
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. October 24, 1978 To:
Dr. David Okrent, ACRS and E at General Electric's Examination of trenches A, B
Subject:
Vallecitos, CA, nuclear facility (GETR)
Except for brief meetings at the beginning and end of Tuesday I spent the day studying those three long trenches in October 17(h personnel from NRC, USGS, GE, their technical concult-company wi Aggregate length of the trenches is more than a antc, and others.
and optimal cleaning and preliminary logging had just been
- mile, completed.
Photographa chould show the story botter than words,
~and I plan to forward several if cuccessful.
Trench A, a couple of miles cast of the reactor cite, was designed to cross any p(rojection of the postulated Verona fault, d minor probably ascismic) slip curfacen were foun As anticipated,but I caw no indications of a large f ault zone.
The in the trench, minor clips are most likely a normal accompaniment of sedimentary Thin trench has been docpened in one loading and later folding, area where bedrock is more deeply covered, and that coction was not It is the one area where a significant fault might yet accescible.
yet be found.
Trench B, close to tha reactor on its went side, begins at the banc of the hillslope and extendo couthwest.
The most cignificant feature expocod is a group of thrustlike shears at the bane of the These are either landslide too thructs or tectonic thruct hill.
faults.
Southwest of the end of trench B, another short trench, exposed a thrust which of f-
"B-1," which had not yet been logged, he coil zone about one foot.
acts the "stanc line" at the base of t This coil is The upper part of the soil is not visibly offect.
postulated to be Holocene and the "stono line" to represent clima-tic conditions about 17,000 years ago.
The dilemma rained by trenchen B and B-1 in that if the thrusts are caused by landsliding, the slide is no old that it no. longer retains a clear topographic exprencion.
On the other hand the thruct in trench B-1 appears to cut the base of a young (Holocenc?) soil.
Trench E wac cut instead of trench C because of an acceso pro-Not much chcaring was found in it, but in part it bottoms blem.
in gravels that appear to be younger than the Livermore gravels (which are cut. by trenchec A and B).
Morcover, trench E, although it crosces a projected trace of the Verona fault, does not reach the base of the hills, which to me ccomo a more likely location for the Verona if it is pontulated to be a cinuous thrust instead of a Sciamic refraction and reflection data in this high angle fault.
nrea may help to resolve the questions,.and en extension of the trench was also diccuaned.
In summary, continuing invectigations are aimed at recolving 78120G0002
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ty/o main questionc:
(1) Arc the thructs near the reactor due to landcliding or tectonic procccces; hov/ old are they?
(2) Do other faults cut through the area and possibly connect vrith the thructc?
Seeing the evidence nov/ exposed in trenches vlas valuable.
A final evaluation must aviait other developing evidence.
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