ML20126D842

Adequacy of Vogtle Site Foundation Exploration

ML20126D842
Person / Time
Site:	Vogtle, 05000426, 05000000, 05000427
Issue date:	06/08/1973
From:	US ATOMIC ENERGY COMMISSION (AEC)
To:
Shared Package
ML20126D803	List: ML20126D800 ML20126D813 ML20126D826 ML20126D842 ML20126D863 ML20126D871 ML20126D887 ML20126D917 ML20126D942 ML20126D970 ML20126D978 ML20127A236
References
FOIA-84-430 NUDOCS 8506150222
Download: ML20126D842 (2)

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3 POSITION PAPER RE: . ADEQUACY OF THE VOGTLE SITE FOUNDATION EXPLORATION In the Vogtle site exploration program a large number of borings was deployed over a large area of investigation. Although we and our consultants, the Corps of Engineers, agree that the general geologic conditions at the site are basically as described in the PSAR, we ,

believe that more specific details of the foundation conditions,

. pertinent to design, may have been overlooked due to the wide spacing (

of the borings covering the critical structure locations. Specifically, some solutioning of the calcareous clay bearing stratum cannot be ruled

. out, because of'its heterogeneous interlayering of sand and fractured I

limestone which could have created solution channels, as evidenced at times by partial or complete loss of drilling fluid in the marl.

We and our consultants therefore recommended that, for the contain-ment buildings locations, additional borings be placed on a minimum

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grid of 50' feet on centers and that they penetrate at least 40 feet of fresh, unweathered marl stratum. Other, less heavy Category I structures should have an average spacing of not more'than 100 feet Lon centers, depending upon the reliance that can be placed on geologic interpretation between borings. An appropriate number of samples should be recovered from these borings and tested to demon-strate.that the upper 15' to 20' of the marl can adequately support the heavy-structures, the high bearing capacities represented in-Table 2.5-2 of the PSAS and the low compressibility characteristics.

8506150222 BM228 PER. FOIA BELLB4-430 PDR

f . .

The applicant has assigned the mechanism causing surface depressions (sinkholes) to the-erosion of the~shell bed above the earl bearing stratum. The applicant should provide assurance that the control

- mechanism for creating sinkholes is due to this entirely, and not in part to deep seated leaching and consolidation of the soils below the bearing' stratum. We,~therefore, recommend that the applicant correlate in detail the geometry, locations, and amount of depression of the sinkholes with the extent and thickness of the shell bed; and provide a detailed discussion of the geomorphology of the area. The additional borings recommended above will provide valuable data in this regard, also.

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