ML19254F417

Summarizes Ks Geologic Survey Rept Re Excavation Site of Svc Spillway at Main Dam

ML19254F417
Person / Time
Site:	Wolf Creek
Issue date:	09/27/1979
From:	Wilson F KANSAS, STATE OF
To:	Lefevre H Office of Nuclear Reactor Regulation
Shared Package
ML19254F415	List: ML19254F417
References
NUDOCS 7911090261
Download: ML19254F417 (2)

Text

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~. s KANSAS GEOLOGICAL SURVEY 2030 ^"nua ^ Ca'"ou" we**

The Univers1Ly of Kansas Environrnental G ology Section Lawrence. Kansas Goo 44 i G13 804 4091 September 27, 1979 Mr. Harold LeFevre U.S. Nuclea. Regulatory Commission Geosciences Branch Div. of Systems Safety Washington, D.C. 20555

Dear Mr. LeFevre:

On Septec3er 26, I visited the excavation site of the service spillway at the main dam of the Wolf Creek Nuclear Power Station near Burlington, Kansas with engineers of the Water Resources Division of the State Board of Agriculture.

Their principal responsibility is to inspect various .ph%es of dam construction to assure that it is being carried out according to t.te plans and specifications of the permit issued by their department. I advise them on the engineering geology, aspects of the site Dave Fenster and Charles Bandolan of Dames and Moore Engineering Company - the geotechnical consulting firm for the project - had also requested that I view some minor shear zones and other structures which had been uncovered in the walls of the excavation.

The formation involved is called the Ireland Member of the Lawrence Formation by the project geologists but which is an unnamed shale sbove the Ireland sandstone according to KGS nomenclature. It is a gray, laminated, silty to sandy shale containing an impure coal about 8 inches thick. About 15 to 16 minor structures were exposed ir an interval from the base of the coal to about 10 feet into the shale above it. These were of two types: 45' shear zones with minor displace-ment, and vertical discontinuities in the coal bed a few inches wide where either overlying or underlying shale appeared to have been " injected" through the coal. Only one of these discontinuities was associated with a shear zone.

Neither the shear zones nor the discontinuities appeared to have extended across the width of the excavatien which is perhaps 50 feet. It was interesting to note that at one place a 45*. shear zone had an apparent dip to the north (approx. , my orientation may have been off) and another about 10 feet away had an apparent dip to the south. The two nearly intersected at the top.

In all instances, both the shear zones and the coal discontinuities died out within a few inches of their ends and strata above and belcw.are undisturbed, deme t-strating that they we " developed shortly after depositien and are not new active.

My tentative opinion and the opinions of the site geologists . ara that the struc-ture= are related to post-burial ecmpaction of the sediments while they were in a semi-indurated state and that they are not caused by tectonic activity.

1 4 355 7911090 M [ .

Mr. Harold LeFevra - page 2 - September 27, 1979 l

This cbserweion, however, should not be taken to mean that tectenic features may not eventually be uncovered at the site. I noted, for example, a miniature

" pop-up" relief structure in the shale on the bottem of the excavation which had occurred very recently. It had an amplitude and width of 2-3 inches and an estimated length of 15-20 feet. The orientatics (abbreviated to north half of compass) was N50*W. It is not certain whether this structure is related to local stress, air slaking of the uncovered shale, or to actual regional ambient stress but I think the latter should at least be considered.

Sinc ely, /

/ ,s-7 / ,

Frank W. Wilson, Chief Environmental Geology Section ,

FUW:elp cc: Ray Seiple Dames & Moore Box 585 New Strawn, KS 66839 7r n r!

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