ML20140B730
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9' mug g8M Tp Steve Brocoum U. S. Nuclear Regulatory Commission as Washington, D. C. 20555 g
Dear Mr. Brocoum:
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i I have thoroughly reviewed the three documents supplied by Consumers Power Company concerning subsurface faulting in the Midland, MI, vicinity.
Together they represent a detailed and exhaustive study of the subsurface geologic structure and stress state for this portion of the Michigan Basin.
Although the originators for each of these documents inevitably differ on a variety of details, the facts that they supply can be used to defend the following conclusions:
1.
It can be demonstrated that both a northwest and a subordinate northeast structural fabric exists within Devonian and Mississippian strata, and that some faulting may be associated with each trend.
2.
Evidence for tectonic faulting is absent within the Pennysivanian Saginaw Formation, suggesting that basin subsidence stopped or, more likely, abruptly decreased in the late Mississippian or Early Pennsylvanian.
Youngest fault displacement (assuming that subsurface faults exist) must, therefore, be of pre-Atoka time (Early Pennsylvanian).
3.
Limited stress field data for the basin does not suggest favorable -
conditions for either faulting or the reactivation qf faults.
4.
Oow Chemical Company's injection processes near the plant site are performed at pressures significantly below litiiostatic loading and are not a potential cause for induced fault motion.
Assuming that all data and interpretations presented in these documents are accurately recorded and impartial to the interests of the parties involved, 0291 &
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- 1 Steve Brocoum March 22, 1982 ESS-2-82-21 I concur that all unresolved issues concerning subsurface faulting or fault reactivation in the Midland, MI, vicinity are satisfactorily addressed within the present limits of available information.
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Sincerely, J
sO Lu___ L4uarc Harry Nicholas Planner Geochemistry, MS F665 HNP:jb Cy: D. J. Cash, ESS-3, MS C335 H. N. Planner, ESS-2, MS F665 CRM0 (2), MS A150-ESS-2 Files, MS K586
'In reference to:
1.
" Description and Evaluation of Bedrock Structure in the Vicinity of Midland Plant - Units 1 and 2, Midland, Michiga'n," Western Geophysical Corporation, February 1982.
2.
" Review of Weston Geophysical's Report (February 1982) on the Bedrock Structure in the Vicinity of the Midland Nuclear Plant," Dr.
J. II. Fisher, March 1982.
3.
" Review and Comments on the February 1982 Report by Weston Geophysical Corporation," Dr. A. T. Cross, March 1982. p 4
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