GENERAL31063

• Permit No: M1980244
• IBM Index Class Name: General Documents
• Doc Date: 4/8/1994
• Doc Name: REMAINING ISSUES CRESSON PROJECT FN M-80-244 AM-06
• Media Type: D
• Archive: No

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DATE: April 8, 1994
TO: Berhan Keffelew
FROM: Allen Sorenson
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RE: Remaining Issues, Cresson Project, File No. M-80-244,
AM-06
Pseudostatic Slope Stability Analysis
The applicant has used the design earthquake peak- bedrock
acceleration established for the project as the seismic coefficient
in the slope stability models developed for the various facilities.
The applicant has stated that this value for the seismic
coefficient was utilized in order to "expedite the permitting
process". The foregoing phrase in quotations was included in the
applicants adequacy responses, and indicates to the Division that
there continues to be disagreement as to how an acceptable seismic
coefficient should be developed. For that reason, clarification of
the Division's position is being provided.
The pseudostatic method of analysis is an attempt to represent the
effects of an earthquake on a potential slide mass by an equivalent
static horizontal force determined as the product of a seismic
coefficient and the weight of the potential slide mass. One of the
problems with this type of analysis is the difficulty in selecting
an appropriate seismic coefficient. The Division has maintained
that selection of the seismic coefficient should be based on
evaluation of ground motions that could occur at the site,
dependent upon potential seismic source characterization. This was
the procedure used during the amendment 5 process which resulted in
the estimated peak ground acceleration of 0.14g. The applicant
subsequently attempted to utilize this estimated peak ground
acceleration to develop an appropriate seismic coefficient for
facilities to be analyzed. The Division reviewed the applicants
effort to generate an appropriate seismic coefficient and rejected
the determination based on the inapplicability of the research
paper cited to the circumstances at the proposed Cresson Project
facilities. The Division's actions in this regard have
subsequently been validated by Jonathan Bray, the consultant hired
by the applicant to resolve the seismic coefficient issue.
Dr. Bray recommended establishment of a maximum horizontal
equivalent acceleration (MHEA) based on the peak ground
acceleration and on the degree of attenuation or amplification of