ML20235N263

Forwards Addl Comments on Seismology Aspects of Draft Remedial Action Plan for Umtrap Sites Located in Slick Rock, Co

ML20235N263
Person / Time
Issue date:	07/06/1987
From:	Weber M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Fliegel M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
References
REF-WM-86 NUDOCS 8707200008
Download: ML20235N263 (5)

Text

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I COVER MEMO SLICK ROCK JUL 0 61987 i

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MEMORANDUM FOR: MyronH.Fliegel,SectionLeadeg,*',.,

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1 Operations Branch

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Division of Low-Level Waste Manacement and Decommissioning, NMSS

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i FROM:

Micnael F. Weber, Acting Section Leader Technical Branch Division of Low-Level Wasto Management and Decommissioning, NMSS

SUBJECT:

SEISM 0 LOGY COMMENTS ON THE SLICK ROCK, C0 DRAFT REMEDIAL ACTION PLAN Enclosed please find additional comments prepared by the Siting Section, LLTB on seismology aspects of the Draf t Remedial Action Plan for the UMTRAP sites located in Slick Rock, Colorado. We were unable to include seismology' comments in our previous submittal for the Slick Rock RAP review (June 8, i

1987) due to constraints on the availability of review personnel. The seismology review was performed by Kristin Westbrook and was coordinated with Michael Blackford, HLTB.

Please contact Kristin Westbrook, our UMTRAP coordinator, if you have any questions.

Original Signed By Michael F. Weber, Acting Section Leader Technical Branch Division of Low-Level Waste Management and Decommissioning, NMSS

Enclosure:

As stated i

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4 SLICK ROCK, C0 DRAP COMMENTS' t

UMTRA DOCUMENT REVIEW FORM I

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SECTION 1 4

i Site: Slick Rock, C0 Date: June 1987 j

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l Document: DRAP Commentor: NRC Staff Geology / Seismology 1

Comment:

1" Page: 0-10k This page states in paragraph 3 that "...the probability of occurrence of a-l

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magnitude g.5 event within any nine-mile (15-km). radius within the region is 0.06 x 10". The recurrence interval of an ME earthquake within any nine-mile (15-km) radius is thus.166,700 years." The bases for the calculated i

earthquake probability and recurrence interval are not clearly stated and-cannot be verified by NRC staff based on the information:given. Calculation of l

earthquake recurrence interval is important with' respect to selecting the 1

i seismologic design basis for the stabilized tailings embankment. The RAP should be revised to provide the detailed calculations'used to determine the i

recurrence of the ME earthquake for the Slick Rock area.

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SECTION 2 Response: Page By:

'Date:

Plans for Implementation:

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i w-SECTION 3 Confirmation of Implementation:

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Checked by:

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Approved by:

,Date:

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SLICK ROCK, C0 DRAP COMMENTS UMTRA DOCUMENT REVIEW FORM SECTION 1 Site: Slick Rock, C0 Date: June 1987 Document: DRAP Commentor: NRC Staff Geology /Selsmology Comment:

2 Page:

D-104 This page indicates that the threshold magnitude that would result in the propagation of a fault rupture to the earth's surface in a tectonic plate interior can be determined by setting fault rupture length equal to zero in the Bonilla, et al., equation and solving for the magnitude. Such a process I

is in error mathematically because the equation requires taking the log of the fault rupture length and taking the log of zero is a undefined number. The process is also in error because the asrumption of a zero, or very small, surface rupture length is an insupportable extrapolation of the Bonilla, et al., data. The RAP should be revised to justify the assumption of a zero, or i

very small, surface rupture length and to demonstrate that this assumption provides conservative estimates of the potential for surface rupture of a fault in the Slick Rock area.

Reference:

Bonilla et al. (M. G. Bonilla, R. K. Mark, and J. J. Lienkaemper), 1984,

" Statistical Relations Among Earthquake Magnitude, Surface. Rupture Length and Surface Fault Displacement," Bulletin of the Seismological Society of America, Vol. 74, No. 6, pp. 237.9-2411.

SECTION 2 Response: Page By:

Date:

Plans for Implementation:

SECTION 3 Confirmation of Implementation:

Checked by:

, Date:

Approved by:

, Date:

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SLICK ROCK, C0 DRAP COMMENTS UMTRA DOCUMENT REVIEW FORM SECTION 1 Site: Slick Rock, C0 Date: June 1987 Document: DRAP Commentor: NRC Staff Geology / Seismology Comment:

3 Page: D-112 l

4 Although Fault Group 1A includes mapped faults up to five km long within one km of the site area, the DRAP asserts that the faults are not capable.

Kirkham and Rogers (1981), however, consider the faults in this area to be potentially active Neogene faults. Use of Bonilla's equation as shown on Page D-104 of this DRAP results in a maximum earthquake magnitude of 6.5 at the site i

for a 5 km-long fault. The 84th percentile Campbell (1981) acceleration for a magnitude 6.5 earthquake would be 0.7, which is much higher than the 0.219 9

used for design purposes at Slick Rock. The RAP should be revised to demonstrate that faults in Group 1A are not capable Neogene faults or to reassess the design seismic acceleration.

References:

Kirkham, R.M., and W.P. Rogers, 1981, Earthquake Potential in Colorado, a Preliminary Evaluation, Colorado Geological Survey, Bulletin No. 43.

Campbell, K. W. 1981.

"Near-Source Attenuation of Peak Horizontal Acceleration " Bulletin of.the Seismological Society of America, Vol. 71, pp. 2039-2070.

SECTION 2 Response: Page By:

Date:

Plans for Implementation:

SECTION 3 Confirmation of Implementation:

Checked by:

, Date:

. Approved by:

, Date:

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8 SLICK ROCK, C0 DRAP COMMENTS ]

l UMTRA DOCUMENT REVIEW FORM

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SECTION 1 Site: Slick Rock, C0 Date: June 1987 f

Document: DRAP 4

Comentor: NRC Staff Geology / Seismology Comment:

4 Page: 0-104 This page makes the following statement: "The probability of occurrence of the FE (Floating Earthquake) within the ning-mile (15km) radius of any site during probability figure (2.25 x 10~3)5 x 10', or less than one percent." appears to be_

the 1000-year design life is 2 2 This The RAP should be revised to correct the FE probability during the 1000-year l

design life of the tailings embankment and to describe the calculations used to estimate this probability.

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l SECTION 2 Response: Page By:

Date:

Plans for Implementation:

a SECTION 3 Confirmation of Implementation:

1 Checked by:

, Date:

Approved by:

,Date:

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