PY-CEI-NRR-1444, Forwards Eighteenth Quarterly Rept,Cleveland Electric Illuminating Seismic Monitoring Network,Apr-Sept 1991

Forwards Eighteenth Quarterly Rept,Cleveland Electric Illuminating Seismic Monitoring Network,Apr-Sept 1991

ML20090A326
Person / Time
Site:	Perry
Issue date:	02/27/1992
From:	Lyster M CENTERIOR ENERGY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20090A329	List: ML20090A331 PY-CEI-NRR-1444, Forwards Eighteenth Quarterly Rept,Cleveland Electric Illuminating Seismic Monitoring Network,Apr-Sept 1991
References
PY-CEI-NRR-1444, NUDOCS 9203020275
Download: ML20090A326 (8)

Text

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PERRY NUCLEAR POWER PLANT 10 CENTER ROAD gi s-Michael D. Lyster  :

PERRY, OHIO 44081 VICE PnESIDENT NUCLEAR PERRY, OHIO 44081 (P16) P59 3737

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February 27, 1992 PY-CE1/NRR-1444 L l U.S. Nuclear Regulatory commission i Document Control Desk l

Vashington, D. C. 20555  ;

4 Perry Nuclear Power Plant Docket No. 50 440 Seismic Monitoring Report 18

, Final Seismic Evaluation -

Gentlement This letter transmits for-your reviev Cleveland Electric illuminating (CEI)

Company's Eighteenth Seismic Honitoring Repott. Ve anticipate this to be our last formal report, as ve have achieved the goals and objectives established ,

for our seismic Monitoring' Program monitoring local injection volls. '

Incorporated in the report is a summary of the last six month period (April 1 through September 30, 1991) and an overview summary of the last si>: years -

monitoring and analysis. With the submittal of the enclosed final report and  !

this transmittal letter, CEI will pursue phased retirement of the CEI network in 1992, gossibly leading to closure. Ve vill eliminate monitoring report submittals to the NRC staff, effective with this Report 18.- Discussions of our network retirement plan and detailed support for this plan are described in the following topics on network phasecut, history, monitoring.results and ,

studies, and conclusions.

Network Phaseout i CE1 has been operating the local seismic network (monitoring the corridor between the 1/31/86 Leroy epicenter and ICI-America injection vells) for almost six-years. Our original commitment was to operate the system for two years, beyond which we have operated for almost four additional years.

CEI has performed several in-depth seismological studies with the aid of our- #

consultant, Veston Geophysical, in the six years following the 1/31/86 Leroy  ;

earthquake. Through a series of 18 formal reports on monitoring results, incorporating'these in-depth studies, CEI has sufficiently evaluated the

. seismic nature of-the local region. CEI believes it has acquired the data '

- necessary to answer the original questions, and-that further monitoring vill

- not add any substantial new information. Thare are no remaining regulatory ,

reasons for continued operation of the network. Any continued tranitoring at reduced levels vould be strictly for CEI scientific-purposes only and vill be restricted to an absolute minimum. ,

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7n addition to the significant cost of analyzing results and preparing ,

quarterly reports, operation of this system at a very lov thteshold of  :

detection (Mc=-0.5) to monitor lot recording microcarthquakes is technically difficult to maintain. Maintaining station reliability is difficult due to telephone failures, electronic equipment problems and required repairs, and l personnel time demands. Therefore, ve. find it necessary to substantially  !

curtail or possibly eliminate monitoring based on the information supplied in this letter. Accordingly, ve are implementing the following schedules Dec emb<, 1991 - Decision to not repair Scli Station downhole installation January-1992 - Last Monitoring Report Preparation February 1992 - Detection Algorithm Threshold Changes

. March 1992 - Temporary Sixth Station GEN Closut e April 1992 - Selection of Stations (2 through 5) for closure May_1992 - Notification of closing Stations to Lessors  ;

j_  : June 1992 - Power / Phone Eliminated for Closing Sites July 1992 - Station Closures / Site Restorations commence September 1992 - New Configuration October 1992 - Site Lease Expirations Through 1992 - Evaluate Optisns Beyond 199?  ;

This schedule' anticipates removal of our 6th temporary station, and closure of 2 to 5 permanent sites by September of this year depending on continued lease arrangements, equipment opetabill'y, and site technical value. Expiring property leases in October 1992 (all 5 expire this year) vill be renegotiated on a case-by-case basis and ate not automatic renevals. Any retained stations vill be adjusted for a threshold detection level at approximately Mc=1.0, or near'" felt" sensitivities. Operation beyond 1992 vill be evaluated based on internal CEI restraints, the technical value of maintaining " free field" sources of seismic data, equipment reliability, and cost.  !

Additionally, CEI vill maintain communications'vith the John Carroll University (JCU) Seismological Observatory to share information on recorded seismicity. CEI has extensively funded the development of their regional network, and has access to their records.

History Following the 1/31/86 Leroy earthquake (magnitude Mb.5.0 about 11 miles south of PNPP) and subsequent regulatory examination, CEI committed in a June 17, 1986, letter PY-CEI/NRR-0478 to install and operate a seismic network in northeast Ohio for about two years or_through 1988. The Leroy earthquake had  ;

been extensivelyLstudied by CEI as documented by the NRC in Supplemental Safety Evaluation Report No. 9, but some scientific questions remained. The

! hypothesis of induced seismicity as the origin of the Leroy earthquake was extensively debated among scientific and institutional organizations (following the event occurrence) at public hearings, meetings, and in technical literature. Therefore, as documented in supplemental Safety i

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USNRC February 27, 1992 [

PY-CEI/NRR-1444 L ,

Evaluation Report No.10 CEI installed the seismic monitoring network to further analyze the seismogenic nature of the atea and to evaluate further the i hypothesis that the 1/31/86 Leroy ear thquake was induced by local injection vells.

A description of the network vas proposed to the NRC in the June 17, 1986  :

letter and also outlined our plan for operation. Those plans primarily "

coresisted of installing a five station digital telemetered network, locating the central receiving station at PNPP, providing the capability to detect and lacate coordinates of micro-seismic events (belov Mc 0.0), and reporting those results to the NRC.

The methodology of reporting to the NRC staff was established betweer. our t licensing staff and the NRC's Structural Engineering and Geosciences staff, as  ;

documented in our first Quarterly Report PY-CEI/NRR-0579L, dated February 2, 1987. That resulted in CEI providing to the Staff Quarterly Reports summarizing the monitoring tesults. Additionally, CEI piovided telephone  :

contact with the staff should unusual events occur such as a " felt" earthquake in the region near the plant. Over the time period ending in 1991 CEI has provided 18 formal docketed reports and made 3 or 4 courtesy telephone contacts for informal notification of locally occut ting "f elt" events by citizens near the epicenter. No events-vere " felt" by employees at PNPP or detected by our strong-motion inplant instrumentation.

In PY-CEI/NRR-0974L dated February 27, 1989, we indicated an intent to continue monitoring through 1990 to allow time to gather additional data i necessary to complete our understanding of the local seismicity. In PY-CEI/NRR-1013L dated June 9, 1989, ve provided information that a

" temporary" sixth _ station was to be installed for monitoring the area near Hadison on the lake. In the transmittal of Report 14, PY-CE1/NRR-13'? dated i June 4, 1991, we indicated that monitoring was sufficiently completed that the program could be re-evaluated. That evaluation result is provided in this transmittal.

r Monitoring Results and Studies Results of our Seismit Honitoring Program have been provided to the NRC staff through a series of 18 reports, with the first submitted on February 2, 1987.

Through these reports we have compiled the cumulative seismic _ record of the local region with an emphasis upon the " corridor" betveen the 1/31/86 1.eroy ,

. epicenter and the ICI America deep injection vells, the 1986 epicentral area, and other areas within or near the network aperture. This cumulative seismicity is summarized in Quarterly Reports 18 and 13 in detail, however a general overviev is valuable.

The January 31, 1986 Hb 5.0 earthquake occurred at a depth of about 5 km, and was followed by 21 aftershocks, varying in size from -0.2 Mc to +2.8 He, and vary in depth from 3.12 km to 6.13 km. The last event occurred on January 17,

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USNRC February 27, 1992 '

PY-CE1/NRR-1444 L 1991. The January 31,-1986 cvent is not considered induced, was purely tectonic and was the only event to trigger in-plant strong motion accelerometers.

Vithin the monitoring netvork aperture and in the local proximity of the deep IL' American injection vells, 62 events were r ecorded over six years, varying in size from -0.7 He to +1.9 He, maintaining a nominal depth of 2.0 km, or slightly deeper based on the model study presented in Report 18, Appendix B. l Most of these events are located to the east and southeast of the injection wells as identified on Figure 3 of Report 18. None of these events vere felt '

by local residents, or detected by in-plant strong motion accelerometers.

This seismicity-is expected to remain-very shallow and at very lov energy levels as recorded. >

l Outside of the network, but within the immediate region, 35 events were recorded, varying in size from -0.5 He to 43.5 He. The two-mc'. notable events were the 1/26/91 Euclid Mc=3.5 event north of Cleveland ar.d the 12/25/88 Hadison Mc=2.4 event, both of which vere felt by local residents but  ;

vere not felt by PNPP personnel or detectef by in-plant strong motion accelerometers.. These are considered typical of the region, and in the Euclid cast Tre locations of historical lov Jevel seismicity.

Some of the llistorical earthquakes which vere theoretically located by " felt" reports to be on-shore,' vere probably located in the lake similar to the 1/25/91 Euclid event. Therefore the uncertainty of historical events is confirmed, and there is no basis for arbitrarily aligning these events to

" fit" theorlos of origin. There are random in-time naturally occurring small events (less than Mc=3.5) throughout the region which are typical of those evaluated during plant licensing, and ere to be expected.- Some of these events occur in areas with historical records of seismicity.

Outside of the network at-a distance of 25 miles, 8 events were recorded, ranging in size from 1.5 Mc to 3.6 Mc. The most notable of these (Mc=3.6 in July 1987 and a Hc=2.8 in August 1989) vere located in the vicinity of Ashtabula, 25 miles east of PNPP near an injection vell. Both of these were felt by local residents, out vere not felt by plant personnel or detected by in-plant strong motion accelerometers. Report 15 evaluated the Ashtabula l events, however this area was not the central focus of our monitoring program.

In order for CEI to better understand the monitoring results and to properly

, evaluate their significance, special studies were conducted and documented in L the Quarterly Reports. A list.of the eighteen Seismic Honitoring Reports is l-provided on Attachment 1 to this letter. Special studies contained in those

, repo rts are listed here.

Report No. 4 - Started Incorporating ICI Injection Vell Data Report No. 10 --Intensity Survey of 12/28/88 Leroy Aftershock Mc-2.8 Report No. 13 - Evaluation of 4 years Seismic Honitoring/Vell Data r

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USNRC -S- February 27, 1992 PY-CEI/NRR-1444 h Report No. 13 - Detailed Examination of Seismicity and Injection Vells Report No. 14 - Evaluation of Local Oll/ Gas Vells influence Report No. 15 - Summary of Ashtabula Seismicity Raport No. 17 - Intensity Survey of 1/26/91 Euclid Mc.3.5 Event Report No. 18 - Summary of Crustal Hodel Investigations Report No. 18 - Evaluation of 6 Years Seismic Honitoring CEI Conclusions These studies, in conjunction with the normal reporting process, have allowed CEI to achieve the objectives identified in Supplemental Safety Evaluation Report 10. Those conclusions related to monitoring are detailed in Monitoring Report 18. Our overall conclusions relating to the monitoring program and its results, and the diminished value for further monitoring, are provided.

As concluded in the-1986 Report " Investigations of Confirmatory Seismological and Geological Issues" the 1/31/86 Leroy earthauake was a purely tectonic event, was not induced, and has expressed a normal aftershock sequence.

The events recorded since 1/31/86 are considered well located and form a solid basis for assessing the seismic potential of the area. Hieroevents recorded within the network occur on the average of once a month, ate very shallow, and are expected to remain very small. Hieroevents within the network aperture and near the ICI injection wells are potentially induced, but cannot be

" timed" vith injection vell operating parameters. Microevents near a Fairport Harbor injection vell and a series of earthquakes near the Ashtabula deep injection vell are also considered potentially induced. '

Operation of the CEI Seismic Network has allowed CEI and our consultant to l better understand the regional seismicity through significant study and

[ analysis of micro-earthquakes in the local regional area. This information, coupled with earlier CEI geophysical studies following the 1/31/86 Leroy event, vill allow quick assessment of future felt events, should they occur.

The seismological character of the area is very well understood. Continued long term operation of the network vill not significantly expand our knowledge of the area seismicity and causal sources. Vith the submittal of 18 reports and their combined information, CEI has completed the objective as described in Supplemental Safety Evaluatlun Report No. 10.

Therefore, based on these conclusions, CEI intends to follov the schedule g outlined in this letter for network reduction or elimination. No further.

I monitoring reports vill be submitted to the NRC staff and only minimal l information vill be collected by CEI from reduced seismic network operation.

l~ Any retained monitoring stations vill be operated until failures appear (electronic equipment f ailure is expected) and vill probably then be retired.

CEI has met its regulatory commitment objective by operating the seismic network over six years, sig 'icantly beyond our original commitment, and 1

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USNRC February 27, 1992 PY-CEI/NRR-1444 L collected sufficient data to demonstrate that the Leroy Earthquake cf 1986 was '

not inducsd. Should your staff have any questions regarding this submittal,

-please contact us.

• Sincerely,

^ )Y,1 Michael D. Lyster HDL:HJlla ss

. Attachment cc: NRC Project Managet NRC Resident Inspector Office-NRC Region III R. Rothman, NRC P. Sobel, NRC i 4

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t PY-CEI/NRR-1444 L Attachment 1 Page 1 of 2 ,

i NO. LETTER REPORT 111C11L1C11T 1 PY-CE1/NRR-0579L - First report summarizing 1986 monitoring records February 2, 1987 utilizing portable analog seismometers in operation <

sinre February 1, 1986 2 PY-CEI/NRR-0640L - Last report utilizing portable analog equipment April 27, 1987 3 PY-CEI/NRR-0697L - First report utilizing digital network array August 17, 1987 - Complete system description

- Identification of first Ashtabula earthquake y Mc.3.6, about 25 miles east 4 PY-CEI/NRR-0769L - Commenced incorporating injection vell operating January 18, 1988 data concurrent with seismicity in each report 5 PY-CEI/NRR-0825L - Noted CEI studying oil / gas well relationship to  !

March 15, 1988 seismicity 6 PY-CEI/NRR-0856L - Detailed review of magnitude Mc=1.9 May 6, 1988 microcarthquake, the largest to occur within i-i network and near injection vells 7 PY-CEI/NRR-0905L - First recorded offshore celsmicity and analysis August 26, 1988 8 PY-CEI/NRR-0940L - Denotes recording the September 7, 1988 magnitude November 28, 1988 Mb.4.6 Kentucky earthquake 9 PY-CEI/NRR-0974L - Identifies monitoring te extsnd beyond 1988 February 27, 1989 commitment, through 1990 '

- First colored maps provided

- Study of the magnitude Mc.2.4 Madison event 1

- Study of role of oll/ gas wells i

10 PY-CEI/NRR-1013L - Intensity survey results of 12/28/88 Mc=2.8 June 9, 1989 Leroy aftershock event

- Analysis of cumulative seismicity and temporary addition of sixth station 11 PY-CEI/NRR-1055L - Very little microseismicity l August 29, 1989 12 PY-CEI/NRR-1105L - 6 month report December 6, 1989 - Noted repeated occurrences of events near Achtabula, 25 miles east 13 PY-CEI/NRR-1165L - Evaluation of all 3 years monitoring data and i April 12, 1990 preliminary conclusions

PY-CEI/NRR-1444 L

• . Attachment 1 Page 2 of 2 No. LEITER REPORT llIGilL1GitT 14 PY-CEI/NRR-1215L - Detailed evaluation .sf local oil / gas wells September 5, 1990 influence on seismicity 15 PY-CEI/NRR-1279L - Additional Ashtabula events and comparison to December 17, 1990 1/31/86 Leroy earthquake 16 PY-CET/NRR-1318L - Very little microseismicity Harch 4, 1991 17 PY-CEI/NRR-1355L - Intensity survey of 1/25/91 Euclid Mc.3.5 event June 4, 1991 18 PY-CEI/NRR-1444L - 6 month report February 25, 1992 - Evaluation of all 6 years monitoring results

- Summary of Crustal Model Investigation

- Elimination of Formal Report Submittal l

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