ML20198F735

Forwards Socioeconomic Impact Study on Facilities,For Info. W/O Encl

ML20198F735
Person / Time
Site:	Washington Public Power Supply System
Issue date:	11/21/1977
From:	Robart A NRC OFFICE OF STATE PROGRAMS (OSP)
To:	Cleary D NRC
References
CON-WNP-1154 NUDOCS 8605290067
Download: ML20198F735 (1)

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November 21, 1977 i

MDIORANDUM FOR: Donald P. Cleary, DSE

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FROM: Andrew W. Robart Special Assistant for State Relations, SP

SUBJECT:

SOCI0 ECONOMIC IMPACT STUDY WNP 1 & 4 Enclosed is a copy of the above socioeconomic impact study on

'GP 1 & 4 which is for your information.

Original signerf by Andrew W. Robe Andrew W. Robart Special Assistant for State Relations Office of State Programs Enclosure

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JAN 3 o ggyg MEMORANDUM POR: Olan D. Parr, Chief Light Water Reactors Branch #3, DPM FROM: J. Carl Stepp, Chief Geosciences Branch, DSE

SUBJECT:

SUPPLEMENT TO THE SER - GEOLOGY AND SEISMOLOGY PLANT NAME: UNP-1 and UNP-4 DOCKET NOS.: 50-460/513 Enclosed is a supplement to the SER following our review of Amendment 23 to the UNP-1 and 4 SAR. Based on our interpretation of the data contained within this a===dmant and other data gathered since publi-cation of the SER, we require that an intensity VIII be postulsted at the site. However, this higher intensity does not alter our con-clusion stated in the SER, that an acceleration of .25g should be applied to the sites.

Original Signed by J. C. Stepp J. Carl Stepp, Chief Geosciences Branch Division of Site Safety and Environmental Analysis

Enclosure:

As stated ec w/o encl:

R. Boyd R. DeYoung ec w/ encl:

W. Casmaill D. Vassallo T. Cox DIS IBUTION: l ,7..tte2e4

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m 2.0 SITE CHARACTERISTICG 2.5 Geology, seismology and Geotechnical Engineering The Safety Evaluation Report for WNP-1 and WNP-4 sites was published in May 1975. In that report we concluded that:

"an intensity VII-VIII is a conservative site intensity for representing the SSE. Thus, we consider a horizontal accel-eration of 0.25g used as the zero period limit of appropriate spectra to be a conservative SSE. This acceleration is to be applied at the foundation of Category I structures."

Since the publication of the Safety Evaluation Report the staff has reviewed extensive additional information concerning the regional tectonic setting of the WNP-1 and 4 sites.

i Because of the acquisition of ~new data the earthquake of December 14, 1872 was relocated near Lake Chelan, Washington.

This earthquake had formerly been located by Milne (1956) in southern Canada. Previously uncatalogued information on the distribution of damaging intensities caused by the 1872 earthquake came to the attention of the NRC on d,ocketing of i

the Skagit Nuclear Project, Units 1 and 2 (Docket Nos. 50-522/

523) Preliminary Safety Analysis Report in August 1974. During the preparation of the site investigations for the Puget Power and Light Company's Skagit Nuclear Project site an investigation of the effects of this earthquake in the United States was conducted by the Bechtel Corporation, geotechnical consultant

to the PSP &L. The results were presented to the NRC in Appendix 2J of the Preliminary Analysis Report for the Skagit Nuclear Project.

Subsequently, the total available information on the intensity effects of this earthquake was evaluated by a Northwest Utilities Task Group. Their report was submitted to the NRC on December 22, 1976. The NRC Staff requested that the USGS reevaluate the size and location of this earthquake based on the total avail-able data, including that obtained during our ' review of the Skagit Nuclear Project and that developed by the Northwest Utilities Task Group. A joint USGS/NOAA panel was formed to review the relevant data. The panel concluded that: (1) the maximum intensity of the earthquake should be a Modified Mercalli IX, and (2) the epicenter could not be accurately located. The data appear, however, to require a location within a region that lies approximately between Entiat, Washington and Chilliwack, British Columbia as defined by the Northwest Utilities Task Group.

In October 1977, in response to staff questions, the Washington Public Power Supply System (WPPSS) submitted a detailed report of extensive geological and seismological investigations of a region between 118 degrees and 122 degrees west longitude and 45 degrees and 50 degrees north latitude. This area S

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o includes parts of the Northern Cascades, Central Cascades, Okanogan Highlands and Columbia Plateau physiographic provinces and the general area of the locations postulated by Milne (1956) and the Northwest Utilities Task Group for the 1872 earthquake.

The additional investigations were initiated: (1) to better define the location of the December 14, 1872 earthquake by either identifying the source structure or associating it to a geologic province, and (2) to evaluate the possibility of a similar earthquake occurring in the Columbia Plateau. To accomplish this the Washington Public Power Supply System and its consultants reevaluated the seismicity of the region including the 1872 earthquake, compiled and analyzed all.known published an/. unpublished geological and geophysical data, evaluated remote sensing imagery data, and developed a compre-hensive plate tectonic model of the Pacific Northwest. These studies were followed up by field reconnaissance and geologic mapping in selected areas identified by the study. The regional studies added considerable additional information regarding plate tectonics and plate boundary characteristics of the Pacific Northwest. As a result of these investigations Washington Public Power Supply System recognized the epicentral location of the 1872 Earthquake as being somewhere within the broad

area which includes Lake Chelan to the south and extends .to the north as far as southern British Columbia. This infor-mation was reviewed by the staff and discussed with the Advisory Committee on Reactor Safeguards. The staff believes that the additional studies support the conclusion that the December 14, 1872 earthquake was centered in the region between Entiat, Washington and Chilliwack, British Columbia, generally north of the Columbia Plateau structural province. The Advisory Committee on Reactor Safeguards is in substantial agreement with this opinion. The Committee and its consultants concluded in a letter of November 15, 1977, that ". . .the 1872 Wenatchee

. earthquake should be considered an intensity VIII.. ." and that " arbitrary movement over extended distances of a prototype 1872 earthquake for purposes of seismic design should be reexamined."

It is the conclusion of the staff that the earthquake should be considered to be a strong intensity VIII MM. We specif'ically use " strong" to indicate that there exists doubt concerning the size of this earthquake, as indeed there exists similar doubt concerning many earthquakes of the last century. For 1

many such earthquakes there exist little more than fragmentary descriptions of their af fects. For the 1872 earthquake the only direct evidence for higher intensity of ground motion appears to be landslide phenomena. Since some landslides have

occurred near the times of earthquakes of small magnitudes, and other substantial landslides have occurred in no way related to any earthquakes, it is our conclusion that landslide phenomena alone, in the absence of additional types of evidence is not a sufficient basis to assign intensity IX to the 1872 earthquake.

The studies conducted by WPPSS show that the Columbia Plateau on which the WNP 1 & 4 sites are located is distinguished from the region north of the Plateau within which the 1872 earthquake was centered on the basis of geologic and crustal structure and geophysical properties. These differences

, include:

1. A high positive Bouguer gravity anomaly over the Plateau indicating anomalously thin crust under the area.

2. The boundary of the Columbia Plateau is characterized by a relatively steep gravity gradient which would suggest high deviatoric stress. The zone of expected high deviatoric stress is in the area of historic epicenters near Chelan and near the southern end of the area within which the 1872 earthquake is believed to have been centered.

3. The trends of major tectonic structures which lie immediately to the north and northwest of the Columbia Plateau structural province are different from those in the Plateau. North and northwest of the Plateau structural trends range between

northwest and northeast, while in the west central part of the Columbia Plateau structural province, where structures are well developed, major structures trend generally east-west.

4. There is a strong contrast in tectonic style between the Columbia Plateau structural province and the region to the north and northwest. The tectonic structures in the area north and northwest of the Plateau province are major faults

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and fault bounded grabens. Displacements on the bounding faults are measured in kilometers. The structures in the Columbia Plateau structural province are mainly elongated folds with associated faults. Maximum displacements on the order of hundreds of meters have occurred on the faults. Thus, the style of deformation is markedly differ-ent within the Plateau.

5. The rocktypes north of the Plateau are principally crystalline metamorphic and plutonic masses with sandstone and shales within downfaulted grabens. The upper rocks of the Plateau

, are basalt flows. *

6. Geophysical data indicate major differences in crustal properties beneath the Plateau.

Based on the above, we conclude that the Columbia Plateau structural province should be considered a separate tectonic province within the meaning of 10 CFR Part 100, Appendix A.

The December 14,,1872 earthquake was centered in an area generally

north of the Columbia Plateau Province. Therefore, a recurrence of this event should not be hypothesized near the WNP 1 and 4 sites.

As stated in our Safety Evaluation Report, there are no geo-

-logical structures in the immediate site area that could cause surface faulting or localize earthquakes. Based on this finding, the seismicity of the Columbia Plateau province, and the earthquake potential of the Rattlesnake-Wallula structure, a site intensity of VII-VIII would appear to be the appropriate intensity for -determining the seismic design basis for the WNP 1 and 4 sites consistent with the requirements of Part 100.

There exist, however arguments, based largely on considerations of regional tectonics, which indicate that an intensity VIII earthquake should be postulated. This is based on the con-sideration that the entire northwest, from a location near Cape Mendocino in northern California northward to the vicinity

, of the international border, must be considered a region of active tectonics. That is, a subducting margin was active in this region until recent geologic time and some measure of convergence may be ongoing along this boundary at present.

There are, therefore, significant uncertainties in our under-standing of the regional tectonic setting and the state of regional lithospheric stress. However, this does not alter our

I 8-conclusion stated in the SER, that an acceleratio$ of .25g should be applied to the sites. This' reference acceleration is to be used to scale Regulatory Guide 1.60 spectra at 33 Hz.

The spectra so scaled are to be applied at the free field finished grade.

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. t REFERENCES

1. Advisory Committee on Reactor Safeguards, 1977, Regional Tectonics of the Paci(ic Northwest; November 15, 1977 letter fren Bender

. to Cossick.

2. Bechtel, Inc., 1976, December 14, 1872 Earthquake: Re' port Prepared for Puget Sound Power & Light, October, 1976.

.- 3. Coombs, H. A. , Milne, W. G. , Nuttli, O. U. , and Slemmons, D. B. ,1976, Report fo the Review Panul on the December 14, 1872 Earthquake: .

Report Prepared for the Utilities of the Pacific Northwest, December, 1976.

4. Milne, W. G.,1956, Seismic Activity'in Canada, West of the 113 Meridian, 1841 to 1951, Publication of the Dominion Obs'ervatory, Ottowa, Vol. -

XVIII No. 7, Ottowa, Canada, 1956.

5. Puget Sound Power & Light, 1975, Preliminary Safety Analysis; Report, Chapter 2.5, Appendix 2J, entitled: Investigation of the December 14, 1872 Earthquake in the Pacific Northwest; Appendix prepared for PSP &L by Bechtel, Inc., June, 1975.

6. Washington Public Power Supply System, 1974, UNP 1/4 Preliminary Safety Analysis Report,.;hapter 2.5.

7. Washington Public Power Supply System, 1976, December 1872 Northwest -

Earthquake: Unpublished Data Submitted to Consultants August 15,

, 1976, and (revised) October 19, 1976. '

8. Washington Public Power Supply System, 1977, New Ceological and Ceophysical Information about the December 14, 1872 Earthquake .

Source Area and the Columbia Plateau, PSAR Amendment 23, Appendix 2R, October, 1977,. .

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