ML20148T942
| ML20148T942 | |
| Person / Time | |
|---|---|
| Site: | New England Power |
| Issue date: | 11/24/1978 |
| From: | Stepp J Office of Nuclear Reactor Regulation |
| To: | Parr O Office of Nuclear Reactor Regulation |
| References | |
| FOIA-79-86 NUDOCS 7812060144 | |
| Download: ML20148T942 (6) | |
Text
,
v -
9 1 ,
%f~/N l NOV 2 4 1979 ]
MEORAICC# FOR: Olan D. Parr, Chief 1 Light Water Reactors Branch #3, DPM j FECM J. Carl Stepp, Chief Geosciences Branch, DSE SUBJECT DRAFT SAFETT EVALUATION REPORT - OPEN ITEM OFFSHORE FAULTING PLA!rr NME: New England 1 & 2 LIC23SIEG STAC*** CP DOCET HCtBSES: 50-568/569 RESPONSILLE 3RANat: L* b 3; R. Stright, LPM REQUESTED C0!FLSTION DATEt N/A REVII'd STATUS! Continuing on January 30, 1978, ve forwarded to you the Geosciences 3 ranch draft input for the Safety Evaluation Report. At that time, two open itema vore identified, the New Shoreham fault and the site geology. The site geology section was forwarded to you en April 3, 1978.
With regard to the section on the & v Shoreham fault tm can now provide further input. Attached is a new section which should be appended to the ex.isting section on the New Shoreham fault. Based on our review of the available infarmation we conclude that this fault is not capable within the me aning of Appendix A to 10 CFR Part 100 and does not constituta a bazard to the NEP 1 & 2 site.
Original Slgned by J. C. Stepp J. Carl Stepp, Chief Geosciences Branch Division of Site Safety and EBri P=1 Analysis Enclosurc*
As stated ec: w/o enclosure R. Boyd R. DeYoung cet w/ enclosure see nert page o'nca > - _ .
suan Aus
- D* 's * . . . , . . . _ . . . ..
NRC PGRM 318 (P 76) NRCM 0240 f( ut s. novsmanswr enenvue orrics iste - ese ea4
~
78120601If
4A' ** % Jgk Olan D. Parr - 2 - NOV 3 .; 33 i
1 cc: v/ enclosure R. Denise T. Miraglia R. Stright j
- J. Stepp i R. Jacksou !
L. Eeiter l M. Cutchin l l
1 l
1 l
1 DISTRIBUTION DOCKET FILE (50-568569)
GB RDG 1
l l
l l
2 l
i i
J DSE:ST:GB
~
i.Reite r
. 11/2N73
)
DSE:S B
-.. ,.. J,.'..:
7 E.7 DSE : ST :G..B
, , , , , , , , , FIJ/cNso :sb JCStepp- ,
pats
- h. .. k .f,b ._. ' k. . O_. 6 NRC FORM $10 (9 76) NRCM 0240 W un s. oovnenure emnvine orrict, s ete - eas.su
l l
New Shoreham Fault .
1
. The New Shoreham fault was first recognized by McMaster (1971) in interpretation of longitudinal seismic reflection profiles l
spaced four to nine kilometers apart off the coast of Rhode Island. l The fault strikes northwesterly in a manner that could be considered anomalous relative to most New England and Appalachian structural trends which generally strike in a northeasterly direction. We also recognized that this fault offsets Cretaceous (136-65 million years before present) units which indicates that the last movement on it 1 post dates the last generally recognized regional tectonic event in 1
the Appalachian system. Post-Triassic (225-190 million years before presenh) offsets on faults in the eastern United States have, however, been previously recognized in a number of places (Darton, 1950; l
White, 1952, York and Oliver, 1976). York and Oliver (1976) have i catalogued and briefly described 33 faults in the eastern United States, 18 of which are located in the Atlantic Coastal Plain and Piedmont, geologic provinces that displace sediments ranging in age from Cretaceous to Pleistocene.
This fault can be traced from ten kilometers west of Block Island, R.I. seaward for approximately 70 kilometers. The most northern extent of the fault is about 20 kilometera south of the proposed site, however, a magnetic anomaly which has a similar strike indicates that it may extend closer to the Connecticut shoreline necr Fisher's Island.
i
(
4 i
2 -
The New Shoreham fault offsets inferred Cretaceous age (136-65 million years before present) sediments by as much as 40 meters with lesser amounts of offset of possible Tertiary age (65 - 1 1/2 million years before present) sediments. More recent sediments of indeterminate Pleistocene age (between 1 1/2 million years to 15,000 years before present) or older are not offset within the resolution of the seismic reflection data. The. data would allow for recognition of several feet of vertical offset.
The applicant and his consultants have undertaken an extensive offshore study of the New Shoreham fault in the form of marine seismic profiling, and stratigraphic correlations. They interpret the data as indicating that last fault movement definitely occurred more than 43,800 years ago and probably before 20 million years ago. This determination of the age of-last movement of this fault is based on several observations, j On the northern end of the fault, young sediments contained in a buried ancestral stYeam channel which crosses the fault are not offset. Based on an analysis of erosional / depositional .
unconformities and estimated correlations with glacial and interglacial episodes these sediments have been determined to be at least 43,800 years old and probably greater than 120,000 years old. On the southern extent of the fault, sedimentary units which have an estimated age of 20 million years before present are not offset. The age of this unit is determined by development of a stratigraphic column based upon the projection of the regional dip of units, projections of drill hole data and bottem samples and
3 -
extensive seismic profiling.
Based upon our review of the available information we generally concur with these conclusions. Due to limitations in assigning ages to the channel-fill sediments, however, we believe that the age of these sediments can only be determined .o be of glacial age ( 1 1/2 million to 15,000 years before present) or older. ,
l l
The New Shoreham f ault lies near a region where, because of early I colonization, there exist historical records of earthquake activity extending back some 300 years. An extensive seismograph network has also been in operation in the New England area for the past three years. Examination of data from these sources indicates approximately ten earthquakes have occurred offshore of Rhode Island within 50 kilo-meters of the coastline. These are mostly small magnitude (less than 3.0) events for which the maximum historical intensity determined was V. Recently, several researchers (Fis'.ter, 1978; McMaster and Collins, 1978) has suggested that several of these epicenters can be correlated with faults or geophysical lineaments. It is very difficult to assess the validity of these correlations in any rigorous way since no more than one or two epicenters fall on any of the 7 or 8 proposed faults or lineaments. Usually a larger nu=ber of events is needed to make such a correlation. One of the small earthquakes (magnitude 2.2) was
4 -
located near the New Shoreham fault 20 kilometers south of Block Island. The other epicenters however, lie to the east and to the north of Block Island away from the fault. The distribution of earthquakes epicenters offshore of Rhode Island shows no evidence that the New Shoreham fanit represents a zone of increased seismicity.
A reasonable assessment of the historical geologic development of the New Shoreham fault including the absence of offset of glacial age channel-fill sediments and Tertiary-age sedimentary units combined with the lack of evidence in the record of historic and instrumental seismicity to suggest earthquake activity associated with the fault, provides reasonable assurance that the New Shoreham fault is not capable within the meaning of Appendix A to 10 CFR Part 100 and does not pose a hazard to the proposed New England Nuclear Plants some 20 kilometers distant.
t
,