ML13303A698
| ML13303A698 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/03/1979 |
| From: | Cardone T, Sobel P Office of Nuclear Reactor Regulation |
| To: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7906210301 | |
| Download: ML13303A698 (8) | |
Text
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1979 Docket N.os. 50-361 & 50-362 MEMORANDUM FOR: '.Robert E. Jackson, Acting Chief Geosciences Branch, DSE FROM:
Tom Cardone, Geologist Geosciences' Branch, DSE Phyllis Sobel, Seismologist Geosciences Branch, DSE
SUBJECT:
SAN ONQFRE UNITS 2 AND 3 GEOLOGY FIELD TRIP' On April 3, 4-and 5, 1979,.'presentatives of the U. S. Nuclear Regulatory'Commission (NRC),
Southern, California Edison Company (SCEC), and'its consultants; and the CaliforniaiDivision of Mines and Geology (CDMG) met to discuss and observe the regional and site geology near the San Onofre Nuclear Power Stations. A list of attendees at-the April 3 meeting is enclosed. SCEC presented information which responded to NRC questions 361.35 and 361.36 in Amendment 14 to the FSAR, and addressed the geologic and seismic comments in the January 16, 1979 letter from James Davis, CDMG to J. Carl Stepp, NRC.
On April 3 geology presentations were made by the SCEC staff and consultants.. The. information presented was an elaboration of tho data and information contianed in the March 16, 1979 submittal to NRC by SCEC. Dr. Perry Ehlig described the geology and'tectonics of the Capistrano Embayment area and the Newport-Inglewood Fault Zone.
Dr. Roy Shlemon presented the results of his study of coastal de formation rates based on an.evaluation of the elevation-of Late,'
Quaternary-(70,000-125,000 years before present) stratigraphic markers Jim McNey described minor unmapped faults located-in the Capistrano Embayment which were discovered during the aerial photolineament analysis and proVided answers to each of CDMG's written comments to NRC. A copy of the CDMG letter is enclosed. A brief summation of SCEC's answers to the-CDMG questions were as follows:
- 1. SCEC believes the feature common to Horno and Dead Dog Canyons, which are approximately.one quarter of a mile apart, is a land slide and is at least 125,000 years old; since it is truncated by Terrace 1 as discussed by Roy Shlemon. The Target Canyon planar features are -unrelated to deformation in the area and to the features seen in Horno and Dead Dog Cany6ns. They are the result of differential consolidation and landsliding..
7906210 OFFICE~'
SURNAME DATE3 MC FORM 318 (9*76) NRCM 0240
- u. 8. GOVERNMENT PRINTING OFF ICE a - 25
-769
R. T79 The features found during excavation (A, B, C, and D features) are not significant.to the'seismic design. They are all trunca ted by Terrace 1 and are-therefore, not capable within the meaning of Appendix A to 10 CFR Part 100.
- 3. Vibroseis studies could not detect small offsets on possible faults associated with the moderate earthquakes that occur in the region.
- 4. Sulphur Creek does show a change in the direction of stream flow. The evidence indicates that landslides dammed Sulphur Creek, causing the change in.direction of stream flow.
- 5. SCEC, agrees with COMG that aeromagnetic data does not show a change in the basement rock complex acrost the Christianitos fault as was indicated on-page 12 of "Recent Geotechnical Studies, SoutherrwOrange County, California, February 16, 1976, Vol. II,",by SCEC.
- 6.
SCEC agrees that the Bouguergravity data does change across.
the continent-ocean boundary. However, SCEC still believes the Mesozoic subduction zone is a valid theory.
CDMG did not indicate a need for additional information-at this time and we believe that SCEC's answers were generally adequate and should aid usin responding to Dr. Davis's questions to-NRC.
Dr. Ehlig discussed current uplift and regional compressional patterns' and indicated that he had not found any active faults in the embayment during mapping or as a result of ground truth.assessment of the lineament study. Jack West reviewed data relating to subsurface structure in the site area and.concluded that most tectonic movement was pre-Pliocene, and that all movement was pre-late Pleistocene based on his interpretation of oil well logs and seismic reflection profiles.
On April 4 we took a helicopter overflight of the area and a bus and foot tour of the areas of interest. During the helicopter reconnaissance we observed Target and'Horno canyons, the' Christianitos.fault, the bluffs along the coast that contain the.marine terrace markers, the Newport Inglewood fault zone, the Cherry Hill. fault, the Pelican Hill fault zone, and the Shady Canyon fault. On the bus tour we observed:
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- 1. An outcrop of Capistrano siltstone.
- 2. Several previously unmapped faults found in the Capistrano Embay ment.
Landfi11 consisting of material from -the San Mateo formation in contact with continental sediments, which had.given the appearance of the possible presence of recent faulting near the construction site. The emplaced landfill sand had-recompacted itself to appear very much like the original San Mateo deposit which occurs in the area.
Outcrops of fhe stage 5e sea level (Terrace 1) (age - 70,000 to 80,000 y.b.p.) above the San Mateo formation north of the plant along the, beach.
- 5. Channel-features in the sea 'cliffs at San Clemente State Beach.
- 6. Terrace deposits and shoreline-angles at Dana Point.
On April 5 we walked to Horno, Dead Dog, and Target canyons. At Horno and Dead Dog canyons, SCEC interpreted the features observed in both canyons asthe backscarp of a lanaslide based on the normal displacement toward the sea. CDMG geologists indicated that these fractures could be associated with a fault which extends through the three canyons and hight control theestraitness of the shoreline in this area. It was also observed that these offset,features, which are approximately.
6 miles from the site, whether due to either landslide or faulting, are capped by Terrace 1 which is at least.125,000 years old, and are nqt capable-faults within the meaning of AppendIix A to 10 CFR 100.
At Target canyon, the fault offset type features observed differ somewhat in.character from those observed in the-other two canyons.
The Target canyon features are more linear which.could argue against a landslide origin and appear to offset by approximately 2 inches the 125,000 year old terrace deposits. These-offsets appear to be small and are about 6 miles from the site. SCEC indicated that this feature also has a landslide origin and even if they have'a fault origin the distance from the site precludes them from being significant to the seismic design of the San Onofre plant structures.
OBURNAME31P.
DATE NX C FORM 318 (9*76) NRCH 0240 U.S. GOVERNMENT PRINTING OPPICE: 1978 - 285 - 769
/MAP3-1979 R,. E.Jackson
-4 In summary, through oral presentations and helicopter, bus and foot reconnaissance, SCEC presented analyses of a number of significant geologic structures which had not been address during the CP review, but which have been extensively studies during the OL review.
DISTRIBUTION:
T caaco DOCKET FILE (50-361/362)
NRR RDG
'Tom Cardone, Geologist GB RDG Geosciences Branch Division of Site Safety and Envirohmental Analysis 0rIaginal Signebg P. A. Sobel Phyllis Sobel Seismologist Geosciences Branch Division of Site'Safety and Environmental Analysis
Enclosures:
As stated cc: w/enclosure H. Rood L. Heller L. Reiter J. Greeves P. Sobel T. Cardone PDR Local -PDR OPF~
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NEC FORM 318 (9 76) NRCM 0240 u.S..covrtRNMEZNT PRINTING OPpicz: 1978 - 26B5-789
En osure 1. Attendance at April 3, 1979 NRC site visit to San Onofre 2 and 3 -
Geology SCE M.0. edford J. L. McNey P. J. West Jim Beoletto David R. Pigott Shawn Biehler, consultant H. Gene Hawkins J. S. Andres H. Peters Roy Schlemon, consultant P. Ehlig, consultant J. L. Smith, consultant J. C. West, consultant NRC Tom Cardone Phyllis Sobel H. Rood S.S. Philbrick (ACRS)
Gary R. Quittschreiber (ACRS)
CDMG Perry Y. Alqimoto Siang S. Tan GUARD Phyllis It. Gallagher, atty.
FOE Grey Garrett for Richard Wharten
T bI F C
G JP.,
EPARTY'ENT OF CONSERVATION
)1VISION OF MINES AND GEOLOGY IVISION HEADQUARTERS
'16 NNTH STREET, ROOM 1341
'CRAMENTO, CA 95814 hone916-45.1e25)
January 16, 1979 J. Carl Stepp, Chief Geology and Seismology Branch Division of Site Safety and Environmental Analysis U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Subject:
San Onofre Nuclear Station Review
Dear Carl:
The comments on the geologic and seismic review of reports on San Onofre Nuclear Station were prepared by our staff, Siang S.
Tan (geologist) and Gordon W. Chase (geophysicist).
The reviewed reports were the following:
- 1. Amendment #11 PSAR (Preliminary Safety Analysis Report)
March, 1972, SCE and SDG & E.
- 2. Recent Geotechnical Studies -
Southern Orange County California, Vol. 1 and 2, February, 1976, SCE and SDG & E.
- 3. Final Safety Analysis Report, Vol. 3 - App. 2.5, March, 1977, SCE and SDG & E.
- 4. Final Safety Analysis Report, Vol. 4 - App. 2.58, SCE and SDG 8 E.
- 5. Geotechnical Studies No. San Diego County, California, October, 1977, SCE and SDG & E.
- 6. Amendment #52, Final Safety Analysis Report, December, 1977, SCE and SDG & E.
- 7. Analysis of-Geological Features at the San Onofre Nuclear Generating Station, July, 1974, Fugro.
- 8. Analysis of C & T Type Features at the San Onofre Nuclear Generating Station, November, 1974, Fugro.
- 9. Final Report on Geological Features at the San Onofre Nuclear Generating Station Unit 2 and 3, August, 1976, Fugro.
- 10.
Safety Evaluation of the Geological Features at the Site of the San Onofre, Jtily, 1975, USNRC.
Carl Stepp, Chief JA 0
p p
- 1.
Further studies are suggested to determine whether the reported n
(pre-terrace deposition) Inndslide features in the Horno Canyon area, 5 miles south of the reactor site, (as reported by Fugro, Inc.
and P.
L. Ehlig) are definitely created by landsliding and not by faulting or a combination of tectonic and subsequent landsliding.
Is the ancient landslide feature exposed at the sea bluff?
Or is it thought to be concealed by one of the younger slope failures at the sea cliff?
If it is considered to be of tectonic origin, it may not be exposed at the sea bluff as it parallels the shoreline.
Similarly, any fault trending parallel to the coast could not be exposed anywhere else since as a vast area along the coast of this region is underlain by thick terrace deposits which are not intersected by drainage channels, deeply eroded into the underlying bedrock, except for the two canyons where these features were reported.
It is important to consider the possible occurrence of faults along the coastline as they parallel the offshore southern extension of the Newport-Inglewood fault zone.
These possible faults may be related to the late Quaternary displacements found more to the south, in the Target Canyon.
Any feasible geophysical exploration (such as deep seismic profiling, vibro seismic, etc.) and digitized method of providing computerized printout of seismic data showing continuous geologic structure along the profile, which allows the interpretation of structure underneath the coastal terrace deposits, will be very useful in evaluating the possibility of the presence of onshore faults paralleling the Newport-Inglewood fault zone.
- 2. The nuclear stations are underlain by a couple of sets of fractures and shear joints, particularly U'nit 1. These features are exposed at the surface after up to 85 feet overburden was removed; they may experience greater seismic,.shaking effects than when they were still buried, although they do not separate different lithologies.
It seems that many of these joint features are well cemented and are normally not open fissures, but no careful study of the characteristics of these failure features which relates them to potential rupture due to seismic shaking was ever performed.
- 3. Offshore subsurface studies of the CaDistrano embayment indicate that several significant faults may underlie the general vicinity of the site, as reported by J. C. West. Although these faults do not show any evidence of Holocene or Pleistocene movement or high seismicity, more detailed subsurface studies, deep seismic or vibroseismic exploration and computerized profiles of seismic data showing continuous structure may reveal some explanation of the origin and significance of small earthquakes in the region.
Seismically active faults may not ahow any distinct Holocene
-isplacement evidence (but mos'
.J'ely Vroduce only small earth
~ ~s,snqller t ha:, L
Carl Stepp, Chief JP 3 0 REC
- 4. Some geomorphologic features indicating possible recent uplift movements may be present in the Cc-pistran' cm:Ument.
The Sulphur Creek seems to have changed its stream flow direction and drainage course but this phenomenon could also be explained by a blockage of drainage due to land sliding. Further studies of these features as related to recent tectonics are recommended.
- 5. On page 12 in "Recent Geotechnical Studies, Southern Orange County, Calfiornia, February 1976, Vol. II, portions of enclosure A" the following statement is made:
"The aero magnetic map indicates there is a change in the basement rock complex from the east to west side of the Christianitos fault."
The amount of aeromagnetic data east of the fault is not sufficient to develop this conclusion.
- 6. Regarding "(Amendment No. 11 to PSAR Unit 2 and 3, March 1972)"
the offshore gravity and magnetic data do not appear to con flict with the associated acoustic sections.
Using current geologic interpretations, the term "Southern California Mesozoic Subduction Zone" (gravity map and text) may be doubtful at this time.
The Bouguer gravity data generally has a transformation from minus to plus values across the continental to oceanic boundary.
We hope these comments will be helpful in the preparation of your forthcoming geologic review on San Onofre Nuclear Station.
Si nc7y J ms F. Day s tate Geologist cc:
Priscilla Grew Perry Y. Amimoto