ML19269D019
| ML19269D019 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/16/1979 |
| From: | Jennifer Davis CALIFORNIA, STATE OF |
| To: | Stepp J Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-04, TASK-2-4, TASK-RR NUDOCS 7902260590 | |
| Download: ML19269D019 (3) | |
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IVISION HEADQUARTERS g.0M3 416 NINTH $fREET, ROOM 1341 ACR Av!NTO. CA 95814 r%,. 9:o 445 ien:
January 16, 1979 J. Carl Stepp, Chief Geology and Seismology Branch Division of Site Safety and Environmental Analysis U.S.
Nuclear Regulatory Comnission Washington, D.C.
20555 Subj ect :
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 6 E.
2.
Recent Geotechnical Studies - Southern Orange County California, Vol. I and 2, February, 1976, SCE and SDG S E.
3.
Final Safety Analysis Report, Vol. 3 - App.
2.5, March, 1977, SCE and SDG 6 E.
4.
Final Safety Analysis Report, Vol. 4 - App. 2.58, SCE and SDG 6 F.
5.
Geotechnical Studies No. San Diego County, California, October, 1977, SCE and SDG G E.
6.
Amendment #52, Final Safety Analysis Report, December, 1977, SCE and SDG G E.
7.
Analysis of Geological Features at the San Onofre Nuclear Generating Station, July, 1974, Fugro.
8.
Analysis of C G 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.
Sa fety Evaluation of the Geological Ft a tures at the Site of the San Onofre, July, 1975, USSRC.
7902260 690
Carl Stepp, Chief JM; 3 C, REC 1.
Further studies are suggested to dete m.ine whether the reported
.;citnt fpre-terrace J:poritica) l'n J s l i dt c' 'tu: n in
+b.
'm en e Canyon area, 5 n.iles south of the reactor site, (as re"oritd by Fugro, Inc. and P.
L.
Ehlig) are definitely created by landsliding and not by faulting or a conbination 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 t r e n d i n,c parallel to the coast could not be exposed anywhere else since as a vast area along the cc.ast 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 <;here these features were reported.
It is important to consider the possible occurrence of faults along the coactline as the' parallel the offshore ;euthern extens: a of the Newp o r t - I n g l e 9. c o d fault none.
These pessible faults ony he related to the late Quaternar' di spl ace:n n t s found me1.
to the south, in the Terret Canyon.
Any feasible geophysical exploration (such as deep seismic profiling, vibro seismic, etc.) and digitined 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 Neuport-Inglewood fault zone.
2.
The nuclear stations are underlain bv 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 j oint 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 Capistre.no 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 vibreseismit exploration. w c-uteri:ed p ' riles c"
- eis ic cata che':ing conti nuous st ruc ture nay reveal sc. expl:m t t ion o
the origin and signi ficance o f soall esrthquakes in t r. e rer. ion.
cally act'. fault.
not
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JAN 3 0 *G-Carl S L'e p p, Chief 4.
Some geomorphologic features indicating possible recent n
- s r :V te press nt in thc Capir -
lo e- '. n.: t uplift The Sulphur Creek see :s to have enanged its c t : e ar: f l ot:
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 recomncnded.
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 :onclusien.
6.
Regarding " (! ; M nt No. 11 to PS.i? Un2r 2 and 3, I!nrch 1972)"
the offsho:
grnvity and r.agnetic data ao it appen" to con-t flict Lith the assoc 5 ted acoustic sections thing -.: tnt i
geologic interrrctntionc, the ter: "fonthe.n Cali fe rr i a
c -r c ic Sulduction :ene" (gravit p and textj
- a y bt doubtful at c i,i s time.
The Bouguer gravity data generally has a transforration 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.
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$ tate Geologist cc:
Priscilla Grew Perry Y. Amimoto