ML20038D055
| ML20038D055 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/25/1981 |
| From: | SAN DIEGO GAS & ELECTRIC CO., SOUTHERN CALIFORNIA EDISON CO. |
| To: | |
| Shared Package | |
| ML20038D050 | List: |
| References | |
| NUDOCS 8112160024 | |
| Download: ML20038D055 (11) | |
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l REPORT ON THE "ALISO CANYON FAULT" AND THE ALLEGED " MOUNTAIN TOP FAULT ZONE" CAMP PENDLETON, CALIFORNIA November 25, 1981 1
I SOUTHERN CALIFORNIA EDISON COMPANY AND SAN DIEGO GAS AND ELECTRIC COMPANY s
8112160024 811211' PDR ADOCK 05000361-o PDR
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During tha' Atomic Safety Lictnsing Board hearings fcr San Onofro Nucicar '
Generating Station Units 2&3, Mr. D. W. Phifer, a retired Marine Corp Colonel, identified what he believed to be six previously undisclosed geologic structures that he alleged were new and could influence the seismic safety of the plant.
The Applicants examined his features with.Mr. Phifer and then, in the field independently and later again with Mr. Phifer and the NRC staff.
Documentation in " Report on Limited Appearance of Mr. D. W. Phifer and Alleged Geologic Features" dated July 29, 1981, was then prepared by the Applicants and it discussed in detail each of his alleged new geologic discoveries.
The features d$scussed and the conclusions reached are:
o "Horno Su=mit Fault" pp. 4-15 Mr. Phifer's suggestion of as much as 20 miles of right lateral displacement is speculative and is contrary to the fact that bedrock for=ations and contacts are continuous across the hypothesized trend of the fault. It is Applicants opinion that the fault does not exist.
o "Horno Canyon Fault" pp. 16, 17 Marine Terraces at elevation 325 project across the fault at Horno Canyon without offset. This surface is 300,000 years old and any fault would be that age or older and not be capable.
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" San Onofre Mountain Fault" pp. 17, 18 The inferred " San Onofre Mountain Fault" is not a tectonic feature; but rather a
collection of geomorphic and sedimentary feature mis-identified as a fault.
o "Piedre de Lumbre/Las Pulgas Canyon Fault" pp. 15, 16 Sediments deposited between these two canyons were layed down as fluvial sediments on a Pleistocene floodplain that is lower in elevation than the adjacent marine terraces.
The lower elevation of the fluvial sediments represents a depositional sequence, not faulting.
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"Mateo Canyon Fault" pp. 19-21 Paired fluvial, terrace surfaces can be catched across San Mateo Canyon and the age of these terraces are judged to be 100,000 years old. Thus any faulting, if present, would be at least that old.
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" San Onofre Canyon Fault" Vertical offset of 20 feet is unsub'stantiated.
Stream cutting across resistant San Onofre breccia and eroding soft strata of the Monterey Formation is a nor=11 erosional process and doesn't require faulting to achieve an offset.
The report concludes that these "are not capable faults" and have no significance relative to the seismic design of the San Onofre Units. Further, Mr.
T.
Cardone, of the NRC. Staff in the response to reviewing the field evidence and the Applicants report on the alleged features states that "...I don't see anything in Mr. Phirer's postulated faults or presentation that poses a hazard to the site..." and that he agrees with t,he. evidence and interpretation by the Applicants (Cardone, Tr. 6024:6-18).
On August 17, 1981, Mr. Phifer forwarded to Edison a draft of a letter and supporting maps and photographs he proposed sending to the Nuclear Regulatory Co= mission.
This information was essentially the same as that submitted to the Commission on October 8,1981.
Contrary to the comment by Mr. Phifer on pg. 3, Mr. McNey and Dr. Ehlig were not in agreement with his conclusions regarding the July 17, 1981 field trip. In addition to the features discussed in the limited appearance report described above, Mr. Phifer identified:
o Cristianitos Fault o
Offshore Zone of Deformation
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o Rose Canyon / Newport Inglewood (Fault Zones) which have been analyzed by the Applicants in detail as apart of the licensing proceedings.
The Cristianitos fault is not capable, the offshore Zone of Deformation is 5 miles west of the site and the Rose Canyon / Newport Inglewood (Fault Zones) are the south and north ends of the offshore Zone o,f Deformation.
Mr. Phifer agreed on page 5 of his October letter they have been studied.
New concerns raised in the letter of October 8,1981 were:
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" Mountain Top Fault Zone" s
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"Aliso Canyon Fault"
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These latter two features are discussed in subsequent paragraphs of this repcet.
N A field trip was then hosted by Mr. Phifer on Septenber 19, 1981 and several members of the geologic co=sunity as well as consulting fires were invited.
Attendees were:
E' 7 Mr. Larry Carlson, USMO Natural Resource.S Office Mr. M. W. Hart, Geocon Consulting Engineers end Geologists Mr. C. T. Farrand, Geocon Consulting EnF' <et: i asi Geologists s,
Mr. A. E. Farcas, Geocon Consulting i 7p n o and Geologists s
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c=J-Mr. D. W. Phifer, Coastal and Nearabore Consultant Mr. J. L. McNey, Southern Califor...a Edison Dr. P. L. Ehlig, Consultant The trip included revisiting those locations identified in the limited appearance report.
They were:
o Vandergrif t Boulevard landslide Piedre de Lumbre/Las Pulgas Canyon fluvial sedEments o
o Las Pulgas Ammo Dump area of the Horno Sum: nit Fault o
Horno Summit Ridge
_o Rifle Range 214 Fad 1t and
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o Fault F loc.ation
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. San Onofre Mountain
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o Horno Canyon landslide at the beach.
The lat+er three stops were to observe features of the alleged " Mountain Top Fault Zone."
While visiting the stops along the " Mountain Top Fault Zone",
origin of the tuff bed, minor faulting and conditions leading to the development of the landslide at the couth of Horno Canyon were described in detail by the Applicants.
Dr. Ehlig and Mr. McNey believe that the interpretation of the geology is in error and without technical merit.
The Aliso Canyon Fault was -not visited.
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" Mountain Top Fault Zons" As described by Mr. Phifer on page 3 of his october 8, 1981, letter to the NRC, the " Mountain Top Fault Zone" (MrFZ) which trends NE-SW, is longer than 3
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miles, has a vertical displacement of greater than 600 feet with the east side up, and a width of about 1 1/2 miles.
The map signed by David Phifer and dated August 14, 1981 accompanying t.he subject ' letter shows the MTFZ bounded by two nearly north-south trending faults.
All of the eastern fault and most of the western fault are portrayed on the map by dashed lines which indicates the faults are inferred according to the map legend.
Between the bounding faults, the map shows seven short faults with trends ranging from aboat north 30 degrees west to north 15 degrees east., In pages 4-5 and 4 of Enclosure 1, accompnaying the subject letter, Mr. Phifer provides additional information on his MIFZ.
J The central part of the fault bounding Mr. Phirer's MIFZ is the same as the F fault which is described along with the E fault (Ehlig, Written Testimony, Contention f3, pp. 1-4; Tr. 2898-2905).
The F fault is exposed in a quarry on the northeast side of the old Coast Highway.
Here the fault is a discrete nearly planar feature with a strike of about north 15 degrees west and an average dip of 78 degrees to the west.
The age. of the fault is imprecisely known, but it cuts rocks 14 to 15 million years old and shows no evidence of cutting the coastal terrace.
The fault is most likely 4 to 10 million years old. The unconformity (erosional surface) separating the base of the Monterey.
Formation from the underlying San Onofre breccia is about 25 feet lower in elevation on the west side of the fault than on the east side.
Striations produced by fault movement occur in more than one direction on the fault
surface but steeply inclined striations predo=inate suggesting movement was primarily down the dip -of the fault.
The age of this fault is uncertain but it was most likely active so=etime between ten million years ago and four cillion years aSo based on regional tectonic relationships (Written Testimony, Contention #3, Ehlig, p. 3:21-26; and p. 4:1-2).
The fault shown on the east side of the MTFZ by Mr. Phifer appears to be conjectui a1.
The Applicants know of no mappable faults along the alignment shown on his map.
Where his inferred fault crosses the mouth of Horno Canyon, 1
two marine terraces project directly across the canyon with shoreline an5 es at about 275 feet and 325 feet above sea level. Based on association with the
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maririe isotope chronoloEy (Shie=on, 1978) the 325 foot platform is at least 500,000 years old.
Thus, if any fault were" present it would be that aSe or
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- older, and it would not be, considered capable according to 10CFR100
' Appendix A.
On page 4-5 of Enclosure 1 acco=panying his letter to the NRC, Mr. Phifer presents reasons for believing significant faulting has occurred within his MTFZ.
His principal reasons include:
1.
The presence of a tuff bed at an elevation of about 800 feet southwest of San Onofre Mountain which he believes is similar to tuff at an elevation of about 200 feet near the mouth of Horno Canyon.
2.
Marine Terraces Qt2, Qt3 and ot4 (Phifer designations) are continuous
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across his MTFZ but'end abruptly near fault F.
3 There is a zone of extensive landslides along the coastal projection of his MrFZ.
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Capistrano Formation is exposed at sinilar elevations as younger San Mateo; Formation along the coastal projection of his HIFZ.
5.
Offshore bathymetry at depths of 30 and 60 feet appears displaced.
In regard to the tuff bed, it is Applicants' understanding that Mr. Phifer is suggesting that a tuffaceous bed in the San Onofre breccia exposed at an elevation of about 920 feet in the cut along San Onofre Peak trail correlates "with a tuff bed which crops ou,t in the breccia a few hundred feet northeast of the old Coast Highway in the area extending from 1/2 miles northwest of Horno Canyon to 2 miles southeast of Horno Canyon.
The latter tuff contains pumice lapilli indicating a nearby source and is about 15 feet thick whereas,the turf on San Onofre Mountain is f ne-grained and only a few feet thick.'
The Applicants find no basis for correlating the two tuff beds. Fine-grained tuff beds have a scattered occurrence within the San Onofre breccia. They indicate volcanism was active in the region simultaneous with deposition of the San Onofre breccia.
Mr. Phifer is correct in noting that re=nants of marine terraces are aligned across his MIFZ from Horno Canyon to near fault F.
There are four terraces in this area, not three as indicated by Mr. Phifer.
They have shoreline angles at elevations of about 275,.325, 375 and 450 feet.
Terraces are present northwest of fault F and have shoreline. angle elevations correlative ;ith those to the southeast of fault F; however, the degree of terrace preservation is less because the area was a headland. The Applicants have observed nothing which would indicate the terraces are offset by faulting.
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r The extensive landslides along the coast are rotational failures which have occurred where wave erosion has removed lateral support from clay <ich beds in the seaward dipping Monterey Formation.
Terrace deposits resting on the i
Monterey Formation have been extensively deformed within these landslides.
However, no deformation or faulting is visible in the in-place terrace deposits exposed in scarps on the landward side of the ' landslides.
The landslides such as that exposed at Horno Canyon are controlled by the
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lithology and seaward dip of the Monterey For ation and are not a canifestation of a deeper seated deformation as suggested by Mr. Phifer.
Mr. Phirer's suggestion that both the Capistrano and San Mateo Formations are exposed where his MIFZ projects to the coast is based on the mapping of Moyle (1973).
. Dating by microfessils demonstrates that the Monterey Formation e
constitutes bedrock beneath the terrace deposits along the entire coast from the Cristianitos Fault to Las Pulgas Canyon (Ehlig, 1977).
The exposed part of the Monterey Formation includes lithologie's similar to parts of the Capistrano Formation and the San Mateo Formation which is a sub=arine fan facies of the Capistrano Formation (Ehlig, 1979).
Contrary to Mr. Phifer's belief, the Applicants see no evidence suggesting displacement of offshore bathymetry at depths of 30 and 60 feet.
In conclusion, the Applicants find no. evidence for Mr. Phifer's Mountain Top -
Fault Zone.
The F fault which forms the west side of the hypothesized zone was previously mapped and reported.
The eastern boundary fault appears to be hypothetical.
We find no evidence indicating a through going fault along the we a e w
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trend shown on Mr. Phirer's cap.
In particular, tha contact betv2cn the Sin Onofre breccia and underlying Eocene sandstone appears to be undisplaced where Mr. Phifer places his inferred fault on the northeast side of San Onofre Mountain.
As indicated by Mr. Phifer, minor faults are locally present within the San Onofre breccia; however, the Applicants attribute this to the cassive, bpittle naturg of the breccia and not to the presence of a zone of faulting.
We agree with Mr. Phirer's observation that 'a group of marine terraces re=nants extend across his hypothesized Mountain Top F ault Zone in an undisturbed alignment.
Because the older terraces are at least 300,000 years old, we find no evidence to support the contention that there are capable, faults within the hypothesized Mountain Top Fault Zone nor does the MIFZ intersect the Horno Canyon Fault to form a deformed zone expressed by landsliding.
Thus, the alleged structure is not supported by the geologic evidence and is considered speculation.
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Aliso Canyon Fault The feature described as the "Aliso Canyon Fault" by Mr. Phifer has been analyzed by ti2e Applicants using geomorphic expression of the marine terraces and drainage and inspecting aerial photographs.
This fault is shown on his cap acco:panying the October 8,1981. letter, and shows a dashed line and querries representing an inferred or questionable fault for essentially the length of the feature.
Access to Aliso Canyon is limited due to military.
activities and because the north-east portion is within a Ca p Pendleton firing range.
The Applicants analysis of the feature determined that marine terrace break-in-slope at the 300, 400 and 500 ft. contours project across Aliso Canyon without deflection.
Re=nant carine terrace surface between
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clevation 460 and 520 are about 1,000 feet wide occur east and west of Aliso
- Canyon, projecting,across with no discernable vertical or horizontal.
separation.
The continuity of topographic expression along ' trend of the -
terrace break-on-slope surface and the presence of accordant elevations in the uniform soils argues for no major structural deformation since the terrace formation.
Terrace surfaces at this elevation north of Las Pulgas were developed over 400,000 years ago (Shlemon, 1978, Figure 12).
If the same relationship holds at this location, any faulting along Aliso Canyon would be
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older.
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The Applicants find no evidence for of'fset bathymetry contours on the, offshore
' aitxis of Aliso Canyon.
Aliso Canyon is over 9 miles southeast of the site and trends about N40E. If a fault is present, the orientation will not intersect the are of the 5 mile radius from the site and lies at least 4 miles beyond such a boundary.
Geomorphic evidence for-significant defor=ation 'is, absent and even if faulting were present, the Offshore Zone of Deformation 5 miles from the site contro'ls the seismic design.
The "Aliso Canyon Fault", if present has no significance to the safety or seimic design of San Onofre Nuclear Generating Station.
The Applicants are not aware of any other geologic disclosures since conclusion of the
. Atomic Safety and Licensing Board hearing's on' August 4, 1981.
JLMcNey:npm
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