ML20234C017
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U. S. ATOMIC ENERGY COMMISSION REGION V i
DIVISION OF COMPLIANCE j
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G.. S. Spencer, Reactor Inspector August 30, 1963 Region V, Division of Compliance f n ie: PACIFIC CAS AND ELECTRIC COMPANY - EODEGA BAY REACTOR D,0CKET NO. 50-205 J
SUMMARY
j The proposed site of the Pacific Gas and Electric Company's Bodega Bay Reactor, Bodega, California, was visited on August 20 and' 23,1963. The parpose of the visit was to accompany and observe the activities of the U. S. Geological Survey team assigned to study and evaluate the excavated areas of the site for evidence of seismic faulting.
The south face of the reactor building excavation has been opened to provide an approximate 100 x 120 f t. araa for the proposed turbine generator basemett.
On the floor of the reactor building excavation (+5 ft. elevation) an annular trench, approximately three feet wide and ten feet deep, was being dog around the proposed reactor centerline at a radial distance of 71 feet from the centerline. The purpose of the trench-is to provide a reinforced concrete collar for edge-of-shoring support of the heavy equipment to be used in' excavating the 138 ft. diameter reactor shaft. Examination of the walls of the 507.-compleced trench excavation revealed no evidence of faulting in the sediments overlying the exposed weathered quartz diorite.
Examination of the cores and associated logs from two recent borings drilled at a distance of approximately 70 f t. due west and southwest of the reactor conter11ne, indicated that hard granite had been encountered from elevation
-38.0 to -49.6 feet, and elevation -49.5 to -58.5 feet, respectively.
DETAIIS I.
Scope of Visit On August 20 and 23,1963 C. S. Spencer and R. H. Engelken, Region V, Division of Compliance, accompanied Mr. J. Schlocker and Mr. M. G. Bonilla, geologists from the U. S. Geological Survey, Engineering Branch, Menlo Park, California on a visit to the proposed site of the Pacific Gas and Electric Campany's Bodega Bay, Reactor, Bodega Bay, California. The visit included:
(a) Observation of the status of the excavation activities in progress.
- 65) Observation of two core sampics taken from recent borings drilled at the west and southwest quadrants of the circumference of the propos+d reector shaft.
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Scope of Visi,e (continued)
(c) Discussion with the U. S. geologists concerning their current observations and findings relative to the seismic activity of site.
(d) Discussion concerning plans for the type of construction to be utilized in shoring the reactor shaft excavation.
Principal contacts during the visit were:
j Mr. J. Schlocker - Geologist, U. S. Geological Survey Mr. M. C. Bonilla - Geologist, U. S. Geological Survey Mr. C. Joslin - Construction Superintendent, PG&E II.
Results of Visit i
A.
Status of Site Preparation The reactor building excavation (described in our previous report l
dated July 24, 1963) was observed to have been further expanded in a southe.rly j
direction to provide an approximate 100 x 120 ft. area for the proposed turbtwe generator basement. On the floor of the reactor building excavation (+5 ft, elevation), an annular trench, approximately three feet wide and ten feet deep, l
was being dug around the proposed reactor centerline at a radial distance of 1
71 feet from the centerline. Mr. Joslin stated that the purpose of the trench is to provide a reinforced concrete collar for edge-of-shoring support of the heavy equipment which will be used for excavating the 138 f t diameter reacter shaft. He explained that the inside edge of the trench is 71 feet from the proposed reactor centerline and is two feet outside the reactor shaft radius of 69 feet. According to Joslin, the decision to employ the use of a cenen.. a collar was based on a serious accident that occurred at a U. S. missile a f ts.
Apparently a large crane toppled into an excavation shaft, killing seven personnel, when the edge of the excavation gave way under the weight of the crane. Joslin said the type of shoring that will be used to support the v6E:
l of the reactor shaft excavation will depend on the condition of the soil as it is uncovered, and could consist of I-beam ring girders with or without sheet piling, wire mesh and gunite, or nothing.
A large trench was dug along the dividing line between the excavations for the reactor building and the turbine generator basement.
Mr. Joslin stated that the purpose of the trench was to provide a sump for drainage of the water leakage being encountered in the two excavated areas. A diesel pump was observed to be located at one end of the trench with installation pf the associated drain piping in progress.
Landscaping of the sloped and benched areas of the open cut excavatien sectors of the reactor site was observed to be in prcgress and appeared to be nearly completed from elevation +50 feet to the top of the cut (elevation
+130 feet).
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1 Results of ylsit (continued) i D.. Examination of Annular Trench Excavation Mr. Schlocker, U. S. Geological Survey geologist, stated that I
his objective during the two visits covered by this' report was to map the major faults observed in the weathered quartz diorite exposed in the aorth-northeast quadrant of the trench. He explained that when'the trench excavation is completed along the south quadrant of the are he
_i would be looking to see whether these faults carried into the sediments exposed in the south quadrant.-
By the end of the second visit, excavation of the trench was approximately 50% completed and mapping of this portion essentially completed by the U. S. geologists..The inspectors accompanied Messrs. Schlocker' and Bonilla.into the trench where the following observations were made, as pointed out by the U. S. geologists.
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Quarcz diorite was exposed from the bottom (elevation -5. feet) to the top (elevation +5 feet) of the trench over a distance of 58 feet along the trench. The bulk of the exposed granite was located in the J
northeast quadrant of the trench and sloped off to a point where it dis-j appeared below the bottom of the trench 34 feet west and 90 feet. east of the northern extension of the north-south centerline of the reactor.
1 The granite material observed in the northeast quadrant' consisted of granular quartz diorite which became weathered. quartz diorite in the due i
i north section of the are formed by the trench. This in turn melded into grey clay in the northwest quadrant. Schlocker voiced the opinion that.
the granular quartz diorite would make a good foundation material due to its porosity and incompressibility. The sediments overlying the slope of the quartz diorite in the northwest quadrant were observed to consist of grey and mottled brown coarse sandy clay with no' sign of bedding.
No evidence of offsetting or other disturbances was noted in this clay.
A distinctive bed of grey gravelly, sandy clay was observed from a point 45 feet (along the arc) northwest of the north-south centerline, to the i
western termination of. the excavated portion of the trench. In_Schlocker's opinion, this clay was less cohesive than the material underlying it. He also indicated that the absence of any offsetting in the clay could be con-sidered further conclusive evidence that no faulting had occurred.
Many shears and fa' ult zones wer.e observed in the quartz diorite exposed in the walls of the trench. These were marked by pale blue clay gouge zones one to three inches thick.. According to Schlocker, there was no dominant directio,n of dip to the fault veins.
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, assults of Visit (continued)
Following their examination of the excavated section of the tr6nch, Schlocher and Bonilla stated that their study of the site to date has revealed no evidence of recent faulting.
C.
Results of Recent Borings Mr. Joslin, PG6E Construction Superintendent, stated that two exploratory bo' rings were recently drilled at the west and southwest quadrants of the circi =ference of the proposed reactor shaf t.
He said that the purposc of the horings was to further define the bedrock surface at those locations.
Le core samples and associated boring logs were examined by the inspectors and the U. S. geologists.
Mr. Bonilla, geologist with the U. S. Geological i
'. arvey, observed that the direction of the faults eviden'ced in the samples
- aken at the quartz diorite level showed a steep vertical orientation rather than the horizontal displacement associated with the San Andreas Fault. He indicated that this was further evidence that the boundaries of the San Andreas I
Fault did not extend into the site.
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The following information was extracted from the log of the borings.
Reference to the coordinates may be found in Plates 1 or 2, Amendment No. 3, l
Part IV D of the application.
I)oring Due. West of Reactor Centerline l
N 20,000 E 9921.68 El. 4.76 i
Elevation +4.76 to -10 feet:
Grey sand i
Elevation -10 to -15.5 feet:
Grey sand or sand and clay Elevation -15.5 to -36.0 feet:
Grey clay with quartz and feldspar Elevation -36.0 to -38.0 feet:
Partially decomposed quartz diorite Elevation -3C.0 to -49.6 feet:
Hard granite Borina Southwest of Reactor Centerline N 19,942 E 9927.2 E1. 3.26 Elevation +3.26 to -18.5 feet:
Alluvial sand Elevation -18.5 to -23.5 feet:
Grey sand or city, or cotrbination Elevation -23.5 to -48.5 feet:
Grey clay with quartz.and feldspar crystals Elevation -48.5 to -49.5 feet:
Soft partially decomposed granite Elevation -49.5 to -58.5 feet:
Hard granite 1
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