ML20125E428

Forwards Seismic Reflection Lines from Savannah River Plant W/Replay Sections for Refraction Lines in Vicinity of Postulated Millet Fault,Per 821029 Request

ML20125E428
Person / Time
Site:	Vogtle
Issue date:	11/12/1982
From:	Dutton D GEORGIA POWER CO.
To:	Eisenhut D Office of Nuclear Reactor Regulation
Shared Package
ML20125E340	List: ML20125E338 ML20125E428 ML20125E444 ML20126A271 ML20126A310
References
FOIA-84-430 NUDOCS 8506130112
Download: ML20125E428 (3)

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h, Georgia Power D. E.}utton ,

I November 12, 1982 Director of Nuclear Reactor Regulation Attention: Darrell G. Eisenhut, Director Division of Licensing U. S. Nuclear Regulatory Comission Washington, D.C. 20555 NRC DOCKET NUMBERS 50-424 AND 50-425 CONSTRUCTION PERMIT NWBERS CPPR-108 AND CPPR-109 V0GTLE ELECTRIC GENERATING PLANT POSTULATED MILLETT FAULT STUDY

Dear Mr. Eisenhut:

As requested at the.0ctober 29, 1982 Postulated Millett Fault Study meeting with members of the NRC staff in Bethesda, Georgia Power Company is for-

i. warding the seismic reflection lines from the Savannah River Plant. Please l find enclosed the replay sections for the refraction lines in the vicinity l of the Postulated Millett Fault, the time cross sections, the top triassic, saprolite, and crystalline rock countour. maps, and the velocity gradient map. Also enclosed are five copies of a report issued as part of the re-l~ flection studies. All this infonnation is available through the Oak Ridge, Tennessee Repository.

Should you have any questions, please inquire.

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. Doug Dut n Rfn Vice President

j. Generating Plant Projects DED/ JAB /sw xc: R. A. Thomas G. S. Grainger J. A. Bailey N

0. Batum E. L. Doolittle D. O, Foster J. M. Grant

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[jh g., UNITED STATES jf . ATOMIC ENERGY COMMISSION

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WASHINGTON, D.C. 20545

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Qhe;N jus a 1g73 Richard C. DeYoung, Assistant Director for Pk 's, ALVIN W. VOCTLE UNITS 1, 2, 3, & 4 PLANT NAME: Alvin W. Vogtle LICENSING STAGE: CP

l. , DOCKET NUMBERS: 50-424 427

. RESPONSIBLE BRANCH: PUR Branch #2 REQUESTED COMPLETION DATE: 6/8/73 APPLICM;TS RESPONSE DATE NECESSARY FOR NEXT ACTION PLANNED ON PROJECT: NA

.1 DESCRIPTION OF RESPONSE: Answar.to Questions 8

REVIEW STATUS: Site Analysis Branch - CP Enclosed are questions on geology and foundation engineering pertaining to proposed units of the subject plant. A copy of I

questions 1, 2, and 3 were previously provided to L. Crocker, RP

'l Pruject Lumswr, who has . submitted them to the applicant. A

position paper, which recomends that additional site exploration j work be-done, is concurrently _being prepared for this project.

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Harold R. Denton, Assistant Director

_ .,, for Site Safety

! Directorate of Licensing 1

Enclosure:

As stated ,

, cc: w/o enclosure A. Giambusso

'W. Mcdonald

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cc: w/ enclosure S. H. Hanauer J. M. Hendrie V. P. Gamill

.K. Kniel -

L. Crocker l

A. T. Cardone hf? gSC525O/OO 1

31 ALVIN W. VOGTLE QUESTIONS DOCKET NOS. 50-424 - -427

1. What is the geologic significance of the clastic dikes mentioned on page 2.5-67

2. On pages 2.5-2, 3 the basement complex is described as also including Triassic sediments. What is the configuration and location, with res.pect to the site of the Triassic basin? What is the evidence that the basin is not bounded by faults, in a manner similar to other fault-bounded Triassic basins in the Piedmont.

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. 3. The cross section (B-B') illustrated in figure 2.5-6 shows a-monoclinal flexure (albeit with vertical exaggeration). Discuss the

' I structural relationship of this flexure and any bounding fault of the Triassic basin.

1- .

Discu'ss possible relationship between the apparently anomalous high

'i seismic response in the zone enclosed by the 8-1/2 value shown on 3_

figure 2.5-26 to basin bounding structures in the basement complex.

4. Provide those boring logs of holes drilled in the proposed plant area that were not submitted in the PSAR. For example, the logs for drill holes 101B, 1073, 146, 148, 149, 150, 151, 183, and 184, which are located in the containment buildirgs locations, were not provided in the PSAR.

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5. Discuss the significance and magnitude of possible subsidence resulting from fluid withdrawal by means of the proposed uater wells that will supply normal make-up water and cooling water during emergency shutdown conditions. Verify your estimate of the magnitude of subsidence by providing the appropriate analyses.

. 6. In order to complete the geologic and tectonic framework for the proposed site,' describe and discuss the geology to the north of the Savannah River, using as guidelfr.es the " Seismic and Csologic Siting Criteria" and the " Standard Format and Content of SAR's for i

'l Nuclear Power Plants." Show in an appropriate figure the extent and locations of th'e nearby Triassic Basin and clastic dikes l

1, mentioned on page 2.5-6.

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(- AEC Question 2.19 What is the geologic significance of the clastic- dikes mentioned on page 2.5-6?

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The cross section (B-B') illustrated in figure 2.5-6 shows a monoclinal flexure (albeit with vertical exaggeration). Discuss the structural relationship of this flexure and any bounding fault of the Triassic basin.

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UMP AEC Question 3.3 The simplified lumped mass and soil spring approach proposed in the PSAR to characterize soil-structure interaction is not appropriate. The use of equivalent soil springs may produce a pronounced filtering of the ground motion response amplitude and response frequencies due to inadequate repre-sentation of soil parameters. Indicate your intent to adopt one of the following methods for soil-structure interaction analysis:

(a) A nonlinear finite element approach with appropriate nonlinear stress-strain and damping relationship for the soil.

3 (b) An iterative linear finite element approach with appropriate nonlinear stress-strain and damping relationship for the soil (pseudo-nonlinear h.,'s approach).

(c) Lumped springs to represent the soil with appropriate dampings (not more than 10% of u-itical damping corresponding to horizontal and vertical springs), uw'lizing a variation in the soil properties corresponding to the span of maximum and minimum strain levels so that the floor response spectra obtained envelop those using the finite element approach. If a pseudo-nonlinear finite element approach is used, identify the manner in which variation in the properties of the soil are accounted for. (Para. 3.7.2.1)

Response

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1 VNP Cretaceous period. Seismic refraction surveys at the site indicate that this basement complex-Cretaceous contact occurs at a depth of approximately 950 feet. More or less constant deposition continued from the Cretaceous through mid-Tertiary i periods in the Savannah River basin area with the youngest identified Tertiary sediments being Miocene in age. Variegated clays and sands lithologically similar to the Miocene Hawthorne I- formation were encountered in the upper portion of one of the

higher holes drilled at the site, but insufficient exposures of these clays and sands were present to show as a mappable unit.

(S For regional geology map see figure 2.5-3.

Figure 2.5-4, which is a portion of the Tectonic Map of North America, shows the relationship of the site, on the essentially undisturbed sediments of the Coastal Plain, to the Piedmont Province to the north and west with its older and more emplex geologic units. The basement complex, as exposed in the Piedmont Province, has undergone at least two periods of granitic intrusion or granitization as well as well-developed faulting and folding. This activity, however, has been essentially quiescent since the deposition of the Cretaceous .

sediments in the coastal plain. This wedge of Cretaceous and younger sediments, which feather out at the Fall Line near Augusta, is reported to reach depths of approximately 4,000 feet at the coastal line near Savannah, Georgia. The lowest

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member of the sediments appears to represent.an alluvial deposit, possibly of coalescing fans derived from the erosion of the older basement rocks to the west and north. The encroachment of a shallow sea in the Uppermost Cretaceous and Lower Tertiary times resulted in the shoreward migration of estuarine and shallow marine deposits. In the vicinity of the site, lignitic sands and clays are replaced by marls, coquinas, and shallow water sand. These deposits grade coastward into deeper water lithological units of the same age, such as limestone and shales. The present dip seaward of these units is approximately 30 feet per mile at the Cretaceous basement complex contact.

The basement complex is described above as including Triassic-sediments. The location and configuration of these sediments with regard to the VNP is shown on figure 2.5-4A. This Triassic basin, its location, and supporting evidence are discussed in reference 2.5.7.2 (Siple , G. E. , 1967). Here Siple discusses the core obtained in the bottom of the holes 3 drilled on the SRP as lithologically characteristic of "the fanglomerate or conglomerate facies of the Newark group of late Triassic age." The outline of the basin has been determined largely on the basis of aeromagnetic surveys which show the Triassic sediments as " lows" compared to the surrounding igneous-metamorphic Piedmont complex.

i 2.5-3 7/6/73 Amendment 3 l

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VNP Based on what are believed to be similar Triassic basin occur-rences in the Piedmont area and on the steep magnetic gradient' delineating the northwest and southeast edges of the basin, it is assumed that at least these sides are bounded by faults and 3 that the Triassic sediments have been preserved in a down-dropped graben within the basement rock.

2.5.1.3.2 Stratigraphy

/ - The stratigraphy applicable to the Savannah River basin area is I. susanarized in table 2.5-1. Igneous and metamorphic rocks varying in age from Precambrian to Paleozoic form the lowest unit believed to be present at the site.

This material was not encountered during drilling or indicated by the deep refraction seismic work, but is known to form the true basement material by direct or inferred means throughout the Georgia-South Carolina area.

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t 2.5-3a 7/6/73 Amendment 3

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. Deposition of continental sediments during the Triassic is known to have occurred fron samples obtained from drilling through the coastal province. Much of this material was oroded during the post-Triassic, pre-Cretaceous time, but local basins containing Triassic sediments were preserved beneath the peneplain surface formed. Aerial magnetic surveys in the past

. decade have disclosed that one of these Triassic basins extends from bcncath the Atomic Energy Commission's Savannah River Project (S RP) in South Carolina to several miles beyond the site of the Vogtle Nuclear Plant in Georcia. On the SRP, the basin was confirmed by seismic reflection studies and deep core holes. The deposits consist of siltstono, claystones, and

,, sandstones resembling those of the typical Newark Group

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.' fanglomerates of the Upper Triassic period. Measurements made at the Vogtle site indicate that a material with refraction velocity of 12,000 feet per second exists at approximately 950 feet below the plant site', which agrees with the Triassic basin sediment data.

Overlying the peneplained surf ace of the Precambrian-Triassic basement complex is the nonmarino Tuscaloosa Formation. This  !

formation is composed largely of detritus derived from the weatheret granitic-metamorphic basement rocks and contains considerable coarse grained quartz, partially altered feldspar, and mica (generally of the muscovite variety) . In gross ap-pearance, it consists of light-grey to light-brown to white, cross-bedded, arkosic to quartzitic sands and gravels inter-

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• beuded with lenses of silt and clay, of red, white, brown, or purple color. Tne variegated clays are generally of relatively pure kaolin and are nined extensively in the vicinity of the Fall Line.

Overlying the Lower Cretaceous Tuscaloosa Formation is the Ellenton Formation, which occurs sporadically and locally within the Savannah River basin, but occurs consistently in the plant site area. Originally described by Siple in his work on the S RP , it is believed to be of Upper Cretaceous age. The Ellenton Formation consists of dark-cray to black, sandy, lignitic, micaceous clay interbedded with mediun to coarse-grained quartz sand in its type area. The lower part of the Ellenton Formation is composed generally of a clayey quartz sand varying in texture from medium to coarse-grained, becoming locally gravelly. Deconposed pyrite or marcasite fragments, lignite, muscovite, and kaolinitic aggregates are quite common.

The Ellenton Fornation is distincuished from the Tuscaloosa Fornation by the latter's marked preponderence of muscovite and kaolin as compared to that in the Ellenton Formation.

Above the Lilenton Formation are the Tertiary deposits of the Eocene through Miocene periods. The lowest of these is the

, 2.5-5

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at least post-Claiborne sediments. Although the second-possibility, seismic activity, is a likely causative force, it also seems probable that the dike itself was formed both by means of infilling, at an equal pace, of overlying material and by the mechanism included in hypothesis 3. So far as is known, there is no material present now in a stratigraphically higher position in the geologic section and similar in composition to the fracture fill that conceivably might have worked down into the fissure as it was being formed. There is, however, greenish-gray clay in the Hawthorne Formation at downdip

( localities that could have been present in this area in the geologic past and would be a likely source for such filling.

There is also similar clay stratigraphically lower in the geologic section - a fact which suggests that possibly some dikes were injected up through the younger Tertiary rocks.

3 Conceivably this injection may have been brought about by the failure of underlying beds to support compressional stresses.

Under such conditions the weight of the overlying material would cause a failure in the substructure brought about by ground water solution of the underlying calcareous beds. , When these beds could no longer support the overlying formations, I fractures would develop as the superstructure collapsed, and l clastic material below would migrate up into the fractures.

Some corroborative evidence for such an origin is indicated by

(, the large number of solution sinks in the vicinity of the dikes, as for example, in the northeastern quarter of the Ellenton quadrangle. , Conversely, dike swarms are indigenous to those areas exhibiting other features of solution and collapse." ,

The Quarternary appears largely represented by the flood plain deposits and valley fill associated with the rivers and larger streams in the area.

2.5.1.3.3 Structure The major structural trend affecting the Georgia-South Carolina region along the southern portion is the pre-Mesozoic Appalachian system. Tectonic activity had ceased on this system before the deposition of the Cretaceous sediments in the Savannah River valley area, as is evidenced by the lack of tectonic folding or documented fault offsets in the sedinents.

Faulting, perhaps of major proportions, appears to have occurred in the basement complex during the pre-Cretaceous, however, to account for the down-warped or down-faulted segments of Triassic sediments found preserved within the basement complex throughout much of the Atlantic Coastal Plain.

The coastal plain sediments indicate une Savannah River basin has remained remarkably stable throughout Upper Pesozoic and .

2.5-6a 7/6/73 Amendment 3

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to 90 feet (+) in Holes 38 and 156, are stratigraphically part of the Oligocene. This is true, also, for the shell bearing horizon in Hole 45 on the SRP.

2.5.1.4.3 Structure The geologic structure in this area is best illustrated by figure 2.5-10 showing the contours on the top of the bearing stratum. Although the surface of this marl bed is believed to

,- be a formational contact, the contours indicate only a minimum amount of differential erosion. The contours were derived from outcrop and drill hole information and indicate a general dip to the south and east of about 30 feet to the mile throughout-the plant site area. The general dip is interrupted on the northeast by a gentle dip to a maximum slope of five percent (3 degrees) to the northwest, and lowers the reversal of the surface of the bearing stratum approximately 50 feet in that direction.

The dip reversal is seen with a 20 to 1 vertical exaggeration on section B-B' of figure 2.5-6. The trend of the axis is approximately northeast-southwest. It is an anomaly that has been the subject of much investigation and discussions.

, Numerous holes were drilled to determine its character, and

\- water pressure tests were made to determine if it affected the ,

watertightness of the bearing stratum. No indication that it I was a . fault controlled feature was found during the extensive l investigations . It does not appear to be an erosional feature i on the top of the unit as it is reflected in both the top and  !

bottom of the bearing stratum to an approximately equal extent. 3 ;

It dips in the wrong direction to reflect possible near-surface expression of the underlying Triassic basin boundaries. No relationship to the assumed boundary fault contact at the  ;

northern edge of the Triassic basin could be found. As the i assumed northern Triassic basin boundary fault would have to be down-thrown towards the sea, the fact that the flexure in the bearing horizon slopes in the opposite direction, i.e. , to the northwest, seems to negate any genetic relationship. It appears to have been formed previous to and in part possibly during the deposition of the thick shell deposits that roughly coincide with the reversal, as may be seen on figure 2.5-10A.

A local, well developed, striated bedding plane was found in

. one hole (' N o . 246) at the base of the marl. This is near the southwestern or lower side of the anomaly and well away from the plant area. Water losses were also noted related to jointing in the upper 15 feet of the marl during some exploratory drilling investigating this feature. These phenomena were not observed elsewhere throughout the plant site inves tigation. It is believed that the reversal represents 2.5-11 7/6/73 Amendment 3

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deposition on an erosional irregularity on the underlying sands, with the possibility of some local differential compaction during or shortly after deposition of the bearing stratum.

,- Solution depressions are readily apparent on the topographic map of the site and, as the site explorations shown on figure 2.5-1 indicate, they were the subject of considerable f

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t 2.5-ila 7/6/73 Amendment 3l3

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The map divides the coterminous United States into the '

following four zones.

l Areas where there is thought to be no reasonable l

expectancy of earthquake damage - Zone 0 '

Areas of expected minor damage - Zone 1 Areas where moderate damage could be expected - Zone 2.

~ Areas where major destructive earthquakes may occur -

(- , Zone 3 The site lies inside Zone 2 where moderate damage could be expected. According to this map, moderate damage corresponds to intensity VII on the Modified Mercalli Scale.

The zones are based principally on the known distribution. of damaging earthquakes, their intensities and geological considerations. Since the Charleston earthquake of August 31, 1886 resulted in .the greatest intensities in this part of the country, the zones there will be based on data from this shock.

The Dutton isoseismal map most probably forms the basis for the zones in this area therefore, since the Dutton map included i

the site in the VII (MM) area, it appears in this zone of the

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risk map even though the site may never have experienced an intensity this high in historic times.

The high seismic response zone enclosed by the 8-1/2 (Rossi-Forel) isosaismal line shown on figure 2.5-26 has been discussed by C. E. Dutton in "The Charleston Earthquake" (USGS 9th Annual Report, 1887-88).

"......The shocks at Columbia, South Carolina, judging'from all accounts, were more forcible than at Savannah. The first two impulses, which appear to have corresponded to the two maxima already described at Charleston, threw the whole city into a state of terror. The swaying of buildings was very great; the jarring, like that of a wagon rumbling over a stony pavement,

, was excessive, shaking down plaster, chandeliers, crockery and light objects, and producing a 3oud rattle, which, added to the a subterranean roaring, caused th greatest consternation.......

Still no instances have been rev erted of the demolition of any buildings.

The most remarkable circumstance, however, connected with Columbia is the f act that a considerably greater intensity is i indicated for that city than for the localities to the southeast of it nearer to the centrum. There is, indeed, a belt of country along the Piedmont region where the same state 2.5-45 7/6/73 Amendment 3 v -- -,

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'throughout the State of North Carolina the vigor of the shocks was very great. . . . . . . . There is, however, a notable difference as a general rule between the eastern part of 'the State within the coastal region and the Piedmont and mountain region. It was notably less forcible in the coastal plain........ There are many indications that the vast masses of littoral deposits of unconsolidated sands, clays, and marls along the Atlantic 3 border and ooastal plain, especially in the Carolinas, greatly-tempered and modified the force of the earthquake. It may be said that they ' cushioned' the shocks, not alastically, but by actually dissipating in some measure portions of the rays of

( energy which here affected the surface........"

2.5.2.11 Earthquake Frequency Table 2.5-10 shows earthquake frequency in the vicinity of the Vogtle site. It is based on actual data from the historic earthquake record of about 300 years, and shows the shocks which were felt in the site area.

2.5.2.12 Summary and Conclusions The first historical quake felt in the eastern United States is listed as occurring in Canada in 1663, so there is an

(~' historical earthquake record of 300 years for the southeastern United States. This area of the country experiences moderate to low earthquake activity with the exception of the Charleston area. The greatest intensity experienced at the site resulted '

from the August 31, 1886, Charleston earthquake about 104 miles

. east of the site. Considering the reports from nearby towns, j the intensity at the site was no greater than a VII.

The great New Madrid, Mo. 1811-1812 shocks were also felt at the site, but with no greater intensity than VI (MM). Other distant and nearby shocks, however, have been barely felt at the site, probably with no greater intensity than IV.

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. -l0 ::'hn MEliORANDUM FOR: Ina B. Alterman, Geologist Geology Section, GSB, DE FROM: Phyllis A. Sobel, Seismologist Seismology Section, GSB, DE

SUBJECT:

SEISMOLOGY REVIEW 0F BECHTEL REPORT," STUDIES OF POSTULATED MILLETT FAULT" I have reviewed the seismicity information in the Bechtel report on the Millett Fault prepared for the Vogtle applicant. The available seismicity information includes (1) felt earthquakes, (2) reciit instrumentally located events, and (3) data from the Savannaf River 2 1ant array, just across the Savannah River from the Vogtle site. The and I agree, that historic seismicity reveals no applicant evidence of concludes' active faulting in the area. The seismicity near the site has been scat.tered and low level (maximum MM intensity VI). No clustering of earthquakes < occurring near the postulated Millett or Statesboro faults. "

Phyllis Sobel, Seismologist Seismology Section Geosciences Branch cc: R. Jackson L. Reiter S. Brocoum P. Sobel A. K. Ibrahim

.