ML20049J767

Forwards Request for Addl Info.Sails at Proposed Foundation Level Are Not Suitable for Direct Support of Seismic Structures

ML20049J767
Person / Time
Site:	Skagit
Issue date:	03/10/1982
From:	Lear G Office of Nuclear Reactor Regulation
To:	Adensam E Office of Nuclear Reactor Regulation
Shared Package
ML19258A028	List: ML19258A027 ML20049J767 ML20054F287
References
NUDOCS 8203220557
Download: ML20049J767 (5)

Text

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DISTRiBUTIOff DCB-016~- Docket !50-522

'U E 1 0 1532 HGE5 Reading l

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Docket '!c. 50-522 l

!!E:10RA:lDU'1 FOR:

Elinor Adensam, Chief Licer. sing Branch flo. 4 Division of Licensing Ff.0:!:

Georne Lear, Chief

. Hydrologic and Geotechnical Engineering Branch Division of Engineering I

SUBJECT:

REQUEST FOR ADDITICML Ii!FOR!!ATICIt - GEOTECiclICAL EllGIt EERIllG j

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Plant :!ame:

Skacit/Hanford f!uclear Project, Units 1 and 2 Dochet l! umber:,50-522

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CP Responsible Branch:

LS-?; ti. fiallory, LFil The Skagit/Hanford fluclear Pr: ject. Units i and 2, has been moved from an area having hard, rock essentially at ground surface to an area having sand to a depth of about 200 ft. The plant foundation design details,'however, have not been changed. The in site soils at. proposed foundation leve?.

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(about.20 ft below grade) at the !!anford site are medium dense to dense ~

sand that, wc conclude, are not suitable for the direct support of sei'smic Category I structures.

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Based on our review, we conclude that suitable bearing material at the Hanford site is located about 40 ft below grcund surface (about 20 ft belcw

roo0 sed foundatien level).

At the nearby !!ashington Public Power Supply Syste, Unit 2 (:,':!P-2) site, similar fcundation conditions were found and re: edi ed by removing unsuitable soils to a depth of about 40 ft below ground surface and replacing them with dense structural fill for foundation support.

Also included in the' attachment are seven additional requests for information.

The resolution of these' additional items is not expected to impact schedules.

The'geotechnicai enginee-ing reviewer for the Skagit/Hanford project is Dr. Owen C. Thomoson.

He is being assisted by Dr. Dinesh C. Gupta, the

-geotechnical engfrieering reviewer for t!!!P-2. '

Origin:! :isn:d 5j Geor;c 1. ear Georne Lear, Chief g6V]

Hycrolocic and Geotechnical Engineering Oranch Sg@

Division of Engineering

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'Elinor Adensam

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R. Vollmer w/ enclosure J. Knight R. Tedesco M. Mallory G. Lear, L. Heller H. Lefevre O. Staley O. Th'ompson i

D. Gupta

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. Request for Additional Information - Geptechnical Engineering Skagit/Hanford Nuclear Project Units 1 and 2 Docket No. 50-522 Q241.1 in Amendment 23, sect' ion 2.5.4 to the PSAR, the applicant has proposed (2.5.4) to support the co: mon foundation mat for the seismic Category I structures,about 20 ft below existing (and final) ground surface (plant grace) at elevation 507 (El 507), on Missoula sediments that occur between about El 520 and El 495.

Plant grade is at El 527.

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The Missoula sediments are described as medium dense.to dense, clean medium sand, gray to black. Field tests in these soils showed.

Standard Penetration Test (SPT) values rang'ing from about 10.to'40

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blows /ft (PSAR Fig. 2QA-1 through 37 and Table 2QB-1).- Below: --

El 507 the SPT values were generally greater than 20.blo.ws/ft The underlying Pre-Missoula sediments, bet' ween abo t El~ 495 and El' ~480

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are described as'.very dense, silty fine sand, dark yellowish-brown to olive gray. The SPT values in the Pre-Missoula sediment were generally on the order of 100 blows /ft. These soils are uriderlain by dense to very dense sand and gravel (SPT values greater than 45 blows /ft).

Based on our review of the applicant's submittals, it is our opinion that the Missoula sands in their present condition are not suitable for the direct support of seismic Category structures because the in-place densities are variable and, in some cases, too low to assure

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satisfactory structural support. Additionally, the proposed. foundation support conditions are significantly inferior to the conditions adopted (and found by the staff to be acceptable).at the nearby Washington Public Power Supply System Unit 2 (WNP-2). The factors-supporting our conclusion are as follows.

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The lower SPT values recorded below proposed foundation level (17 to 23 blows /ft near Unit 1,13 to 22 blows /ft near Unit 2) correlate to relative densities near or below 60% (PSAR Figs.

2QA-38 and 39)'. The in-place relative densities may, in fact, be near or below 50% according to recent studies by the Waterways Experiment Station (ASCE Journal, GT-11, November.1977, page 1295).-

5. The applicant determined in-place relative densities of 9% to 53% in the exploratory trenches (PSAR Table 2QB-6)'. The applicant suggested that the tests were not representative because of soil layering. We believe that they are also indicative of loose, unsuitable in situ soil conditions.

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the At the WNP-2 site, shallow sands having STP values genera i

dersities in range of 15 to 40 blows /ft were judged to have relat ve i

4 and A-3 the range of 30 to 50% (UNP-2 FSAR, App. 2.5F, F gs.T in order below grade and recompacted to about 80% relative density throughA-7).

to provide suitable foundation support.

i between Based on the applicant's submittals and a telephone discuss on d that the the staff and the applicant on March 2,1982, we understan l for applicant concluded that the Missoula sands are suitab e

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foundation support based on the following factors.

1..The average SPT values of 25 to 30 blows /ft and corr ill relctive densities of 75% to 80% are within ranges.that wd tha

. provide suitable foundation support anfoundation ma loose pockets.

l The p' late load tests in the exploratory trenches show i

high elastic modulus values for the Missoula sands (10 t

under 2.

to 20,000 psi) so tha. calculated settlements of struc ures static loads are small.

ities The geophysical studiesishow relatively 3.

of structures under earthquake loads are small.

l The applicant believes that removing and reccmpactin ils.

sands may not produce improved densities in the bearing so 4.

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t resolve We find that the applicant's information and evaluation doe

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d as a our concern for the suitability of~the in-place Missou a san T

H foundation bearing material.

an alternative to the presently proposed plan

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guidance, the applicant should refer to the WNP-2d to a depth

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wherein medium dense to dense sands were ex tablished l

a by use of structural backfill.

acceptable for the WNP-2.

d Poisson's Table 2L-5 shows "P" wave and "S" wave values and calculateProv ratio values that appear to be inconsistent.of the b Q241.2 (App 2L) d bedding provide a description of the anticipated bearing conditions an d its.

details for soil-supported seismic Category I pipes and con u kfilling.

Provide a summary of the specifications for bedding and bac

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Q241.3 l _

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3-0241.4 Frovide a correlation between the seismic Category I. structures listed (2.5.4.5) under "S.

Other Structures" on Sheet '22 of Table 3.2-1 cnd the numerical i

listing on Figure 1.2-1.

Identify the proposed foundation elevations j

s and conditions of any seismic Category I structures that are not shown i

on Figure 2.5-15.

0241.5 Provide a commitment to notify the NRR staff in. advance of the r.

(2.5.4.5) completion of foundation excavations so that the staff may inspect the excavations.

Q241. 6 -

Provide a description of the procedures that will be adopted to (2.5.4.5)'

protect and maintain temporary soil sicpes and to provide adecuate drainage around structures so as to assure that foundation soils will net be damaged by local heavy fains and erosion during construction.

Include a descr.iption of the periodic inspection procedures that will ass 0re proper maintenance of temporary slopes and dra'inage facilities.

Q241.7 '

Discuss the efficacy of using the Proctor method (ASTM D-1557) for (2.5.4.5) field de.n'sity control of the clean sands in view of the testing difficulties encountered during the exploration, as described on page 2Q5-4.

Propose alternatives for field control of. backfill.

Q241.8 Specify the gradation limits that will be acceptable for structural (2.5.4.5 backfill material.

Also describe how the excavated soils that are used for backfilling will be mixed and blended to provide homogeneity; that is, describe how problems wi.th ob,taining relative density c

values in compacted fill will be avoided in view of the problems encountered with determining relative density in the exploratory test trenches (see page 2Q-11, page 2Q-14 and Table 2QS-6).

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-Attachment 2 Attendance List Skacit/Hanford Geotechnical Meetino

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March 17, 1982 ji Meetino Attendees Orcanizati' n I

o Mike Mallory NRC/LB-4

. A. Scangenberg NESCO i

T. L. Grebel NESCO J. M. Ashley Bechtel L. Heller (Part-time)

NRC/DE/HGEB D. Gupta NRC/DE/HGEB Owen 0. Thompson NRC/DE/HGEB Tom McCormick Bechtel

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l Dennis B.~ Hacking NESIC 9

John Byrne d' older Associates'

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l GeorgeLear(Part-time)

HRC/HGEB -

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l MEETING

SUMMARY

DISTRIBUTION f

Docket File dT> #O TM G. Lear NRC/PDR S. Pawlicki Local PDR V. Benaroya TIC /NSIC/ TERA Z. Rosztoczy APR 7 1987-LB #4 r/f W. Haass H. Denton D. Muller

1. g$

E. Case R. Ballard A.

D. Eisenhut W. Regan D

R. Purple R. Mattson

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B. J. Youngblood P. Check b'

ei ' b

.gfO$g19 A. Schwencer

0. Parr 5

F. Miraglia F. Rosa 4

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7 J. Miller W. Butler G. Lainas R. Houston u,s *(

U R. Vollmer J. Hulman

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J. P. Knight W. Gammill Y

g R. Bosnak L. Rubenstein 4

F. Schauer T. Speis R. E. Jackson W. Johnston Attorney, OELD f S. Hanauer

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C. Berlinger ACRS (16)

F. Schroeder R. Tedesco D. Skovholt M. Ernst K. Kniel NRC

Participants:

G. Knighton A. Thadani M. Mallory D. Tondi

0. Thompson J. Kramer D. Gupta D. Vassallo ^

J. Kimball P. Collins I. Alterman D. Ziemann A. Ibrahim F. Congel S. Brocoum J. Stolz H. Lefevre M. Srinivasan I

L. Yang R. Baer D

E. Adensam g.

auht Project Manager M. Mallorv L. Heller I.icensing Assistant M. Duncan bcc: Applicant & Service List i

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