ML20093C231

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Forwards Hydrdological & Geotechnical Engineering Branch Input for Testimony at ASLB 821027-1104 Hearings Re Bearing Capacity Beneath Diesel Generator Bldg,Piping Svc Water Pump Structure & Permanent Dewatering
ML20093C231
Person / Time
Site: Midland
Issue date: 10/14/1982
From: Lear G
Office of Nuclear Reactor Regulation
To: Adensam E
Office of Nuclear Reactor Regulation
Shared Package
ML19258A087 List: ... further results
References
CON-BX17-017, CON-BX17-17, FOIA-84-96 NUDOCS 8211030222
Download: ML20093C231 (9)
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UNITED STATES NUCLEAR REGULATORY COMMISSION o

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p WASHINGTON, D. C. 20555

~ % n. % st E A l % m 4 f b 6 b ll% 8 11 Docket Nos.: 50-329/330 MEMORANDUM FOR: Elinor G. Adensam, Chief Licensing Branch #4, DL THRU:

( James P. Knight, Assistant Director for Cc,mponents & Structures Engineering, DE FROM:

George E. Lear, Chief l

Hydrologic and Geotechnical Engineering Branch, DE

SUBJECT:

MIDLAND ASLB HEARINGS - GE0 TECHNICAL ENGINEERING INPUT Plant Name: Midland Plant Units 1 and 2 Licensing Stage: OL Responsible Branch: LB No. 4, M. Miller, D. Hood and R. Hernan, LPM Requested Completion Date: October 13, 1982 Status: Completed 4

In response to the verbal requests of W. Paton and M. Wilcove of OELD, we have enclosed our input for staff testimony in preparation for the upcoming ASLB hearings. The h?arings scheduled for October 27 through November 4, 1982 are to cover (1) bearing capacity beneath the Diesel Generator Building, (2) underground piping, (3) Service Water Pump Structure and (4) Permanent Dewatering.

In the enclosure under Part I, we have identified the pertinent SSER sections where the geotechnical engineering staff'has addressed the topics scheduled for the upcoming hearings. Under Part II of the enclosure we have identified either the SER or SSER sections or we have provided our response to the safety issues listed in the Stamiris and Warren contentions that are related to the identified hearing topics.

Any questions that you may have on the enclosed input may be referred to J. Kane (28153), Geotechnfr.al Engineering Section, HGEB.

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George E. Gar, Chief Hydrologic and Geotechnical Engineering Branch Division of Engineering

Enclosure:

As stated i

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Midland Plant, Units 1 and 2 Docket Numbers: 50-329/330

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Geotechnical Engineering Input into Staff Testimony Prepared by: Joseph D. Kane, HGEB, NRR PART I - PERTINENT SSER SECTIONS FOR HEARING TOPICS

1. - Hearing Topic: Bearing Capacity beneath the Diesel Generator Building SSER Section with Staff Safety Evaluation: Section 2.

4.4.2, P.249 J.2.5.4.5, i

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Hearing Topic: Underground Piping

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.t. do SSER Section with Staff Safety Evaluation:, Sections 2.5.4.4.5.12.5.4.6.2,g 3

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Hearing Topic: Service Water Pump Structur %.2-N 5 Y'*I*s S

SSER Section with Staff Safety Evaluation: Sections 2.5.4.4.1.12.5.4.5.2 L

Sh44.a.3Aggp42,.5 4 gggg.g,,gg.h84 43 4.. Hearing Topic: Permanent Dewatering SSER Section with Staff Safety Evaluation: \\ Sections.2,5.4.4.4,' 2.5.4.5.5.

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PART II - RESPONSE TO CONTENTIONS 1.

Stamiris Con'tention 4.C.b as supplemented on 4/20/81 and as it pertains to this hearing session, reads as follows:

U Consumers Power Company performed and proposed remedial actions regarding soils settlement that are inadequate as presented because:

A. ------

B. ------

C. Remedial soil settlement actions are not based on adequate evaluation

'e of dynamic response regarding dewatering effects, differential soil settlement, and seismic effects for these structures:

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b. Service Water Intake Building and Its Retaining Walls
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1 With respect to the concern on differential soil settlement, it is the y

staff's understanding of this contention that it is directed to the J.

adequacy of the soil-structure interaction study for earthquake loading j

and whether that study for the underpinned Service Water Pump Structure properly evaluated the effects of differential soil settlement.

During earthquake loading the amount of settlement which will result in the foundation soils has been estimated using dynamic soil spring constants.

As indicated in SSER Section T.5.4.5.6 the staff has concluded that the soil shear moduli values, adopted by the applicant for use in dynamic aialysis, are reasonable and acceptable and the applicant's decision to allow + 50% variation in the resulting soil spring constants is conservative.

Therefore, the staff concludes that differential soil settlements have been Properly addressed 1p%

ynamic analysis of the underpinned Service W the d Pump Structure. %

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<m% u k u, % ag tr %.%,e a e. 2 4 6 e r the seismic Category I retaining wallg14gg.g j

Remedial foundatio...,mw.a.,

n measures l-adjacent to the SWPS were not required. The staff has concluded that thIQE %kj C, t plant fill pmblem did not extend to the foundation of this retaining wall.

2.

Stam{ris ntention 4.D, parts 1) and 2) reads as follows:

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O Consumer Power Company performed and proposed remedial actions regarding soils settlement that are inadequate as presented because:

A. ------

B. ------

C. ------

Pemanent dhtering D.

1) would change the water table, soil and seismic characteristics of the dewatered site from their originally approved PSAR character-1stics - characteristics on which the safety and integrity of the plant were based, thereby necessitating a reevaluation of these l

characteristics for affected Category I structures; il j

2) may cause an unacceptable degree of further settlement in safety

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related structures due to the anticipated drawdown effect; _,...

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Response to Part 1) of 4.D.

The NRC staff has considered the following information in its evaluation of f

the dewatering effects on the various plant subsoil layers at the Midland site.

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Because the long tenn dewatering will lower the grorcuater level in a.

the upper perched groundwater system to approximat'!i cl. 595 feet, there will be minimum effect to plant subsoils below this level thich would include the approximately 150 feet thick preconsolidated impervious clay layer which separates the two groundwater systems. This impertious clay layer has been shown by subsurface explorations to be located between approximately el. 580 feet and bottom el. 430 feet in the auxiliary building area.

b.

In the depths of subsoils which will be affected by dewatering, the staff anticipated both improvements to the engineering properties of the foundationi soils above el. 595 and certain adverse effects due to dewatering as discussed oelow.

Reevaluation of soil engineering properties has been perfonned by methods that include additional subsurface explora-i tions, laboratory testing and seismic surveys in the field.

The staff's conclusions on this work are presented in SSER Sections 2.5.4.1.3, t

2.5.4.2 and 2.5.4.3.

An increase in the shear strength of the subsoils would reasonably be c.

expected as dewatering would remove pore water and lower the water content of the foundation soils.

This increased shear strength would result in higher margins of safety against bearing capacity type failures. The staff has not required the applicant to estimate th improvement in safety if acceptable levels of safety had been demonstrated under the more severe conditicas (e.g. non-dewatered condition).

d.

l.owering the groundwater to levels below the walls of embedded structures will reduce lateral forces on foundation walls by removing l

water pressures.

This reduction will result in an increase in structure stability.

A potential adverse effect of long tenn dewatering could be the removal e.

i of soil finds caused by lowering and pumping of the groundwater in the dewatering wells. The staff's position has been, since the time t

dowatering was initially selected as a remedial measure, to ensure that a high quality dewatering system would be designed and properly controlled and installed in the field so as to avoid the loss of soil i

fines problem. The staff efforts in this regard are documented in 50.54(f) questions numbered 24, 47, 49, 50, 51, 52 and 53.

The staff has met on several occasions and has participated in numerous conference i

calls with the applicant to resolve its safety concerns on the design and installation of the dewatering sy. stem. One of the more important i

documents which summarizes the staff's review effort is the letter of

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June 18,1981 from R. Tedesco, NRC to J. Cook, Consumers power Company.

As a check on the acceptability of the dewatering system design and field installation, the applicant has successfully completed the full 1

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3 scale field drawdown and recharge test. The monitoring of loss of soil fines which has been completed with portions of both the 1-temporary construction and permanent dewatering wells in operation i'

has indicated that the dewatering system can safely operate and meet the required' conservative acceptance criteria on loss of soil n

particles. - The established criteria which ensures that the e

7 detrimental loss of soil particles will not occur requires that soil fines larger.than 0.005 mm that are measured in the collected e4 seepage water are not to exceed 10 parts per million.

If this level is reached during plant operation the applicant is reouired to determine which well or wells are causing the loss of fines and to

.i stop pumping from the wel1(s).

If necessary, the problem well(s) will

,1 be repaired or replaced.

5 On the basis of the above information and our review of addigjonal infonnation provided by the applicant on permanent dewateringathe the FSAR and technical reports, the staff has concluded in SSER j

Section 2.5.4.5.5 that th; permanent dewatering system will eliminate y

the potential for liquefaction.

1 Response to Part 2) of 4.d.

The major disadvantage of dewatering on the plant subsoils is the removal of buoyancy. This removal causes an increase in the effective weight of the soil mass which in turn places greater loads on the foundation soils leading to greater soil compression. The staff pursued resolution with the applicant of its concern for increased soil compression due to dewatering in 50.54(f) questions numbered 33, 39(1 ), 40(1 ), 41 (2)(b),

42(2)(e), 44(2) and 47(9). The staff is satisfied that the settlements estimated by the applicant to occur due to dewatering during plant operation are conservative and acceptable for use in structural analysis which evaluate the effects of these sett1e' ments.

In addition, long term settle-ment monitoring during plant operation will be carried out to verify that estimated settlements are not being exceeded.

3.

Warren Contention 2B expresses a concern for liquefaction of the foundation F

soils. The staff's evaluation of this issue has been provided in Section j

'1 2.5.4.5.5 of the SSER.

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'ij Attachment 1

The remaining contentions, some of which raise similar if not identical concerns, read as folinws:

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Stamiris Co'ntentions i

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Consumers Power Company perfonned and proposed remedial actions j

regarding soils settlement that are inadequate as presented because:

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A.

Preloading of the diese? generator building

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1) does not change the composition of the inproper soils to

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meet the original PSAR specifications;,

02r.N. MW 2) does not preclude an unacceptable degree of further

'j Q o M i,t-32 differential settlement of the diesel generator building; I ~cd.wo2. 2 7-3) does not allow proper evaluation of compaction procedures because of unknown locations of cohesionless soil pockets; 6d552 smt M

4) may adversely affect underlying piping, conduits or nearby

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O d.Re.2 55 5E.

5) yields effects not scientifically isolated from the effects of a rise in cooling water and therefore not measured properly; Maq t%2. CeR B.

Slope stability of cooling pond dikes is not assured because h 2-so,b SS.b7 they were built with the same improper soils and procedures (NCR

- }QF172);

C.

Remedial soil settlement actions are not based on adequate g

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evaluation of dynamic responses regarding dewatering effects, differential soil settlenent, and seismic effects for these

.j EC'040h structures:

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Aux. Bldg. Electrical Penetration Areas & Feedwater isolation Valve Pits Voe 4 c.b

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Service llater Intake Building & its Retaining llalls a

c.

Borated Water Storage Tanks d.

Diesel Fuel Oil Storage Tanks s

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Related Underlying Piping & Conduit D.

Pemanent dewatering d.bwe. k k 1) would change the water table, soil and seismic

/d characteristics of the dewatered site from their originally u

V.Gowade.s approved PSAR characteristics - characteristics on which the No(%2 sessi safety 'and integrity of the plant were based, thereby 3

necessitating a reevaluation of these characteristics for 4

affected Category I structures; N

sa)fety related structures due to the anticipated drawdown

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2 may cause an unacceptable degree of further settlement in 1

effect;

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3) to the e. stent subject to failure or degradation, would 3), QQ allow inadequate time in which to initiate shutdown, thereby Np%2. sessio,,

necessitating reassessment of these times.

Warren Contentions Qes voe, h 1.

The composition of the fill soil used to prepare the site of the d,

ne.Se Midland Plant - Units 1 and 2 is not of sufficient quality to assure orhcipded that pre-loading techniques have permanently corrected soil settlement b W2. session problems. The flRC has indicated that random fill dirt was used for backfill. The components of random fill can include loose rock, broken concrete, sand, silt, ashes, etc. all of which cannot be compacted through pre-loading procedures.

Pg.syorce. h 2A. Because of the known seepage of water from the cooling pond into

.R.C.3entcde3 the fill soils in the power block area, permanent dewatering procedures Q g.tuo, being proposed by Consumers Power Company are inadequate, particularly in the event of increased water seepage, flooding, failure of pumping.

systems and power outages.

I!nder these conditions, Consurers cannot provide reasonable assurance that stated maximum levels can be

.j maintained.

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28. Given the facts alleged in Contention P..A, and considering also

] pg that the Saginaw Valley is built upon centuries of silt deposits, these highly permeable soils which underlie, in part, the diesel generator j,

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gg building and other class I structures may be adversely affected by p'yi increased water levels producing liquefaction of these soils.

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following will also be affected:

  1. %2W1.Sc.se 1) borated water tanks
2) diesel fuel oil tanks.

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Pre-loading procedures undertaken by Consumers Power have induced 4

0["t stresses on the diesel generating building structure and have reduced the ability of this structure to perfonn its essential functions under 4

(7 cpN hat stress.

Those remedial actions that have been taken have produced 4

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%2.sesm uneven settlement and caused inordinate stress on the structure and circulating water lines, fuel oil lines, and electrical conduit.

Sinclair (OL) Contention #24 I

24. The present site for the liidland facility is not only inappropriate b nde.

for the reasons set forth in Contention 9, but also affirmatively

,6 unsa fe. Serious questions have been raised concerning the ground o4c,$gj stability of portions of the site. At least one of the essential UN buildings of the reactor complex is reported sinking, and construction has been halted on that building.

As a result of the serious and unresolved questions concerning ground stability, the findings required j

by 10 C.F.R. SS 50.57(a)(3) and 50.57(a)(6) cannot be made.1/

1 liarshall (OL) Contention #2 2.

Present geological conditions, according to newspaper accounts, is causing the settling of the generator building at the fluclear Power Plant site.

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This contention should be read to raise an issue not of site suitability, but of the quality of soils used at the site. ' Disregard the reference to Contention 9.

The soils quality issue is. raised

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by other contentions, such as llarren #1 and Stamiris 4A and 48, for i

example.

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