ML20054C418

Confirms 820326 Verbal Concurrence W/Plan to Proceed W/Installation & Operation of Const Dewatering & Observation Wells for Svc Water Pump Structure Based on Review of Preliminary Procedures & 820326 Recommendations

ML20054C418
Person / Time
Site:	Midland
Issue date:	04/02/1982
From:	Tedesco R Office of Nuclear Reactor Regulation
To:	Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
References
ISSUANCES-OL, ISSUANCES-OM, NUDOCS 8204210024
Download: ML20054C418 (18)

Text

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W JKramer NRC PDR Hr. J. W. Cook RMattson Local PDR Vice President RHartfield, MPA NSIC Consumers Power Corpany JKane TIC 1945 West Parnall Road RLandsman ACRS (16)

Jackson, Michigan 49201 FRinaldi

Subject:

Staff Concurrence for Installation and Operation of Construction Dewatering and Observation Wells for the Service Water Pump Structure

REFERENCES:

1)

J. W. Cook letter of March 23, 1981, announcing bin wall concept 2)

Structural Design Audit, April 20-24, 1981, Ann Arbor 3)

J. W. Cook letter of August 26, 1981, with " Technical Report on Underpinning the SWPS"

4) Hecting of September 17, 1981, on SWPS underpinning

$)

J. W. Cook letter of November 6,1981, providing information requested during September 17, 1981, meeting 6)

J. W. Cook letter of November 6,1981, with report " Test Results, SIMS Soil Boring and Testing Program" 7)

J. W. Cook letter of March 2,1982, with report " Evaluation of Cracking in SWPS at Midland Plant"

8) Hecting of February 23-26, 1982 9)

J. W. Cook letter of March 2,1982, with report "SWPS Three-Dinensional, Finite-Elenent Itodels"

+

By an audit meeting on March 16-19, 1982, and by several referenced reports and neetings, you have described the renedial underpinning planned for the Service Water Punp Structure (SWPS) for Hidland Plant, Units 1 and 2.

Preparations for this underpinning activity include temporary dewatering of the immediate area by approximately 65 construction wells to be located inside the SWPS, inside the adjacert Circulating Water Intake Structure, and the remaining perimeter outside the SWPS. Staf f concurrence to proceed with this dewatering was requested by Mr. J. Mooney of your Company on March 17, 1982.

During the audit neeting on March 17, 1982, the staff was provided copies of the subcontractor's plan (Enclosure 1) and the prelininary procedure (Enclosure 2) for construction dewatering.

Several changes to the procedures were discussed including:

(1) The nethod of well placenent will be changed to the nothod pre-viously accepted by the staff for the interceptor and area per-manent dewatering wells.

G204210024 820402 PDR ADOCK 05000329 omcn >

g pon SURNAME) pare p NRC FORM 313 0040MRCM oua OFF1CIAL RECORD COPY

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Mr. J. W. Cook (2) The depths of the dewatering wells should be increased so as to maintain the water table below the bottom of the underpinning pier foundations.

(3) Consumers Power Company is considering an optional approach for the excavation drift which would relocate the drift from beneath the structure to the exterior edges of the structure, where those exterior walls are accessible (i.e., along the northwest and northeastwalls). Location of the construction wells would be positioned to acconnodate this option.

These and other natters regarding the construction dewatering plans were further discussed during a telephone discussion on March 26,1982 (Enclosure 3). Pages 4 and 5 of Enclosure 3 identify several changes which were agreed to as a result of staff recornendations. We have discussed Q-listed aspects of this dewatering with our Region III Office and have included the following itens froa to be of particular interest in this respect:

1.

That the depths for piezometers and filter. sand identified by paragraph 3a be achieved; 2.

That the minimum two foot depth between the upper phreatic surface and the bottom of any open underpinning excavation, as discussed by paragraph 3c, be maintained; and 3.

That nonitoring for the loss of fine soil particles be performed consistent witn the corpromise position discussed in paragraph 3e.

On the basis of our review of the information provided, and the intended changes identified which Consumers has comitted to making, the staff agrees with your plan to proceed with construction dewatering for the Service Water Purp Structure area.

This confirms the verbal concurrence by our Project Manager to Mr. J. Mooney on March 26, 1982.

Sincerely, Origin:J signed by Robey L Todesoo Robert L. Tedesco, Assistant Director for Licensing Division of Licensing

Enclosures:

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MIDLAND Mr. J. W. Cook Vice President Consumers Power Conpany 1945 West Parnall Road Jackson, Michigan 49201 Mr. Don van Farrowe, Chief cc: Michael I. Miller, Esq.

Division of Radiological Health Ronald G. Zamarin, Esq.

Department of Public Health Alan S. Farnell, Esq.

P.O. Box.33035 Isham, Lincoln & Beale Lansing, Michigan 48909 Suite 4200-1 First National Plaza

. William'J. Scanlon, Esq.

Chicago, Illinois 60603

'2034 Pauline Boulevard Ann Arbor, Michigan 48103 James E. Brunner, Esq.

Consumers Power Company

.U.S. Nuclear Regulatory Commission 212 West Michigan Avenue Resident Inspectors Office Jackson, Michigan 49201 Route 7 Midland, Michigan 48640 Ms. Mary Sinclair 5711 Summerset Drive Ms. Barbara Stamiris Midland, Michigan 48640 5795 N. River Freeland, Michigan 48623 Stewart H. Freeman Assistant Attorney General Mr. Paul A. Perry, Secretary State of Michigan Environmental Consumers Power Company Protection Division 212 W. Michigan Avenue 720 Law Building Jackson, Michigan 49201 Lansing, Michigan 48913 Mr. Walt Apley Mr. Wendell Marshall c/o Mr. Max Clausen Route 10 Battelle Pacific North West Labs (PNWL)

(

Midland, Michigan 48640 Battelle Blvd.

l SIGMA IV Building Mr. Roger W. Huston Richland, Washington 99352 Suite 220 7910 Woodmont Avenue Bethesda, Maryland 20814 Mr. I. Charak, Manager NRC Assistance Project Argonne National Laboratory Mr. R. B. Borsum 9700 South Cass Avenue Nuclear Power Generation Division Argonne, Illinois 60439 Babcock & Wilcox 7910 Woodmont Avenue, Suite 220 James G. Keppler, Regional Administrator t

i Bethesda, Maryland 20814 U.S. Nuclear Regulatory Commission, Region III Cherry & Flynn 799 Roosevelt Road Suite 3700 Glen Ellyn, Illinois 60137 Three First National Plaza Chicago, Illinois 60602 Mr. Steve Gadler i

2120 Carter Avenue St. Paul, Minnesota 55108

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l Mr. J. W. Cook :

I cc:

Commander, Naval Surface Weapons Center ATTN:

P. C. Huang White Oak Silver Spring, Maryland 20910 Mr. L. J. Auge, Manager Facility Design Engineering Energy Technology Engineering Center P.O. Box 1449 Canoga Park, California 91304 Mr. Neil Gehring U.S. Corps of Engineers NCEED - T 7th Floor 477 Michigan Avenue Detroit, Michigan 48226 Charles Bechhoefer, Esq.

Atomic Safety & Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C.

20555 Mr. Ralph S. Decker Atomic Safety & Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C.

20555 Dr. Frederick P. Cowan Apt. B-125 6125 N. Verde Trail Boca Raton, Florida 33433 Jerry Harbour, Esq.

Atomic Safety and Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C.

20555 Geotechnical Engineers, Inc.

ATTN:.Dr. Steve J. Poulos 1017 Main Street Winchester, Massachusetts 01890 e

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n Service Walcr Psme Struebe - Dconferias P l

The fellowm3 pracdure ss n sam fted bY flse sulcontra re.useweA. Rev s s sons well be re.g v ors) is m the procass e4 henn reloc zisd outsik 841kr. access desEfs a OVERALL DISCRIpTION OF TEE SYSTD{

h.0 k.1 ApprnM=tely h2 devatering vens vill be instaned at 6* feet on 9 feet center along the north and east sides of the SWPS, about These outside the proposed access excavation for the underpinning.and vin consist vens vin be from existing grade, elevation 63hof 6" I.D. P full depths.

h.2 Approximately 18 devatering ve11s vill be install j e tr",

( 8' nese vens win be installed from elevation 620.

n devatering vens win be instaned from within the Crecuat# Water 592.

Intake Structure (CWIS) west of the easternmost vall extend f

1 All wells located within structures will be spaced at an average 41 to elevation 610.

feet on center and vill consist of a 3" I.D. galvanized lov carbon steel screen.

h.3 An devatering vens vin be located to miss existin5 utilit pipe lines, etc.

All vells vin extend to the bottom of the deepest sand stratum. or to a minimum elevation of 5B5 vbere cla drawings for approval.

is encountered above that rinimum.

of any well, a drill permit (see Attachment A) vill be obtained from

Bechtel, k.h Two inch (2") eductor pumping units vill be used to pump the wells.

Tbe eductor pumping units vill be of sufficient size and nu=ber to lover The eductor pressure the water in each ven to the bottom of the ven.

and return headers, 8" in diameter, vin be located to suit the site conditions and will connect all eductor units to a control pump station.

The pucp station vin have an electric operating pump and 100% stand-by The diesel powered pu=p capable of operating the eductor units.

The discharge from the devatering system vill be piped to the pond.

The devaterin6 volume of water pumped vill be recorded by a meter.

system vill be installed and maintained in operating condition for the duration of the subcontract althouGh Pu= ping may be discontinued when not required.

h.5 Pieza=eters (observation vens) vill be installed at the approximate location shown on the subcontract dravings.

h.6 Apprne-te locations of major co=ponents of the devstering system vill be shown on the devatering shop drawing which vin be submitted Inrta11ation vill not proceed until said approval j

to Bechtel for approval.

is granted.

50 EOUIIMD.T AND PJ.TERI AIS I

5.1 Devatering well screens vill consist of 6" I.D. slotted PVC pipe for wells outside the structures and 3" I.D. continuous tiot galvanized Slot low carbon steel as manufactured by loughney -Devatering Inc.

j size vill be 0.018 inches for the 6" I.D. PVC screen and 0.008 inebes j

for the 3" I.D. galvanized steel screen.

f 5 2 Two inch eductor pu= ping units vill have an approximate capacity

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of 7 gallons per minute (GPM).

5 3 The electric operating pump vill have a motor rated at 150 horsepover (EP) and vill be capable of pu= ping 800 GPM at an approximate pressure l

of 125 pounds per square inch (PSI).

I 5.h The stand-by diesel power pump vill also have a motor rate'd at 150 HP and be capable of pumping 800 GPM at apprmimately 125 PSI.

5 5 The meter for measuring discharge volume vill be a " Badger" flov-meter sized according to the discharge volume which develops.

5.6 Observation vell screenu vill be 1\\ inch I.D. by 3 feet long slotted The riser pipe vill be 14, inch I.D. FVC.

PVC.

5 7 The select filter sand vill have approrimately the folloting gradation:

Percent Passing

. Sieve Size _

100 h

90-100 10 i

75-100 l

16 60- 98 20

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25-1 0 30 k0 3-15 0- 2 50 5 8 The filter for devatering wells inside the structures and fcr the observations wells vill consist of Ottava Flint Shot (OFS) sand.

5 9 Drilling mud vill be mixed using " Revert" as manufactured by U.O.P. Johnson Company or an equivalent organic drillingr fluid.

1 1

1 t

,.O. DC/11 MIG TROCEDUEE 6.1 Devateri,ng vens outside the ctructre 6.1.2 Bydraulic Rotary Dr11 Hug Metnoa - A rotary drilling rig capable of drilling a 14". diameter hole to an 80 foot depth, such as Failing A

1500, vin be used to drin the holes for the devatering vill be mixed in the pit and then pumped through the top of theThe rotating drill stem and out the bottom of the 14" dia=

up around the outside of the drin pipe and conv the bottom of the ditch and the pit.

After which until the hole has been drined to the desired depth.

a 2" pipe vill be inserted to the bottom of the hole and f in the Revert fluid win be flushed out of the hole and disposed oA 6*

The drins rods and bit will be removed.

diameter PVC ven screen and riser vill be installed in the a controlled manner.

s.

The ven screen vill extend from the bottom of the hole

.3 The last 7 to 10 centered.

to within 7 to 10 feet of the ground surface.Se annulus between the 6" ven scre

'I feet win be 6",FFC riser.

d The filter and the hole vin be filled with a select filter san.

d the 2" vater sand win be placed by shoeveling it into the annulus anThe procedure. vin line graduany removed as the filter is placed.

be repeated for each devatering well.

6.2 Devatering Wens Inside the Structures - The eductor wells Where the ground-the SWPS and the CWPS vill be instaned as. fonovs:

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~ vin be made to water level is above eleiration 620 and 610 provis on i

its d the casing installation with a 6" casing sealed in the concrete, anA hole of sufficient dia win extend above the groundvater level.to acen=adate a h

on the bottom vin be drined through the concrete.

t sand open drive shoe vill be driven to the bottom of the deepes t red above stratum or to elevation 585 where the clay tin is encoun e casing vill be cleaned out with clean water as At no time vill a slurry, drining mud, Revert elevation $85 The f the k" I.D.

it is being advanced.

or similar additives be used during the installation oa 5

casing.

above the prevailing groundwater level.

ing vin be win be installed inside of the 4" casing and then the c removed.

the bottom of the concrete floors.

and it vill be within 2 feet of i

ven above the screen vill be 3" galvanized steel p peAny void s De procedure vin sealed in the concrete.

screen and the soil win be fined with OFS sand.

be repeated for each ven.

6.3 Piezameters - piezometers sh11 be instaned at an elevatio t il lover than 2'-0" above the original undiriturbed natural ma er a,

A chart 1

as determined by Bechtel's resident Geolop5 h piezameter; its vill be prepared that vill show the location of eacnu th to vater, and the elevation of the water level.

l tion Bechtel within one week.of each piezameter's re Piezometers win prior to the installation of the access shafts.be insta date.

location.

e 6.31 - Piezo=eters outsida the struc following e ner.

vill be rotary drilled to vithin 6 feet ing Revert as the acco=modate a k" I.D. pipe of the proposed tip of the observation ven us illed A r.ininu= of h" I.D. casing vin be set in th drilling fluid.

hole to the bottom of the hole. Using the clean water the hole flushed with vater; the h" casing with clean water.

l vill be drined to the tip elevation; the ho eone fo ttom; an observation h

vell screen and riser placed in the hole; t e the hole fined for a depth of 5 feet; the casing raised 2 feet; d 2 feet and the

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with one foot of bentonite seal; the casing raiseThis procedure hole filled with sand in 2 foot increments.

d.There is only repeated until the casing completely is remove.

one bentonite seal.

' Provisions win be made to balance any 6.3.2 Piezameters located within the struct floors in the fonoving manner. hydrostatic head that is above the to location with an

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elevation 610.and 620 at each observation vellAt each

1. C exterior casing sealed in the concrete.

ill be drined sufficient diameter to accommodate a k" I.D. pipe vvin be drilled Below the concrete the hole h

bservation through the concrete.using Revert to within 6 feet of the prop ven. A rin4*ne of h" I.D. casing vin be setbottom of the hole.

The and extended from the working level to theReve 3

ter..Using s

%A tion; the hole l

clean water the hole vin be drined to the tip e l

d at the the hole; the bottom; observation ven screen and riser p f 5 feet; the casing raised 2 feet; the hole fined with one d in 2' inerenentt the casing reaised 2 feet and the hole filled with san floors elevation This procedure repeated to the top of the concrete There is only one bentonite seal.

620 or 610.

in the 4" casing,

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At an times during the installation the water level

^

d at least 7 feet ym the exterior casing and the hole vin be maintaine y.

above the prevailing groundwater level.

rete floors, Where the groundwater level is above the top of the concd an elevation 620 or 610 the 4" casing vill be removeleft at er above the casing and the observation well riser win beWhere the g vin be cut off groundwater level.

i of the concrete. floor the observation ven r s h riser sealed in the concrete floor.

i 6.h After completion of the devatering and obser g.

8 P.A. 19'(2, which is an records for these vens as required by ACT 21 Quality Control Act amendaent to ACT 29h P.A.1965, Ground WaterThe d leted l vens. The for every ven or a composite record made for severa be prepared.

f onditions are composite record may be used where the subsur ace cd the st similar, the surface relief relatively level, anDepending on v level at a constant depth.

sites may be ne ess TI be prepared Meg, sma cWe dean as h*th ce. tan several e one'o conditionsSsers we l

Copies of these records shall be submitted to Bechte.

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7 OPERATION AND MAINTENANCE 7 1 Development - After each vell is instan ed it vill be developed and tested in accordance with the established procedures and upon approval activated. During thevell develop =ent tests SVP and Loughney personnel vill aid Bechtel in any manner required.

All observation vens vill be tested by either a ming test or a falmg head test to ascertain whether they are functioning properly.

During initial connection of the eductor pumps to the header system suitable petcocks, bushings, and nipples will be installed at each 4

devatering well for obtaining vater quality samples.

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7 2 The devatering operation shall be controned so the amount of The soil particles in the discharge water is limited to 10 ppm.

j vater level in the observation vens and the volume of water being 4

pumped and the operating pump pressure vill be recorded once each

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day five days a week. The stand-by diesel pump vill be started once a week. The component parts of the devatering system vill be checked routinely and adjustments made as required.

8.0 RD!OVAIS n..W 8.1 Devatering vens buried or left in place under or near the structures -

shall be sealed with grout after the devatering operation is discontinued, in accordance with the most recent Michigan Wells Act and to the satisfaction of Bechtel. Approval of Bechtel shall be obtained prior to grouting wells.

8.2 All holes drilled in the SWPS and CWIS for use in devatering shan h;

be repaired using materials furnished by Bechtel and in accordance-

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with Section 10 5 of Specification 7220-c-194(Q) Revision 1.

Lyb' 8.3 All piezameter holes shall be sealed vith grout after the devatering operation is discontinued.

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90 REVISIONS Should it develop that the condi.tions encountered during the installation or operation require deviations in the sobve stated procedure, the modificaticc.s dee=ed necessary vill be submitted to the on-site geotechnical engineer for approval.

l

I Attnehzxnt A 1

CDNCRITE DRILLING PERMIT Project 7220 Permit No.

p,ge of Prepared By:

Discipline:

Date Unit Bldg.

Area Elev.

i Location of Q-Listed blockwall or mured Resident Engineer approval f or attachment to wall substituted for Q-Listed bloctwall Q-Listed blockwall or poured wall substituted l

for a Q-Listed blockwall.

Appy'd Not Appy'd Date

'i By:

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V (1) SEE LATEST DESIGN DRAWING REVISION AND CHANGE ADDENDA PRIOR Notes:

(2) DO NOT CUT REBAR WITHOUT FIELD ENGINEERS APPROYAL. NO REBAR

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ALLDWED IN Q-LISTED CONCRETE BLOCKWALLS OR POURED WALLS SUBSTITUTED Q-LISTED CONCRETE BLOCKWALLS.

Spscific Instruciton and Location Tolerance:

, Note:, If rebar encountered, notify If ground cable encountered, Loads per drawing C-2050:(list only for at-notify tachments to Q-Listed blockwalls or poured 5tfore moving hanger, notify walls substituted for Q-Listed blockwalls)

Reference Drawings:

Approved By: (Not required for attachments to Q-listed blockwall or poured walls substituted for Q-listed block walls.)

Civil Date Piping Date uste E1cet Date

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ENCLOSURE 3 q

c a RECORD OF TELEPHONE C0!iVERSATION DATE: March 26, 1982 8:30 am to 11:30 am PROJECT: Midland RECORDED BY: Joseph'Kane CLIENT:

TALKED'WITH: CPC Bechtel_

COE GEI_

NRC T. Thiruvengadam J. Anderson ll. Singh S. Poulos-J. Kane K. Razdan L. McKelvey R. Ramanujam C. Russell W. Paris S. Afifi N. Swanberg ROUTE T0:

Information:

S. Poulos G. Lear L. Heller H. Singh D. Hood R. Landsman F. Rinaldi R. Gonzales The purpose of this call was for the Staff to. respond MAIN SUBJECT OF CALL:

to CPC on three review issues which had been discussed during the March 16-19, 1982 audit.

During the audit the Staff indicated they would respond to Consumers.

by March 26, 1982. The review issues involved include adoption of soil. spring constants, settlement monitoring and construction dewatering for underpinning l

work related to the Service Water Structure.

l l

ITEMS DISCUSSED:

Adoption of Soil Spring Constants. (Reference - Calculations by Bechtel 1.

12/10/81 and 2/22/82; Calculations dated 12/11/81 by DQ.29(Q) dated G. W. Cowling; App. A entitled Service Water Pump Structure, Three-Dimensional, Finite Element Model provided by Carl Dirnbaver on 2/23/82).

Bechtel indicated that values of soil spring constants deterniined in G. W. Cowling's calculation for System' 5, (Long tenn conditfordare

= 230 KCf for adopted differential settlement Kmain = 190 KCf and Ku/ pin condition of 0.2" beneath portion on till and 0.5" beneath underpinning For adopted differential settlement condition of 0.4" beneath wall.

portion on till and 0.1" beneath underpinning wall the spruig constantThe Staff.

= 1150 KCf.

values are b ain = 95 KCF and Ku/ pin

= 190 KCf and Ku/.

= 230 KCf as its agreement with the valves of k being reasonably conservative for tN" design of the.SWS.E'ihe Staff g

did not object to adoption of the other spring constant valves but do not feel the differential settlement which is assumed in this conditi like,1y to occur._

2 The valves of the short term soil springs for seismic loading (System 4) are not identified in Table 1 App. A but were provided in previous testimony and technical reports by Consumers.

The Staff has not completed their review of the seismic spring constants and will respond to Consumers at a later date on the appropriateness of these valves.

= 150 KCF, The valves of spring stiffnesses adopted for system 3 (kmain ku/ pin = 400 KCF) and FSAR load combination conditions are acceptable to the Staff. The Staff noted that the valves adopted for ' system 5 (kmain "

190 KCF arid ku/ pin = 230 KCF) would also,be a reasonable estimate of.

stiffnesses for FSAR load combination conditions under System 4.

There was considerable discussion on Systems 1 and 2' in Table 1, Appendix A with respect to how structural stresses have been detemined due to jecking loads and also due to settlements which have already occurred.

The geotechnical area of concern is identifying the appropriate soil stiffnesses to use for these loading conditions.

Because of the inability to reach an agreement on these issues, it was suggested that L. McKelvey from Bechtel and S. Poulos from GEI get tog' ether by conference call next gj, week to work out an understanding on what conditions require analysis.,

Following their discussions, another conference call would be arranged with the parties of today's conference call to inform both Consumers and the Staff on what agreements c'ould be reached and what soil spring stiffnesses are required.

1 i

2.

Settlement Monitpring Dur.ing Service Water Structure (SWS) Underpinning.

(Reference - Drawing C-2003).

As agreed upon between Consumers and the Staff during the March 19, 1982 audit, a permanent bench mark will be added near the southeast corner of the SWS.

Locating this new pemanent l..

benchmark on the east wall as far south as it can conveniently be positioned

! -r near SW-3 is acceptable to the Staff. The major reason for this addition l

is to pemit the differential settlement to be accurately established between the portion of the SWS founded on till and the overhanging I

portion presently founded on the fill.

The Staff and its Consultants indicated their difficulties with Consumers previously stated intent not to require control of underpinnning operatior.s t4RC difficulties include with established allowable settlement limits.

the strain gage approach proposed by Consumers may not be a sensitive control and may not give as early a warning as measured settlements on the bench marks.

The Staff and its Consultants recommended that, similar to what is being carried out for the Auxiliary Building, allowable settlement limits be established at the pemanent benchmarks based on a structural analysis, where critical stresses due to differential settlement beyond rigid body motion have been calculated.

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Consumers indicated their concerns with establishing allowable differential settlement limits which included recognition of the more rigid structure and considerably shorter length c{ the main portion of the SWS on till in comparison to the Auxiliary Building.

These conditions, in Consumers epinion, would result in very small settlement limits which would be impractical to measure and would possibly be overshadowed by daily fluctuations due to climate changes.

This matter, after considerable

?.

discussion, was not resolved but an understanding was reached that the Staff would not take a position until after their review of the strain monitoring program had been completed. This program was to be provided i

by Consumers in early April.

Consumers agreed to consider the Staff's

]

recommendat' ion and provide a more definite indication on the magnitude of differential settlements which are i.nvolved, With respect to the frequency of readings indicated in Step 3 on Drawing C-2003, the Staff made the'following recommendations:

I At least one week prior to the start of excavation below the foundation a.

slab of the SWS, good background settlement data should be obtained for the three permanent benchmarks by increasing the frequency to_a minimum of three times a day in order to observe the effects of climate changes.

Consumers indicated their agreement to this Staff request.

b.

When excavations below the SWS foundation slab proceed in order to install corner piers 1, 2, 3 and middle pier 4 and during the jacking of these piers, the frequency of settlement monitoring should be increased to a minimum of twice per shift. The frequency of readings can be lengthened to once every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after corner pie'rs 1, 2 and 3 are completed and before work on pier 4 is initiated, if access to the piers is by way of an excavation outside the SWS as presently being considered by Consumers.

Consumers expressed agreement with this request.

Following the successful construction of piers 1, 2, 3 and 4 the 3

c.

frequency of readings as presently proposed by Consumers on Drawing i

C-2003 would be acceptable to the Staff.

It was indicated to Consumers that this increased frequency of readings during the more critical underpinning operations was also applicable to the strain gage monitoring program. Consumers agreed' to consider the need for increased frequency of strain monitoring' in their current work in developing this program. The frequency of.

readings proposed by Consumers for building settlement markers other than the permanent bench marks is acceptable to the Statf.

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(Reference - Plan of Construction Dewatering, Construction Dewatering.

Sections A-A and B-8, and Dewatering Procedure transmitted February 26 3.

1982 from Spencer, White and Prentis, Inc. to Bechtel Power Corporation).

The Staff indicated their acceptance of the locations of the dewatering wells and piezometers (observation wells) and made the following recomendations on the above referenced information:

The depths of the six proposed piezometers should extend to at least

~

The top of the filter sand in the piezometers a.

elevation 570.

should extend to elevation 590 and.then be sealed above 'this ele The type of piezometer to be instilled should be sensitive (e.g.,

3/8" maximum inside diameter or an air pressure cell ' type) to sudden b.

piezometric changes in order to avo.id long periods of time lag responses..

The specification for installing and operating the construction.

' dewatering system should establish a construction control on the c.

This control should require a minimum upper phreatic surface.2 foot depth between the upper phreatic surface b dewatering and the bottom of any open. underpinning excavation at any The depths of.the proposed dewatering wells should then given time.

be drilled accordingly to accomplish this construction control on the upper phreatic surface.

Placement of the filter sand in the dewatering wells should be by the tremie method rather than shoveling from the ground surface in d.

particles in holes order to avoid segregation of the filter sandConsumers agreed to modify the larger than 6-inch in diameter. construction dewatering plans and spe Staff's recommendations for above items 3a., 3b., 3c., and 3d.

(

The Staff recommended that paragraph 7.2 of the dewatering procedures-provided by Consumers be modified to define what constitutes soil e.

particles in the discharg'e water (inorganic, non, metallic naterials coarser than 0.005 niillimeter) and to indicate the frequency of testing similar to the agreements reached with the Staff as reflected 18, 1981 letter from R. Tedesco to J. Cook. Consumers.

responded that the const'ruction dewatering is a temporary system and

.in the June 18, 1981 therefore not subject to the agreements reached in the June There was.

letter which covered the permanent dewatering system.

considerable discussion on the safety significance and impact that a filter media criteria of 0.005 mm-versus 0.05 mm (Cons have on underpinning operations for both the Auxiliary Building and l

The Staff acknowledged that the 0.05 m l

Service Water Structure.

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.. criteria proposed by Consumers would not result in a serious for removal of foundation soil particles if this condition persistedO a period of several weeks.

the volume of soil fines which could be removed to be soils finer than 0.05 mm were being removed by dewatering over th anticipated one year period when underpinning work was being c The past' monitoring procedures employed by Consumers on con permit a conclusion to be reached as to whether a real problem existed for fines sized between 0.05 m and 0.005 m.

dewatering did not The Staff suggested a compromise where the' q

filter criteria but requiring the.testin g* for soil particles atConsumers both the 0.05 m and 0.005 m filters.

results to the attention of I&E inspectors and HRR of any test wher r

the amount of soil particles in the discharge water exceeded the i

At that time limiting 10 ppm.when measured on the 0.005 m filt

'the ' developing condition based on actual seepage pumping ra If the loss of soil particles' were deemed are not now available.significant enough during the remaining Staff would require remedial actions to reduce that loss.

In response to Consumer's request for NRC approval in thei with construction dewatering, the Staff indicated their concerns have now been resolvedbut that approval must come from Divis The Staff indicated D. Hood would be notified of the results of today's conference call and suggested that Consumers Licensing.

directly contact him sometime later this afternoon, On a matter not directly related to the subjec locations at

. test at locations near, but not in the actual pier t

This.

both the Auxiliary Building and Service Water Structure areas.

planning is in the early stages and it is Consu i

very near future.

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