ML19211A554
| ML19211A554 | |
| Person / Time | |
|---|---|
| Site: | Vogtle, 05000426, 05000427  |
| Issue date: | 12/06/1979 |
| From: | Thompson O Office of Nuclear Reactor Regulation |
| To: | Rolonda Jackson Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19211A548 | List: |
| References | |
| NUDOCS 7912200096 | |
| Download: ML19211A554 (9) | |
Text
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NUCLEAR REGULATORY COMMISSION y
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December 6, 1979 MEMORANDUM FOR: Robert E. Jackson, Chief Geosciences Branch, DSS THRU:
Lyman Heller, Leader Gectechnical Engineering Section Gecsciences Branch, DSS FROM:
Owen O. Thompson, Geotechnical Engineer Gectechnical Engineering Section Gecsciences Branch, DSS
SUBJECT:
TRIP REPORT - INSPECTION OF ERODED FOUNDATIONS PLANT NAME: Vogtle Units 1 & 2 LICENSING STAGE: Post CP DOCKET NUMBERS: 50-424/427 MILESTONE N0.: R-18 TAC NO.:
5347 RESPONSIBLE BRANCH: LWR-4, C. Stahle, LPM REVIEW STATUS: Awaiting additional information On November 20, 1979, I visited the Vogtle Nuclear Plant with I&E Region II inspectors Milton Hunt and Jack Harris. The complete list of attendees is attached to this report (attachment fl).
The visit by Geosciences Branch, NRR, was requested by I&E (through DPM) because recent heavy rains had caused severe erosion in the vicinity of seismic Category I foundations. These conditions caused I&E to issue a stop work order on construction of backfill in and around power block structures and placement of concrete on affected structures (Confirmation of Action letter from J. O'Reilly, I&E Region II, to J. H. Miller, Georgia Power Company, Nov. 15,1979).
The plant excavation extends from existing grade at about El 220 down to the top of marl at about El 130. Groundwater, at about El 160 pricr to construction, is supposed.to be controlled by a granular french drain around the base and sides of the excavation. Water is pumped from three sumps on the south side of the excavation. The structures are founded on the marl or on a silty sand (SM to SP) controlled structural backfill.
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.._.._y R. E. Jrakson l At the time of our site visit the excavation was complete and backfilling had progressed to roughly three levels: to about El 135 in the south I
part, to about El 150 to El 160 in the center, and to about El 186 in the north part. The principal structures in these areas are:
a) south part -- nuclear service cooling water towers and basins (emergency heatsink).foundedonmarl,auxiliarybuilding,foundedabout20ftintomarl.
b) central part -- containment units 1 (east side) and 2 (west side) f ourded on structural backfill except the reactor foundation which is founded on marl; control building and electrical tunnels founded on structural backfill.
c) north part -- turbine generator building founded on structural backfill.
The auxiliary building foundations were complete and structural construction j
was in progress. The tenden gallery for Containment Unit 1 was about 20 ft j
high. The control building electrical tunnels were partly constructed and i
part of the foundation for containment unit 2 tendon gallery was in place. Steel for the foundation mat of the turbine generator building was being erected on the mud mat.
The sequence of events leading to the stop work order, as recorded by the licensee, is provided in an interoffice communication from B. Harbin to K. Gillespie, Georgia Power Company dated November.16,1979 (attachment #2). Heavy rain on or about November 2, 1979, caused severe erosion of the backfill slope on the south side of the turbine generator building, between containment unit 1 and the control building, and around containment unit 2.
Some of the erosica had been temporarily repaired. However, it was apparent that erosion gullies were a number of feet deep, and that loss of support of foundations or mud mats may have occurred along the south side of the turbine generator building, at the southwest side of containment unit 1 tendon gallery, at the southwest side of the control room electrical tunnel, and along the north part of containment unit 2 tendon gallery. There is also a possibility that the northeast corner of the control building could have been adversely affected j
by the slope above this area (the slope at the edge of the turbine generator building). All of.these events of concern are at the edges or corners of existing i
foundations. Of even greater concern was the presence of seepage from north to south, under the completed (north) portion of containment unit 2 tendon gallery.
Both sides of the foundation had been recently covered by temporary fill so we would not see the extent, if any, of piping or erosion under the foundation.
A second, related problem with groundwater was identified during our site visit.
Groundwater has been accumulating for some time in the low area north of the auxiliary building and backfilling has not been possible. The licensee informed us that l
after unsuccessful attempts to lower the groundwater level with french drains, a dewatering contractor, Moretrench American Corporation, has been hired to install a system of well points for dewatering this area, cormiencing November 26, 1979.
We informed the. licensee that operating a dewatering system would not be permitted until we hac reviewed the proposed program because of the potential for damage to existing foundations.
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R. E. Jackson We observed three test pits in the backfill within containment unit 1.
Water was standing about 2 ft below the backfill surface. We did not approve the applicants plan to. install a temporary drainage system within the containment.
We did, however, approve continued backfilling in this area provided that the earthwork specifications were met.
Wa briefly inspected other parts of the site. The exterior grade around the excavation appeared to be adequately sloped to prevent water from surrounding areas entering the excavation. The low (El 130 +) area east of the auxiliary building was wet
~
and the licensee indicated that a drain would be installed to dry out the area and carry the water to the perimeter drain. A trench was being excavated in the earl on the south side of the excavation to enhance removal of water from the excavation.
The construction slopes in the fill southeast of the turbine generator building were being treated with fibreglass and asphalt. Other slopes were, in some areas, moderately to severely eroded and the licensee indicated that dressing of all slopes will be done as part of the surface water management and protection program.
The Region II. inspectors and I prepared a list of NRC concerns (Attachment 3) which were given to the licensee by the inspectors after I left the site.
During the site visit I took approximately 30 color print photographs.
Owen 0. Thompson, Geetechnical Engineer Geotechnical Engineering Section Geosciences Branch, DSS cc:
L. Heller
- 0. Thompson GB Files 1632 270
Attachment #1 Meeting Attendance Record Noh.20,1979 Name Comoany EdwinD.Grocher QASiteSuperhisor QA-GPC Joseph M. Duffy CihilContractor Walsh Co.
B. C. Harbin Civil P.S.S.
GPC R. W. McManus CihilQCSuct.Sup.
GPC M. H. Googe Ass.t Mgr. QC GPC K. M. Gillespie Const. Proj. Mgr Const/GPC J. E. Mahlmeister Bechtel Resident Engr Bechtel Cecil R. Miles, Jr.
GPCQAFieldSupYsr GPC J. R. Harris Reactor Const. Insp. NRC, I&E
- 0. O. Thompson Geosciences Branch NRC HQ M. D. Hunt Project. Inspector NRC, Reg. II D. A. Klinger SR QA Field Rep.
QA-GPC 1632 271
' ?,,'icroffica Communication GeorsinexerA Attachment #2
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PaUc 1 of 4 Pages
[jj
, k November 16, 1979 eeM o o
Memo To:
Mr.
K. M. Gillespie
Subject:
Vogtle Nuclear Plant - Units 1 and 2 Erosion Problems Category One Backfill File No.: X2AP01 Correspondence No.:
C-1098 The following is a discription of what has transpired due to heavy rains on November 2 and 10, 1979:
1.
Night of November 2, 1979--At about 4:15 p.m.,
rain began to fall heavily.
By Saturday morning, November 3, 1979, a 5-3/4" rain was recorded by site rain gauges.
During this period, 3-3/4" rain fell between 8 and 9 p.m. Friday.
2.
November 3, 19 79--Field Engineer Fcger Duncan and Civil Q.C.
Inspoetor Foy Conner noted severe erosion damage to fill sicpes between the Turbine Building and Units 1 and 2 Containments.
Clean-up cperations began by Walsh on Saturday, which consisted of removing standing water and mud frcm the icwer level around the south s de of the Auxiliary Building.
Cleanup wcrk continued Saturday, Sunday, and into Menday.
8 3.
Saturday, November 3, 1979--Eroded areas were located, flagged, and Nonconformance Report Number CD-595 was issued.
4.
Monday, November 5, 1979--NCR's CD-600, CD-601, CD-602, CD-603, and CD-605 were issued.
5.
Monday, November 5, 19 79--NCR CD-59 5 was presented to Bechtel for approval.
Approval was given and corrective action was taken on November 6, 1979.
6.
Tuesday, November 6, 1979--Corrective action was started on other NCR's (CD-600 through CD-603 and CD-6 0 5) which consisted of placing sand bags in and around voids under mud slabs to prevent fur-ther erosion until permanent corrective measures could be agreed upo'n.
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- D Pa e 2 of 4 Pages File No.:
X2AP01 Correspondence No.:
C-1098 November 16, 1979 dcPoG4 3#li7%
e 7.
Wednesday, Mcm.im-7, 1: 70--Dr. Vas Srinivasan (Bechtel) was on site, and while on site he was asked to review and comment on proposed dewater-ing backfill plans for areas north of Auxiliary Building 'and west of Unit 1 Containment.
The purpose of the backfill would be to reduco sloping surfaces,'therefore reducing crosion.. The dewatrer-ing plan was reviewcd and approved,and trenching was begun on. November I, 1979, to install a drain north and parallc1 to the Auxiliary Building.
After opening appfoximat'cly 15 to 20 feet of ditch, six feet deep, movement of the walls in previous backfill in the ditch was, observed.
This movement and sloughing of the walls was due to the high moisture content of the backfill.
Operations were ceased, and NCR CD-610 was issued.
Plans were revised and approved by Bechtel to raise the invert of the drain so that the trench would be only three to four feet deep.
On Friday,' November 9, 1979, trenching was begun and wall sloughing was observed.
A Stop-Work Order was issued on further trenching north of the Auxiliary Building, and the trench was filled with stone to prevent further sloughing.
8.
Thursday, November 8, 1979--Roy Kiser (Geologist-Bechtel) arrived on site for marl foundation inspection east of the Auxiliary Buildino, Mr.
Kiser's presence on site was in no way connected with backfill problems north of the Auxiliary Building.
9.
Friday, November 9, 19 79--Civil Field Operations contacted Mr. Vas Srinivasan, who was asked to return to the site.
Mr. Srinivasan and Mr. Ecbert Bush arrived on site Tuesday, November 13, 1979, and began site inspection.
10.
Saturday night,' November 10, 1979--Rain began and ended Sunday, November'll, 1979.
A 2+-inch rain fell during this period.
11.
Monday, November 12, 19 79--Cleanup, repair, and erosion operations were. continued.
An NCR (CD-613) was issued for a washout under a mud slab for Unit 1 Tendon Galle~ry Access Shaf t between the 1632 273
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emM mM ML Page 3 of 4 Pages File No.:
X2AP01 Correspondence No.:
C-1098 November 16, 1979 Auxiliary Building and ' Containment Unit 1.
Tem-porary fill was placed to prevent further erosion.
12.
Tuesday,' November 13,1979--A review was made of site conditions, and a meeting was held to discuss 6"/~ 4 solutions to erosion and sa'turated backfill north e.~
of the Auxiliary Building.
(Attendees present is he attached.)
13.
Wednesday, Novehber 14, 1979--Mr. Jack Harris (NRC) arrived on site and began a site inspection with Chet Sarver (. A.).
Q 14.
Wednesday, November 14, l'979--Civil Field Operations presented a plan at the Project Review Meeting to de-water the backfill in the power block, which consisted of:
A.
Installation of well points north of Auxiliary Building.
B.
Filter drains east and west of Auxiliary Build-ing and in Units 1 and 2 Containments (if required).
C.
Sump on northeast corner of Turbine Building slab.
8 (See attachment, Correspondence No. C-1097.)
15.
Thursday morning, November 15, 1979--Q.A. requested Civil Q.C. to meet with Mr. Jack Harris (NRC).
R. W. McManus (Civil Q.C. Section Supervisor), Joe Seagraves (Assistant Civil Q.C. Se'ction Supervisor),
Nelson Lankford (Soils Inspection Supervisor), and Barry Fairley (Soils Inspector) met with Mr. Sarver and Mr. Harris.
Mr. Harris' questions were directed toward moisture control and certain unclear state-ments in the field procedures.
Mr. Harris did not ask about the problems associated with erosion.
16.
Thursday, November 15, 1979--Bechtel and Field operations continued design of dewatering, erosion control, and repair of eroded areas in the power block.
(See attached Bechtel memo SRE-25 and GPC memo C-1097.)
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Page 4 of 4 Pages File No.:
X2AP01 D "" "" 0 "D
T' Correspondence No.:
C-1098
'J-November 16, 1979 17.
Thursday, November 15, 19 79--In the af terncon, received verbal Stop-Work Order from NRC which was confirmed by receipt of DEX copy of the Stop-Work Order.
18.
Friday morning, November 16, 1979--Civil Q.C.
issued Step-Work Order for concrete and backfill except concrete operations on Auxiliary Build-ing and NSCW Towers.
l s4W&'
Robert W. McManus Civil Q.C. Section Supervisor
$C c
B. C. Harbin Civil Project Section Supervisor RhM/SCH/dw Attachments n
1632 275 O
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Attach: rent r3
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r:RC CC::CLRiiS 1.
Erosien undar slabs for Control Building cable tunnels, South '.'est corner Unit 1 Containment and Unit 2 Tendon Gallery.
(Consider the effects of piping).
2.
Possible adverse effects on existing foundations of dewatering recm well potats.
Surface drainage and water control as it ibpacts on the safety related 3.
building foundations.
4 Potential safety aspects related to stability of the slope around the iorth side of the Control Building.
5.
Frocedures and controls for Judging the acceptance of inplace backfill.
6.
Monitoring settlement of structures.
~
I.
I'cnitoring of piezccetric levels in fill.
(Relating to sicpes).
8.
Maintenance program for construction slopes.
1632 276 i
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