ML19343D380
| ML19343D380 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 04/27/1981 |
| From: | Chavelle Hedges, Logan T, Pettersson C HOUSTON LIGHTING & POWER CO. |
| To: | |
| References | |
| ISSUANCES-OL, NUDOCS 8105040374 | |
| Download: ML19343D380 (33) | |
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UNITED STATES OF AMERICA CM NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of:
5 HOUSTON LIGHTING & POWER Docket Nos.
50-4980L COMPANY, g AL.
5 50-4990L 5
(South Texas Project, 5
Units 1 & 2) 9 5
TESTIMONY ON BEEALF OF HOUSTON LIGHTING & POWER CCMPANY, E AL.
OF MR. C. BERNT PETTERSSON MR. TIMOTHY K. LOGAN MR. CHARLES S. HEDGES MR. W. STEPHEN McKAY ON THE STRUCTURAL BACKFILL PROGRAM, AT STP D
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of:
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HOUSTON LIGHTING & POWER 5
Docket Nos.
5 50-4990L 5
(South Texas Project, 5
Units 1 & 2) 5 l
TESTIMONY OF C. BERNT PETTERSSON, TIMOTHY K. LOGAN, CHARLES S.
HEDGES and W. STEPHEN McKAY ON THE STRUCTURAL BACKFILL PROGRAM AT STP Q. 1 Please state your names.
A. 1 C. Bernt Pettersson, Timothy K. Logan, Charles S.
Hedges, and W. Stephen McKay.
Q. 2 Mr. Petterson, Mr. Hedges, Mr. McKay and Mr.
Logan, by whom are you each employed?
A. 2 (CBP): I am employed by Brown & Root, Inc. (B&R)
(TKL): I am employed by Houston Lighting & Power Company (HL&P).
(CSH): I am ergployed by Woodward-Clyde Consultants (WCC), a consulting firm specializing in geotechnical en-gineering.
(WSM): I am employed by Pittsburgh Testing Laboratory (PTL), an independent testing agent which performs earthwork inspection and testing and other services at nuclear power plants.
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Q. 3 What is your position and what are your current responsibilities?
A. 3 (CBP):
I am Assistant Discipline Project Engineer (Civil Structural Discipline) for the South Texas Project (STP).
Since 1974, I have been group leader for geotechnical engineering.
My responsibilities include development of B&R specifications for selection of structural backfill materials, and for backfill placement, compaction, inspection and testing.
I report directly to the structural Discipline Project Engineer for STP.
(TKL): I am Froject QA Supervisor for HL&P's W.A.
Parish Unit #8 Project, a 650 MWe coal fired generating unit under construction at Thompsons, Texas.
I have primary responsibility for the implementation of the QA program on the project.
(CSH):
I am Project Manager for WCC's work at STP.
I have been Project Manager at STP for the past 5 years, and for 2-\\ years prior to that I was periodically involved in the site studies and preparation of the STP PSAR documents.
As Project Manager,for WCC, I supervise other task leaders and staff engineers working at STP.
I also perform engineer-ing work related to STP geotechnical activities.
(WSM): I am the Corporate Manager for Quality Assurance (QA) at PTL.
I am responsible for the development and implementation of PTL's QA programs at several nuclear "
t plants.
I have worked for STP since March 1976, when I became PTL's Site Manager.
In July 1976, I left the STP site, but have remained involved with the Project by perform-ing regular QA audits of PTL activities at STP, selecting PTL personnel for STP, and reviewing all of PTL's correspon-dence between the site to the home office.
Q. 4 Please summarize your professional qualifications.
A. 4 (CBP): I have a degree in civil engineering from the Technical Gymnasium in Norrkoping Sweden, and degrees in geology with geotechnique and business administration from Stockholm University.
I am a Registered Professional Engineer in Texas, and am a member of the American Society of Civil Engineers (ASCE), the Geological Society of America (GSA) and the Swedish Geological Society.
Prior to joining B&R in 1974, I spent approximately eleven years as a geologist, and as a civil and geotechnical engineer in the United States and Sweden.
(TKL):
I have a Bachelor of Science degree from the l
l University of Houston (1972) and have taken post-baccalaureate j
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courses at the same, university, specializing in structural and geotechnical engineering.
I am a registered Professional Engineer in Texas and a past member of the Texas Society of Professional Engineers and the American Society of Civil Engineers.
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From 1968 until 1973 I was employed by HL&P in the engineering department, where I performed civil / structural design work involving foundations and structures for trans-mission, distribution, and substation facilities.
From 1973 until 1976 I was employed by Raymond Technical Facilities, Inc., an engineering consulting firm, as a designer and design engineer, performing civil and structural design for industrial facilities.
I rejoined HL&P in June of 1976 as a Senior Engineer in the QA department assigned to STP.
I was responsible for performing QA surveillance of all civil related activities, including backfill placement and PTL activities.
In June, 1977 I was promoted to Lead Engineer.
In this capacity, I supervised the two to three HL&P personnel who perforued QA surveillance of all civil related activities at the site.
I served in this capacity until June, 1978.
From January to July, 1980, I returned to STP to serve on various task forces and audit teams as a technical advisor, HL&P QA representative, and Group Leader.
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I have a Bachelors degree and a Master of Science degree in Civil Engineering from Georgia Institute i
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of Technology, with specialization in geotechnical engineer-l ing.
I am a registered Professional Engineer in Illinois, Georgia, Florida and Louisiana.
I am a member of the American Society of Civil Engineers (ASCE), the American Society for i
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Testing and Materials (ASTM), the Louisiana Engineering t
Society, the American Council of Engineering Consultants the i
Sigma XI Research Fraternity, and the American Nuclear Society.
I ma a past~ member of the ASCE Nuclear Structures Subcommittea for which I helped draft industry guidel'ines and standards relating to geotechnical engineering for nuclear power plants.
I have twenty-four years of experience in geotechnical engineering and civil construction, including sixteen years experience in the geotechnical engineering aspects of nuclear power plants.
This experience includes preparation of site selection studies starting with Florida Power & Light's Turkey Point Nuclear Power Plant, and preparation of licens-ing studies, geotechnical engineering designa and operating procedures.
(WSM): I have a Bachelors degree in civil engineering i
from the Carnegie Institute of Technology, and am a Registered Professional Engineer in Virginia and South Carolina.
I am a former member of the ASCE and a present member of the American Concrete Institute (ACI) and the American Society for Quality Control (ASQC).
I am a Certified Level III Inspection Engineer under the American Society of Mechanical l
Engineering (ASME) Code and under the American National Standards Institute (ANSI) criteria.
I am also a certified lead auditor under ANSI standards.
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i I have nineteen years of inspection and testing experi-
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ence including four years in PTL's soil mechanics department, seven years as its District Manager in Roanoke, Virginia, and eight years associated with PTL contracts for nuclear power plant construction services.
Q. 5 Mr. Hedges, please describe WCC's long-term relationship with STP.
A. 5 (CSH):
WCC has been a subcontractor to B&R on STP since early 1973.
Following initial STP work relating to geotechnical exploration techniques, WCC became involved in site exploration and geotechnical evaluation of.the STP site.
This site related work by WCC led to the engineering, geology and seismology analyses and evaluations for plant design and PSAR preparation.
After the STP Construction Permits were issued in 1975, WCC continued its involvement as consultant to B&R during the construction phase of STP and assisted in the FSAR preparation.
WCC has worked with the B&R geotechnical group in performing, studies, analyses and consultation.
At the same time, WCC regularly has made independent recomme,ndations to B&R based on its own evalua-tions.
Q. 6 Panel, what is the purpose of your testimony?
A. 6 (Panel):
The purpose of our testimony is to describe the respective activities performed by HL&P, B&R, PTL and WCC in developing and implementing the Category I i
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structural backfill program at STP, the Task Force review and other special evaluations conducted in response to the NRC Show Cause order, and the results of all the Show Cause activities.
Q. 7 Please describe briefly how backfill is placed at STP.
A. 7 (Panel):
The backfill is placed, compacted, and accepted in individual layers or lifts.
The backfill placed at one time in a specific area is called a placement and several placements of backfill are generally required to complete one lift over an entire building foundation aree.
Depending upon the work space requirements for other construc-tion activities, a lift over an entire building area may not be completed before an overlying lift is started.
In any event, all placements are. compacted before an overlying placement is made.
Q. 8 Mr. Pettersson, Mr. Hedges and Mr. Logan, please describe the development of the requirements and specifica-tions that govern material selection, placement and compac-tion of backfill at STP.
A. 8 (CBP, CSS and TKL): No specific code or standard governs placement and compaction of Category I structural backfill for the safety-related structures at STP.
The i
physical properties of the backfill must be consistent with the structural design criteria for foundations and embedded walls of all Category I structures.
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i requires that soils supporting nuclear power plant foundations j
must be able to withstand certain types of loads without excessive settlement; i.e.,
the backfill must have sufficient density to provide an adequate safety factor against liquefac-tion.
To satisfy these general provisions, specification requirements were developed jointly by B&R and WCC based in large part on WCC's selection of backfill material and its testing, evaluation and analysis of the backfill material ultimately used at STP.
HL&P then reviewed and approved all specifications prior to their implementation.
The.specifica-tions have not varied significantly since the beginning of the Project.
WCC, in cooperation with B&R, conducted a regional investigation of possible structural' backfill material sources in 1974.
The Eagle Lake Area (Colorado River alluvium),
approximately 55 miles from the STP site, was determined to be the best source area based on the type and volume of l
material available.
Based on laboratory tes, ting of this material, WCC recommended that an 80% relative density requirement for i
I backfill at STP would provide an ample factor of safety against liquefaction.
This requirement was based on the STP design basis Safe Shutdown Earthquake (SSE) criteria, and j - _.
I was considered conservative in view.of geotechnical engineer-ing practice and the low seismicity at STP.
This 80% require-ment was incorporated into 5 2.5.4 of the PSAR, and is the only commitment regarding granular backfill compaction in the construction permit licensing documents.
1 WCC performed additional analyses and recommended, consistent with the PSAR, that backfill compacted to a minimum relative density of 75% and an average relative density of 80% would provide a more than adequate safety factor against liquefaction.
To be conservative, B&R adopted a specification requirement for STP providing for a minimum i
relative density of 80% and an average relative density of l
84%.
WCC also recommended gradation limits for the backfill material to be used at STP, and these gradation criteria were incorporated by B&R into the specification.
HL&P l
t reviewed and approved the material, gradation and density requirements of the specification.
Based on WCC recommendations, B&R Engineering then developed a construction specification requiring that uncom-pacted backfill lif,ts be limited to an 18 inch maximum thickness.
Under the specification, uncompacted lifts of 24 inches are permitted to be used at the option of Construction if the adequacy of the backfill compaction is demonstrated by a documented test fill (field test) program.
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Based on additional recommendations by WCC, a specifi-I cation was developed requiring at least one field density test for every 20,000 square feet of unrestricted backfill lift.
The specification criterion was based on the uniform gradation of the STP backfill, the planned placement and compaction operations and the volume of material contained in each density test area.
This tnsting provides data t
demonstrating the relative density of the total volume of i
category I compacted structural backfill.
For every fourth field density test, at 1 east one l
laboratory maximum-minimum test and one gradation test is to i
be performed.
The decision to require one test in four was based on the degree of uniformity of the STP backfill, and was considered conservative by industry standards.
The i
purpose of the maximum-minimum laboratory test is to deter-l mine a material's maximum density when well compacted, and its minimum density when uncompacted in its most loose l
state.
The actual in-place relative density value is deter-mined by a mathematical formula utilizing the laboratory determined maximum,and minimum density values and the in-place density value determined by the field density tests.
The actual relative density value is then compared to the 80%
acceptance criteria.
The purpose of the gradation test is l
to determine the particle size distribution in backfill material.
The results of this test must meet applicable specification requirements. -
Q. 9 Mr. Pettersson and Mr. Hedges, please describe the development of the construction procedures governing backfill at STP.
A. 9 (CBP, CSH):
Construction procedures were de-veloped in 1976 based on the STP specification requirements and on standard industry practice.
It has always been understood by construction that these are "end product" procedures requiring backfill to be compacted until the proper density is achieved.
It is the result of testing that we rely upon to assure adequate density has been achieved, not the number of passes of the compaction equipment.
Except for minor editorial variations, the procedures origi-nally developed were the same as those in effect at the time of the NRC Order to Show Cause.
A 10-ton steel drum vibratory roller was selected to ensure effective compaction of 18-inch lifts.
The decisiog was made to limit the lifts to 18 inches, thereby rejecting l
the option of using 24-inch lifts.
Although the specification does not require use of a j
formal test fill'pr,ogram to verify the acceptability of I
compaction of 18-inch lifts prior to placement in Category I l
areas, Construction decided to conduct an informal, voluntary I
test fill program to confirm the adequacy of the compaction l
E methods.
This test fill program was conducted in.1976 by placing several lifts and compacting them with the roller l.- -
planned to be used in actual construction of the fill.
The number of roller passes on each lift was varied on different portions of the lift.
Density tests were then taken at several depths to determine the density achieved by the different compaction efforts'.
B&R's Site Geotechnical Engineering representative evaluated the results of this program and conservatively recommended that a minimum of 12 roller passes be incorpo-rated into the construction procedures.
Construction, in developing the construction procedures, concluded that a minimum of 12 passes would be necessary only on the surface lift, which would not receive further densification by compaction of overlying lifts, and that a minimum of 8 passes would be acceptable for the lower lifts.
of course, if the 8 or 12 passes did not compact the structural backfill to the required density, additional passes were required until a minimum of 80% relative density and an 84% average relative density had been achieved.
After 8 or 12 passes, it would be appropriate to begin in-place density te, sting to evaluate the adequacy of compac-tion.
The first twenty field density tests made in unre-stricted Category I areas verified the adequacy of the relative density achieved by this procedure.
Q. 10 Mr. Pettersson, Mr. Logan and Mr. McKay, please describe how the backfill program at STP was monitored to f
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assure compliance with applicable specifications and proce-dures.
A. 10 (CBP, TKL, WSM): An Earthwork Inspection and Testing Specification was developed and was to be imple-mented by PTL.
This specification das developed to provide general criteria for quality control of the backfill place-ment and compacti.n activities, and has not been signifi-cantly modified since it was first developed.
Specifically, PTL Inspectors are to provide continuous inspection of the placement of all backfill material, which means that the Inspectors are required to be present in the general work area where backfill is being placed or compacted, and are required to observe the type of material used, lift thick-nesses and operation of compaction equipment to ensure compliance with applicable specifications and procedures.
With B&R review and approval, PTL developed procedures i
to implement the specification requirements relating to inspection and testing of the backfill.
In addition, PTL developed several procedures relating to all 18 criteria of 10 C.F.R. Part 50,, Appendix B and other specified codes.
These procedures include provisions for personnel certifica-tion, equipment control and documentation.
First, as backfill material was placed in ex'avated c
areas, PTL QC Inspectors determined the actual lift thickness j
to assure that it did not exceed 18 inches.
If deviations l
were observed, B&R Construction personnel corrected them before compaction began, and the PTL Inspectors reviewed the work for final compliance.
The Inspectors then recorded their observations on checklists and on Earthwork Inspection Reports (EIR's).
The latter provide a narrative description of the entire placement and compaction process.
In completing these checklists, the PTL Inspectors generally marked that the lift thickness was 18 inches, indicating tht it was 18 inches or less and,that it satisfied the applicable B&R specifications.
This procedure subsequently was amended as a result of the NRC Inspection Report 79-19, which.is dis-cussed later in this testimony.
Compaction generally was performed for several hours depending on the size of the rolled areas.
Before this process was started, PTL QC Inspectors checked the equipment to be used, and before the process was completed, the Inspectors checked to be sure that the minimum required number of roller passes had been made and that the compaction process was uniform.
Again, all observations were recorded on checklists and in the EIR's, and deviations were corrected and reviewed before the next backfill placement could begin.
PTL Inspectors remained in the area where compaction was taking place until the process was completed.
- However, because the B&R procedure requires only a minimum number of roller passes, the Inspectors only observed the actual _..
4 performance of the roller passes long enough to assure themselves that this minimum number had been achieved.
After that time, consistent with their understanding of the continuous inspection requirement, they generally observed the compaction efforts but did not necessarily observe each and every pass.
When compaction was completed and they were satisfied, they indicated on the checklist that the compac-tion effort was " acceptable" under the applicable construc-tion procedure.
This procedure was amended as a result of NRC Inspection Report 79-19.
To determine the density of each lift after compaction, PTL Inspectors generally performed at least one field density test in accordance with the specification requirements.
Although there originally was no specified test depth, the Inspectors generally tested at the top of the immediately underlying lift.
If the tests revealed a relative density of less than 80% or less than an 84% average, additional rolling had to be performed until acceptable test results were achieved.
As a result of NRC Inspection Report 79-19, B&R amended its specification to provide for specified test depths, and PTL amended its procedures accordingly.
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Inspectors indicated on the checklist, in the EIR, and in separate Density Test Reports whether the test confirmed that the compaction had been successful; i.e., whether the required relative density had been achieved.
They also
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obtained backfill field samples for the laboratory tests.
To verify that the backfill met the 80% relative density requirement, PTL QC Inspectors' established field acceptance criteria by averaging twenty maximum-minimum laboratory tests.
The twenty-test sample, which was based on considera-tion of the' gradation uniformity of the STP backfill material, provided a sufficient data base from which to derive represen-tative field acceptance criteria.
The results of the laboratory tests were recorded in separate Laboratory Test Reports.
Although it was not required, the Inspectors generally kept informal, Field Density Test Log Books which list all the tests by number and indicate which test locations have been used to obtain samples for laboratory testing.
Completed EIR's, checklists, Density Test Reports and
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Laboratory Test Reports were provided to the PTL STP Site Manager for his review.
Tney were then transmitted to the 1
B&R QA/QC Supervisor in' charge of PTL activities for his review and signature.
Finally, these reports were transmitted to B&R Construction,and Engineering Supervisors for their j
information and to the STP QA vault for filing as Project QA records.
Since August 1976, tne B&R QA/QC Supervisor has been located in the PTL facilities at the STP site wh're he has e
had daily contact with the PTL site manager and other PTL 1
personnel.
Accordingly, B&R QA/QC has additionally monitored
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PTL activities and has improved the QA program implementation through daily discussions with PTL personnel at the site.
In addition to this daily monitoring activity, B&R QA personnel have performed regular surveillance of PTL's inspection and testing activities, and B&R's Audit Group has performed audits of the STP backfill program at least annually.
PTL also has an internal audit program, and has audited its own activities at least annually.
The results of these audits have been transmitted to B&R.
Q. 11 Mr. Logan, please describe the surveillance performed by HL&P QA on the Category I structural backfill program at STP?
A. 11 (TKL):
Backfill material qualification, placement, inspection and testing were monitored by HL&P QA personnel through the use of prepared surveillance checklists.
The 1
cpecklistsconsistedofspecificquestionsregardingrequire-ments from the B&R specifications and B&R and PTL procedures.
l There were two checklists which covered all the major aspects described above.
One of these checklists dealt with field activities; i.e., material placement, compaction, inspection, and in-place density testing.
The other QA checklist covered laboratory analysis; i.e., material qualification testing, compaction testing, and B&R QA surveillance of PTL.
Another checklist that also affected the backfill area covered calibration of laboratory equipment as a part of all measuring l
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and test equipment.
Surveillance using the checklists was performed a minimum of once per month.
Between March 1976 and September 1980, HL&P utilized the checklists to perform surveillance on the PTL laboratory 57 times.
Between May 1976 and September 1980, surveillance of field activities utilizing the checklists was performed 53 times.
In addition to the formal, documented surveillance described above, HL&P QA perso"nel performed random daily informal monitoring of project activities.
Findings from the informal monitoring activities were generally transmitted orally to the proper B&R or PTL personnel.
Any resulting documentation was generated by the affected organization.
Q. 12 Mr. Pettersson and Mr. Hedges, were backfill placement and compaction methods other than those described in the previous answer'ever used?
If so, explain these methods.
A. 12 (CBP, CSH)i In areas close to plant structures or otherwise too confined to permit use of the vibratory rollers, backfill was placed using hand operated compaction equipment.
Specific procedures describe how the placements should be made and tested in these restricted areas.
In isolated areas, methods other than the ones pre-viously described were used to densify the structural backfill or to provide adequate foundation support.
The methods._
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employed were vibroflotation, static rolling and grouting --
i all three of which are common construction industry practices.
i vibroflotation is a field procedure identified in the Structural Backfill specification which may ba used when approved by Engineering.
The vibroflotation procedure employs mechanical vibration and simultaneous water-jetting to densify a soil mass.
This process was used to densify i
category I backfill loosely placed in an exploratory trench approximately 10 feet deep which was dug to evaluate the extent of suspected contaminated backfill; i.e., backfill
.g containing soil types different from the granular material.
f Use of 18-inch lifts compacted by a vibratory roller was not feasible in this instance because of the depth, small area 1
and moisture conditions in and around the trench.
Following the vibroflotation treatment, ten borings including Standard Penetration Tests (SPT) were made.
The results of the tests verified that a satisfactory density had been achieved for the vibrofloated backfill material.
Static Rolling refers to the use of the 10-ton vibratory roller with the vib,rator shut off.
The first lift placed l
over natural subgrade was statically rolled when necessary to prevent subgrade pumping, and the first lift placed over concrete mudseals was statically rolled when necessary to prevent damage to those items.
In some cases, static rolling l
was employed along with water saturation to densify the final backfill surface more thoroughly.
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To verify that the reported statically rolled lifts received adequate compaction, WCC conducted an evaluation of the incidents of static rolling, and confirmed that the vibratory rolling of succeeding lifts had taken place until the statically rolled lift satisfied the density requirements.
Grouting refers to placement of a cement-sand-water shrink mix into small voids which are otherwise inaccessible for backfill placement and compaction.
This method was used at STP to fill surface voids which had developed under the edges of previously poured concrete slabs due to erosion from rainwater runoff.
The grout in these small areas is inherently stronger than the backfill it has replaced and is therefore considered to be acceptable.
As discussed below and in the testimony of Mr. Stanley D.
Wilson and Mr. Thomas Kirkland, these backfill placement methods were reviewed in response to the NRC Show Cause Order by an HL&P/B&R Task Force and an independent Expert Committee.
The Expert Committee composed of Mr. Wilson and Drs. H. Bolton Seed and A. J. Hendron reviewed the use of these methods and found them to be appropriate in all instances.
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Q. 13 Mr. McKay and Mr. Logan, were there problems i
identified by Project personnel regarding QA activities j
prior to the NRC's Order to Show Cause?
If so, what were those problems and how were they resolved?
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A. 13 (WSM, TKL): Both B&R Audic Group personnel and HL&P QA personnel identified procedural and hardware problems regarding the QA program.
For example, a Stop Work Order was issued in 1976 when B&R's QA auditors discovered that PTL had not correctly calibrated their sand cones used for in-place density tests.
Consequently, several density tests previously accepted by PTL were found not to meet the accep-tance criteria established when the sand cones were recali-brated, and the tests were dispositioned as nonconformances.
After B&R reviewed the situation and found the tests to be acceptable, the nonconformances were closed out.
To prevent a recurrence of such problems, PTL increased the frequency of its internal audits and provided additional home office support to STP.
In 1976, pursuant to a different B&R audit of PTL l
activities, the B&R QA Department found several procedural discrepancies in PTL's inspection and testing program.
Equipment was identified incorrectly, forms were not completed l
l and equipment was not always calibrated with sufficient frequency.
As a re,sult of these problems, PTL clarified its procedures for ease of understanding, improved its overall management control, increased its on-site technical support, and implemented a training program.
In addition, the B&R QA/QC Department become more closely involved in the daily management and surveillance of PTL's on-site work. _-
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HLEP surveillance also discovered a few problems with
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respect to the B&R QA and PTL activities.
The problems, which had no effect on the quality of the backfill, generally concerned minor errors in completing, reviewing and filing l
forms.
These discrepancies all were corrected.
Q. 14 Mr. Logan and Mr. McKay, what did the NRC audits reveal about the STP backfill program prior to late 19797 A. 14 (TKL, WSM) The NRC audited the backfill program at STP several times between 1976 and late 1979.
Generally, these audits found the activities at STP to be in compliance with specifications and procedures concerning placement and compaction of backfill.
For example, in Inspection Report 76-07 dated December 21, 1976, the NRC reviewed the STP sieve analyses, the relationship between laboratory and field testing, and backfill placement and compaction activi-ties.
The backfill quality and construction activities were found to meet applicable specifications and procedures.
In Inspection Report 77-06 dated May 16, 1977, the NRC found that the STP in-place density tests were in compliance with applicable specifications.
In Inspection Report 78-10 dated i
June 20, 1978, the in-place density tests, laboratory maximum-i minimum tests and gradation tests were found satisfactory.
In addition, B&R QA surveillance of PTL activities was found j
to comply with applicable procedures.
In Inspection Report 79-18 dated January 16, 1980, the NRC found backfill compac-tion and in-place density testing to be satisfactory. l
Inspection Report 77-06 dated May 16, 1977 did note noncompliances regarding the QA program in that B&R surveil-lance of PTL activities was not conducted frequently enough, improper personnel were reviewing the surveillance reports, and those reports were not filed and retained as required.
These noncompliances were resolved and closed out in the subsequent NRC Inspection Report 77-09, dated October 12, 1977.
Q. 15 Panel, what actions were taken as a result of findings regarding the STP backfill program contained in the NRC Inspection Report 79-19 dated April 28, 1980?
A. 15 (Panel):
The NRC reported six items of noncom-pliance regarding the STP backfill program in Inspection Report 79-19: (1) PTL's" procedures did not provide instruc-tions for depth of in-place density testing; (2) B&R construc-tion procedures failed to set forth an identified and docu-l mented basis for the acceptability of the required minimum of 8 roller passes for embedded lifts; (3) PTL did not record the actual number of roller passes or the actual lift thicknesses in the,EIR's; (4) the PTL relative density test l
apparatus was broken for a period between November 1979 and i
January 1980, and backfill placement proceeded although the required laboratory tests could not be perforned; (5) WCC used a nonconforming hammer for Standard Penetration Tests of the backfill from January 28, 1980 to February 4, 1980; and (6) WCC used a nonconforming split spoon for its Standard Penetration Testing.
All of these items have been satisfac-torily closed out by the NRC in Investigation Reports 80-17 and v0-19, dated July'16, 1980 and August 8, 1980, respectively.
First, B&R, with HL&P review and approval, amended its backfill specification to provide criteria for the density testing depth of embedded and surface lifts.
Out of every ten tests, six tests must be taken near the top of the underlying lift, two tests near the center of the underlying lift and two tests near the bottom of the surface lift.
Tests near the bottom of surface lifts must always.be ac-companied by tests in the underlying lift to ensure that all lifts are actually tested.
Density tests of surface lifts located immediately below foundations must be taken at a depth of six to twelve inches.
PTL subsequently amended its procedures to conform to the revised specification.
Second, the NRC examined the results of the 1976 and 1980 test fill programs and concluded that B&R did in fact have an adequate basis for its procedural requirement that a
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minimum of eight ro,ller passes be made for 18-inch embedded lifts.
The density test results obtained from these programs verified that the incremental gain in density rapidly dimin-ishes for each roller pass beyond eight and that the overall density in an embedded lift is greatly increased after 8 passes on the overlying lift.
Therefore, B&R's procedure --
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requiring at least eight passes before beginning in-place density testing was found to be appropriate.
Third, B&R, with HL&P review and approval, amended its Earthwork Construction Specification in June 1980 to require that the PTL Inspectors. determine and record the actual number of roller passes and the actual uncompacted lift thicknesses.
The number of roller passes must be determined either by actually counting the passes or by inspection to ensure adherence to a specific roller pattern defined in the newly amended backfill specification and in construction procedures.
Fourth, PTL replaced its defective equipment used for maximum density determination and obtained back-up equipment.
The untested backfill samples which had been collected during the period when the equipment was not functioning were subsequently tested and accepted.
Finally, the two nonconforming pieces of equipment used in several of WCC's Standard Penetration Tests were replaced with conforming equipment.
The WCC test procedures were modified to include dimension and weight tolerances.
WCC also evaluated the tests performed with those nonconforming items and found that the test results were not significantly affected by the nonconformances.
As a result of NRC's description of these findings at 1
the exit interview on January 26, 1980, B&R and HL&P asked i
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WCC in January 1980 to begin a soil test boring program to evaluate the overall backfill quality at STP.
The results of this program indicated that all of the backfill in the Unit 1 area had relative densities equal to or greater than 80%, but that there were four small areas in the vicinity of Unit 2 with a relative density less than 80%.
Further tests of the four questionable areas were made by B&R and WCC with the assistance of Dr. H. B. Seed, a noted authority on the beharior of soils.
These tests indicated that the backfill in the four areas was sufficiently dense to provide a sub-stan't.ial degree of safety against Jiquefaction, and that no further testing or remedial work was necessary.
Q. 16 Mr. Pettersson, as a result of Inspection Report 79-19, were any additional changes made to B&R's surveillance program regarding STP backfill?
A. 16 (CBP):
Yes.
Effective June 20, 1980, B&R Resident Engineering personnel are required to review on a j
daily basis PTL's inspection and testing activities and to review PTL's documentation prior to issuance.
These personnel also are required to note all observations in reports and document any de.ficiencies and subsequent corrective actions.
Q. 17 Mr. Pettersson, Mr. Logan and Mr. Hedges, please describe the actions taken with respect to the STP backfill program in response to the Show Cause Order.
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A. 17 (CBP, TKL, CSH):
Immediately after the NRC issued its order to Show cause, a joint B&R/HL&P Task Force was set up to respond to the specific items in the Order regarding the backfill program.
This Task Force subsequently spent approximately seven months reviewing thousands of quality control documents to verify the overall adequacy of the backfill material and the backfill placement, compaction, testing and inspection.
In addition to the Task Force, an independent Expert Committee of acknowledged leaders within the geotechnical profession was retained to review the backfill placement and compaction program at STP and to determine the overall engineering adequacy of the in-place backfill.
Finally, WCC performed additional special studies necessary for the Show cause effort, including a comprehen-sive statistical analysis of the Category I structural backfill field density results.
The following activities were conducted with respect to Category I structural backfill placement in response to the Show cause Order:
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(1)
A test fill program was established to confirm the I
adequacy of the construction methods used during the category I structural backfill placements; (2)
The backfill material tested for the design studies was compared to the material actually placed for the Category I structures; j
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1 (3)
Cross-sectional drawings were developed to show the sequence of backfill placements and lift thicknesses and to show the locations of the in-place density tests and results; (4)
EIR's were reviewed to determine whether the reported work demonstrated compliance with the backfill specifications and the construction procedures; (5)
The field density tests were analyzed to determine the density distribution and the representativeness of the tests; (6)
The relative density requirements of the. backfill were evaluated to determine the effect of localized areas with rele.tive densities of less than 80%;
(7)
The density distribations within the surface lift immediately below structural foundations were analyzed; (8)
WCC's previgusly-performed boring programs were reexamined to obtain additional data on the engineering adequacy of the backfill; (9)
The maximum / minimum laboratory density test results were verified by a,different laboratory from the on-site QC Soils Laboratory; and i
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Data concerning generic or specific problems with l
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the backfill construction and QC procedures was evaluated, ll and corrective actions were developed as required.
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Q. 18 What were the results of the Show Cause verifica-tion activities?
A. 18 (CBP, TKL and CSH) The results of these Show Cause verification activities demonstrate that the structural backfill at STP has a ralative density which exceeds the design requirements, Ubat the frequency of backfill testing has exceeded the specification requirement, and that the construction procedures utilized have been adequate to ensure that the quality of the in-place backfill satisfies applicable specifications.
In-place Category I structural backfill material at STP was confirmed to be from M.he same geologic formation and to have the same grt.dation and particle shape as the material tested for the STP design studies.
Minor changes which have occurred during the last four years in the gradation and uniformity of the backfill have slightly c'ianged the minimum and maximum dry density of the backfill, but the liquefaction analysis performed for the STP design and presented in the.
FSAR was still found to be valid.
The results of,B&R's June 1980 test fill program confirm that: (a) the STP vibratory rollers are capable of compacting the specified lift thicknesses to the required densities; (b) the compaction throughout the backfill is uniform; and (c) eight roller passes on underlying lifts and twelve roller passes on surface lifts provide satisfactory minimum I
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compaction criteria to ensure safety.
The Expert Committee confirmed these conclusions.
The Expert Committee's findings as to the quality of the STP backfill are presented in a separate piece of testi-mony.
The Task Force found that relative density tests I
were not performed on the backfill placed for the Essential Cooling Water (ECW) system piping trench as a result of a PTL and B&R QA misinterpretation of the STP specification requirements.
This backfill material, however, was the same as the material placed concurrently in the STP plant area, where samples were obtained and subjected to relative density testing.
The tests from the plant area were then used by PTL for acceptance of the ECW system piping backfill.
Because PTL used acceptance criteria from the plant area, and because the backfill used at STP is especially uniform, the deviation with respect to testing on the ECW i
area was of no great concern.
Nevertheless, pursuant to a program to reexamine welds in the buried ECW pipe, the backfill in the ECW trench is being removed to uncover tile pipe.
Backfill below the pipe will be tested and relative density tests vill be performed during replacement of the backfill in the trench.
Q. 19 Mr. Pettersson, Mr. McKay and Mr. Logan, were any programmatic changes made in the STP backfill QA/QC l
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program as a result of the Show Cause verification activities?
If so, please explain those changes.
A. 19 (CBP, WSM, TKL):
Included in the B&R/HL&P Task Force studies was a review of the PTL EIR's to determine whether the _nspection activities meet applicable specifi-cations and procedures.
While the sequence of backfill construction could be established from these records, the j
Task Force uncovered several deficiencies in the EIR's including inconsistent or missing test numbers, test locations and dates, and a failure to document certain completed lifts, compaction efforts, and retests.
The Expert Committee concluded that the foregoing deficiencies are of no technical significance.
Nevertheless, B&R issued Corrective Action Requests (CAR's) on these matters to assure that the quality control records for future backfill construction will provide self-supporting evidence of the adequacy of the backfill.
Specific corrective actions to be implemented include amplified reporting for work in progress, logs for tracking work requiring remedial action, systematic verification of loc,ation descriptions, advance inspection schedules and control of reporting, and indoctrination of PTL Inspectors regarding the necessity of filling out accurate and complete reports.
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Q. 20 Mr. Hedges, what is your professional opinion of the testing and overall quality of the in-place backfill at l
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A. 20 (CSH):
The in-place backfill at STP is generally of equal or higher quality, has a more consistent gradation and is more highly compacted than backfill I have evaluated at other nuclear power plants.
In addition, the high density achieved gives the STP backfill a factor of safety well beyond the design requirements.
The STP backfill testing and inspection program has been well-planned from its inception, and provides for more frequent and systematic field and laboratory tests than t
programs I have observed at other nuclear power plants.
Q. 21 Mr. Pettersson and Mr. Logan, what is the present status of the backfill program at STP?
A. 21 (CBP and TKL):
The backfill construction activi-l ties at STP have continued uninterrupted.
Backfill placement i
and compaction for Category I areas, including the ECW 1
l system piping, is 75% completed.
Approximately 560,000 yards of backfill have been placed for the Units 1 and 2 Reactor Containment, Fuel Handling, Mechanical-Electrical l
Auxiliary and Diesel Generator Buildings.
Approximately 20,000 cubic yards, remain to be placed in the main plant area, and 120,000 cubic yards remain to be placed around the ECW system piping.
All future backfill activities will be i
performed in accordance with the amended specifications and i
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procedures, and will be monitored closely pursuant to B&R's QA program to ensure compliance with applicable specifications.
These activities also will be audited by B&R and HL&P.
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