ML19320C029

Revised Final Deficiency Rept Re Placement of Earthfill in Essential Raw Cooling Water Spray Pond.Insufficiently Compacted Matl Was Removed & Replacement Fill Recompacted. Util Will Use Penetrometer Tests for Fill Operations

ML19320C029
Person / Time
Site:	Yellow Creek
Issue date:	07/11/1980
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19320C025	List: ML19320C024 ML19320C029
References
NCR-YC-077, NCR-YC-77, NUDOCS 8007150663
Download: ML19320C029 (4)

Text

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, ENCLOSURE O.

YELLOW CREEK NUCLEAR PLANT - UNI'T 1 ,- ,'

. PLACEMENT OF EARTHFILL IN ERCW SPRAY POND

10CFR50. 55 (e)

NCR YC-077 CONSTRUCTION QA AUDIT DEFICIENCIES YC-C-80-07 j REVISED FINAL REPORT

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Descriotion of Deficiency During a QA audit conducted by TVA, seven items were noted which appeared to be in noncompliance with TVA general construction

+. specification G-9 These' items'poncern the placement and inspection ,,

) of earthfill in the unit 1 ERCid' spray pond. They are:

1. Polyethylene and roots left in earthfill.

2. Earthfill was placed with insufficiently compacted saterial.

3.

• Earthfill was in and against standing water.

4. Earthfill was placed on previously placed earthfill that had a

. dry surface and had not been scarified.

5. Foundation surface was not rolled before placing earthfill.

6. No moisture checks were made.

7 No evidence of required steps taken after one-point proctor tests failed to fall withiis the established family of curves.

8. Penetrometer was not always being used.

Safety I=clications The. concerns expressed in the audit were referred to T7A's Division of s

Engineering Design for evaluation. It has been determined thLt items 1, 3, 5, 6, 7, and 8 are all within the intent of G-9, and no corrective action is required. Therefore, these conditions create no safety ha ard. Hewever, some additional testing will be conducted in some cases to verify TVA's evaluation and disposition (see corrective

. action).

_.e Ite=s 2 and 4 require that some earthfill be removed and reworked in order to establish the adequacy of construction (see corrective action). Therefore, these items, if uncorrected, could have adversely ~

. affected the integrity of the ERCW spray pond and could lead to its failure to perform the intended safety function.

Corrective Action

1. Auditors observed six pieces of polyethylene less than the size of a handkerchief in the fill. Occasionally a piece two inches square was sighted. ,Approximately six to eight roots were ,

observed. All roots were less than 1/2 inch in diameter and less than one foot long. There were days, or periods of days, where the auditors observed no roots at all. Although the specification states that no unsuitable material shall be allowed to be included in the fill, this was not intended to be an , ,e absolute value. It is unrealistic to assume that the fill used i

in a construction project of this magnitude could be root free.

Therefore, it is TVA's judgement that the amount of unsuitable material included in the fill is insignificant and will not

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. . l 0 impact the integrity of the spray pond. Therefore,'nb corrective

. action is required. -

To minimize this concern in the future, two laborers will be assigned to the continuous task of removing all visible unsuitable material during fill placement.

2. All of the insufficiently compacted material was completely removed and the replacement fill was recompacted. The area in question was approximately 15 by 35 feet and six to nine inches thick.

• An inplace density test will be taken in this area to verify proper compaction. This testing will be completed by July 11, 1980.'

3. The portiens of G-9 which relate to water and seepage state in part that "there shall be no free water on the foundation when i earthrill is placed. upon it" and " provisions shall be made to l handle rainwater and seepage water so there is no free water '!

on foundation or fill surfaces on or against which fill is to be placed." Within the intent of G-9, " free water" means )

standing water, ponded water, or flowing water whose magnitude ,

and volu=e is such that the adequte ce=psetion within all the specification requirements cannot be met. A foundation surface that is da=p or slightly wet is not considered " free water" if the water will not affect the proper placement of the overlying Till. TVA has determined that the earthfill in question is adequate,'and no corrective action is required.

'To completely justify our position, an inplace dennity test will be taken in each area. It is expected that our tests will be

, co=pleted by July 11, 1980.

4. The c:aterial placed on .the dry surface will be removed to the

• top of the first lift. The top surface will then be dampened and scarified. This will be followed by spreading replacement f fill to achieve a compacted layer of approxi=ately six inches.

In addition, af ter co=pleting compaction, an inplace density ,.-

test will be taken in this area.

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5. The area in question is the in situ chert foundation at the botto= of the spray pond. Approxi=ately 1/3 to 1/2 of the bottom surface was rolled. However, the roller drum was tending to bounce along, breaking some of the chert into smaller .71eces.

As a result, the rolling was discontinued. Before 'beginning backfilling, the foundation team required rolling of the bottom surface where it was necessary to scrape off material to achieve the prescribed grade. It was- felt that the process of scraping off material above grade would disturb and loosen the top few inches at grade. Therefore, the team required rolling the surface to produce a firm, tight base. Based on the observations of the roller drum, the surface had adequate firmness.

Accordingly, the foundation is considered to be adequate and no correct've action is required.

To further increase our assurances as to the reliability of the

unit 1 spray pond liner, TVA plans to; double the number of block

/- sa=ples tested over the present requirements for the bottom of the pond. It is expected that testing will be complIted by September 1, 1980. . .e,W.

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6. In general, the natural moisture contudttof the borrow soils )

is fairly close to the specified moisture content limits for

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fill ce=paction. Experience and test results on fill operations '

for si=1lar soils in the turbini~buildinpaiea have indicated i that there is no problem in controllirig ns" field ' moisture l content for achieving specified coijiactdoii level. TVA believes I

~ that this compaction is adequate andSUdt' no corrective action~

is required. .

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For future earthfill operations,i mdistdpe' content tests will be made at 1, east daily and as often as the soil changes. For

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the inplace fill, the nu=ber of blodf sasples will be doubled to assure that shear strength of inplace: fill meets design require =ents. It is expected that the.bl.ock samples will be

• ce=pleted by September 1, 1980. , , g , , ,-] ,

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7 Earthfill test number SP-1 indicatied she ~1 po' int proctor curve fell slightly below the Class VII b curie. The dinerence between the maxi =um de 1sities for SP-i^ind 'Cla'as VH b is 3.9 pet. The field densit,y test indicated -thati the soil was ce=pacted to 100 percent of the maxi =us dry density or class VII

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b which is conservative; and, therefore, ~n'o corrective action is required. ,.

Earthfill test SP-5 rell between Clasi III-SM and mm IV-SC.

The inspector classified this soil as Class III-SE Atterberg li=it tests indicated this soil had a plasticity index of.9 71 ,

which means that the soil should have been clasified as Class IV Sc.

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Density test indicated 101.2 percent'ce=paction which was 6.2 percent above the specified. The soil classification has been changed to Class IV-SC. No other corrective action is required ,

since the compaction is conservative.

. 8. The penetrometer test serves as an index test only to assure '

overall adequacy of fill co=paction, andthe field inspector will still have to rely upon his judgment. Before the initiation of earthfill operations, test' fills 'were constructed for all borrow soil classes using all ty' pes of rollers available at the site. "'hese test fills p2ovided infor=ation to achieve the specified aensity. Additionally, a penetra=eter was used when the inspector suspected the. adequacy of fill compaction.

A total of 13 sand-cone denity. tests have been conducted through - - - -

Jun;s 20,1980. "In all' cases, the level ~o f co=paction (varying from 95 to 106 percent) was equal to or higher than the specified 95 percent. Therefore, TVA believes that.the. compaction fill is adequate, and no corrective action is required. In the l

future, TVA will use penetrometer tests for all fill operations as a supplement.to the tests specified in Section II of General Construction Specification G-9.

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In addition, . quality control inspectors in the QC-materialsi and civil unit have been retrained in the requirements relating to earthfill placement on the ERCW spray pond.

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