ML19320C540

Final Deficiency Rept Re Placement of Earthfill in ERCW Spray Pond.Qa Audit Revealed Eight Items of Noncompliance Re Placement & Insp of Earthfill.Laborers Will Be Assigned to Remove All Visible Unsuitable Matl During Fill Placement

ML19320C540
Person / Time
Site:	Yellow Creek
Issue date:	07/10/1980
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19320C538	List: ML19320C537 ML19320C540
References
NCR-YC-077, NCR-YC-77, NUDOCS 8007170344
Download: ML19320C540 (4)

Text

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ENCLOSURE YG. LOW CREEK NUCLEAR PLANT - UNI'T 1 -

PLACEMENT OF EARTHFILL IN ERCW SPRAY POND llh 10CFR50. 55 (e)

NCR YC-077 CONSTRUCTION QA AUDIT DEFICIENCIES YC-C-80-07 FINAL REPORT Descriptien of Deficiency During a QA audit conducted by TVA, seven items were noted which appeared to be in nonec=pliance with TVA general construction specification G-9 These' items',cencern the place =ent azul inspection ,,

of earthfill in the unit ,1 ERCW' spray pond. They are:

1. Polyethylene and roots left in earthfill.

2. Earthfill was placed with insufficiently co=pacted material.

3.

• Earthfill was in and against standing water. .

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

. dry surface and had not been scarified.

5 Foundation surface was not rolled before placing earthfill.

6. No =oisture checks were made.

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

8. Penetrometer was not always being used.

Safety I=clications The. cencerns expressed in the audit were referred to TVA's Division of Engineering Design for evaluation. It has been determined that items i 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

'arety hazard. However, some additional testing will be conducted in so=e cases to verify TVA's evaluation and disposition (see corrective

. action). '

f Ite=s 2 and 4 require that so=e earthfill be removed and reworked in i 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 si=e of a handkerchief in the fill. Occasionally a piece two inches square was sighted. , Approxi=ately six to eight roots were ,

observed. All roots were less than 1/2 inch in diameter and less than ene foot long. There were days, or periods of days, where the auditors observed no roots at all. Although the specification states that no unsuitable =aterial shall be allowed to be included in the fill, this was not intended te be an je absolute value. It is unrealistic to assume that the fill used in a construction project of this magnitude could be root free.

Therefore, it is TVA's judge =ent tbit the a=ount of unsuitable

=aterial included in the fill is insignificant and will not 8007170 3 W

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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.

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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.'

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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 earthfill is placed. upon it" and " provisions shall be =ade to 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, pended water, or flowing water whose magnitude and volu=e is such that the adequte compaction within all the specification require =ents cannot be =et. 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 fill. TVA has deter =ined that the earthfill in question is adequate, and no corrective action is required.

'To co=pletely justify our position, an inplace density test will

be taken in each area. It is expected that our tests will be

, co=pleted by July 11, 1980.

4. The caterial placed on.the dry surface will be removed to the top of the first lift. The top surface will then be da:pened and scarified. This will be followed by spreading replacement .#

fill to achieve a compacted layer of approximately six inches.

In addition, after completing compaction, an inplace density test will be taken in this area. _.-

5. The area in question is the in situ chert foundation at the bottom of the spray pond. Approximately 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 pieces.

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 =aterial to achieve the prescribed grade. It was- felt that the process of scraping off caterial 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 fir = ness. ,,'

Accordingly, the foundation is considered to be adequate and no corrective action is required.

To further increase our assurances as to the reliability of the

unit 1 spray pond liner, TVA plans to. double the namnber of block samples tested over the present requirements for the bottom of the pond. It is expected that testing will be complIted by

. September 1, 1980. rt. 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 till co=paction. Experience and test results on f:111 operations for si=ilar soils in the tarbine~bdilifing alea;have i indicated that there is no. problem in control.lingtth content for achieving specified compaction,e fieldTVA level. moisture believes

, that this co=paction is adequate andIEhat' no corrective action is required. .., Y-7 -

For future earthfill operations; mdistdrie' content tests will be made daily and as often as dictatsd"byTsoil changes. For the inplace fill, the number of bloclFsam;iles 'will be doubled

• to assure that shear strength of inplace fill meets design requirements. It is expected that the .blo'ck sa=ples will be 't completed by Septe=ber 1, 1980. -

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.. l 7 Earthfill test number SP-1 indicated -the ~1-point proctor curve fell slightly below the Class VII b curve. The dir.rerence ,

between the maximum densities for SPdind tla'ss VII b is 3.9 pcf. The field density test indicated:thati the soil was compacted to 100 percent of the maxi =um dry density of Class VII t

b which is conservative; and, therefore,'no corrective actica l

.is required.

.. . . . . l Earthfill test SP-5 rell between Clas's III-SM and t'-m IV-SC. ,

The inspector classified this soil as Class III-SM. Atterberg  !

limit tests indicated this soil had a plasticity index of.9 71 .

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- 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 classificaticn has been changed to Class IV-SC. No other corrective action is required .,,,

l since the ce=paction is conservative.

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

overall adequacy of fill co=paction, and the 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 types of rollers available at the site. These test fills provided infor=ation to achieve the specified density. Additionally, a penetrameter was used when the inspector suspected the adequacy of fill compaction.

A total of 13 sand-core denity. tests have been ecaducted through i June 20, 1980. In all cases, the level of co=paction (varying i from 95 to 106 percent) was equal to or higher than the specified 95 percent. Therefore, TVA believes that the compaction i

fill is adequate, and no corrective action is required. In the )

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 inspector's in the QC-materials and civil unit have been retrained in the requirements relatin5 to earthfill placement on the ERCW spray pond.

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