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Division of United Nuc! ear Corporation PO Bos 3951 4801 indian school Acad. N E.

A UT1C RESOURCES Corecany Albuoverque. New Meoco 87190 Albuquerque. Ne a Meuco 87110

Telepnone 505 265 4421-

September 12, 1979

"dC2. ,e-

Mr. Thomas E. Baca 4.,1;JggDirectorNM ENVIRONMENTAL IMPROVEMENT DIVISION #'T Dir's offre.

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P. O. Box 968Santa Fe, NM 87503

REFERENCE: Uranium Tailings Dam SpillChurch Rock Mill

Dear Mr. Baca:

On the morning of July 16, 1979, the taili:1gs dam breachedat UNC's Church Rock mill, releasing approximately 280 acre-

. * feet of tailings solution and 1100 tons of tailings solids,which eventually flowed into the Rio Puerco and traces of thespill reached as far as Navajo, Arizona.

UNC Mining and Milling immediately initiated cleanup andmonitoring operations and these are continuing to date. UNC'

expects to be in compliance with the EID requirements as statedin your letter dated August 13, 1979.

Although tailings spills have occurred at other mill sites inthe past, there are unusual aspects associated with this-

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incident that warrant further study. Now that the immediateand reactive cleanup effort has been largely accomplished, UNCintends to undertake a comprehensive monitoring, sampling andtesting program. We feel that it is essential that certainkinds of data be developed, not only to evaluate the presentimpact of the spill but also to provide reference points forfuture study.

Routine monitoring data collected prior to the spill, as well asdata collected since the spill, will be used as baselinecomparatives relative to the ongoing program described in theattachment to this memo. We see several benefits in a monitoring-program of this kind, not only to UNC Mining and Milling, butalso to ciher agencies or entities who may have need of thiskind of information in the future. As one example, we expect

to greatly increase our efficiency in continuing cleanupoperations as a result of this program.

1643 219

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UnC.

It is UNC's intent to implement this program, in its entirety,beginning on September 11, 1979. We propose to give a fullpresentation of the program and results to date to the EID andother interested parties on or about September 21, 1979.

Should you have any questions, please contact my office byMonday, September 17th. As you can see, this is a very ambitiousprogram and we would appreciate being made aware of any commentsor suggestions about the implementation or procedures outlined"

herein prior to our investment of the many dollars and manhourswhich will be required.

Sincerely,

.m /) -

-.xH. J. Abbiss, P.E.Vice president

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Environmental and Safety Services"

Enclosure-

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LKILieutJ CHORCil NOCK 1AILitiGS DAM DRLACli ik)N110 RING PROGRAM

ttuttutR OF SNiPt [5 OR TYPE Arid TREA1 MENT ANALYSES TO BE|

M*3 ITG FROGRtJ1 SAMPtihG $11LS OBSERVA110NS PER SITE OF SAMPLES FREQt:ENCY PERFORMED

, Helicopter survey Arroyo from NECR dam to Record location of all yellow -- One-time --

j for yellow salt Navajo,AZ. salt formations present in sampling''formations waterway..

100 yds. upstream in all 3 sampler per site equally Composite of 3 samples each, One-time U natural Ra-226Background -

I sediments m..jor drainages of arroyo spaced from each bank of I ft. deep x l-1/2" 0.D. sampling Th-230, **

: and Rio Puerco from itECR drainage arroyo. gross ganima,*

i dam to idavajo, AZ.Average I sampling per sec-

;tion.

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Contaminated arroyo Arroyo and Rio Puerco from 3 samples per site equally Con.posite of 3 samples each. One-time U natural, Ra-226sediments. HECR dam to itavajo, Al. spaced from each bank of I ft. deep x l-1/2" 0.D. sampling Th-230,

Sariple at each section line waterway. gross gacuna.crossing. Additionalsampling sites determinedby gross ganina measurements.

Groundwater Arroyo and Rio Puerco from One sample per site. Sand points driven 2-3 ft. One-time Every sample--NECR dam to Navajo, AZ. into bottom of waterway. sampling sulfate, chloride

Sa.aple at each section line pH, conductivity

. crossing. Additional to determine total' sampling sites determined extent of plume.

by results. Every 4th sample--groundwater para-

'meter list spect-fled in 8-17-79sonitoring programto determine whereplume ends.

Leach tests Tailings pile sample, One sample from each site. Prepare 4 f t. column with One-time U natural, Th-230,,

2 contaaiinated arroyo contaminated soils in top leach Ra-226i

sampling sites. half and non-contaminated testing.

soils in bottom half and usetreated minewater asleachate.

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| STEYE OF NEW MEXICO Geor9e 5 Goldstein, Ph.D-L _._______w - SEGETARYuT p'fg^ '% y '* ENVIRONMENTAL IMPROVEMENT DIVISIONH ~ P.O. Box 968, Santa Fe, Nt r "fexico 87503

L "Y l Go'd n. M.5.. M.P.H.$ ENVIRONMENT (50s) 827 52712 g] g 5 ...m .,a

DEPUTY 5ECRETARYe

a a Thomas E. Baca, M.P.H.. Director

September 24, 1979

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~ H.J. Abbiss, Vice PresidehtEnvironmental and Safety ServicesUNC Mining and MillingP.O. Box 3951Albuquerque, New Meuico 87190

Dear Mr. Abbiss :

Your letter of September 12, 1979, has been reviewed and we are forwardingthe following com=ents for your ongoing monitoring program proposal. Until

such time that data has been received from UNC demonstrating that the.,*

contamination clean-up has been effective in reducing the contamination tobackground and is below the levels for Radium-226 and Thorium-230 as identi-fled in paragraph (7) of EID's letter of August 13, 1979, we do not agreethat the "immediate and reaction clean-up effort has been largely accomplished".We will be looking forward to your data to demonstrate your compliance with*

EID's August 13, 1979 letter. In order to =aximize the use of the BattelleMobile Laboratory, instructions for sampling procedures are being forwardedseparately.

We agree that a follow-up monitoring program is desirad and necessary. This

follow-up program certainly needs to provide data useful to UNC and ethers whowill be examining this spill in the future. Consideration must be given to

sample analysis, quality control using split samples with EID. Water samplesshall be filtered and acidified within 12 hours of collection.

.

1. Helicopter survey for yellow salt formations-frequency should be" repeat as necessary", since reappearance of the salts may occurand this type of survey is the quickest method of determiningwhether such contamination will be a recurring problem.

2. Background sediments - sampling sites should be upstream in uncontam-inated drainages of arroyo and Rio Puerco. Type and treatment ofsamples - core saeples should be three to four feet deep rather thanone foot. Each sample should be analyzed separately and then averagedfor the composite value for cach contaminate. Analyses to be performed-Lead-210 should be added alcng with soluable (or leachabic) sulfates,pH and' conductivity.

EQUAL Q*PoRTUNITY EMPLOYER

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Mr. Abbiss' '

Se*pt ed.be r 24, 1979 -

Page 2 .

3. Contaminated arroyo sediments - include known or suspected rentam-inated side arroyos or pools. Gross gamma measurements are notconsidered satisfactory to identify low level alpha contaminants.Type and treatment of samples - core samples should be three tofour feet deep. Each sample should be analyzed separately and thenaveraged. Frequency of sampling af ter clean-up; repeat after six weeksand each three months thereaf ter. Analyses to be performed - Lead-210should be added along with soluable (e leachable) sulfates, pH andconductivity, TDS.

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4. Ground water - Sand points (2'-3' depth) in the bottom of the waterway are inadequate for plume definition. Shallow monitoring wells are

needed near the stream bed for samples to check for plume. Frequencyshould be monthly for three months then quarterly.

5. Leach Tests - Define contaminated samples and two non-contaminatedsamples (pre or post spill). A location of the source of tailings

pile sample should be provided. Type and treatment of samples -contaminated and non-contaminated soils in separate colurns, then haveleachate move through contaminated column first. Consideration should

. : be given to stream water, if constituants are known rather than " treated=inewate r : . Frequency - =sy need to be repeated af ter clean-up. Analysesto be performed - Le.md-210 should be added plus the constituants forgrcund water above.

6. Livestock sampling - Sampling sites and animal sampling should becoordinated with state veterinarian office. Number of samples or

observations per site - Both milk and urine samples should be taken asappropriate. Fecal samples are necessary. Frequency - Depending onresults of the sampling, every six months may be desirable. Analyses to

'be performed - Include Thorium-230 and trace metals (moly, selenium, etc.).'

7. Vegetation sampling - Type and treatment of sampics - Livestock generallygraze no lower than about two inches above the ground surface, thus theneed for root analyses may not be necessary. Frequency - May need to besemi-annual for a couple of sampling periods. Analyses to be proformed 'Add Lead-210 to corn samples and trace metals (moly, selenium, etc.) toboth vegetatica samples.

8. Can=a Survey - At this time, based on two gamma surveys already accomplished,this may not be necessary.

9. Floodwaters - Type and treat =ent of samples should include sediment afterficoding and installation of simple automatic stream water samplers at Rt.566 bridge and Gallup bridge. Analyses to be preformed should includeLead-210, Frequency - Extend to 12 months to insure that seasonal are reflected.

10. Air sampl'ing - Sampling sites should include in the stream bed. Analyses to be

perfo rme d - Include Lead-210 .md Radon.

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.Mr. AbbissSeptember 24, 1979P.,ge 3 2

Surface water (stream) should be added and include total and11.dissolved samples. Frequency shauld be weekly for the first threemonthL, then monthly for three months followed by quarterly.Analyses to be performed - Fluid chemistry to include tracemetals and radiological paraceters.

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Sincerely,

.. . / /:/. :.. . .- . . r.w.:..- .

" Gerald W. StewartProgram Manager

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AUG 23 1979 vRScarano -

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EDO R/FMr. Thomas Baca, DirectorEnvirom1 ental Improvement Division .

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Department of Health and Envirognent -

P.O. Box 968, Crown BuildingSanta Fe, New Mexico 87503 .

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Dear Mr. Baca: .,

This letter is to advise you of the results of our review efforts to dateconcerning the tailings impoundment failure at the Church Rock uranium mill' ofUnited Nuclear Corporation. This letter also confims discussions between ourstaffs over the past several weeks concerning radioactive contamination cleanup'limits and points which should be incorporated into the operator's monitoringprogram. Further, we ask that you obtain from the operator certain additionalinfomation we need to complete our geotechnical evaluation of ?.he impoundmentfailure.

'*e appreciate your assistance in this matter and are confident that continued,

cooperation between our staffs will promote a speedy resolution of the problem.So far, the NRC staff and our geotechnical consultants have visited the site,reviewed documents made available by the operator, and carried on continuing-

discussions with the State Engineer's office and your Radiation ProtectionSection staff concerning the results of sampling and analysis conducted todate. gFCLEAi;UP OF CONTAMItiATION -

% g g {U 1 1 M .,UUn Un

On the basis of (1) evaluation of the results of the limited sampling and analysisccr. ducted to date, (2) evaluation of potential radiological exposure pathways, and(3) the desirability of reducing exposure to the maximum extent reasonably achiev-able, we consider that an acceptable cleanup would be removal of contamination -

to levels which are no greater than 10 pCi/gm Ra-226 and 30 pCi/gm Th-230(both inclusive of background).

These levels are selected as one which will bc- protective of public health.Varicus potential exposure paths which affect human health were evaluated withrespect to the levels of radioactive contamination in the arroyo following cleanup.Specifically, we looked at five major pathways: inhalation of radon daughters,direct gamma exposure, inhalation af contaminated windblown particulates,in';estion of beef cattle which graze near and drink from the Rid Puerco, and in- t

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- . . . ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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of the pathway evaluations is contained in Enclosure 1). Using conservativeassumptions about such factors as location and . occupancy of structures near ,the contaminated arroyo we fcund, for each pathway, that exposures were .

below levels which would pose a threat to publ.ic; health using the abovementioned cleanup criteria. , , j.The staff chose not to apply in this case criteria that it has previously issuedfor land: cleanup (" Staff Technical Position Fuel Processing and Fabrication.Brqnch-- Interim Land Cleanup Cq1teria for Decomissioning Uranium Mill Sites"- *

itay,1970). .The land cleanup criteria are based on situations where radon anddirect gama exposure pathways are dominant. Because the contamination in this' ,case is in an arroyo where structures will not be constructed, the-land cleanupcriteriave not appropriate and are not used. '

~

These criteria appear fro the limited data gathered to date to be reasonableones and consistent with the objective of reducing contamination to as low asreasonably achievable (ALAM). Recent measurements of Ra-226 using the highlyaccurate radon emanation measurement technique appear to show that radium levelsin areas belcw the dam breach are on average a few pCi/gm. Early measurementsmade by the operator were much higher (as much as 10 pCi/gm and higher). Theradium measurenent techniques should be checked closely. If it is confirmedthat the lower Ra-226 measurements are representative of the contaminated area,we consicer that a limit of 5 pCi/gm Ra-226 (inclusive of background) would bemore consistent with the ALARA principle and should be specified.

.

As we told your staff during the week of August 5, we agree with your letter toU.1C of August 10, 1979, requiring promp't cleanup actions and prompt implementa-tien of a more comprehensive monitoring program than has been conducted to dateby the operator. With regard to radiological contamination, we consider itparticularly important to determine more completely the extent to which contami-nation has penetrated into the soil and arroyo sediments, the extent to whichthe daughters of radium are present, and the extent to which the contamination

'has spread and ccncentrated in localized areas within the arroyo (such as instranded pools).

We ask that you send us copies of reports required of the operator in yourAugust 10, 1979 letter as they become available so that we can continue closefollow cf the cleanup and monitoring efforts. .

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EVALUATION OF TAILIriGS Il4P0UtlDMENT

liRC staff and consultant geotechnical experts have visited the Church Rock site 'as the first step in a full evaluation of (1) the cause of dam failure, and(2) adecuacy of the impoundment for future operations, in light of the failure.It is imperative that before operatinns resume at the Church Rock mill (includingconstruction on the impoundment) such a full evaluation be performed. We have...,- a> ,. a ,-.s ,. -.s-.a . -- ,.a -- - -..--.a-. cz- +- a m. + u ., ,, e + n

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! r. Thomas Baca -3-.

The principal consultants for us in this review are Drs. John Nelson of ColoradoState University and Roy Williams of Idaho University. Dr. Joseph Kane of NRC

is also contributing to the review. Based upon site visits of these censultants,and ' review of documents related to impoundment construction and stability madeavailable to date, we have identified the need for additional information to '

complete our review. Specifically, we request that information identified inEnclosure 2 be obtained from UNC. This infonnation is in addition to that re-cuested by the Corps of Engineers in letter to you dated July 27, 1979, andthat previously requested of your staff by Drs. Nelson, Williams, and Kane in, *

theii site visit. These latter information requests made by our consultantsare summarized in Enclosure 3. ,

Our preliminary review efforts indicate the strong need to evaluate 'the adequacy.of the current site for tailings disposal from the point of view of long temimpoundment stability. The' current tailings area has a sizeable upstream .

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drainage which is undesirable from the point of view of water erosien and While-flooding which can act to disrupt the tailings over long periods of time.operations might be resumed for a limited period of time at the current site,evaluations of long term stability should be conducted by the mill operator ofother sites where tailings could be disposed of in a manner consistent with yourrecently proposed regulations and the conclusions in the recently issued draftGeneric Environmental Impact Statement on Uranius Milling (NUREG-OSil of _ April,1979).

~ Finally, you will find in Enclosure 4 progra matic recomnendations that resulted'

frcc our initial site visit on July.18-20,1979.

The effort of our staffs have been well coordinated.I trust that through

continued cooperation the contamination cleanup effotts will be carried out ina manner which assures public health and safety, and that resumption of operationswill begin only after we have fim confidence that the tailings impoundment is

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stable..

Sincerely,.

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(Sigr.:::) Lee y, ac:3;c3

L. V. Gossick* Executive Director for Operations

Enclosures: .

1. Evaluation of Potential Pathways2. Info needed by NRC Re Impoundment3. Documents previcusly requested ' "' QNMSS4. Programmatic Reconnendations NR fJl/ucc: T. Wolff, New Mexico

. Ravnolds. New Mex. State Enoineer , , 8/ /79 sf 9 /79< :11. J. Abiss, Unitec Nuci r Lorrorauon n SP E00

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1648 228.

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EVALUATION OF POTENTIAL EXPOSURE PATHWAYS

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A description of the specific pathways we have considered; using analyticalresults available to date, and our conclusions about them are as foi-low.Cur evaluations of these pathways have included conservative assumpti

~ bout such factors as location and occupancy of structures near the ,onsa

contaminated arroyo, food and water ingestion and grazing of cattle.

1. ; Inhalation of Radon Daughters *- -

Significant exposure via radon inhalation should ~not occur. Exposure'

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to radon becomes an important health hazard to individuals when a. structureis occupied on top of radium contamination, where radon daughters can -

concentrate and exposure would be long and continuous. The constructionof a structure in the arroyo is highly improbable. Structures occupiednear the arroyo,. with cleanup at or below the interim cleanup '

levels, would contain undetectable and insignificant quanitities of radon.

above background. Therefore, at the interim cleanup levels, exposuresunder the worst of conditions would be insignificant to public health.

2. Direct Gamma Exposure

Direct gamma exposure is also considered to be minor since the presence ofpeople in.the arroyo is unlikely and, when present, would be for short timeperiods only. Calculations were made, using conservative assumptions, ofannual gamma exposure to people living near the edge of the arroyo. Atthe interim cleanup levels, the remaining contamination present in thearroyo would provide no significant increase in exposure over the naturalbackground level.

3. Inhalation of Particulates

This potential exposure pathway involves resuspension of dried contaminatedarroyo sediments and inhalation of these particulates by a person livingnear the arroyo. Using conservative assumptions about such factors asareas available for dusting and location of a receptor in the downwinddirection near the edge of the arroyo, we estimate worst case individualexposures to be les,s than a millirem per year. This is well withinexisting exposure limits such as the EPA's pending uranium fuel cyclestandard (40 CFR 190).

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Enclosure 1- -

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4.. Food Ingestion ..

Exposure could occur to people eating cattle grazed near the arroyo.The route considers meat ingestion with the cattic receiving theircontaminants via two paths: (1) from drinking water; and (2) from airparticulates settling on the ground and vegetation which cattle then

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ingest. Assuming that a person cats only meat from cattle grazing near thearroyo contaminated at or below the interm cleanup level and drinking only'

' arroyo water, maximum exposure would only be a few millirems per year; .

again, this level of exposure is well within existing exposure limits. ,

,

5., Wate,r Ingestion ,'

Poor water quality is assumed to preclude direct drinking of the Rio,Puerco's water on a continued basis. However, it was assumed that ifsomeone were to brink the water for several weeks the exposure receivedwould be on the order of a few millirem. This is well within the 1-evelswhich exist nornally due to the presence of mine water.

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Enclosure I.

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ADDITIONAL INFORMATION NEEDED

The following information and investigation are requested for NRC review andanalysis of the Church Rock Tailings Dam failure. These items are requestedin addition to the information and investigation requested by the U.S. ArmyCorps of Engineers, Albuquerque District (attachment to letter to T..E. Bacadated 27 July 1979 from Bernard J. Roth) and the documents previously requestedby J. D. Kane (hand delivered to Jerry Stewart, NMEID by J. Nelson, CSU during

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week; of August 13,1979)'.

A field survey shoulq be.perfomed that will define the boundaries ofl '.,

the failed zone. This survey should define the cross-section of the,

breached area and its location with respect to the dam abutment.

2. In addition to the borings requested in item 4C by the ' Corps of Engineers,.two borings at distances of 125 feet and 200 feet downstream from thedownstream toe should be drilled in accordance with the procedures 'out-lined for the other borings. Additional borings or test pits may be-necessary to define the depth to soils unaffected by the slide, theshear planes of the slide, if one exists and the slope of the "escapment"at the upstream side of the beach.

3. The sampling interval specified in item 5a of the list prepared by theCorps of Engineers should be decreased to 5 feet. All undisturbedsamples should be obtained by samplers that are hydraulically pushedand not driven under hammer impact (Ref. U.S. Army Corps of EngineersManual EM 1110-2-1907, 1972).

4. In addition to laboratory testing of samples at in situ condition, testingshould be performed on fully saturated specimens in order to allow forpossible saturation of foundation soils resulting from seepage.

Stability analyses should attempt to duplicate pre-failure conditions5.(seepage, height of dam, tailings in basin and at downstream toe, etc.)Factors of safety should be computed based on shear strengths for insitu and saturated foundations conditions. Stability analyses shouldalso include consideration of a longitudinal crack in the dam filled with

It is understood that such a crack had been observed at the locationwater.of the break.

The appropriateness of shear strengths adopted in the 1978 stability study6.should be reevaluated. The sof t foundation soils indicated in boring No.5 and the highly compressible soil indicated in boring No. 30 should beconsidered in the reevaluation.

Consolidation tests should be performed to establish the potential for7.collapsing soils. These tests should be performed on representativesamples from each significant foundation :one.

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1648 231

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Enclosure 2

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Pinhole tests should be performed to identify the dispersive characteristics8.of the foundation and embankment soils. These tests should be performedin accordance with ASTM recommended performed using tailings liquor insteadof water. ,

A seismic refraction investigation should be performed to define on a9.continuous basis the bedrock profile long the entire axis of the tailingsd en.

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10. Locations at which fenmer arroyos intersected the dam axis and areas in'

'which cracking of the dam has been observed and/or repaired should belocated on a map of the dam. Details and cracking depths, widths andrenedial measures should be presented.

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11. Casagrande typ*e piezometers or equivalent should be located along atransverse to the dam axis at the depth close to the top of the bedrock.Holes should be sealed above the piezometer tip zone. These piezometersshould be located as near to the center of the impoundment as possible,at the upstream toe of the dam, at the centerline of the dam, at thedownstream toe of the dam. The line of piezometers should be locatedto the north of the breach as near as practical. Additional lines ofpiezometers may be requested after the bedrock profile has been defined.

12. Aerial photographs taken of the site both prior to and during constructionshould be obtained.

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Documents Previously Recuested

,, ,By J. D. Kane (MRC)

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Church Rock Project -

Documents Needed by Geotechnical Engr.(Updated with corrections, etc.)

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Sergent, Hauskins & Beckwith Engineers" Church Rock Uranium Mill & Tailings Dam, Church Rock, HM" *

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Job No. C78-5026, Feb. - Hov.1976"

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Kaiser Engineers " Design of Tailings Disposal System,

United Nuclear Corp., Church Rock Uranium MillMcKinley County, NM," Feb.1976 -

Sergent, Hauskins & Beckwith Engineers" Preliminary Geotechnical Investigation Report, Tailings DamChurch Rock Uranium Mill, United Nuclear Corp.,Church Rock, New Mexico," . Job No. E78-1076,Oct. 18, 1974

Sergent, Hauskins & Beckwith Er.gineers," Report of Additional Geotechnical Engineering Studies,Church Rock Uranium Mill Tailings Dam, Church Rock, NewMexico," Job No. E75-ill5, Jan.16,1976

Sergent, Hauskins & Beckwith Engineers, " UnitedNuclear Corporation Tailings Dam & PondChurch Rock Uranium MillChurch Rock, New Mexico," Job No. E76-1013, May 17,1976

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Hemphill Corp. " Soils and Foundation Investigation,

Church Rock Uranium Mill - United Nuclear CorporationGallup, NM, Jan. 30, 1969

Geotechnical & De -ign Devieopment, Investigation ReportTailings Disposal vstem AnalysisUnited Nuclear Chu.uh Rock Mill, Church Rock, fM"Job No. E78-1041 July 26,1978 Volumes 1. 2 & 3

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Enclosure 3

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Programmatic Recommendations

COMMENTS AND RECOMMENDATIONS DERIVED FROM VISIT TO UNITEDNUCLEAR CORPORATION ClVRCH ROCK URANIUM MILL TAILING DAM BREACH

July 18-20, 1979 *

A. The State should adopt a quicker-response capability for analyzingradionuclide content'of environmental samples." '

B. The State should immediately determine from the license.and tie-downconditions what procedures the licensee stated would be-followed .

regarding the operation of the tailing impoundment. Logs and recordspertaining thereto should be examined. This includes periodic -

inspection of the condition of the impoundment.

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Enclosure 4

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