ML19262B513
| ML19262B513 | |
| Person / Time | |
|---|---|
| Issue date: | 08/23/1979 |
| From: | Gossick L NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Baca T NEW MEXICO, STATE OF |
| Shared Package | |
| ML19262B504 | List: |
| References | |
| FOIA-80-529, FOIA-81-8, REF-WM-28 NUDOCS 7912280148 | |
| Download: ML19262B513 (9) | |
Text
n UnC mining AnD mlLLinG
'# m E 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;Jgg Director NM ENVIRONMENTAL IMPROVEMENT DIVISION
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P. O. Box 968 Santa Fe, NM 87503
REFERENCE:
Uranium Tailings Dam Spill Church Rock Mill
Dear Mr. Baca:
On the morning of July 16, 1979, the taili:1gs dam breached at 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 the spill reached as far as Navajo, Arizona.
UNC Mining and Milling immediately initiated cleanup and monitoring operations and these are continuing to date.
UNC expects to be in compliance with the EID requirements as stated in your letter dated August 13, 1979.
Although tailings spills have occurred at other mill sites in the past, there are unusual aspects associated with this incident that warrant further study. Now that the immediate and reactive cleanup effort has been largely accomplished, UNC intends to undertake a comprehensive monitoring, sampling and testing program. We feel that it is essential that certain kinds of data be developed, not only to evaluate the present impact of the spill but also to provide reference points for future study.
Routine monitoring data collected prior to the spill, as well as data collected since the spill, will be used as baseline comparatives relative to the ongoing program described in the attachment to this memo. We see several benefits in a monitoring-program of this kind, not only to UNC Mining and Milling, but also to ciher agencies or entities who may have need of this kind of information in the future. As one example, we expect to greatly increase our efficiency in continuing cleanup operations as a result of this program.
1643 219
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P, age 2 UnC It is UNC's intent to implement this program, in its entirety, beginning on September 11, 1979. We propose to give a full presentation of the program and results to date to the EID and other interested parties on or about September 21, 1979.
Should you have any questions, please contact my office by Monday, September 17th. As you can see, this is a very ambitious program and we would appreciate being made aware of any comments or suggestions about the implementation or procedures outlined herein prior to our investment of the many dollars and manhours which will be required.
Sincerely,
.m /)
-.x H. J. Abbiss, P.E.
Vice president Environmental and Safety Services Enclosure-1648 220
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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 l
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-226
Background
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.
d' Contaminated arroyo Arroyo and Rio Puerco from 3 samples per site equally Con.posite of 3 samples each.
One-time U natural, Ra-226 sediments.
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. Additional sampling sites determined by 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 8-17-79 sonitoring program to determine where plume 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-226 i
sampling sites.
half and non-contaminated testing.
soils in bottom half and use treated minewater as leachate.
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GOVERNOR E
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_._______w SEGETARY uT p'fg^
'% y ENVIRONMENTAL IMPROVEMENT DIVISION H
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Thomas E. Baca, M.P.H.. Director September 24, 1979
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H.J. Abbiss, Vice Presideht Environmental and Safety Services UNC Mining and Milling P.O.
Box 3951 Albuquerque, New Meuico 87190
Dear Mr. Abbiss :
Your letter of September 12, 1979, has been reviewed and we are forwarding the 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 to background 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 agree that 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 Battelle Mobile Laboratory, instructions for sampling procedures are being forwarded separately.
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 who will be examining this spill in the future.
Consideration must be given to sample analysis, quality control using split samples with EID.
Water samples shall be filtered and acidified within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> of collection.
1.
Helicopter survey for yellow salt formations-frequency should be
" repeat as necessary", since reappearance of the salts may occur and this type of survey is the quickest method of determining whether 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 of samples - core saeples should be three to four feet deep rather than one foot.
Each sample should be analyzed separately and then averaged for 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
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 not considered satisfactory to identify low level alpha contaminants.
Type and treatment of samples - core samples should be three to four feet deep.
Each sample should be analyzed separately and then averaged.
Frequency of sampling af ter clean-up; repeat after six weeks and each three months thereaf ter.
Analyses to be performed - Lead-210 should be added along with soluable (e leachable) sulfates, pH and conductivity, TDS.
s 4.
Ground water - Sand points (2'-3' depth) in the bottom of the water way are inadequate for plume definition.
Shallow monitoring wells are needed near the stream bed for samples to check for plume.
Frequency should be monthly for three months then quarterly.
5.
Leach Tests - Define contaminated samples and two non-contaminated samples (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 have leachate 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.
Analyses to be performed - Le.md-210 should be added plus the constituants for grcund water above.
6.
Livestock sampling - Sampling sites and animal sampling should be coordinated with state veterinarian office.
Number of samples or observations per site - Both milk and urine samples should be taken as appropriate.
Fecal samples are necessary.
Frequency - Depending on results 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 generally graze no lower than about two inches above the ground surface, thus the need for root analyses may not be necessary.
Frequency - May need to be semi-annual for a couple of sampling periods.
Analyses to be proformed '
Add Lead-210 to corn samples and trace metals (moly, selenium, etc.) to both 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 after ficoding and installation of simple automatic stream water samplers at Rt.
566 bridge and Gallup bridge.
Analyses to be preformed should include Lead-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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p Mr. Abbiss September 24, 1979 P.,ge 3 2
Surface water (stream) should be added and include total and 11.
dissolved samples.
Frequency shauld be weekly for the first three monthL, then monthly for three months followed by quarterly.
Analyses to be performed - Fluid chemistry to include trace metals and radiological paraceters.
Sincerely,
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" Gerald W. Stewart Program Manager C;v'S/sh 1648 225 e
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- EDO R/F Mr. Thomas Baca, Director Envirom1 ental Improvement Division Department of Health and Envirognent P.O. Box 968, Crown Building Santa Fe, New Mexico 87503
Dear Mr. Baca:
This letter is to advise you of the results of our review efforts to date concerning the tailings impoundment failure at the Church Rock uranium mill' of United Nuclear Corporation.
This letter also confims discussions between our staffs over the past several weeks concerning radioactive contamination cleanup' limits and points which should be incorporated into the operator's monitoring program.
Further, we ask that you obtain from the operator certain additional infomation we need to complete our geotechnical evaluation of ?.he impoundment failure.
'*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 Protection Section staff concerning the results of sampling and analysis conducted to date.
gF CLEAi;UP OF CONTAMItiATION
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UUn Un On the basis of (1) evaluation of the results of the limited sampling and analysis ccr. 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 with respect 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 e ~,.. e. s e,~.. a 4, v 4 ~, <
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of the pathway evaluations is contained in Enclosure 1). Using conservative assumptions 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 above mentioned cleanup criteria.
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The staff chose not to apply in this case criteria that it has previously issued for 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 and direct gama exposure pathways are dominant.
Because the contamination in this',
case is in an arroyo where structures will not be constructed, the-land cleanup criteriave not appropriate and are not used.
~
These criteria appear fro the limited data gathered to date to be reasonable ones and consistent with the objective of reducing contamination to as low as reasonably achievable (ALAM).
Recent measurements of Ra-226 using the highly accurate radon emanation measurement technique appear to show that radium levels in areas belcw the dam breach are on average a few pCi/gm.
Early measurements made by the operator were much higher (as much as 10 pCi/gm and higher).
The radium measurenent techniques should be checked closely.
If it is confirmed that 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 be more 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 to U.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 date by the operator. With regard to radiological contamination, we consider it particularly important to determine more completely the extent to which contami-nation has penetrated into the soil and arroyo sediments, the extent to which the daughters of radium are present, and the extent to which the contamination has spread and ccncentrated in localized areas within the arroyo (such as in stranded pools).
We ask that you send us copies of reports required of the operator in your August 10, 1979 letter as they become available so that we can continue close follow cf the cleanup and monitoring efforts.
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 (including construction on the impoundment) such a full evaluation be performed. We have a>
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! r. Thomas Baca.
The principal consultants for us in this review are Drs. John Nelson of Colorado State 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 made available to date, we have identified the need for additional information to complete our review.
Specifically, we request that information identified in 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, and that previously requested of your staff by Drs. Nelson, Williams, and Kane in, theii site visit. These latter information requests made by our consultants are 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 tem impoundment stability. The' current tailings area has a sizeable upstream.
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 of other sites where tailings could be disposed of in a manner consistent with your recently proposed regulations and the conclusions in the recently issued draft Generic 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 in a manner which assures public health and safety, and that resumption of operations will begin only after we have fim confidence that the tailings impoundment is stable.
Sincerely, (Sigr.:::) Lee y, ac:3;c3 L. V. Gossick Executive Director for Operations
Enclosures:
1.
Evaluation of Potential Pathways 2.
Info needed by NRC Re Impoundment 3.
Documents previcusly requested
' "' Q NMSS 4.
Programmatic Reconnendations NR f Jl/
u cc: T. Wolff, New Mexico
. Ravnolds. New Mex. State Enoineer,, 8/
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1648 228
EVALUATION OF POTENTIAL EXPOSURE PATHWAYS A description of the specific pathways we have considered; using analytical results 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,ons a
contaminated arroyo, food and water ingestion and grazing of cattle.
1.
Exposure to radon becomes an important health hazard to individuals when a. structure is occupied on top of radium contamination, where radon daughters can concentrate and exposure would be long and continuous.
The construction of a structure in the arroyo is highly improbable.
Structures occupied near 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, exposures under 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 of people in.the arroyo is unlikely and, when present, would be for short time periods only.
Calculations were made, using conservative assumptions, of annual gamma exposure to people living near the edge of the arroyo.
At the interim cleanup levels, the remaining contamination present in the arroyo would provide no significant increase in exposure over the natural background level.
3.
Inhalation of Particulates This potential exposure pathway involves resuspension of dried contaminated arroyo sediments and inhalation of these particulates by a person living near the arroyo.
Using conservative assumptions about such factors as areas available for dusting and location of a receptor in the downwind direction near the edge of the arroyo, we estimate worst case individual exposures to be les,s than a millirem per year.
This is well within existing exposure limits such as the EPA's pending uranium fuel cycle standard (40 CFR 190).
1640 229
~
4..
Food Ingestion Exposure could occur to people eating cattle grazed near the arroyo.
The route considers meat ingestion with the cattic receiving their contaminants via two paths:
(1) from drinking water; and (2) from air particulates settling on the ground and vegetation which cattle then ingest.
Assuming that a person cats only meat from cattle grazing near the arroyo 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 if someone were to brink the water for several weeks the exposure received would be on the order of a few millirem.
This is well within the 1-evels which exist nornally due to the presence of mine water.
~
1640 230.
Enclosure I
ADDITIONAL INFORMATION NEEDED The following information and investigation are requested for NRC review and analysis of the Church Rock Tailings Dam failure. These items are requested in addition to the information and investigation requested by the U.S. Army Corps of Engineers, Albuquerque District (attachment to letter to T..E. Baca dated 27 July 1979 from Bernard J. Roth) and the documents previously requested by J. D. Kane (hand delivered to Jerry Stewart, NMEID by J. Nelson, CSU during week; of August 13,1979)'.
A field survey shoulq be.perfomed that will define the boundaries of l '.
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 the downstream 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, the shear 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 the Corps of Engineers should be decreased to 5 feet.
All undisturbed samples should be obtained by samplers that are hydraulically pushed and not driven under hammer impact (Ref. U.S. Army Corps of Engineers Manual EM 1110-2-1907, 1972).
4.
In addition to laboratory testing of samples at in situ condition, testing should be performed on fully saturated specimens in order to allow for possible saturation of foundation soils resulting from seepage.
Stability analyses should attempt to duplicate pre-failure conditions 5.
(seepage, height of dam, tailings in basin and at downstream toe, etc.)
Factors of safety should be computed based on shear strengths for in situ and saturated foundations conditions.
Stability analyses should also include consideration of a longitudinal crack in the dam filled with It is understood that such a crack had been observed at the location water.
of the break.
The appropriateness of shear strengths adopted in the 1978 stability study 6.
should be reevaluated. The sof t foundation soils indicated in boring No.
5 and the highly compressible soil indicated in boring No. 30 should be considered in the reevaluation.
Consolidation tests should be performed to establish the potential for 7.
collapsing soils. These tests should be performed on representative samples from each significant foundation :one.
9 1648 231
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2_
Pinhole tests should be performed to identify the dispersive characteristics 8.
of the foundation and embankment soils.
These tests should be performed in accordance with ASTM recommended performed using tailings liquor instead of water.
A seismic refraction investigation should be performed to define on a 9.
continuous basis the bedrock profile long the entire axis of the tailings d en.
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 be located on a map of the dam. Details and cracking depths, widths and renedial measures should be presented.
11.
Casagrande typ*e piezometers or equivalent should be located along a transverse to the dam axis at the depth close to the top of the bedrock.
Holes should be sealed above the piezometer tip zone.
These piezometers should 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 the downstream toe of the dam. The line of piezometers should be located to the north of the breach as near as practical.
Additional lines of piezometers may be requested after the bedrock profile has been defined.
12.
Aerial photographs taken of the site both prior to and during construction should be obtained.
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Documents Previously Recuested By J. D. Kane (MRC)
Church Rock Project Documents Needed by Geotechnical Engr.
(Updated with corrections, etc.)
Sergent, Hauskins & Beckwith Engineers
" Church Rock Uranium Mill & Tailings Dam, Church Rock, HM" Job No. C78-5026, Feb. - Hov.1976 Kaiser Engineers " Design of Tailings Disposal System United Nuclear Corp., Church Rock Uranium Mill McKinley County, NM," Feb.1976 Sergent, Hauskins & Beckwith Engineers
" Preliminary Geotechnical Investigation Report, Tailings Dam Church 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, New Mexico," Job No. E75-ill5, Jan.16,1976 Sergent, Hauskins & Beckwith Engineers, " United Nuclear Corporation Tailings Dam & Pond Church Rock Uranium Mill Church Rock, New Mexico," Job No. E76-1013, May 17,1976 Hemphill Corp.
" Soils and Foundation Investigation Church Rock Uranium Mill - United Nuclear Corporation Gallup, NM, Jan. 30, 1969 Geotechnical & De -ign Devieopment, Investigation Report Tailings Disposal vstem Analysis United Nuclear Chu.uh Rock Mill, Church Rock, fM" Job No. E78-1041 July 26,1978 Volumes 1. 2 & 3
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g y ;.
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Programmatic Recommendations COMMENTS AND RECOMMENDATIONS DERIVED FROM VISIT TO UNITED NUCLEAR CORPORATION ClVRCH ROCK URANIUM MILL TAILING DAM BREACH July 18-20, 1979 A.
The State should adopt a quicker-response capability for analyzing radionuclide content'of environmental samples.
B.
The State should immediately determine from the license.and tie-down conditions what procedures the licensee stated would be-followed regarding the operation of the tailing impoundment.
Logs and records pertaining thereto should be examined. This includes periodic inspection of the condition of the impoundment.
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