ML20215J789

Identifies & Discusses Two Items Requiring Followup Per DOE 870128 Response to NRC Comments on Grand Junction Draft Remedial Action Plan.Both Items Pertain to Groundwater

ML20215J789
Person / Time
Issue date:	05/28/1987
From:	Lohaus P NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	James Anderson ENERGY, DEPT. OF
References
REF-WM-54 NUDOCS 8706250113
Download: ML20215J789 (2)

Text

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Mr. James R. Anderson, Project Manager E~

t-Uranium Mill Tailings Project Office U.S. Department of Energy Albuquerque Operations Office P.O. Box 5400 Albuquerque, New Mexico 87115

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Dear Mr. Anderson:

On January 28, 1987, DOE submitted responses to NRC comments on the Grand Junction draft Remedial Action Plan (RAP). NRC staff have contacted TAC personnel to clarify various technical questions. The purpose of this letter J

1s to identify the few items for which we, believe additional follow-up is These items, both relating to ground water, are described below:

necessary.

1 Low-permeabilitylayeratCheneyReservoir-(gwc],

Following review of the draft RAP, NRC staff requested information on the low-permeability layer to be constructed beneath the tailings material. This information included additional-permeability results of the subgrade material,.

projections of leachate quality and quantity emanating from the tailings,-and the beneficial aspects of the layer for protecting ground water. DOE responded that the decision on using the bottom layer would be based on the presence of perennial ground water and results of infiltration modeling, but conceded that i

the bottom layer would likely be removed because perennial. ground water did not exist. NRC staff conclude that use of a bottom layer could significantly reduce contaminant concentrations through neutralization of leachate emanating from the pile. This was a generic point of agreement between NRC and TAC technical personnel. Therefore, NRC is requesting that any decision to remove the bottom layer from the design should be based on analyses considering geotechnical'and geochemical, as well as hydrogeological aspects of the disposal plan.

Impact of Grout Contaminated Wells on Water Quality Results Although NRC did not coment directly on this aspect of site characterization-in the draft RAP, the staff considers the problem of using grout contaminated wells for water sampling to be an open issue.

It is currently unknown what.

effect grout cement in the well bore has on water-quality data results. It is.

possible that concentrations of contaminants in the sampled water may be significantly altered from that of water not~1n contact with grout' cement, thus resulting in unrepresentative data. This is due to a rapid increase in pH as ground water is drawn into ceatact with the grout cement. This results in lower solubilities of several cation constituents in ground water (e.g., iron and lead) which may result in their precipitation, thus leading to erroneous data.

8706250113 870528 PDR WASTE WM-54/MF/87/05/11 WM-54 PDR

4 James R. Anderson 2

NRC staff has asked DOE to evaluate whether grout contam' nation in monitor wells significantly alters water-quality results.

Until it can be demonstrated to NRC staff ' hat grout contamination in monitor wells is insignificant, NRC cannot.

rely on water quality results from these wells.

NRC considers this an important

. issue because these water-quality data are used to support conclusions regarding the extent of ground-water contamination.

If you have any questions on these concerns, please contact Mark Haisfield at FTS 427-4722.

Sincerely, 1

Nidinal Signed By Paul H. Lohaus, Acting Chief Operations Branch Division of Low-Level Waste Management and Decommissioning cc: Richard Sena, DOE / Albuquerque Larry Coons, TAC / Albuquerque 1

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OFFICIAL RECORD COPY WM-54/MF/87/05/11 1