ML20235N793

Forwards General NRC Comments on Draft Remedial Investigation Rept for Sheffield Hazardous Waste Disposal Sites. Info About Status of Remedial Investigations & Actions at Sheffield Chemical Site Will Be Appreciated

ML20235N793
Person / Time
Site:	02700039
Issue date:	07/06/1987
From:	Weber M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Pierard K ENVIRONMENTAL PROTECTION AGENCY
References
NUDOCS 8707200231
Download: ML20235N793 (4)

Text

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                                                                                                       } J JUL 0 0 B M 2/-39/MFW/87/07/02/ RCRA

__ s . gy~- Mr. Kevin M. Pierard FV i RCRA Enforcement Section . XE ;[ - - U.S. Environmental Protection. Agency _ Region 5 .

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230 South

Dearborn Street ,

Chicago, Illinois 60604

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Dear Mr. Pierard:

In response to your letter of March 26, 1987, the NRC staff has reviewed the r draft Remedial Investigation (RI) Report.for the U.S. Ecology, Inc. facility  ; at Sheffield, Illinois. Enclosed please find our. general comments on the RI, l which I d1scussed with you in May 1987. The hydrogeologic characteristics j l described in the report are generally consistent with our understanding of the j hydrogeology of the Low-Level Radioactive Waste (LLRW) site at Sheffield. The report is of considerable interest to us with respect to,its generic implications for assessing releases of hazardous non-radiological constituents from low-level radioactive waste disposal sitos. An earlier NRC study of the Sheffield LLRW site (NUREG-1183) indicated that hazardous organic constituents were migrating northeast away from the site in a tritium-contaminated groundwater plume. At the time we finalized our report, we were u'icertain - about the extent to which this organic contamination was caused by the LLRW site. The RI indicates that the predominant cause of the organic contamination observed in the tritium plume is the old chentical disposal site located north -{ of the LLRW. We would appreciate being kept informed about the status of remedial investigations and actions at the Sheffield chemical site. We also encourage , you to coordinate yout investigations with the Illinois Department of Nuclear l Safety because Illinois not NRC now has the regulatory authority over the LLRW  ; at Sheffield under an NRC Agreement State Program. Please contact me at  ! (301)427=4746 if you have any questior.s or comments about our review. 1 Sincerely. Michael F. Weber, Acting Section Leader Technical Branch Division of Low-Level Waste'Mancgement and Decommissioning

Enclosure:

As Stated l cc: Terry Lash, IDNS 8707200231 870706 PDR ADOCK O2700039 C PDR 2

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GENERAL NRC COMMENTS ON THE

                              " DRAFT REMEDIAL INVESTIGATION REPORT FOR THE
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SHEFFIELD HAZARD 0US WASTE DISPOSAL SITES" y

1. Exposure Pathways The Remedial Investigation Report (RI) identifies the surface water transport pathway as the exposure pathway with the greatest potential for human exposure-(pg. 7-2). Although the assessment recognizes that groundwater is the dominant transport pathway for contaminants from the Sheffield sites, it does )

not consider human exposure to contaminants via a groundwater pathway. The RI does not conservatively assess the risks posed by existing groundwater contamination et the Sheffield sites because it does not consider human exposure to contaminants via a groundwater pathway. The RI should be revised- 1 to assess potential hazards to the public and environment posed by ingestion of contaminated groundwater at Sheffield.

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T.he purpose of the RI is to assess the extent of contamination associated with the Sheffield sites and tc characterize the hazards posed by such contamination. The RI concludes that although the public is not currently exposed to contaminants released from the facility, ingestion of contaminated I surface water north and northeast of the site is the most probable hypothetical j exposure pathway. The exposure assessment, however, does not consider the more significant exposure pathway of contaminated groundwater ingestion.  ; i l l After site closure, individuals adjacent to the site may extract and ingest contaminated groundwater. Contaminant concentrations in the groundwater are orders of magnitude greater than the surface water concentrations used in the , exposure assessment. For example, the maximum observed concentration of l arsenic in the north wall seep was 9 ppb compared with the maximum measured l concentration of arsenic in groundwater of 2430 ppb (cf. pages 7-4 and 5-27).  ! Use of the surface water exposure pathways in-place of' groundwater pathwa}s may mislead decision makers by resulting in significantly lower calculated  : lifetime risks. In addition, the groundwater exposure pathway may be more I likely than surface water exposure because future residents in the area'may be  ! more inclined to obtain drinking water from shallow aquifers rather than from l surface seeps and surface water bodies efeated by strip mining, j l The RI should be revised to assess the more-conservative-groundwater exposure pathway as the basis for assessing hazards posed by contaminated groundwater ' and designing remedial actions to control the contamination.at Sheffield. [ Alternatively, the RI should demonstrate why the groundwater exposure pathway is insignificant with respect to estimating human exposure and risks associated with groundwater contamination at the Sheffield _ sites. ,

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27-39/MFW/87/04/ ATTACHMENT

2. Consideration of Radionuclides  ;

The exposure assessment does not consider potential health effects associated with exposure to radionuclides (e.g., tritium 1 that are present at elevated levels in groundwater northeast of the LLRW site. The RI should be revised to consider the potential effects of human and environmental exposure to radionuclides in addition to the non-radiological contaminants in groundwater adjacent to the site.

3. Flume Migration and Duration  !

The RI does not estimate the future rate of contaminated groundwater migration  ! or the duration of any hazards posed by such contamination. The rate and duration of contaminant migration may significantly influence conclusions  ; about the extent of such hazards and decisions about appropriate measures to i mitigate or eliminate the hazards. The RI should be revised to ertimate the f rate of contaminant migration and duration of groundwater contamination.

4. Characterization of Contaminated Seeps The exposure assessment in the RI is partially based on a scenario in which an  !

individual consumes groundwater reieased from seeps along the North Wall of j the Sheffield rites. The RI, howeser, does not characterize the location, extent, and the rate and variability of flow of the seeps. Without such information, the hazards posed by the contaminated seeps cannot be  ! defensibly evaluated. Although present at Sheffield, the seeps may not be a likely source of drinking water because their yield may be too low or too ) variable. The RI should be revised to characterize the North Wall seeps and to determine whether the seeps represent a hazard to residents near Sheffield.

5. Erosion Protection Section 2.4 (Page 2-7) indicates that the site is relatively protected against l surface flooding because it is more than 50 feet above the 100-year, 24-hour l

flood elevation of Kings Creek. The RI does not consider, however, the erosion potential of small streams and intermittent drainages on and adjacent to tim site. The RI should be revised to consider erosion that may be caused by streams and intermittent drainages nehrer to the site than Kings Creek.

6. (Jse of Effective Porosity The RI appears to use the terms " effective porosity" and " porosity" interchangeably, despite the significant difference in their meanings.

For example, the text appears to substitute " effective porosity" for

                      " porosity" in describing the factors that influence terrain conductivity j                      measurements in Section 4.3.1 (Page 4-25). The text, however, does not indicate why pore interconnectedness influences terrain conductivity measurements. In addition, Sections 5.2.3 (Page 5-21) and 5.3.3 (Page 5-38)

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   ' 4-27-39/MFW/87/04/ ATTACHMENT'

_ 3 - -. substitute " effective porosity" for " porosity" in determining the volume of contaminated groundwater at the sitcf. This substitution reduces the calculated volume of contaminated grour.dwater because effective porosity is always less than or equal to porosity. The text does not justify the substitution. The RI should be. revised to justify the use of " effective; i porosity" in calculating volumes of contaminated groundwater or to use total L porosity in the calculations. l Further. Section 4.2.3 (Page 4,17) indicates that the " effective' porosities" of 91.acial samples were characterized using water characteristic' curves. Effective porosity is usually determined by laboratory column or-field tracer tes,ts so that the effective porosities are representative of the transport characteristics of the medium being investigated. The, text does not describe how effective por'>sity (as compared with total porosity) was characterized using a water characteristic cerve technique that is not conventionally used to measure effective porosity. . The RI should be revised to describe how

                " effective porosity" was determined using water characteristic curve techniques and to ensure that the terms." effective' porosity"'and " porosity" are used in a manner' consistent with their conventional definitions.

7. Ground Water Elev6 tion Map Figure 4-27 (Page 4-67) is a map of the water table surface beneath the Sheffield sites. The map and the accompanying text, however,~do not indicate whether this map represents the potentiometric surface in the shallow glacial I units beneath the site, the potentiometric surface in bedrock, or some composite of heads in the shallow glacial and bedrock units. The RI should be revised to indicate whether this map represents the potentiometric surface in the glacial units or bedrock and to assess the potential for vertical migration of groundwater contaminants neath the sites.

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