ML20059N998

Cimarron Corp Response to Comments Concerning Risk Assessment for Groundwater

ML20059N998
Person / Time
Site:	07000925
Issue date:	09/21/1998
From:	Jim Larsen Cimarron Corp
To:	Jones G Document Control Desk, Office of Nuclear Material Safety and Safeguards, State of OK, Dept of Environmental Quality (DEQ)
Shared Package
ML20062C036	List: ML20059N998
References
Download: ML20059N998 (4)

Text

'

L ___ - -

S. JE:,S LARSEN VICE PRESIDENT CIMARRON CORPORATION P.O. BOX 25861 OKLAHOMA CITY, OKLAHOMA TJT~5 September 21, 1998 Mr. Gfen W. Jones Assistant Director Water Quality Division Oklahoma Department of Environmental Quality P. 0. Box 1677 Oklahoma City, Oklahoma 73101-1677 Re:

Risk Assessment for Groundwater Cimarron Corporation, Crescent, Oklahoma

Dear Mr. Jones:

Cimarron Corporation (Cimarron) appreciates the comments on our Risk Assessment for Groundwater provided in your letter dated August 12, 1998. Cimarron has prepared this letter of response to your comments and has incorporated the changes as discussed below into the revised document which accompanies this letter. Cimarron would encourage that the previous version of the risk assessment document, dated June 2, 1998, be discarded.

For convenience. the comments from the August 12 Jetter have been stated below and the specific response to the comment follows each comment.

1.

Section 1.2 should include a reference to the NRG Risk Evaluation documents specifically with the major conclusions from that document in the text.

Appropriate text summarizing the conclusions in the Decommissioning Plan Ground Water Evaluation Report submitted to the NRC has been included in the document on page 1-5.

2.

The concluding paragraph from Section 2. 1 states that there is no exposure to the media, when it would be more correct to state that there is no hazard from exposure to the media.

3.

Concur. The sentence has been revised to incorporate the suggested change on page 2-2.

The data summary in Section 2. 2 states that recognized standard field sampling a analytical procedures were used. Please reference the analytical

e Glen W. Jones ODEQ September 21, 1998 Page 2 procedures by EPA or NRG method number.

Please clarify whether analyses for uranium were reported in mg/kg or picocuries per liter. In this section, please include an acknowledgment of the jumps in levels of nitrates, etc., around 1994. Some sort of rationale for these sudden elevations may help the reader who is less familiar with the site understand that there may be an explanation as to why these levels are so much higher.

The following analytical procedures were utilized: Isotopic uranium - modified HASL 300; nitrate - EPA Method 353.2; and fluoride - EPA Method 340.2. The results for uranium have been reported in both mg/L and pCi/L Since the risk assessr,ent addressed only chemical toxicity based on the mg/L results, only the mg/L results were included in the data tables in Appendix A.

The levels of nitrate peaked at the "seeps" (#1206 and 1208) in 1994. This peak is probably attributable to the leading edge of the plume reaching the area of the "seeps".

4.

Section 2. 3, in the last paragraph, the first two sentences appear to be conflicting.

Please clarify.

The paragraph has been rewritten in order to clarify that the upgradient (e.g.

background) deep groundwater system exceeds the MCL for uranium.

Further, the variance in the deep groundwater system uranium concentrations for both upgradient and downgradient wells are within the variance expected for the deep groundwater system and are therefore, not in excess of background levels.

5.

Section 3. 1. 1 details demographics from the 1990 census.

Prior to 1990 there appeared to be a rather rapid increase in development with several golf courses and housing developments. There is at least some reasonable potential to expect future residential development in the near vicinity.

Please acknowledge that demographic patterns may exhibit strong changes at the next decennial census. Should the "re-opening criteria" be utilized, a current demographic assessment must be made.

A statement as requested has been added to Section 3.1.1 as well as to Section 8 on page 8-1 to indicate that the demographic patterns will be re-evaluated at the time the "re-opening" criteria is utilized.

6.

Table 3.2 gives a value of 0.5 for Exposure Time (ET). The text gives a value of 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> per event. Please clarify. Please specify which EPA document is used for the various defaults and for the chemical specific permeability constants. Table 3.2 has a 30 year exposure duration for the trespasser scenario, but Table 3. 4 uses 8 years for exposure duration. It would be more appropriate to use the 30 year duration exposure.

Please recalculate the Risk estimates to reflect this. If an 8 year exposure duration is actually proposed, then further justification for less than a standard exposure must be provided.

e Glen W. Jones ODEQ September 21, 1998 Page 3 The 0.5 value in Table 3.2 was a typographical error. An exposure time of 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> per trespass event was utilized in all of the calculations. The EPA documents utilized as references have been cited in Table 3.2. Tables 3.3 and 3.4 have been amended to reflect an exposure duration of 30 years. Because the exposure duration is utilized in both the numerator and denominator in the average daily intake calculation equation, there are no differences in the calculated average daily intakes and no resultant changes in any of the calculated hazard indices.

7.

Section 4. 2. 1 details the toxicity for nitrates. There is no mention of a carcinogenicity assessment for nitrates. Please include the information as to whether nitrates have been classified for carcinogenicity.

A statement indicating that nitrates are not known to have carcinogenic potential and have not been classified as to carcinogenicity has been added to Section 4.2.1.

8.

Section 4. 2. 3 details the toxicity of uranium. Please include in the discussion the fact that the NRC documents address the radionuclide risks, and that those risks are not a part of the chemical toxicity assessment. Please relate the dose in mg/kg-day to the radiological dose of picocuries per liter for comparison sake only.

Text has been added to Section 4.2.3 (page 4-3) that indicates that radionuclide risks are being addressed by the NRG and have been included in the report entitled, Decommissioning Plan Ground Water Evaluation Report, dated July, 1998.

As requested a comparative radiological intake of pCi/kg-day has been calculated based on the Cimarron specific mg to pCi conversion.

However, since hypothetical radiation dose calculations are conducted using International Commission on Radiologlcal Protection (ICRP) methods and dose conversion factors, there is no direct correlation between the RfD and radiation dose.

9.

Section 7. 1.2, second paragraph, second sentence should be amended to state that the uranium concentrations were within Oklahoma Water Quality Standards as established by the Oklahoma Water Resources Board, and did not exceed upstream or background concentrations.

The requested text has been added to Section 7.1.2 on page 7-3.

10.

Section 7. 1. 5, please clarify the meaning of the heading for this section.

The heading contained a typographical error; the correct heading is "Selection of Endpoint to Receptor 11

11.

Section 8. O should include the statement that, should re-opening criteria be addressed, MCLs and background concentrations existing at the time of re-opening will be used to

~--*.. ---**

- -- -* --*- --*- * ~-

e Glen W. Jones ODEQ September 21, 1998 Page 4 assess the applicability of the re-opening criteria. The Sentence which states that "This represents an extremely conservative basis, since EPA generally allows the use of a target hazard index of 1" is confusing. The calculation of a hazard index was done with standard EPA defaults so is no more or less conservative than the usual method.

The text has been amended to include a reference to the MCL and background concentrations and to delete the confusing sentence.

12.

Section 9.0 should explain in the last paragraph the rationale for developing re-opening criteria at this time, and an explanation of when and how the criteria would be used.

(This is a repetition of the section on re-openers, but is needed here for clarity.)

Text has been added to Sectton 9.0 (page 9-1) to reiterate the use of the "re-opening criteria 1

Cimarron sincerely appreciates the timely manner in which you and your staff reviewed the prior submission and also this opportunity to respond to the comments provided by the Department. We trust that our response will be satisfactory and a letter of approval for the risk assessment and concurrence with the summary and conclusions presented in Section 9 will be forthcoming. If you have any questions, please do not hesitate to contact me.

e Sincerely,

~rs~

Vice President Enclosure jl092198.le1