ML20003D996
| ML20003D996 | |
| Person / Time | |
|---|---|
| Site: | Wood River Junction |
| Issue date: | 10/13/1980 |
| From: | Dan Warner DON L. WARNER, INC. |
| To: | Shum E NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| CON-NRC-02-80-076, CON-NRC-2-80-76 17798, NUDOCS 8104010825 | |
| Download: ML20003D996 (4) | |
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Dear Dr. Shum:
Ng' I am writing to respond co Task II-a under NRC Contract 02-30-076, which is:
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Whether or not the residual radioactive and nitrate contamination of the site and underlying groundwater reservoir compromise public health and the environment and/or linit future reuse of the site by industry or for public water supply. To be completed two weeks after contract award."
The contract was awarded September 17, but I did not receive the package of infomation from your office until the afternoon of !!andly, September 29. Accordingly, my response date to this task is October 13.
The task seems to me to contain two parts. The first part is the detemination of whether or not the residual radioactive and nitrate con-tamination of the site compromises public health and the environnent and/or limits future reuse of the site.
I interpret this question to mean con-tanination of the soils underlying the site.
I do not have data to allou me to aake such an assessment at the cresent time.
I will need to have
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clarification of the intent of this part of the task and, if I am to nake any judgments on the nature of residual soil contamination, arrange.ent will have to be made for me to have data on the present extent and magnitude of such residual contanination.
- The second part of the task concerns residual radioactive and nitrate contanination of groundwater underlying the site. Abundant grotadwater quality monitoring data were supplied to me, but not in any c'tronological or otherwise organized fom. Because of the volume of the infomation, it was not practical for me to try to organize it at this tine. Therefore, I have used the graphical infomation prepared by your office and attached to a package entitled " Background Information on UNC-Nood River Junction Occket No.70-320."
In addition, I have examined the actual values as given in the laboratory reports for a few months during 1977-1980.
I have compared the values for nitrate, gross alpha, gross beta, radium-226 and radium-228, and strontium-90 with the maximum contaminant levels for drinking water as'specified by the U.S. Environnental Protection Agency in the National Interin Primary Drinking Water Regulations. The respective maxinin contaniaant values are:
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Dr. Edward Shum October 13, 1980 Page Two Maximum Contaminant Contaminant Levels nitrate (as N) 10 mg/l gross alpha 15 pCi/1
- gross beta 50 pCi/1 radium-226 + radium-228 5 pCi/1
- strontium-90 8 pCi/1
- These are average annual values based on quarterly samples The principal wells that have been used to evaluate the extent of ground-water cc:.camination are wells T-2, T-3, 76-U, 77-B, and 77-D.
For this preliminary evaluation, only those five wells will be considered. The wells are listed in the order of their location relative to the lagoon area. Well T-2 is located imediately to the northwest of the lagoon area wells 77-B and 77-D are farthest from the lagoon area to the northwest in the direction of groundwater flow. Of the five wells, the data for well T-2 seem to exhibit perhaps the clearest pattern of behavior.
In this case, the plotted data for nitrate, gross alpha, and gross beta all appear to show a considerable decline in contaminant level during 1977-1980.
A sample collected from well T-2 December 17, 1977, exhibited 15 pCi/1 of gross alpha activity and 352 pCi/1 of gross beta activity and contained 400 mg/l of nitrate nitrogen. A sample collected from well T-2 in March 1980 exhibited <2 pCi/1 of gross alpha activity and 9 pCi/1 of gross beta activity and contained 7 mg/l of nitrate nitrogen. On the basis of these three parameters and others included in the March 1980 analysis, water from well T-2 would have met EPA drinking water standards at that time.
It would appear that the majority of the contamnants from the lagoon area that were originally present in the groundwater at well T-2 have been trans-ported away by natural groundwater flow.
Analyses of water from well T-3 during 1977-1980 show erratic levels of the indicator parameters, but there does appear to be a general pattern of decline in the concentration of nitrate and alpha emitting radioisotopes.
Gross beta activity does not seem to have permanently declined. A water sample taken from well T 3 in June,1977, exhibited 3545 pCi/1 of gross alpha activity and 361 pCi/1 of gross ba a activity and contained 143 mg/l of nitrate nitrogen. A water sarple taken from well T-3 in March 1980 exhibited <2 pCi/1 of gross alpha activity,174 pCi/1 of gross beta activity,
.1 Dr. Edward Shum October 13, 1980 Page Three 8.7 pCi/1 of strontium-90 activity, and 6.7 pCi/1 of radium-226 and 228 activity. The sampic contained >100 mg/l of nitrate nitrogen. Ground-water at well T-3 was not suitable for drinking in March 1980, since all of the indicator parameters were present in excess of the maxinra allowable concentrations.
The plots for water analyses from wells 76-U, 77-B and 77-D that were prepared by your office seem to show an overall decline in IcVels of gr'oss alpha activity during 1977-1980 for all three wells but the trend of con-centrations for nitrate nitrogen and gross beta activity are less obvious.
However, examination of some actual values of these parameters for a few selected months during 1977-1980 (see below) does show distinctly lower concentrations for some of the more recent analyses.
It will probably be necessary to perform a statistical analysis of all of the available data to establish a quantitative trend and its level of reliability.
Well 76-U 6/77 9/79 1/80 3/80 or 8/79 Gross alpha (pCi/1) 72 103 6
26 Gross Beta (pCi/1) 385 170 95 55 Nitrate nitrogen (mg/1) 406 150 36 Well 77-B Gross alpha 60 64
<2
<2 Gross beta 217 227 206 188 Nitrate nitrogen 837 500
>100 Well 77-D Gross alpha 45 40 17
<2 Gross beta 26 310 206 190 Nitrate nitrogen 473 200 78 In any case, although levels of contamination in groundwater at wells 76-U, 77-B and 77-D are probably lower than in 1977, the groundwater was still too contaminated to be suitable for drinking purposes when sampled earlier this year.
In sumary, groundwater in the plume of contamination northwest of the lagoon area at the UNC site appears to have improved in quality immediately near the lagoon area to the extent that it met EPA drinking water standards for radionuclides and nitrogen when sampled at well T-2 in March 1980. Farther toward the northwest, at wells T-3, 76-U, 77-B, and 77-D, the quality has also probably improved since 1977, but the groundwater still contained concentrations of radionuclides and nitrogen in excess of EPA standards in :! arch 1980.
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Dr. Edward Shum October 13, 1980 Page Four Insofar as I know, the groundwater contamination discussed above does not pose any immediate threat to public health, since, according to the infomation I have, none of the contaminated water is being withdrawn for drinking-water supply.
I believe that the reduction in contaminant levels has resulted principally from transport of the contaminants toward the northwest by natural groundwater flow and by their eventual discharge by seepage into the Pawcatuck River.
I would not expect the small amount of contaminants that would be discharged by seepage to be sufficient to significantly affect the quality of river water, but I have not specifically examined this question.
If, as would be expected, the groundwater system continues to flush contaminants from beneath the site and if there is no continuing source of contaminant supply, then the groundwater will eventually be suitable for industrial and/or drinking water use, and the future reuse of the site will not be limited.
As a next phase of the contract, I will proceed to evaluate the rate of transport and resulting cleanup of contaminants in the groundwater system.
I will plan to report on my preliminary findings in that area by November 3.
Sincerely yours, h
Don L. Warner Consulting Geological Engineer DLW/jk d
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