SITE INFORMATION AND CORRESPONDENCE_1992

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RD/RA Work Plan Memorandum -5- 30 March 1992 DDRW, Sharpe be clarified prior to construction of the ponds. We are concerned with pond design if high concentrations of contaminated ground water are discharged to land in a pond. Addition of Ammonia. The Work Plan states that the addition of ammonia may be necessary in order to prevent the formation addition of trihalomethanes (THMs) for the short term injection tests. The source of the water for the short term injection tests is the potable water supply which presumably has been chlorinated and thus may already have minor concentrations of THMs. Because the injection tests are in an uncontaminated portion of the aquifer (although there are no monitor wells in the immediate area of the injection tests) , we assume that THM concentrations would be very low or non-detect. Therefore, it is unclear if the addition of ammonia was proposed as a precautionary measure in case the free chlorine from the potable water supply may react with humic acid or other organics to form the THMs. In general , because these tests are short term tests, the addition of ammonia may be unnecessary. Long Term Injection Tests. The Work Plan indicates that the long term injection tests will be performed over a period of about three months. Because this test will last one quarter, it is anticipated that the one of the ground water monitoring quarterly reports will depict the affects of the injection on the potentiometric surface. Ground water level contour maps may depict steeper gradients in Plumes 7&8 and Plume 6. Upgrading IRMs. Other than the section on modeling, the Work Plan does not clearly discuss incorporation of the IRMs in the North and South Balloon Areas in the final ground water remedial action. The ground water ROD must include upgrading the North and South Balloon extraction and treatment systems to capture all of the VOC plumes with concentrations greater than 5 µg/1 . CKW:cw