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4.2 Considerations <br /> Although the push-pull test demonstrated that a carbohydrate substrate (molasses) may <br /> be effective method for promoting in-situ biodegradation of TCE, the observed increases <br /> of selenium and arsenic concentrations to above-MCL levels are of concern for any <br /> anaerobic ISB treatment approach, particularly given the presence of drinking water <br /> wells with the Ripon Study Area. A large increase in total dissolved solids is also <br /> anticipated, which is already a serious groundwater quality problem in the Ripon area <br /> due to the land application of high-TDS water at the former Neenah Paper Company and <br /> City or Ripon wastewater treatment facility. The complete degradation of TCE was not <br /> observed during this push-pull test. However, additional injection of carbohydrates could <br /> result in complete degradation of TCE, and would require additional pilot testing of this <br /> approach. For these reasons, the application of ISB is not currently planned but may be <br /> implemented at a later date if groundwater extraction is not sufficiently expediting <br /> cleanup. The side-effects of ISB on groundwater chemistry would have to be carefully <br /> managed and controlled. <br />