ARCHIVED REPORTS XR0003742 - Laserfiche WebLink

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Sulfate After DO and nitrate have been depleted in the ground water, sulfate may be used as an electron acceptor for anaerobic biodegradation If sulfate concentrations vary inversely with hydrocarbon concentrations, anaerobic biodegradation of fuel hydrocarbons is probably occurring Ferrous Iron. In some cases ferric iron acts as an electron acceptor during anaerobic biodegradation of petroleum hydrocarbons In this process, ferric iron is reduced to ferrous iron, which may be soluble in water Therefore, if the ferrous iron concentrations vary directly with hydrocarbon concentration, anaerobic biodegradation may be occurring Sampling for this parameter will be conducted during an upcoming quarterly ground water monitoring event If necessary, these parameters can be evaluated on several occasions to further assess intrinsic bioremediation Continued Quarterly Monitoring including DO Monitoring Cambria proposes to continue quarterly ground water sampling All samples will be analyzed for TPPH, BTEX, and MTBE Cambria will also monitor DO concentrations quarterly in the ground water monitoring wells to evaluate ground water oxygenation by ORCs Once the DO concentrations decrease to pre-ORC concentrations, new ORCs may be installed in the wells We estimate that the ORCs in a given well will last between 6 and 12 months, depending on site-specific oxygen utilization Wells containing elevated DO concentrations due to ORCs will be sampled without purging to avoid removal of oxygen-rich ground water CONTINGENCY PLANS The CAP includes a contingency plan depending upon the results of the periodic GWE Depending upon the hydrocarbon removal rate and change in hydrocarbon and MTBE concentrations, GWE could continue on a periodic basis, a GWE system could be put in place, or GWE could be stopped The long term plan will also be dependent upon the amount of hydraulic control that the periodic pumping is able to maintain across the site Ground Water Extraction System Installation If the periodic GWE is not effective in reducing the hydrocarbon and MTBE concentrations or in maintaining hydraulic control over the site, a GWE system will be installed and operated The primary purposes of the system under these circumstances would be to provide hydraulic control over the source area and to prevent down gradient migration of hydrocarbons and MTBE Additional purposes for the system are to remove MTBE and other hydrocarbons from the ground water source area and to draw oxygenated ground water through the source area • Initially, the system would extract ground water from RW-1 and possibly MW-5 using the existing underground piping If needed, the system could be expanded to enable pumping from other wells, 240-0783 28