ARCHIVED REPORTS XR0000257 - Laserfiche WebLink

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Project No 58100-06-11 A June 29, 1995 Pump and treat as a groundwater remediation alternative has been shown to be successful in providing ' plume hydraulic control and retarding the lateral migration and spread of impacted groundwater Factors that influence the feasibility and cost associated with pump and treat include, but are not limited to, 1) the flowrate of extracted groundwater required to gam hydraulic control of the plume, 2) the number and ' location of extraction wells required, 3) the existence of naturally occurring dissolved minerals and sediment in the groundwater and 4) site specific discharge points for extracted groundwater Typically, the performance of a groundwater pump test is necessary to evaluate aquifer characteristics and determine the required number and location of extraction wells In-situ bioremediation typically includes the extraction of groundwater to gain hydraulic control of the plume, the addition of dissolved oxygen and nutrients in an aboveground treatment plant(with or without ' contaminant removal) and the re-injection of groundwater into upgradient monitoring well(s) Other m- situ bioremediation variations include using air spargmg to increase the dissolved oxygen levels in groundwater, the direct injection of nutrient and microorganisms into the groundwater and the use of ' downgradtent trenches as bioreactors A groundwater pump test is necessary to evaluate plume capture and chemical analyses of soil below the groundwater surface is necessary to evaluate baseline levels of hydrocarbon degrading microorganisms, organic carbon,nitrogen and phosphorus For an initial feasibility ' and cost projection, aquifer characteristics could be assumed to evaluate groundwater pumping requirements and the necessity for nutrient and oxygen amendments can be assumed in order to evaluate in-situ bioremediation to other alternatives Because the characteristics of soil below the groundwater surface are site specific, highly variable and difficult to assess without analytical data, a final evaluation of in-situ bioremediation should be based on ' the collection and evaluation of biochemical data and a bench study to evaluate TPHg and benzene in-situ biodegradation rates The effectiveness and cost of air sparging is influenced by the permeability distribution of saturated zone sediments,the volatility of the compounds to be stripped from groundwater, ' the number and locations of air injection wells and air injection flowrate and pressure A sparge pilot test which includes a vapor extraction component is necessary to evaluate air injection rates, capture zone and injection well placement and vapor extraction requirements 74 RECOMMENDATIONS Geocon recommends that additional investigation be performed at the site to establish the lateral extent of TPHg impacts to groundwater The installation of four additional groundwater monitoring wells is recommended to attempt to establish the lateral extent of TPHg impacts The proposed well locations are depicted on Figure 6 A vapor extraction field pilot test should beerformed to obtain design criteria for P g o a soil vapor extraction system and to test the effectiveness of source removal from vapor extraction well VW-1 15