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' Geological rechn(cs Inc Page 4 George's Service Feasibility Study Project No 425 2 Apnl 28, 2004 ' This can be achieved by circulating water-based solutions through contaminated soils and groundwater to enhance biological degradation of organic contaminants Nutrients, oxygen, ' or other amendments may be used to enhance bioremediation and contaminant desorption from subsurface materials There is evidence of ongoing biodegradation activity at the site However, the rate is extremely slow as evidenced by the stable groundwater contaminant concentrations exhibited in MW-2 and the increasing concentrations in MW-1 The plume shows the ' following relationships Alkalinity of the contaminated zone was enriched compared to background • Nitrate of the contaminated zone was depleted compared to background ' o Sulfate depletion is recorded in the plume core compared to background i Oxidation-reduction potential of the contaminated zone is lower compared to background ' • The measured pH in the water table wells range between 7 0 and 7 9 This pH range is conducive to maintaining aerobic biodegradation activity Enhanced bioremediation is not a viable option for the site for several reasons • Contaminant concentrations are high and may be toxic to microorganisms • Groundwater flow rates are very slow Ma The plume is not stable ® Remediation times are often years, depending on the degradation rates of contaminants and site characteristics ' O Nitrate injection to groundwater may be a concern 2.5 Pump and Treat ' Pump and treat remediation involves the pumping of contaminated groundwater from the subsurface and then treating the water with some type of technology Groundwater that has ' been treated can usually be easily discharged to the local wastewater treatment plant under permit This site, however, does not have a nearby wastewater treatment system and therefore a pump and treat system is not feasible for the site without a Waste Discharge Requirement (WDR) or a National Pollutant Discharge Elimination System (NPDES) ' permit These two permits are not easy to obtain when the discharge is to adjoining property, not on the subject property ' Pump and treat remediation at a site with discharge limitations may be restricted by the climate During rainy days discharge would have to stop in order to contain water run-off Discharge to neighboring fields would require extensive plumbing under Highway 33, access agreements with the railroad and landowners, and water containment structures such ' as earthen dams or berms Continuous costly site visits would be required to make sure there is no run-off occurring at ' the discharge location Costly monitoring routines, sampling events and laboratory analyses would be iequired under a WDR or NPDES permit