ARCHIVED REPORTS_XR0010358 - Laserfiche WebLink

Home Browse Search

5.3 ALTERNATIVE_3 INSITU BIOREMEDIATION Alternattve_Descnption This alternative consists of installing a series of wells for placement of an oxygen releasing ' compound into groundwater within the plume. The wells would be spaced 10 feet apart. One row of wells would be installed parallel to the width of the plume near the south end (aligned with MW-2A) The second row would be placed in the middle of the plume. Approximately 20 wells would be installed. The number of wells to implement this alternative was approximated by using an estimate of the groundwater velocity to distribute the dissolved oxygen. The velocity of the groundwater was estimated to be 6.7 feet/year based on hydraulic conductivity (slug test data- WESTON, 1992) and the current groundwater gradient(WESTON, 1997) Twenty wells are required to distribute oxygen throughout the estimated significant portion of the contaminant plume in approximately 5 years Four-inch diameter PVC wells would be drilled to the bottom of the contaminated zone These wells would be installed to depths of approximately 70 feet and be screened over the entire groundwater interval The magnesium peroxide compound would be placed in permeable membranes and lowered into the wells where contact with groundwater would initiate the release of oxygen It is estimated that the peroxide compound would be replaced approximately every 8 months as it is used up Time release of oxygen would oxygenate the groundwater, which would carry oxygen to the microbes and enhance the biodegradation of the BTEX compounds Since groundwater travels approximately 6 7 feet a year, this system would need to operate for approximately 5 years Changes in the contaminant levels would be monitored by ground water sampling to determine when the process could be discontinued Groundwater sampling would be performed every 6 months, and would include MW-2, MW-2A, MW-3, MW-6, MW-7, and MW-9 and two new wells, one deep (screened at 65 to 75 feet bgs) and one shallow (screened across the water table) Lto be installed near MW-2A Groundwater monitoring would be conducted for a period of 6 years tEffectiveness This alternative is expected to be effective Biodegradation of BTEX occurs under most circumstances when supplied with oxygen Because oxygen is generated in the ' contaminant source area, the source is destroyed in place; this technology is more effective than other technologies that try to remove the source through diffusion or other mass transfer mechanisms The effectiveness of this alternative will ultimately depend upon the radius of ' influence and downgradient dispersion of the oxygenated water There may be some uncertainty as to the uniformity of treatment because of the variability in aquifer characteristics and because the efficacy of the process is more difficult to verify LIPR0JECiSISANM\HSMACr10NPL 39