ARCHIVED REPORTS_XR0006136 - Laserfiche WebLink

Home Browse Search

i • a i re provided in Table 1 and presented graphically m Appendix C UVB-MW1 is located approximately 5 feet from the UVB well, screened from 35 to 40 feet bgs, and approximates ' the same depth interval of the lower screened interval of the UVB well, which was used for groundwater extraction As presented in the UVB-MW 1 hydrograph (Appendix C), the concentrations of benzene and TPH-g when operation of the UVB began in February 1997 were 7,200 }Lg/L and 99,000 µg/L, respectively Concentrations decreased to 1,200 µg/L benzene and 17,000 µg/]L TPH-g in October 1997 After October 1997, the benzene and TPH-g concentrations increased to 12,000 µg/L and 130,000 µg/L, respectively, in ' September 2000, when the UVB system was shut down Groundwater concentrations in well UVB-MW 1 have remained near the current levels of 11,600 µg/L benzene and 122,000 µg/L - TPH-g since the UVB system was shut down Because operation of the UVB system hadt-�rm�GJu little or no effect on concentrations of hydrocarbons in a monitoring well located within 5 feet, UVB is not considered an applicable technology, given site conditions ' • Ozone Sparging. Ozone is a relatively strong oxidant when compared with persulfate, hydrogen peroxide, and permanganate However, it is very unstable The short half-life of ozone greatly limits its travel distance even within ideal conditions of permeable and homogeneous soils Ozone is not considered an applicable technology for this site for the following reasons The free hydroxyl radicals generated by ozone can only react with dissolved phase compounds Thus, ozone is not an effective remedial technology for free-phase or residual ' . LPH in source areas Because the saturated zone is heterogeneous and largely silty, infected material is not expected to be uniformly distributed and instead flows in preferential channels in the saturated zone, making hydrocarbon removal from fine-grained materials difficult These preferential pathways for groundwater movement may help explain the limited effect air ' sparging had due to site conditions Air spargmg was conducted in conjunction with SVE at the site from February 1994 through August 1996 in and downgradient of the former tank field Though spargmg well SW2 is located approximately 15 feet upgradient of well UVB- ' MW1, the hydrocarbon concentrations in groundwater measured in UVB-MW1 did not substantially decrease in this area due to spargmg ' • Groundwater Pump-and-Treat. Groundwater pump-and-treat is a traditional technology which is widely used due to its conceptual simplicity The lack of solubility of hydrocarbons in groundwater and partitioning of hydrocarbons between groundwater and soil limit the effectiveness of groundwater pump and treat systems A pump-and-treat system at this site would generate a significant amount of groundwater for treatment and disposal over an extended period of time, while potentially promoting the migration of hydrocarbons and ' MTBE from neighboring offsite sources As this technology is less applicable for sites containing LPH, it should not be implemented as the only means of remediating the site It is, however, being considered in conjunction with dual-phase extraction as a means of ' dewatering the site and therefore enhancing the effectiveness of dual-phase extraction 1 CrlProjects173942VMASTER�WP\%M3031Wft doc 16