ARCHIVED REPORTS XR0006513 - Laserfiche WebLink

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wells MW 1 through MW 10 DATE Pounds TPH- m Sod Pounds Benzene in Soil ' February 1989 624345 7298 June 1997 2129 <1 ' Percent removed 9966% X99 86% Soil testing performed in 1997 identified greater than 99% attenuation of the estimated TPH-g and benzene mass in soil 6.0) GROUNDWATER MONITORING The groundwater plume of dissolved gasoline range e hydrocarbons has been reduced in size and ' concentration The site has been remediated through a combination of air sparging and soil vapor extraction The removal rates associated with air sparging augmented biodegradation can not be directly measured Comparison of aggregate groundwater monitoring results obtained in 1990 ' and 1997 provides conf rnvng data that 99% of the benzene and 69% of the TPH-g had been removed by 1997 after seven years of enhanced remediation operations Groundwater monitoring results identified an overall dissolved mass reduction of 97 83% in TPH-g and 99 99% as benzene from January 1990 to January 1999 DATE Pounds TPH-Q rn Water Pounds Benzene in Water ' January 2, 1990 2985 1435 June 1997 904 10 ' January 1999 65 0 008 1 Percent Removed 9783% 9999% In addition, dissolved TPH-g and benzene concentrations in the discharge area decreased significantly in groundwater during the first two years of enhanced remediation at the site from 1990 to 1992 Continuing, significant TPH-g and benzene reduction was confirmed in 1999 Plume reduction was identified in 1999 as compared to 1992 results, confirnvng spatial stability of the approximate 1% remaining benzene mass Figures 3,4,5, and 6 represent TPH-g measurements obtained in January 1990, December 1992, May 1998, aid January 1999, respectively Figures 7,8,9, and 10 represent benzene measurements obtained in January 1990, December 1992, May 1998, and January 1999, respectively 6.1) Depths to Water On January 8, 1999, depths to groundwater were obtained andoundwater samples were r p ee 5