Laserfiche WebLink
26 GROUND WATER MONITORING <br /> Ground water elevations and samples were collected routinely between <br /> ' April 1999 and November 2001 from the three wells installed at the site <br /> The ground water samples were analyzed for purgeable hydrocarbons <br /> and BTEX constituents as well as general water quality parameters <br /> ' Recent sampling events have also included .fuel oxygenates, <br /> 1,2-dichloroethane, and organic and total lead A summary of the <br /> quarterly ground water sampling results for the site is included in Table 2 <br /> ' The only concentrations of TPH-g detected in ground water since the <br /> ' April 1999 investigation were in monitoring well MW-2 Results of <br /> quarterly ground water samples at this location are normally below <br /> the reporting limit of 50 µg/1, although concentrations of 57 7, 52 8, and <br /> 135 µg/1 have been detected in this well <br /> Detectable concentrations of organic lead were observed in all samples <br /> submitted from the Second Quarter 2001 (June 22) ground water <br /> monitoring event Analysis for organic lead was also run on samples <br /> collected during the Fourth Quarter 2000, Furst Quarter 2001, and Third <br /> Quarter 2001 events Concentrations of organic lead were not observed <br /> above applicable method detection limits in these samples We believe the <br />' organic lead results obtained during the Second Quarter 2001 are <br /> anomalous and not indicative of site conditions based on these three other <br /> non-detections of organic lead at the site <br /> 2.7 MASS CALCULATIONS OF TPH-G REMAINING AT THE SITE <br />' As required by Item#13 of the PHS/EHD checklist, a mass balance <br />' calculation of the substance treated versus that remaining must be <br /> presented No treatment has been completed at this site for the residual <br /> impacts of the former UST, however, a calculation has been completed to <br />' approximate the amount of TPH-g remaining at the site based on <br /> investigation and ground water monitoring data As presented below, a <br /> conservative estimate of the residual mass of TPH-g shows that a minimal <br />' amount of gasoline remains in the subsurface <br />' The extent of hydrocarbon release to soil and ground water is estimated <br /> based on the results of site investigations, the calculations are provided in <br /> Appendix B The lateral and vertical extent of TPH-g in the site soil is <br /> Iimited to a localized area in the vicinity of the former UST, in a zone <br /> between approximately 10 and 35 feet bgs Based on data obtained during <br /> the investigation, the mass of TPH-g remaining in the site soil is estimated <br /> to be approximately 8 04 kilograms (17 7 pounds) This mass would be <br /> ERM 8 <br /> 9343 50f UPRR/02/13/03 <br />