SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Subject: Notification of Remediation System Shutdown Date: 11/18/2005 Page 2 of 4 Groundwater Monitoring A summary of the analytical data for groundwater samples collected from four wells (MW-1 through MW-4) is presented in Table 1. Since operation of the remediation system began in November 2003, the concentrations of Total Petroleum Hydrocarbons (TPH) as gasoline and benzene, toluene, ethylbenzene, and xylenes (BTEX) have decreased by approximately two to three orders of magnitude in groundwater samples collected from well MW-2 located near the former UST. Furthermore, TPH-gasoline, benzene, toluene, ethylbenzene, and fuel oxygenates were not detected in the sample collected from well MW-2 in July 2005. TPH-gasoline, BTEX, and fuel oxygenates have not been detected in groundwater samples collected from wells MW-1, MW-3, and MW-4 since January 2003. The remediation system did not operate from March 1 to May 20, 2005 due to a mechanical problems. Quarterly groundwater monitoring was performed on May 12, 2005 while the system was off. The analytical data for groundwater samples collected from the wells on May 12, 2005 are presented in Table 1. The sample collected from well MW-2 contained TPH-gasoline at 1,500 micrograms per liter (µg/L), benzene at 7.1 µg/L, toluene at 5.1 µg/L, and xylenes at 36 µg/L. Ethylbenzene and fuel oxygenates were not detected in the sample from well MW-2. TPH-gasoline, BTEX, and fuel oxygenates were not detected in the samples collected from the other three monitoring wells. The analytical data for groundwater give a preliminary indication that remediation has been effective in reducing the concentrations of petroleum hydrocarbons. A significant "rebound" of contaminant levels was not detected following the two and one-half months of system inactivity. Remediation System The vapor flow rates and analytical data for the influent of the AS/SVE system are presented in Table 2. Since November 2003, the AS/SVE system has extracted approximately 186 pounds of TPH-gasoline from the subsurface. A graph illustrating the concentration of TPH-gasoline in the soil vapor influent over time is attached. The graph shows that the highest concentrations of TPH-gasoline were detected in the influent from 2003 to early 2005. The concentrations of TPH-gasoline in extracted soil vapor have been consistently low since the remediation system was restarted in May 2005. A second graph illustrating the cumulative amount of TPH-gasoline extracted from the subsurface over time is attached. The graph shows that the highest removal rates for TPH- gasoline were from 2003 to early 2005. Since May 2005, the TPH-gasoline removal rates have decreased significantly. As indicated in Table 2, the current TPH-gasoline removal rate is approximately one pound per week. In summary, the concentrations and removal rates for TPH-gasoline in soil vapor appear to be reaching low asymptotic levels. PSC:ENVIRONMENTAL SERVICES 210 West Sand Bank Road,Columbia,IL 62236 (618)281-1543 (800)733-7173 Fax(618)291-7020