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r r 06 February 2004 �) AGE-NC Project No 01-0865 Page 2 of 9 sloping topography of the land,the very shallow depth(generally less than 5 feet below surface)and the fact that it is surrounded on all sides by either drainage ditches or canals,any discharge of treated ground water on the site (land disposal) will drain into surface water The HHM site is surrounded by agriculture land, there is no municipal sanitary sewer system or storm drain system at the site Domestic sewage is discharged to private septic systems AGE believes that discharge of EHM-treated ground water into a surface water body will be a cost effective alternative compared to extracting ground water and hauling it off-site to a state certified ground water treatment facility(1 e pump and haul) 12 Description Of Events That Caused The Ground Water Pollution On 30 October 1991,three underground storage tanks(USTs)were removed from the site by Warren E Gomes Excavating,Inc Although no groundwater was encountered,the bottom of the tanks were rusted Total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d) and benzene, toluene, ethylbenzene and total xylenes (BTEX) were detected in soil samples collected from the UST excavation at depths between 9 feet and 12 feet below surface grade (bsg), at maximum concentrations of 4,800 milligrams/kiIogram (mg/kg) TPH-g, 37 mg/kg benzene, 93 mg/kg ethylbenzene and 500 mg/kg xylenes in sample TK2-N and 350 mg/kg toluene in TNI-N Lead was detected in samples TNI-S and TN2-N and the soil pile at 7 mg/kg, 10 mg/kg and 11 mg/kg, respectively Subsequent ground water monitoring events have detected petroleum hydrocarbon compounds and fuel additives at concentrations as high as 110,000 ug/1 TPH-g, 540 µg/l benzene, 930 µg/1 toluene, 40 µg/I ethylbenzene, 750 4g/1 xylenes, and 190,000 µg/1 MTBE, in well MW-2 13 Description Of The Proposed Ground Water Extraction Pump And Treat System AGE intends to implement an interim ground water pump-and-treat system at the site utilizing one ground water extraction well(EW-1),located in the area ofhlghest petroleum hydrocarbon-impacted water, the well is screened between 4 feet and 19 feet bsg AGE will install a dedicated, 3 5-inch diameter air-driven(pneumatic)submersible pump(model AP-4/13L)inside the extraction well The pump will be designed to operate continuously at low flow rates ranging between 0 and 10 gallons per minute(GPM)or more,and can adjust Its pumping rate to match the well's recharge rate,thereby providing a continuous cone of depression Ground water will be routed to a multi-media treatment system The first stage of the pump and treat system will utilize 2,000 pounds (two 1,000-pound vessels) of granular activated carbon (GAC) to address TPH-g,BTEX and the fuel additives MTBE,TAME and TBA,the second stage will address Advanced GeoEnvfronmental,Inc