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S 15 October 2000 AGE-NC Project No 96-0232 Page 2ofII would not permit the discharge of treated ground water from Flag City Chevron AGE believes that discharge of Flag City Chevron treated ground water into a surface water body will be a cost effective alternative compared to extracting ground water and hauling off-site to a state certified ground water treatment facility (i a pump'and haul) 1 2 Description Of Events That Caused The Ground Water Pollution On 31 ;March 1995, three 12,000-gallon gasoline USTs and one 12,000-gallon diesel UST were replaced at the site During excavation activities, ground water was encountered in the UST cavity at approximately 8 feet below site grade (bsg) Dissolved total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d) were detected in grab ground water samples at concentrations as high as 18,000 micrograms per liter (,ug/1) Dissolved benzene, toluene, ethylbenzene and xylene(BTEX compounds) were detected at concentrations as high as 860/.zg/l TPH-g was detected in a soil samples beneath the former product piping at a concentration of 1 5 milligrams per kilogram (mg/kg), BTEX compounds were detected in the same soil samples at concentrations ranging as high as 0 18 mg/kg TPH-d was not detected in any of the analyzed soil samples Methyl tertiary butyl ether (MTBE) was detected in subsequent ground water monitoring . events at concentrations as high as 5,700,ug/I (29 June 2000) from Flag City Chevron ground water monitoring well MW-1 1 3 Description Of The Proposed Ground Water Extraction Pump And Treat System AGE Intends to implement a multi-media ground water pump-and-treat system at the site utilizing 8 ground water extraction wells screened between 10 and 35 feet bsg Ground water will be extracted from each well utilizing dedicated, submersible Grundfos pumps at pumping rates varying from 3 to 6 gallons per minute for a total discharge rate of 25 gallons per minute Ground water will be routed to a multi-media treatment system The first phase of the ground water pump and treat system will utilize 5,000 pounds (two 2,500 pound vessels) of granular activated carbon (GAC) to address TPH-g, TPH-d and BTEX, the final phase will address MTBE utilizing 5,000-pounds (two 2,500 pound vessels) of SunSolve, a patented material that has an affinity to absorb MTBE A schematic diagram of the GAC/SunSolve ground water treatment system is depicted in Figure 3 The estimated usage of filtration media based on ground water data collected to date is estimated at 125 pounds per - day for GAC and 44 pounds per day for SunSolve, additional information is in Appendix A It is estimated that the break through time for each 2,500 pound vessel of GAC will be 20 days and for each 2,500 pound vessel of SunSolve will be 57 days 14 Site Characteristics The property is currently utilized as a Chevron fueling facility and a mini-market The site consists Advanced GmEnvironnmatal,Inc I l