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6.0 REQUEST FOR REGULATORY CASE CLOSURE <br /> 6.1 Leak Has Stopped — Ongoing Sources Removed <br /> Both the northern and southern USTs that appear to have been responsible for the leaking of <br /> gasoline and diesel fuel to soil and groundwater beneath the site were removed and replaced with <br /> new USTs in February and October 1998. Quarterly groundwater monitoring of wells located in <br /> close proximity to the former and existing USTs over the past nine years indicates decreasing <br /> concentrations of all fuel-related hydrocarbons and additives, providing no evidence in <br /> groundwater monitoring that any additional releases have occurred. In addition, to Stratus's <br /> knowledge, the USTs currently installed and in use at the property are in compliance with <br /> periodic County and/or State tightness testing. <br /> 6.2 Site is Adequately Characterized <br /> Environmental investigations at the site began in January 1997, when petroleum-hydrocarbon <br /> impact was identified during pre-UST removal characterization activities. Since that time, more <br /> than sixty vertical soil borings have been drilled at the property and in surrounding areas. From <br /> these borings, more than one hundred soil samples at depths up to 73 feet bgs were collected and <br /> analyzed to evaluate the presence and distribution of fuel-related hydrocarbons and oxygenates <br /> in soil beneath the site. In addition, twenty-two of the soil borings were converted to permanent <br /> groundwater monitoring wells screened across three intervals of water-bearing strata beneath the <br /> `. site. Quarterly groundwater monitoring and sampling was initiated in February 2000, and is <br /> currently ongoing (thirty-four quarterly sampling events). <br /> Based on historic soil analytical results, it appears the lateral and vertical extent of TPHg, BTEX, <br /> and MTBE impact to soil beneath the site and site vicinity was minimal in nature and has been <br /> adequately characterized by the boring/samples collected (see Section 3.3.1 for additional <br /> information). <br /> Based on current groundwater analytical results, the only COC in groundwater remaining <br /> (MTBE) in Sands A and B appears adequately assessed to the secondary MCL in all directions in <br /> both zones, with the exception of to the northwest of well MWA 3A/B in which the presence of <br /> Interstate 5 precludes additional assessment. To close this gap, modeling of the expected fate <br /> and transport of MTBE in this direction has been performed by Stratus (see Section 5.1 for <br /> additional information). Based on current groundwater analytical data and analytical results of <br /> grab water samples collected from deep CPT borings, the lateral extent of impact to Sand C is <br /> adequately characterized and the vertical extent of impact to groundwater beneath the site <br /> (beyond Sand C) also appears adequately characterized at this time (see Section 3.3.2 for <br /> additional information). <br /> Page 23 57-RATUO <br />