Laserfiche WebLink
33 SITE CHARACTERIZATION <br /> ERM drilled and sampled four soil borings and constructed monitoring <br /> ' wells within these borings at Former Tank Site #2 during a Phase I <br /> investigation conducted in March 1992 These characterization activities <br /> and the extent of hydrocarbon release to soil were summarized in the <br /> ' PAR <br /> The site investigation indicated that the lateral extent of TPH and BTEX in <br /> ' soil was limited to the area immediately northeast of the former tank <br /> location, and that the vertical extent was primarily limited to a zone <br /> ranging from approximately 5 to 8 feet bgs The volume of soils <br /> containing TPH as gasoline in excess of the 100 mg/kg cleanup goal for <br /> TPH was estimated to be approximately 500 to 700 cubic yards <br /> Based on monitoring data, the extent of TPH and BTEX in ground water at <br /> Former Tank Site #2 is limited to a localized area surrounding monitoring <br /> ' well MW-1 A, located immediately north of the former tank location <br /> ' 34 EXCAVATION <br /> Soil excavation activities at Former Tank Site #2 were conducted in <br /> October 1993 concurrently with the Former Tank Site #1 excavation work <br /> Excavation and confirmation sampling activities were summarized in a <br /> letter report submitted to PHS/EHD on 2 March 1994 <br /> The excavation at Former Tank Site #2 extended to a depth of <br /> approximately 8 to 9 feet with areal dimensions of 115 feet in length and <br /> 40 feet in width (including side slope dimensions) For excavation near <br /> the building, the excavation was sloped at a minimum 11 slope to avoid <br /> undermining the building structure Ground water seepage was <br /> encountered at excavation depths below 7 feet Further soil excavation <br />' and confirmation sampling below this depth required dewatering of the <br /> excavation using a vacuum truck Soil excavation activities proceeded <br /> until mobile laboratory analytical results indicated that the cleanup goal <br />' (100 mg/kg for TPH) was attained at the excavation sidewalls and bottom <br /> or until building structures prevented further excavation A total of 18 <br />' soil confer ation-si� ides were collected The approximate volume of soil <br /> remove fr in Site #1 uring excavation activities was 1,467 cubic yards <br />' Prior to backfilling, the saturated bottom of the excavation was stabilized <br /> by placing a 4-foot-1hick rock base, consisting of 1- to 2-inch-diameter <br /> rock, over a geotextile fabric liner The excavation was then backfilled <br /> ERA4 l CA CLLLUS/2996 10-10/1-4/99 <br />