ARCHIVED REPORTS_XR0005075 - Laserfiche WebLink

Home Browse Search

.. 11 February 2003 AGE-NC Project No. 98-0520 Page 2 of 7 1 Geology, 1977). Rocks composing the basement complex of the Province have not been'completely defined but are.bell eved to be metamorphic and igneous in origin. 1 The Modesto, Riverbank and Turlock Lake Formations and overlying.Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin (Basin 5-22). This basin is drained primarily by the San Joaquin River. 2.2. LOCAL GROUND WATER SETTING The nearest surface water features in the vicinity of the property are the San Joaquin River and Little ' John Creek, located approximately5 miles southwest and north, respectively, of the site. Ground water at the site is currently encountered at a depth of approximately 24 feet below surface grade (bsg); and has .a northwesterly flow direction. Presently, ground water occurs- in an interval'of ' predominantly clayey silt, informally referred to as layer 2 (Figures 3 and 4); this layer is approximately 15 feet'thick; at between 20 and 35 feet below surface grade (bsg). Apparently discontinuous, 3 to 5-foot thick sand lenses occur sporadically in layer 2. 2.3. UST REMOVAL 1 AGE has been informed that one 10,000-gallon re lar gasoline UST one 8,000-gallon unleaded l� g gasoline UST and one 550-gallon waste oil UST were removed from the site in 1988. During UST 1 removal activities, soil samples were collected and analyzed from beneath the ends of each UST. Total xylenes were detected at a concentration of 230 micrograms per kilogram (µg/kg) in a soil sample collected from the base of the gasoline UST Tank No. 2 excavation at a.depth of 15 feet ' below surface grade (bsg). Total petroleum hydrocarbons quantified as motor oil (TPH-mo) was detected at a concentration of 97 milligrams per kilograms (mg/kg) in a soil sample collected at a depth of 12 feet bsg from the base of the waste oil UST (Tank No. 3) excavation. However, 1 laboratory detection limits were elevated and may not have indicated low concentrations of petroleum hydrocarbon compounds above standard reporting levels. According to an EHD inspection report, soil discoloration and petroleum hydrocarbon odors were noted,beneath USTs' ' Tank No. 1 and Tank No. 2. Additional information regarding history of the UST use, tank tests, product inventory and repairs are not known to AGE. Advanced GeoEnviron mental,Inc.