ARCHIVED REPORTS_XR0005079 - Laserfiche WebLink

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3 ' WELL SURVEY. ' A well survey was performed in October 1999 to identify municipal, domestic,industrial,irrigation or monitoring wells and septic tanks located within a 2,000-foot radius of the site.' The nearest ground water wells were two City of Manteca wells (No. 7 and No. 19) located approximately 2,300 feet northeast of the site-and one commercial well located approximately 1,000 feet southeast of the site. In addition, ground water monitoring wells were observed approximately 300 feet northwest, 1,000 feet northwest and 1,5.00 feet southeast of the site. No other receptors, including, septic tanks, were identified within the 2,000-foot radius. ' UST REMOVAL. AGE has been informed that one 10,000-gallon regular gasoline UST, one 8,000-gallon unleaded ' gasoline UST and one 550-gallon waste oil UST were removed from the site in 1988. During UST 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, 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. PREVIOUS SUBSURFACE INVESTIGATION ' On 05 February1999,AGE advanced four soil robe borings at the site.Probe borings B-1 and B-2 p g g were advanced within the former UST No.2 and'No. l excavations to depths of 40.25 and 25.25 feet ' bsg,respectively.Probe boring B-3 was advanced within the former waste oil UST No.3 excavation to 20.25 feet bgs. The fourth boring, B-4 was advanced northwest of the former dispenser islands to 20.25 feet.bgs. ' TPH-g and various BTEX compounds except benzene were detected in the soil samples collected from between 20 and 25 feet bsg from all of the borings, at concentrations as high ' as 570 mg/kg and 13 mg/kg(xylenes),respectively,in soil sample B-2-20.25 ;TPH-mo was detected in soil samples collected between 20 and 25'feet bsg in borings B-2 through B-4 at a maximum concentration of 120 mg/kg (B-2-20.25'). Fuel oxygenating compounds, including MTBE, were not detected above the elevated reporting limit. Advanced GeoEnvironmental,Inc.