WORK PLANS - Laserfiche WebLink

Home Browse Search

t11 September 2001 AGE-NC Project No. 98-0466 ' Page 13 of 24 ' • Zinc - 50 to 2,200 mg/kg; • Arsenic - 6 to 11 mg/kg(teepee area); and ' • Chromium - 30 to 65 mg/kg(burn pits) Sample 63599, collected at 10 feet below surface grade (bsg) in the north bum pit, contained 30 mg/kg nickel, 11,000 mg/kg copper, 1,500 mg/kg lead,400 mg/kg zinc,and 65 mg/kg chromium. ' Among the 1992 soil samples analyzed,only the lead concentration in sample 63599 and the arsenic concentrations in the teepee area exceeded the PRGs for industrial soil issued by Region 9 of the US ' EPA. Table 3 shows the Title 22 Total Threshold Limit Concentration TLC), Soluble Threshold Limit Concentration(STLC),the Maximum Contaminant Level(MCL)Jbr drinking water,and EPA Region 9's PRGs for industrial and residential soil. ' In addition to metals, sample 63599, collected in the backfill in the northern pit in 1992, contained 6 micrograms per kilogram(µg/kg)dichloromethane(DCMA), 8 gg/kg trichloroethene(TCE),and ' 27 µg/kg tetrachloroethene (PCE). Sample 70858, collected at 5 feet bsg in the south bum pit did not contain detectable concentrations of these analytes.No other samples were analyzed for solvents. ' Three samples(63599, 70858 and 70864-south bum pit,5 feet bsg)contained 15 mg/kg,26 mg/kg and 18 mg/kg diesel-range hydrocarbons. Five other samples from 5 feet bsg and 15 feet bsg in the two burn pits did not have detectable concentrations of diesel-range hydrocarbons. Following excavation of the burn pits and teepee area, soil samples collected from the excavation walls and floors 1994 by Stockton Service Station Equipment Company (SSSE) contained lead concentrations ranging from less than 4 mg/kg to 10 mg/kg. Soil samples collected from the teepee area in 1994 contained arsenic concentrations were equal to or less that- 0.55 mg/kg- less than the the mean background concentration in California soils and less than t ie PRG for industrial soil. ' Concentrations for the other metal analytes did not exceed the TTLC, rSTLC or applicable PRGs. Sampling location and analytical results were included in AGE's Site Environmental History report, ' dated 04 May 2001. AGE visited the burn pit areas on 15 October 1999 and noted that the excavated soil is still ' stockpiled on site east and north of the bum pit area.The north burn pith id approximate dimensions of 45 feet x 47 feet x 14 feet depth, with a volume of approximately 1,1100 cubic yards. The south bum pit had dimensions of approximately 30 feet x 40 feet x 10 feet deep, with a volume of ' approximately 450 cubic yards. A drawing of the teepee area shows a ircular area with a 57-foot diameter that is excavated to a depth of 4.5 feet, for a potential volume f approximately 850 cubic yards. ' AGE proposes to advance three soil borings to ground water, two in the north burn pit area(PB 11 and P12), the third near the former teepee structure incinerator (PB9) to assess ground water for ' petroleum hydrocarbons,volatile organic compounds,formaldehyde an dissolved copper,lead and Advanced GeoEnvironmental,Inc. 1