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Field Sampling Plan for the Former UST Location at Stockton FMS #24 California Armv National Guard Table 3-2. (Continued) Sample Sample Depth Concentration Reported Water Quality Goal Number (feet bgs) Analyte in mg/L (gg/L) (gg/L) Toluene 0.38 (380) 150 (Primary MCL) Ethylbenzene 2.3 (2,300) 300 (Primary MCL) Xylenes 3.72 (3,720) 1,750 (Primary MCL) TAME <0.002 TBA <0.01 DIPE <0.002 EtBE <0.002 MtBE <0.001 Lead <0.05 bgs = below ground surface NS = not sampled DIPE = di -isopropyl ether PRG = Preliminary Remedial Goal EtBE = ethyl tert-butyl ether TAME = tert-amyl methyl ether MCL = maximum contaminant level TBA = tert-butyl alcohol mg/L = milligrams per liter TPHD = total petroleum hydrocarbons as diesel MtBE = methyl tert-butyl ether TPHG = total petroleum hydrocarbons as gasoline ND = non -detect pg/L = micrograms per liter Notes: Bold indicates contaminant concentration exceeds listed Water Quality Goal. Reported concentrations have been converted from mg/L to gg/L for comparison. Source: Versar, Inc., 2004 Regional Water Quality Control Board, 2003 north by borings B30 and 1332. Concentrations of TPHD have been defined vertically within B31 at 40 feet bgs, where TPHD was non -detect. At 40 feet bgs, all detected TPHG, BTEX, and lead concentrations were less then 100 mg/kg and residential PRGs. 3.2.3 Groundwater samples were collected from three boring locations in first groundwater around the vicinity of the previous USTs as follows: B30 located northeast of the UST excavation; B31 located southeast of the UST excavation; and B32 located northwest of the UST excavation (see Figure 3-1). Groundwater samples were analyzed for the following; TPHG, TPHD, BTEX, and oxygenates, and lead by EPA Methods SW8015G and D, SW826013, and SW6010B, respectively. Results of the groundwater sampling analysis indicate that the maximum concentration of TPHD (1,400 micrograms per liter [µg/L]) and TPHG (74,000 gg/L) in boring B30 exceed Taste and Odor Thresholds of 100 µg/L and 5 µg/L, respectively. The highest concentrations of benzene (up to 24,000 gg/L) and ethylbenzene (up to 2,300 pg/L) were reported in boring B32 and exceed the primary maximum contaminant levels (MCLs) of benzene (1 pg/L) and ethylbenzene (300 pg/L), respectively. The highest concentrations of toluene (up to 6,000 µg/1..) and xylenes (up to 4,900 pg/L) were reported in boring B30 and exceed the primary MCLs of toluene (150 gg/L) and xylenes (1,750 µg/L), respectively. All detected concentrations of BTEX, except for xylenes in boring B31, in groundwater were greater than their associated primary MCL. The detected concentrations stated K:\Wprocess\00251\CA ARNG\Stockton FSP\FINAUStockton FSP.doc 12 August 2006