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k'q KLEINEELDER i 10-times the STLC Regulated Level is commonly used as an indicator as to whether or not a STLC analysis is appropriate to be ran on the sample I The upper limit of the total lead concentrations reported at the site (7 8 mg/kg) was found to be well below the Residential PRG level for total lead of 400 mg/kg Additionally, it is Kleinfelder's experience that the concentrations of total lead detected are representative of naturally occurring background levels in soil of the area ' 4.4 COMPARISON TO REGULATORY LIMITS GROUNDWATER ' The groundwater sampling results were compared to EPA California Regional Water Quality Control Board, Central Valley Regions document titled "A Compilation of Water Quality Goals", dated August 2000 and a City of Stockton, Department of Municipal Utilities Table titled "Self Monitoring Sample Program", summarizing acceptance criteria for discharge of water into the sanitary sewer system ' Eight (8) analytes or compounds were detected in groundwater from the requested suite of analyses as listed in Section 3 3 These analytes were compared to State and Federal Primary Maximum Contaminant Levels (MCLs) and to acceptance criteria as presented by the City of Stockton for discharge to the sanitary sewer system as applicable to the specific analytes Seven of the eight analytes were reported as gasoline constituents TPH-G, BTEX and two oxygenates (MTBE and DIPE) The eighth was total lead Seven of these constituents were detected in a single groundwater sample collected from pushprobe boring GP-12 Three of these ' analytes, benzene, toluene and ethylbenzene were only detected at this location TPH-G was detected in a total of three groundwater samples from the Mission Area at concentrations ranging from 0 20 to 4 3 mg/l There is no MCLs set for this compound The City of Stockton discharge limit is 100 mg/l for "total petroleum hydrocarbons" Total lead was detected in all fifteen groundwater samples collected in the two areas ranging from 0 24 to 13 mg/l These total lead concentrations exceed the State and Federal Primary MCL of 0 015mg/l However, these ' concentrations do not exceed the City's limit of 2 0 mg/l From the four BTEX constituents and one oxygenate (MTBE) detected in the Mission Area, ' benzene and MTBE were found to exceed either State and/or Federal MCLs and the City's discharge limits Benzene was detected in a single groundwater sample (GP-12) at a concentration of 990 µg/l, which exceeds both the Pnmary and Secondary MCLs of 1 and 5 µg11, ' respectively This benzene concentration also exceeded the City's discharge limit of 500 µg/1 The highest total BTEX concentrations also detected from GP-12 was 1,245 µg/l, which is below ' the City's limit of 4,570 µg/1 Toluene, ethylbenzene and total xylene values detected in groundwater sample/s were found to be well below State and Federal Primary MCLs MTBE was detected in two groundwater samples in the Mission Area (GP-8 and GP-12) at concentrations of 5 5 and 86 µg11, respectively The concentration of 86 4g/1 MTBE (GP-12) exceeds the State Primary and Secondary MCL of 13 and 5 µg/l, respectively and the City's limit of 0 5 µg/1 The MTBE concentration of 5 5 µg/1 (GP-8) detected also exceeds the State ' Secondary MCL of 5 µg/1 and the City's discharge limit of 0 5 µg/1 28699 E01 /ST03R793 Page l 1 of 16 Copyright 2003,Klemfelder,Inc July 21,2003