ARCHIVED REPORTS_DRYWELL CLOSURE AND INVESTIGATION

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W I^'r 0A I NOA Drywell Closure and Investigation Page 23 of 2!, �V19 May 30, 2014 U_Tl lµ 4 TCLP limit, 0.5 mg/L. This concentration of Trichloroethene is belo Hazardous Waste TCLP ' limit. The TPH-Gas concentration does not need exceed the threshold for disposal at a standard MSW Type I Landfill. Therefore, soil can be disposed of as non-hazardous waste in accordance with federal regulations. ' A Total Analysis determines the total concentration of a constituent present in a sample. In contrast, a TCLP analysis is used to determine if a material will leach chemicals into soil or groundwater and therefore determines toxicity for waste to be disposed of at a landfill. The ' results of a TCLP extraction test report the concentration of constituents that leached out of the solid. In the TCLP procedure, the original sample is diluted with acidic extraction fluid at a volume that equals 20 times the weight of the sample. The concentration of total constituents in the original sample cannot be determined. ESLs and Regulatory Limits are prepared considering Total Analysis. Therefore, TCLP results should not be compared to ESLs or Regulatory Limits. Furthermore, this value should not be considered the concentration of chemicals that would leach into groundwater in non-landfill conditions. The extraction fluid used for the TCLP method is highly acidic because it is intended to simulate rainwater infiltrating a landfill, reacting with waste, and then leaching through waste; it is not comparable to rainwater infiltrating the subsurface in normal conditions such as those at the subject property. As discussed above, comparison with Hazardous Waste limits, as intended for TCLP analysis, indicates that the samples are non-hazardous waste. Forward Landfill, Inc. in Manteca, California required further analysis for waste profiling in accordance with California State regulations. Two (2) composite samples were analyzed for ' CAM-17 Metals by the Total Threshold Limit Concentration (TTLC) method. This method is used to characterize hazardous waste under California State Regulations. TTLC determines the total concentration of each target analyte in a sample. If a target analyte exceeds the TTLC limit, the waste is classified as hazardous. If the target analyte is more than ten (10) times the STLC limit, a STLC analysis is necessary to determine whether the waste is hazardous. If the TTLC value is less than ten (10) times the STLC limit, the waste is not hazardous and no further analysis is required. None of the total concentrations of metals are above the Hazardous Waste TTLC limit or STLC Threshold (10 x STLC limits). Therefore, the soil was classified as non- hazardous waste and was accepted by Forward Landfill, Inc. in Manteca, California. ' 6.0 CONCLUSIONS .fid t, g'(. No soil samples collected beneath the drywells contain chemical concentrations above any ' regulatory limits or background 'levels. Groundwater collected beneath DW-1 at 75 feet bgs contains elevated levels of Total Petroleum Hydrocarbons (TPH) as Diesel and Total Recoverable Petroleum Hydrocarbons (TRPH). Groundwater collected beneath DW-2 at 58.5 ' feet bgs also contains elevated levels of TPH as Diesel, although at a significantly lesser concentration than in DW-1. Groundwater encountered in DW-1 is likely the regional aquifer, SC wo e and groundwater encountered in DW-2 is likely a perched lens. The perched lens and the °fe'ckeo,' w,lc regional aquifer are interpreted to be separated by an impermeable aquitard. t` wwa+ ,�vuh As discussed above, no soil samples analyzed are impacted with C PCs. Of particular note, the COPCs identified in groundwater, TPH as Diesel and TRPH, are not etected in any soil samples above regulatory limits. The soil sample collected at 60 feet bgs i DW-2 is the only soil sample t Q'e41ey s VSA o+ ' 902 Industrial Way•Lodi, CA 95240•209.367.3701 • Fax 209.333.8303 02014 Neil 0.Anderson&Associates,Inc.