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' Fuller Mobile glome Park 365 F_ Louise Ava,Lathrop, California February 23, 1995 Phase HSite Characterization- Continued Page: 5 ' tested only if their corresponding samples were found to contain contaminants Immediately prior to sampling, water levels and well depth measurements were taken in all wells at the site Each well was evacuated using a stainless steel bladder pump (which does not introduce air into the water column) or a Teflon bailer The pH, temperature, and electrical conductivity of the water was monitored as the well was evacuated, and were noted on the field logs (Table 3 & Appendix D) Instruments calibrated to known standards were used to monitor these parameters At least five well volumes (or more, if necessary) were evacuated from each well until the above parameters became stable Wells that are de-watered before the evacuation of five well volumes had been accomplished were sampled upon eighty percent recovery of the initial water level The wells or other sampling points were sampled in the order of least contaminated to most contaminated, as best known or estimated The samples were pumped from a stainless steel bladder pump or carefully poured from a Teflon bailer into clean glass vials with Teflon-lined screw caps and half gallon plastic containers provided by the laboratory Care was taken to ensure that no air space existed in the vials by inverting to check for bubbles and re-sampling if necessary tThe samples were analyzed or extracted within 14 days according to their EPA methods Water samples collected for analysis were analyzed by EPA method 602 for BTX&E compounds, method 5030/modified 8015 for gasoline range hydrocarbons and method 3510 for diesel range hydrocarbons The minimum detection limits used for each analyte were 0 3 uglkg for BTX&E, 0 5 mg/l for gasoline and 0 1 mg/kg for diesel Analyses were conducted by GeoAnalytical, Inc of Modesto, California, a State-certified laboratory 4.0 Soil Conditions The subsurface lithology of the Fuller Mobile Home Park site in Lathrop, California, is characterized by silty, clayey sands with thin interbedded silts and clays This is typical of the valley fill deposits in the region Analyses of soil samples show BTEX, Gasoline & Diesel contamination in the samples below 10 feet, except for one isolated gasoline analysis at five feet in MW-2 This sample was probably from wood cutting (chainsaw) activities and shop/garage activities immediately adjacent to the well No BTEX or Diesel contamination was detected (Table 2) Lithologic cross-sections were constructed from data from all borings (Figures 5 & 6) Contamination cross-sections were constructed from analytical data from all borings