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I LEEDSNILL-NERREkNo". INC_ Reference point (RP) elevations were established by licensed surveyors to within 0.01 foot at each of the monitoringwells. All and subsequent calculations are baed on these RPrsundwater level measurements 4. 2 GROUNOWATER SAMPLING As mentioned in Section 3 .1 Soil Sampling, grab water samples were collected on September 5 and 6, 1990 from soil borings SBI , SB4, and SB6 using either a bailer or a "hydropunch" . On October 1 , 1990, representative groundwater samples were collected from each of the monitoring wells using established protocol as specified in the USGS "National Handbook of Recommended Methods for Water Data Acquisition, " which provides guidelines for the collection of representative groundwater samples. The monitoring wells were sampled with a 3-inch diameter acrylic bailer. Several well volumes of water were removed prior to sampling, while field measurements of conductivity, pH, temperature, and visual observations were made to ensure the collection of stable, representative groundwater samples. Quantitative groundwater sampling field data sheets are included in Appendix E. All sampling equipment was cleaned with a trisodium phosphate (TSP) and water solution before sampling each monitoring well to prevent potential cross- contamination. Water samples were collected in sterile sampling labeled and preserved according to standard EPA ethds. All nsamples were rcooled to 4 degrees Celsius at the site and maintained at that temperature until received at the laboratory within 24 hours of collection under appropriate chain- of-custody procedures, and extracted prior to expiration of approved holding times. Chain-of-custody forms are presented in Appendix E. 4.3 SAMPLE ANALYSIS Groundwater samples were collected on September 5 and 6, 1990, from soil borings SBI using a hydropunch and SB4 and SB6 using a bailer. These samples were analyzed for benzene, toluene, ethyibenzene, and xylene (BTX&E) , total petroleum hydrocarbons (TPH) as gasoline and diesel , and total dissolved solids (TOS) . On October 1 , 1990, one week after well development, groundwater samples were collected from the monitoring wells and analyzed for BTX&E, TPH as gasoline, TDS, and total coliform. The analytical methods referred to above conform to EPA Test Methods for Evaluating Solid Waste: Physical Chemical Method (SW-846, 2nd Edition) , Methods for Organic Chemical Analysis of Municipal and Industrial Wastewater, USEPA 600- 14-057, applicable methodologies from Standard Methods for the Examination of Water and Wastewater, 16th Edition, and/or as specified in the Leaking Underground Fuel Tank Manual (LOFT) , modified EPA SW-845 Method 8015. i 18