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Evaluation of-Natural Attenuation: 7500 West Eleventh Street, Tracy, CA. Page 17 <br /> which the well is installed. To monitor the recovery times for the purged wells SJC used <br /> the conductivity water depth probe and a stopwatch. The observations made are presented <br /> in the Field Notes in Appendix B. <br /> ;. i <br /> IJ <br /> In the preponderance of the wells, water levels recovered within 6-9 minutes. However, <br /> =: some, notably MW-6 and MW-12, recovered in less than 3 minutes while others, most <br /> notably MW-15, required in excess of 30 minutes to recover. These variations reflect the <br /> differences in the mean hydraulic conductivity of the local stratigraphy in which they are <br /> installed and are consistent with the stratigraphic interpretations shown on the cross- <br /> sections presented in Figures 6 and 8. <br /> 4.3.3 Disposal of Purge Water <br /> 'a <br /> For economy and efficiency, purge water will be held in the 1,100-gallon storage tank <br /> located on the Navarra Site until the storage tank is full. It will then be discharged into a <br /> -= vacuum truck and transported to a recycling facility, where the petroleum hydrocarbons <br /> will be recycled into beneficial use before the cleaned water is discharged. <br /> 4.3.4 Groundwater Sampling and Analyses for Components of Fuel Hydrocarbons <br /> J After purging, samples were recovered from the 27 Monitoring Wells on the site using <br /> disposable bailers. Water brought to the surface in the bailers was decanted via a <br /> discharge spigot valve placed in the bottom of the bailer so as to completely fill clean <br /> ._� glassware supplied by the laboratory containing, where applicable, pre-dispensed <br /> - preservatives. The sample vials were then tightly closed, labeled for identification, <br /> entered into chain-of-custody control and packed on chemical ice for transport,within ten <br /> hours, to Severn Trent Laboratories' (STL) laboratory in Pleasanton, California for <br /> analysis. <br /> Each groundwater sample recovered was analyzed at the laboratory for the following <br /> suite of analytes. <br /> F Analyte Method of Analysis <br /> F.7' Total Petroleum Hydrocarbons EPA Method 8015M <br /> (quantified as Diesel) with pre-treatment by <br /> -' EPA Method 3630. <br /> Total Petroleum Hydrocarbons EPA Method 8260B <br /> �--:i <br /> (quantified as Gasoline) <br /> LJ <br /> Benzene EPA Method 8260B <br /> Toluene EPA Method 8260B <br /> Ethyl benzene EPA Method 8260B <br /> sic <br />