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Report:Groundwater-quality Monitoring—October 27,2004, 7500 West Eleventh Street, Tracy, Cr1. Page 10 <br /> are lighter than water, regardless of the temperature, conductivity and pH data obtained, <br /> to purge a minimum quantity of groundwater equal to the casing volume plus the void <br /> space in the annular filter pack between the casing and the borehole wall. That volume(in <br /> this case, 15 gallons) is much greater than the three to five casing volumes that is often <br /> erroneously considered to be sufficient to purge adequately a well of that type and it is <br /> ,6w almost always greater than the volume that would be permissible based on the physical <br /> properties of the purge water alone. <br /> 2.2.1 Disposal of Purge Water <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 /> 2.3 Recovery of Groundwater Samples from Monitoring Wells <br /> After purging, samples were recovered from the 22 Monitoring Wells MW-1 through <br /> MW-19 using disposable bailers. Water brought to the surface in the bailers was decanted <br /> via a discharge spigot valve placed in the bottom of the bailer so as to completely fill <br /> clean 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 /> 2.4 Analyses of Groundwater Samples <br /> Each groundwater sample recovered was analyzed at the laboratory for the following <br /> suite of analytes. <br /> Anal e Method of Analysis <br /> Total Petroleum Hydrocarbons EPA Method 8015M <br /> (quantified as Diesel) with silica gel cleanup <br /> Total Petroleum Hydrocarbons EPA Method 8260B <br /> (quantified as Gasoline) <br /> bpw <br /> Benzene EPA Method 8260B <br /> Toluene EPA Method 8260B <br /> Ethyl benzene EPA Method 8260B <br /> Total Xylene Isomers EPA Method 8260B <br /> sic <br />