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103 West Eleventh Street, Tracy, California January 7, 1993 <br /> Chevron U S A Products Company Page 5 <br /> 37 Monitoring Well Development <br /> Following well installation the new monitoring wells were developed to remove fine-grained sediments <br />' from the well and filter pack Approximately 30 gallons of water was extracted from each well using <br /> surge and bailing methods This technique insures an even sand filter pack, removes fines, and <br /> rehabilitates the borehole sides The fines are drawn from the well by the bailer until the well water is <br /> visibly clear Purge water generated during the development process was stored in a DOT-approved <br /> purge water trailer and transported to the Chevron refinery in Richmond, California for recycling <br /> 3.8 Groundwater Monitoring <br />' On December 14, 1992, the water table in the three new monitoring wells was gauged to determine <br /> the static level and thickness of any separate-phase hydrocarbons (SP) The water table level was <br />' measured using an ORS Environmental Equipment INTERFACE PROBETm Well Monitoring System, <br /> consisting of a dual optical sensor and electrical conductivity probe that distinguishes between water <br />' and petroleum products No SP was present The data revealed a northeast groundwater flow <br /> direction at a gradient of 0 003 (Figure 3) <br /> r39 Groundwater Sampling <br /> Prior to sampling, the wells were purged of a minimum of four well casing volumes using a small <br />' diameter submersible pump Conductivity, pH and dissolved solids were also measured during <br /> purging The groundwater samples were collected under the observation of an on-site representative <br /> of SJCDEH using a Teflon sampler cleaned with an industrial-strength detergent and distilled water <br /> Immediately prior to the collection of the water samples, a distilled water ansate blank was collected <br />' from the Teflon sampler as a quality control check on the cleanliness of the sampler A trip/lab <br /> blank was also collected for quality control Each sample was acidified, labeled, and placed on ice in <br /> an insulated container for delivery to a State-certified laboratory The samples were accompanied by <br /> a chain-of-custody manifest during transport and analyzed for TPH-G and BTEX by EPA methods <br /> 5030/8020/8015 Purge water generated during the sampling process was stored in a DOT- <br /> approved purge water trader and transported to the Chevron refinery for recycling <br /> GROUNDWATER <br />' TECHNOLOGY <br />