ARCHIVED REPORTS XR0000403 - Laserfiche WebLink

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FIELD AND LABORATORY PROCEDURES Sampling Procedures Sampling equipment is thoroughly cleaned prior to each sample. The sampling procedure for each well includes measuring the water level and checking for the presence of separate-phase hydrocarbons (SPH), using either an electronic indicator and a clear Teflon® bailer or an oil- water interface probe. Wells not containing SPH that do not have submerged screens are then sampled without purging. Wells that have submerged screens are purged of approximately three casing volumes of water (or to dryness) using a submersible pump, centrifugal pump, gas displacement pump, or bailer. The equipment and purging methods used for the current sampling event are noted on the attached field data sheets. During purging, temperature, pH, and electrical conductivity are monitored in order to document that these parameters are stable prior to collecting samples. After purging, water levels are allowed to partially recover. Groundwater samples (both purge and no-purge) are collected using a disposable Teflon® bailer, placed into appropriate EPA-approved containers, labeled, logged onto chain-of-custody documents, and transported on ice to a California state-certified laboratory. Laboratory Procedures The groundwater samples are analyzed for the presence of TPHg, benzene, toluene, ethylbenzene, xylenes (total), and MtBE using EPA Methods 5015 (modified) and 8020. Chevron samples were also analyzed for fuel oxygenates: methyl-tertiary-butyl-ether (MtBE), ethyl-tertiary-butyl-ether (EtBE), di-isopropyl ether (DIPS), tertiary-amyl-methyl-ether (TAME), tertiary-butyl-alcohol (TBA), 1,2 dichloroethane (1,2 DCA), and 1,2 dibromoethane (EDB), methanol, and ethanol were analyzed by EPA Method 5260. The methods of analysis for the groundwater samples are documented in the certified laboratory analytical report. Purge and Rinsate Water Disposal Water generated during well sampling and equipment cleaning for ARCO wells is pumped into a SECOR truck-mounted water tank. The water is transported to ARCO's holding tank facility in West Sacramento, California, for temporary storage. Water is then transported by Integrated Waste Management (IWM) to Seaport Environmental in Redwood City, California for disposal. Water generated during well sampling and equipment cleaning for Chevron wells is pumped into a G-R truck mounted water tank. Water is then pumped into DOT approved 55-gallon drums onsite, for temporary storage. Water is then transported by IWM for disposal at an appropriate facility.