ARCHIVED REPORTS_XR0011186 - Laserfiche WebLink

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i . ATTACHMENT V WELL SAMPLING,DECONTAMINATION,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. If the measured water level in the well is below the top of casing elevation, the well may be sampled without purging. For non-purge wells, one set of water quality parameters are collected and the well is sampled with a disposable bailer. Wells not containing SPH that do not qualify as non-purge wells are purged of approximately three casing volumes of water (or to dryness) using a submersible pump, centrifugal pump, gas displacement pump, or bailer. The optimal purging rate is approximately 1 gallon per minute. The equipment and purging methods used for the current sampling event are noted on the attached field data sheets. During purging, temperature, pH, electrical conductivity, and dissolved oxygen 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 clean disposable TeflonO bailer, placed into appropriate EPA-approved containers, labeled, logged onto chain-of-custody documents, and transported on ice to a State of California-certified laboratory. Decontamination Procedures Prior to sampling each well, reels and pumps are decontaminated with a steam cleaner. Sensitive equipment such as the water level sounder are sprayed with a non-phosphate soap and deionized water solution and rinsed with deionized water. All water used for equipment decontamination is collected and contained in a truck-mounted water tank. Laboratory Procedures The groundwater samples are analyzed for the presence of TPHg, benzene, toluene, ethylbenzene, xylenes (total), and MtBE using EPA Methods 8015 (modified) and 8021, and fuel oxygenates using EPA Method 826013. The methods of analysis for the groundwater samples are documented in the certified laboratory analytical report.