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%WW -.. frame as possible, and before the first well is purged. Measurements are taken from a point of known elevation on the top of each well casing as determined in accordance with surveys by licensed land surveyors. Groundwater Monitoring Well Purging Groundwater wells are purged using low-flow protocol at a flow rate of less the 1 liter per minute using a bladder pump. The purge intake is placed opposite the portion of the saturated zone expected to contain the greatest hydrocarbon impact, and the depth of the purge intake is recorded during and after purging. The water level in each well is monitored, and care is taken that the well is not dewatered. The conductivity, temperature, and pH of the delivered effluent are monitored and recorded using a flow- through cell during purge operations. Purge operations are determined to be sufficient once three successive measurements of pH, conductivity, and temperature of the purged water at 3 to 5 minute intervals following the evacuation of on system or line volume vary by s 0.1, s 3%, and s 10%, respectively. System or line volumes, actual purge volumes, and the purging equipment used are recorded on the field data sheets. Groundwater Sample Acquisition, Handling, and Analysis Following purging operations, groundwater samples are collected from each of the wells, using a low- flow bladder pump.The groundwater sample is discharged from the pump tubing to the sample container before the water passes through the flow-through cell. The sampling equipment is recorded on the field data sheets. �— Collected water samples are discharged directly into laboratory provided, pre-cleaned, and chemically preserved sample containers for the analyses requested. Preservatives are used in the samples if appropriate for the analyses, i.e.,hydrochloric acid(HCI)for TPPH,BTEX,and fuel oxygenates by EPA Method 8260B. Labels documenting sample number, well identification, collection date and time, type of sample and type of preservative(if applicable)are affixed to each sample. The samples are then placed into an ice- filled cooler for delivery under chain of custody to a certified laboratory.The type of preservative used is documented on the chain of custody form. To help assure the quality of the collected samples and to evaluate the potential for cross contamination during transport to the laboratory, a distilled-water trip blank accompanies the samples in the cooler.The trip blank is analyzed for the presence of volatile organic compounds of concern.For _ petroleum hydrocarbons,the trip blank is typically analyzed for TPPH,BTEX, and fuel oxygenates by EPA Method 8260. Organic Vapor Procedures Soil samples are collected for analysis in the field for ionizable organic compounds using a PID with a 10.2 eV lamp. The test procedure involves measuring approximately 30 grams from an undisturbed �. soil sample, placing this subsample in a ZiplocTM-type bag or in a clean glass jar, and sealing the jar with aluminum foil secured under a ring-type threaded lid. The container is warmed for approximately 20 minutes (in the sun); then the head-space within the container is tested for total organic vapor, _ measured in parts per million as benzene (ppm; volume/volume). The instrument is calibrated prior to drilling. The results of the field-testing are noted on the boring logs. PID readings are useful for indicating relative levels of contamination, but cannot be used to evaluate petroleum hydrocarbon levels with the confidence of laboratory analyses. Workplan for Decommissioning Monitoring Well MW-4 SOMA Environmental Engineering, Inc.