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The potentiometeric surface elevation is calculated as TOC -DTW + 0 74PT Where TOC =top-of-casing elevation, DTW= depth to water(interface), and PT=PSH thickness If PSH thickness is less than 0 02 foot,and the well is planned for purging prior to sample collection, the well is purged and sampled in accordance with the sample collection section of this SOP If the PSH thickness is 0 02 foot or greater,the PSH is bailed from the well, and left onsite in a labeled and sealed container No sample is collected for analysis from wells having a PSH thickness of greater than 0 02 foot 4. No-Purge Sampling Well purging is not conducted prior to sampling if purging is not needed to meet technical and/or regulatory project requirements Following collection of water level measurements,wells that are not purged are sampled according to the protocol in the sample collection section of this SOP 5. Purging Procedures Well purging is conducted prior to sampling if purging is needed to meet technical and/or regulatory project requirements If purging is conducted, the monitoring wells are purged using a vacuum truck, submersible electric pump, bailer, hand pump,or bladder pump, as appropriate for site conditions A surge block may be used if it becomes apparent during purging that the well screen has become bridged with sediment or the produced groundwater is overly turbid During the purging process,groundwater is monitored for temperature, pH,conductivity, turbidity, odor, and color These parameters are recorded on a water sample log Purging continues until all stagnant, water within the wells is replaced by fresh formation water, as indicated by removal of a minimum number I of well volumes and/or stabilization of the above-outlined parameters Sampling is performed after the well recharges to at least 80 percent of hydrostatic Purge water is stored on site in Department of Transportation-approved, 55-gallon drums until water sample analytical results are received from the laboratory If active groundwater treatment is occurring at the site, purge water may be disposed of through the treatment system, or the purge water may be transported off site as non-hazardous waste to an approved off-site disposal facility If permanent pumps are installed in the wells for groundwater remediation, purging may be accomplished by operating the pumps for at least 24 hours before sampling to ensure adequate purging i Mmft\D%nwonmenta[\ParmarTexaco\Reports\SARI203 wpd