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TREVOR SANTOCHI <br /> PAGE 3 <br /> of this data would be helpful. <br /> Because the well screen intervals have been substantially under the water table <br /> during this investigation, purging of the wells has always been conducted by hand <br /> bailing, and no data is available to determine if any drawdown occurred during <br /> purging, it cannot be determined whether the water samples collected from the wells <br /> represent the water table area or the deeper area where the wells are screened. <br /> Therefore, PHSIEHD recommends gathering additional data from the existing wells <br /> utilizing a pump that could draw down a sufficient amount of water so that <br /> representative water from the water table would be brought into the well to be <br /> sampled. Continuous depth to water measurements taken during the purging process <br /> will give an indication of the amount of drawdown actually being experienced in the <br /> well. However, without an actual pump test, the area of drawdown influence may be <br /> unknown or difficult to determine. <br /> Please be advised that there has been only one excavation attempt at this site and <br /> that activity occurred in March of 1993. All other soil samples obtained from the tank <br /> pit cavity prior to this date were taken by simply moving the soil in the pit around. <br /> The stockpiled soil that was at the site prior to the excavation date was generated <br /> from the original tank removals in June of 1990. In fact, the tank pit cavity had been <br /> open since June of 1990 until it was backfilled after the March 1993 excavation <br /> activities. The groundwater data gathered in March of 1993 was obtained before the <br /> excavation and backfilling of the tank pit took place. It may be helpful to evaluate <br /> and discuss the possible influence the removal of the bulk of the impacted soil and <br /> the subsequent backfilling of the tank pit had on the contaminant concentrations at <br /> the site. <br /> If you have any questions or would like to discuss this letter in more detail, please <br /> call me at (209) 468-3441. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> I <br /> Linda Turkatte, Senior REHS Diane . Hinson, REHS <br /> Site Mitigation Unit Supervisor <br /> LT <br /> C' CVRWQCB-Beth Thayer c: CRC Environmental-Jim Phillips <br /> c: New West Federal-Kathleen Schnieder c: SEACOR-Richard Casias <br />