Laserfiche WebLink
was 1 2 ppb 1,2-DCA in the groundwater sample collected from 83-feet <br /> bgs in boring CPT-23 No 1,2-DCA was detected in groundwater samples <br /> collected from any of the shallower zones in this boring <br /> 12 -2 HVdrogeologic Factors Involyina the Migration of Contam.)Datio <br /> There is a consistent zone of high permeability soil shallower than 20- <br /> feet bgs throughout the area, and another consistent zone of high <br /> permeability from as high as 30-feet bgs to a depth of at least 40-feet <br /> bgs Beneath the second zone of high permeability, the layers become <br /> highly variable with some areas exhibiting a high number of layers of <br /> various permeability and other areas exhibit predominately low <br /> permeability soils In general, there are fewer high permeability layers <br /> below 55-feet bgs farther to the north away from the site There are also <br /> fewer high permeability layers at depth to the northeast These areas o f <br /> low permeability to the northeast may be a barrier for the migration of <br /> MTBE at these depths It is likely that the domestic wells in that area are <br /> deeper, which may explain why few wells to the northeast of 17886 <br /> Airport Way contain detectable contamination <br /> 12 .3 Effectiveness of Groundwater Remediation <br /> Since late September 2000, ASE has been operating an interim "pump a n d <br /> treat" groundwater remediation system at the site The purpose of this <br /> remediation system is to capture contaminated groundwater prior to it <br /> leaving the site to the north Analytical results for the groundwater <br /> monitoring wells north of the site, along the northern shoulder of West <br /> Yosemite Avenue, have in general, shown a decreasing trend in <br /> concentrations since the beginning of remediation This does show that <br /> the system has been successful in the control of the plume migration off- <br /> site However, borings drilled during this assessment west of the line of <br /> recovery wells show significant groundwater contamination beyond the <br /> calculated capture zone for the existing recovery wells Additional <br /> recovery wells will be required west of the existing recovery wells to <br /> further assist in the groundwater remediation effort at the site <br /> 12 .4 Extent aDd source of 1,2-DC:A <br /> None of the on-site soil or groundwater samples collected to date <br /> contained 1,2-DCA in addition, 1,2-DCA has not been detected in <br /> groundwater samples collected from the wells on the north shoulder of <br /> West Yosemite Avenue, downgradient of the site The closest boring that <br /> has contained a concentration of 1,2-DCA is boring CPT-26, on the vacant <br /> Franks One Stop Report — March 2001 <br /> -21 - <br />