Laserfiche WebLink
Project No S8100-06-IIA <br /> June 29, 1995 <br /> • Groundwater exits beneath the project boundaries at a depth of approximately 19 5 meters (64 <br />' feet) bgs with a general flow direction trending from southeast to northwest at a gradient of <br /> 0 0002 to 0 001 <br /> • Groundwater quality data indicates that dissolved TPHd, TPHg and benzene exist beneath the site <br /> at maximum reported concentrations of 600 ug/L TPHd, 28,000 ug/L TPHg and 5,300 ug/L <br /> benzene, respectively <br />' Benzene concentrations are in excess of the California Maximum Contaminant Level (MCL) of <br /> 1 0 ug/L <br />' The lateral limits of dissolved TPHg in groundwater have not been adequately delineated to allow <br /> for the implementation of a groundwater remedial action plan <br />' Additional investigation would be required to further delineate the extent of TPHg impacts The <br /> installation of four additional groundwater monitoring wells is recommended to attempt to <br /> establish the lateral extent of TPHg impacts <br /> • Initial evaluation of groundwater remediation options indicates that several feasible alternatives <br /> exist to facilitate groundwater restoration Site specific data collected to date indicates that <br /> groundwater extraction and treatment (pump and treat), in-situ bioremediation and air spargmg <br /> remain as feasible groundwater remediation alternatives <br /> ' 72 ADDITIONAL INVESTIGATIONS REQUIRED <br /> The source area and the extent of impacted soil is limited to the vadose zone soil beneath the former UST <br /> locations A minimum of one additional soil boring within the former UST excavation would be required <br /> ' in order to better estimate the volume of vadose zone soil impacted with TPHg and to estimate the <br /> resulting mass of TPHg <br /> Petroleum hydrocarbon impacts to groundwater were identified in the five new groundwater monitoring <br /> wells Additional investigation would be required to further delineate the extent of petroleum hydrocarbon <br /> impacts to groundwater The installation of four additional groundwater monitoring wells is recommended <br /> ' to attempt to establish the lateral extent of TPHg impacts <br /> 73 DISCUSSION OF REMEDIAL OPTIONS <br /> Environmental studies performed at the site indicate that petroleum hydrocarbons exist in vadose zone soil <br /> and groundwater beneath the site Presented below are discussions of the remedial options typically <br /> ' employed for soil and groundwater impacted with petroleum hydrocarbons <br /> 13 <br />