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. Ms Margaret Lagorio Protect 20805-152 008 <br /> October 12, 1998 <br /> Page 5 <br /> may have influenced migration of vadose zone impacts laterally and vertically away from <br /> the on-site source areas Other factors that may influence the distribution of impacts may <br /> include root cavities and small-scale fractures present within the silt units <br /> Groundwater was not encountered in on-site and off-site soil borings and the vertical <br /> extent of soil impacts has been defined The estimated depth to groundwater of <br /> approximately 396 feet bgs is separated from the hydrocarbon mass by approximately 270 <br /> Leet of geologic matenals The paved site property and Patterson Pass Road provide a cap <br /> overlying the on-site and off-site hydrocarbon mass and reduce the potential for <br /> infiltration of precipitation in the areas with greatest impact <br /> SJCPHS LOW RISK CRITERIA <br /> The SJC PHS low risk soil closure case criteria state that no further action is required <br /> when the following conditions are met <br /> • The leak has been stopped and ongoing sources have been removed or <br /> • remediated <br /> • The site has been adequately characterized <br /> • No groundwater or surface water impact currently exists No water wells, deeper <br /> drinking water aquifers, surface water, or sensitive receptors are likely to be <br /> impacted <br /> The site meets these low risk criteria The USTs, piping and dispenser replacement <br /> removed the source of the prior release The remaining hydrocarbon mass is defined and is <br /> separated from the water bearing strata by approximately 270 feet of geologic materials <br /> It does not appear that the site represents a threat to groundwater, therefore, Pinnacle is <br /> requesting site closure be granted ARCO intends to keep on-site vapor extraction wells in <br /> service for potential future use therefore, the quarterly status reporting should be replaced <br /> with an annual well head inspection and reporting event Pinnacle also recommends <br /> proceeding with proper abandonment of off-site vapor extraction wells <br /> sAc'1c\Sci\2NDQ-R-i161ooMAss DOC-461mtt 1 <br />