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T f <br /> • �""� 44asibility Study—Enhancement of <br /> Existing Remediation Activities <br /> 8200 N. Highway 99, Stockton, CA <br /> Page 2 of 10 <br /> • GZA agrees with. EHD and the screen intervals will be modified to I0-foot lengths. <br /> • Mr. Price discussed the screen interval modifications with Ms. Duncan on September 20, <br /> 2007. <br /> Paragraph 5: Regarding MtBE mass estimates <br /> "...Please submit the calculation and data to SJC/EHD no later than August 10, 2007". <br /> • GZA submitted the information to EHD along with the Groundwater Monitoring Well <br /> Installation and Soil Boring Permit Application dated August 1, 2007. <br /> Paragraph 6: Regarding groundwater contamination near MW 12 <br /> "A feasibility study of remediation methods...was not provided". "..While While source area removal <br /> does need to be addressed, it does not seem likely it will enhance the remediation of the <br /> groundwater contamination remaining in and near MW12, which is some distance removed from <br /> the onsite source area". <br /> • The following Feasibility Study focuses on remediation methods to enhance the cleanup of <br /> groundwater near MW 12. <br /> • After the analysis of soil samples collected from the confirmation boring near MW 1 and <br /> SB2 has been reviewed, GZA will evaluate the need to enhance remediation near the former <br /> tank pit (source area). <br /> Paragraph 7: Regarding submittal of feasibility study <br /> "Please proceed with submittal of the now overdue feasibility study for enhancement of the <br /> remediation of remaining groundwater contamination. The study should compare at least two <br /> cleanup alternatives for both cost and potential remedial effectiveness". <br /> • The following Feasibility Study addresses two alternatives (additional groundwater <br /> extraction and in-situ chemical oxidation via ozone sparging) to enhance existing <br /> remediation activities at the site. <br /> Paragraph 8: Regarding well permit application <br /> "Please proceed with submittal of a San Joaquin County well permit application..." <br /> • GZA submitted the Groundwater Monitoring Well Installation and Soil Boring; Permit <br /> Application dated August 1, 2007. <br /> • The Well Permit Application was submitted on August 1, 2007. SJC issued the permit <br /> (SR# 51533) on August 6, 2007, <br /> 1.0 REMEDIAL ACTIVITIES TO DATE <br /> Remedial actions to date have included groundwater extraction and treatment to control of migration of <br /> dissolved contaminants in the source area and downgradient of monitoring well MW 12 as well as soil <br /> vapor extraction to address both vadose soil contamination and free product in the source area. <br /> As a result of both vapor extraction and groundwater extraction, the concentrations of dissolved <br /> contaminants in groundwater at the site have decreased substantially. However, significant levels still <br /> remain and the mass-removal rate is low. We propose to improve the current groundwater remediation <br /> G:IGROUNDZEITULEBURGIReparts10709 FS rem enhancement.doc <br />