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Meeting Notes <br /> May 13, 2020 <br /> Subject/Client: Tosco/Unocal#05643 Ref. No. 11193145 <br /> 1502 El Dorado St, Stockton <br /> Central Valley RWQCB Case#391068 <br /> From: Morgan Hargrave Tel: (530) 387-5712 <br /> Venue/Date/Time: Teleconference <br /> Copies To: Central Valley Regional Water Quality Control Board <br /> Attendees: Vera Fischer/Christopher Flower <br /> Ryan Bast/Morgan Hargrave <br /> On May 13, 2020, GHD hosted a teleconference meeting to discuss current site conditions and the path to <br /> case closure.Attendees included Vera Fischer and Christopher Flower from the Central Valley Regional <br /> Water Quality Control Board (CVRWQCB), and Ryan Bast and Morgan Hargrave from GHD. Topics <br /> discussed during the meeting are summarized below. <br /> MW-24 Analytical Results <br /> • New B' Zone monitoring well MW-24 was installed to the east of the site to provide additional <br /> delineation to define the extent of the release to water quality objectives (WQOs) in the B' Zone. <br /> • Concentrations of TPHg (870 pg/L), benzene (78 pg/L), MTBE (43 pg/L), and 1,2-DCA(4.8 pg/L) <br /> were detected above WQOs, indicating the B' Zone plume may not be defined. <br /> • Further sampling events are required to confirm the initial concentrations. <br /> 1,2-DCA Concentrations and Delineation <br /> • In a letter dated March 26, 2020, CVRWQCB staff requested that 1,2-DCA plume maps be <br /> included in future groundwater monitoring and sampling reports. <br /> • 1,2-DCA plume maps were included in GHD's April 16, 2020 First Semi-Annual 2020 <br /> Groundwater Monitoring Report. <br /> • The plume maps indicate that additional wells are required to the north and northeast of the site to <br /> provide additional plume delineation to define the extent of the release above WQOs in the B and <br /> C Zones. <br /> • One B Zone well should be sited along or within Sperry Avenue, east-northeast of well MW-14. <br /> GHD <br /> 4080 Plaza Goldorado Circle Suite B Cameron Park California 95682 USA <br /> T 530 677 5515 W www.ghd.com <br />