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r i3crm.xn Az lir len s YLrnm t herd Quarter 1998 L,nuindwater Momtonng NOVemhc r 23 1998 r Page 2 • Based on the results of the Geoprobe investigation Condor recommended that monitor wells be installed at the r site to Investigate and monitor the lateral extent of the gasoline, and diesel contamination plume in the groundwater On Septcmbi,r 10, 1997, Condor Installed tour monitor wells at the site The Report - Additional Sail and Groundlvalet Investigation dated December 1 l 1997, was prepared by Condor to describe the ' investigation results TPIi-G, BTFX constituents, MTBE, tertiary butanol, and tertiary amyl methyl ether (TAME) were detected in some of 111c boil and groundwater samples collected during the investigation Groundwater elevation data ' sndicated that groundwater flow at the site was probably controlled by the very active island drainage pumping system adjacent to the site 1-he above referenced report rccommcnded quarterly groundwater monitoring, surface water sampling, and Risk Based Corrective Action (RBCA) to further characterize the site and to ' evaluate options for remediation or site closure In a telephone conversation on March 23, 1998, Mr Ronald Rowe of the San Joaquin County Public health ' Services/I nvironmental Health Department (PHS/EIID) Indicated that based on his review of the report dated December 1 i, 1997 (referenced above), lie was requesting that quarterly groundwater monitoring continue at the site Furthermore, he requested that a work plan be prepared for conducting quarterly surface water sampling and additional investigation of the gasoline oxygenate/additive plume to the east of monitor well MW-2 Condor subsequently prepared the Work Plan Additional Soil and Groundwater InvestigationlSurface Water Sampling, dated May 27, 1998 In a faxed note dated June 1, 1998, Mr Rowe approved the work plan with the stipulation ' that a work plan addendum be prepared describing installation of additional borings to those proposed in the work plan and grab trampling of the Herman & Helen's Marina drinking water source Condor subsequently prepared the Work Plan Addendum, dated July 9, 1998 In a fax dated July 27, 1998, Mr Ron Rowe approved the work plan addendum adding that both the facility pre-treated drinking water and the post-treatment water should be sampled and analysed by appropriate methods A comprehensive site background is included in Appendix B 3. THIRD QUARTER, 1998, GROUNDWATER MONITORING 3.1 FIELD METHODOLOGY ' On September 30, 1998, a Condor representative was on site to conduct quarterly groundwater monitoring activities The monitoring activities included measurement of water levels in the site monitor wells and at surface water measurement stations and the collection of groundwater samples from the monitor wells All field ' equipment was decontaminated in the field with a solution of laboratory-grade, non-phosphate detergent and hydrocarbon-free water and rinsed with hydrocarbon-free water prior to use in each well All field instruments were calibrated to the manufacturer's recommended standards The water level in each well was measured to the ' nearest 0 01 foot with a battery-operated, flat-tape, water-level meter A new, disposable, polyethylene bailer was lowered into each well to collect a field-inspection sample The bailer sample was inspected for floating product, sheen, discoloration and/or odor Floating product or sheens were not observed in the groundwater ' removed from any of the monitor wells during the groundwater sampling Petroleum hydrocarbon odors were not detected in the groundwater samples collected from the four monitor wells The purging and sampling sequence for the monitor wells was MW-1, MW-3, MW-2, and MW-4 The wells were purged with a Grundfos Readiflo lI submersible pump For the purpose of evaluating intrinsic bioremediation, various parameters were monitored during the purging of each well, including dissolved oxygen, reduction-oxidation potential, pH, electrical conductivity, and temperature The purge water was discharged to ' 55-gallon drums and left on site to await disposal Groundwater Monitoring field Forms are included in Appendix C 1 ' � CONDOR