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I Mr. Robert McClellon January 29,2016 Page 2 monitoring wells were installed at the site on June 12, 2006. Following the installation of the ground- water monitoring wells, groundwater samples were collected quarterly and analyzed for VOCs.Mr. Ross Atkinson of the Regional Water Quality Control Board, Central Valley Region(CVWB),requested collecting and analyzing groundwater samples for metals and general minerals(only total dissolved solids [TDS] after the first event)starting in 4Q06. During a meeting on May 24,2007, Mr. Atkinson concurred with the recommendation in the Quarterly Monitoring Report dated April 30, 2007,to suspend groundwater monitoring activities for VOCs because VOC analysis results were similar in magnitude during the past 4 quarters,and these results were less than their respective established levels. In the IQ I letter report to SJCEHD dated April 29,2011, URS recommended reducing the frequency of monitoring from quarterly to annually because the results of monitoring activities for measuring methane gas concentrations in monitoring probes had been less than 5%by volume since December 2006 (following installation of the passive soil vapor extract trench). SJCEHD agreed with URS' recommendation. The annual monitoring activities are usually conducted during the fourth quarter of each year. In a letter to CVWB dated May 20, 2011, URS recommended no further action for groundwater activities.CVWB agreed that on-site groundwater issues had been resolved to their satisfaction and issued a letter to proceed with well decommissioning on December 2, 2011. URS decommissioned the groundwater monitoring wells on December 9, 2012. FIELD ACTIVITIES Annual Monitoring Activities On December 3,2015, URS measured landfill gas concentrations(i.e.,methane, oxygen,and carbon dioxide)using a handheld portable gas monitor,a GEM 2000,within the gas migration monitoring probes(VW-1 though VW-10),extraction wells(EW-1 and EW-2), and passive vents(VP-1 through VP-4). URS recorded these measurements in the project logbook. RESULTS The methane concentrations measured during the quarter were 0%in all gas-migration monitoring probes. Methane concentrations measured in the vapor extraction wells were 0.5%in EW-1 and 4.9% in EW-2. Methane concentrations measured in the passive vents were 0.3%in VP-1, 1.0%in VP-2, 2.1% in VP-3,and 5.8%in VP-4. Oxygen concentrations measured at all sample locations during the quarter ranged from 0.0%to 19.4%. Carbon dioxide concentrations measured at all sample locations during the quarter ranged from 0.3%to 27.9%. Table 1 summarizes results for each probe, each extraction well,and each passive vent.