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URS Mr. Robert McClellon April 30,2007 Page 2 extraction wells was less than 5 ppmV. Based on these results,there was a potential for VOC constituents to be present in groundwater.To assess the presence or absence of VOC constituents in the groundwater,three groundwater monitoring wells were installed at the site on June 12, 2006.Following installation of the groundwater monitoring wells, groundwater samples have been collected and analyzed quarterly for VOCs.The Regional Water Quality Control Board(RWQCB)requested that groundwater samples also be collected and analyzed for metals and general minerals beginning the fourth quarter of 2006. FIELD ACTIVITIES During the first quarter of 2007,the landfill gas concentrations were measured within the probes, extraction wells,and passive vents every two to three weeks. The quarterly groundwater monitoring activities were completed on March 14,2007. Each gas-migration monitoring probe,each extraction well,and each passive vent was measured for methane,oxygen,and carbon dioxide using a handheld portable landfill gas monitor.These measurements were recorded in a field log book. The groundwater samples were collected from the three monitoring wells using the following procedures: • The water level from each monitoring well was measured using an electronic water level sounder. • Prior to groundwater sample collection,each well was purged using a bailer. During purging,groundwater parameters (pH,temperature, and conductivity)were recorded on the Monitoring Well Sampling Log form(Attachment 1)at least once per well casing volume. Purging was completed when the groundwater parameters had stabilized to within 10 percent.The purged water was placed in 55-gallon drums. • A groundwater sample was collected from each well,using a bailer.The groundwater samples were placed into the analytical laboratory-prepared sample containers. • The groundwater samples were labeled and placed in an ice chest with ice. The samples was shipped to EMAX analytical laboratory in Torrance,California under proper chain-of- custody procedures for VOC analysis by U.S. Environmental Protection Agency(EPA) Method 8260B,dissolved metals(CAM 17)by EPA Method 6010/6020/7470,and total dissolved solids(TDS)by EPA Method 160.1. RESULTS Soil Vapor.Methane concentrations measured during the quarter in VW-1,VW-2, VW-3, VW-4, VW- 7S,VW-7D,VW-8S, VW-8D, VW-9, and VW-10 were all 0 percent. Methane concentrations for the remaining vapor probes ranged from 0%to 0.5%in VW-5S, from 0.4%to 1.0%in VW-5D, from 0.7% to 4.2% in VW-6S, and from 0.9%to 2.4% in VW-6D.