CORRESPONDENCE_2008-2010 - Laserfiche WebLink

Home Browse Search

URS Mr. Robert McClellon January 31,2008 Page 2 samples confirmed the presence of VOCs where the total VOC concentration in each of the vapor extraction wells was less than 5 ppmV. Based on these results,VOC constituents could 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 the installation of the groundwater monitoring wells, groundwater samples were collected quarterly and analyzed for VOCs. Mr. Ross Atkinson of the Regional Water Quality Control Board(RWQCB)Central Valley Region requested that groundwater samples be collected and analyzed for metals and general minerals (only total dissolved solids [TDS] after the first event)starting the fourth quarter of 2006. In a meeting on May 24, 2007,Mr. Atkinson concurred with the recommendation in the Quarterly Monitoring Report dated April 30, 2007,to suspend the groundwater monitoring for VOCs. FIELD ACTIVITIES Landfill gas concentrations were measured within the gas-migration monitoring probes,extraction wells, and passive vents and the quarterly groundwater monitoring activities were completed on December 13,2007. Using a handheld portable landfill gas monitor(a GEM 2000) each gas-migration monitoring probe, extraction well, and passive vent was measured for methane, oxygen,and carbon dioxide. These measurements were recorded in a field logbook. 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 Data 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, collected from each well using a bailer was placed into the analytical laboratory-prepared sample containers. • Groundwater samples were labeled and placed in an ice chest with ice.The ice chest was shipped to EMAX analytical laboratory in Torrance, California, under proper chain-of-custody procedures for dissolved metals (CAM 17)by U.S. Environmental Protection Agency(EPA)Method 6010/6020/7470 and TDS by EPA Method 160.1. RESULTS Soil Vapor. The methane concentrations measured during the quarter in the gas-migration monitoring probes were 0.3% in VW-1, 0.3% in VW-2, 0.3% in VW-3, 0.3% in VW-4, 0.3% in VW-5S, 1.0% in VW-5D, 2.8% in VW-6S, 1.6% in VW-6D, 0.2% in VW-7S, 0.3% in VW-7D, 0.3% in VW-8S, 0.3% in VW-8D, 0.3% in VW-9, and 0.3% in VW-10. The methane concentrations measured in the vapor K:\Wprocess\25532\WorldEnterprise\Quarterly Rpt\2007\4Q07\CovLtrRpt.doc