ARCHIVED REPORTS_2008_20 - Laserfiche WebLink

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uRWARD LANDFILL 9999 S. Austin Road Manteca, CA 95336 (209) 982-4298,Fax(209) 982-1009 cover. Historically, similar exceedances of inorganic CLs have been measured and verified in samples collected from detection monitoring program(DMP)monitoring wells at the Forward Unit, followed by no release demonstrations(NRDs),which have concluded that the inorganic CL exceedances are likely the result of naturally occurring conditions and therefore not indicative of a release from the Forward Landfill. On behalf of Forward, GLA has submitted a request to the DISC to-update the CLs for the Forward Unit. During the fourth quarter 2008 monitoring period the leachate results are generally similar to those observed historically. During the fourth quarter 2008 monitoring period, eight dissolved metal constituents were measured with six above their PQL; nine VOCs were measured with eight above their PQL; and eight SVOCs were measured with six above their PQL in the leachate sample collected during the fourth quarter 2008 monitoring period. No herbicides or pesticides were detected in the leachate sample. The results of the annual leachate sample indicate that there was one potentially new constituent of concern(COC) (2,4-dichlorophenol). Verification testing of leachate for this SVOC (2,4-dichlorophenol)will be performed in May 2009. During the fourth quarter 2008 monitoring period, methane concentrations did not exceed the regulatory limit of five percent in perimeter soil-pore gas probes at the Forward Unit. Forward continues to install additional landfill gas extraction wells(as needed),and makes regular adjustments to the landfill gas extraction system to optimize efficiency of the landfill gas extraction system. Groundwater quality conditions beneath the Austin Unit during the fourth quarter 2008 monitoring period are generally similar to historical results. Excluding suspected field/laboratory contaminants, CLs were exceeded in DMP wells AMW-6,AMW-7, AMW-13, and AMW-14. However,none of the CL exceedances exhibited statistically significant increasing trends. In the CAP wells,trend analyses are performed instead of comparison to CLs. During the current monitoring period,one or more statistically significant increasing trends were noted for VOC constituents in CAP wells AMW-1, AMW-10, and AMW-19,while decreasing VOC trends were noted in CAP wells AMW- 4,AMW-5/5R,AMW-10, and AMW-1 1. The increasing vinyl chloride and/or cis-1,2- DCE trends in wells AMW-I and AMW-10 suggest that active reductive dechlorination is occurring in the vicinity of these wells. During the fourth quarter 2008 monitoring period the leachate results are generally similar to those observed historically. During the fourth quarter 2008 monitoring period, nine dissolved metal constituents were detected with five measured above the PQL; two VOCS were detected with one measured above the PQL; and one SVOCs (bis[2- ethylhexyl]phthalate),a confirmed laboratory contaminant, was measured. No pesticides,or herbicides were detected in the leachate sample collected during the fourth