ARCHIVED REPORTS_2013_6 - Laserfiche WebLink

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Groundwater Treatment Facility Operations The Groundwater Treatment Facility(GTF) at the Austin Unit has been operational since 1994 to mitigate impacts from landfill releases. Impacted groundwater is extracted from five wells (EW-1, EW-2, EW-3, EW-3R, and EW-4) that pump groundwater through an air stripper treatment system to remove VOCs. Treated groundwater is discharged to an infiltration pond(constructed in 2003)north of the Austin Road Unit of the Forward Landfill. Due to limited recharge in extraction well EW-3, the well was taken offline and replaced with extraction well EW-3R. To increase the volume of groundwater recovered in this area, well EW-3R was installed adjacent to and deeper than well EW-3. During the monitoring period, the GTF treated 19,184,100 gallons of groundwater at an average flow rate of 213,157 gallons per day. During the monitoring period, it is calculated that the GTF removed approximately 2.09 pounds of VOCs. 3.2 SUMMARY Groundwater quality conditions beneath the Austin Unit during the second quarter 2013 monitoring period were generally similar to historical results. During the current monitoring period, non-statistical exceedances for VOCs were identified at DMP wells AMW-6, AMW-13 and AMW-14. Trend analyses indicate that statistically significant increasing temporal trends were calculated for PCE and TCE in well AMW-13 and a statistically significant decreasing temporal trend was calculated for PCE in well AMW- 14. These results are similar to previous results and it has been recommended that wells AMW-6, AMW-13, and AMW-14 be re-designated as CAP wells since they have historically contained VOCs. For the routine inorganic monitoring parameters, CLs were exceeded for constituent concentrations in DMP wells AMW-6, AMW-7, AMW-12, AMW-13, and AMW-14. Trend analyses indicate that statistically significant increasing temporal trends were calculated for barium concentrations in well AMW-14 and for chloride concentrations in wells AMW-12 and AMW-14. In the CAP wells, trend analyses are performed instead of comparison to CLs. During the current monitoring period, statistically significant increasing trends were noted for three VOCs in CAP well AMW-1, while decreasing VOC trends were noted for several VOCs in CAP wells AMW-1, AMW-4,AMW-10, and AMW-19BR. The increasing trend exhibited for cis- 1,2-DCE at well AMW-1, and generally decreasing(organic and inorganic) trends noted in most of the CAP wells, suggests that corrective action measures have been successful in reducing facility related groundwater impacts downgradient of the Austin Unit. Surface water samples collected from the upstream and downstream surface water monitoring stations during the second quarter 2013 monitoring period are generally consistent with each other and no VOCs were detected. These results suggest that landfill operations are not impacting surface water. The retest results for leachate have confirmed the semi-VOC (2-methylphenol)which was first detected in the annual leachate sample collected during the fourth quarter 2012. c:U013-0021\ea_2Q13.aac 12 Geo-Logic Associates