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Forward Landfill – 2023 Annual Corrective Action Evaluation Report <br />www.arcadis.com <br />Forward Landfill 2023 Annual CA Eval Rpt_08012023 1 <br />1 Introduction <br />Arcadis U.S., Inc. (Arcadis) has prepared this Annual Corrective Action Evaluation Report for the Austin Road <br />Unit (ARU) of the Forward Landfill on behalf of Forward, Inc. (Forward) and in accordance with Section B.5 of the <br />February 14, 2014 Monitoring and Reporting Program (MRP) R5-2014-0006. On February 26, 2002, Forward, Inc. <br />submitted the Evaluation Procedures for Proposed Corrective Action at Austin Road Landfill, Addendum to May <br />2001 EFS (Revised August 2001) (Evaluation Procedures Report). The report described procedures for <br />evaluating the effectiveness of groundwater corrective action measures at the ARU. The California Regional <br />Water Quality Control Board (RWQCB) later incorporated these procedures into Section B.5 of the MRP. <br />Corrective action measures implemented to date at the ARU include landfill gas management, groundwater <br />pumping, and an artificial groundwater recharge area. Landfill gas collection began in 1985. Groundwater <br />pumping at extraction wells EW-1 and EW-2 has been ongoing since 1994; groundwater pumping at extraction <br />well EW-4 has been ongoing since May 2009; groundwater pumping at extraction well EW-3R has been ongoing <br />since October 2009; and groundwater pumping at EW-5 has been ongoing since August 2019. The artificial <br />recharge area was constructed in October 2002 and has reportedly been in use since May 2003. The extracted <br />groundwater is currently treated by two 10,000-pound GAC vessels, which were installed in January 2020. <br />The Evaluation Procedures Report specifies three criteria that shall be used for evaluating groundwater corrective <br />action measures at the ARU. Any of the following shall constitute an exceedance: <br /> An exceedance of the total volatile organic compound (TVOC) mass Threshold Limit (TL); <br /> An increase in TVOC mass for four consecutive monitoring events; or <br /> An exceedance of any of the individual well TVOC concentration TLs. <br />The Evaluation Procedures Report specifies a TL for TVOC mass that is derived from modeling data using <br />historical groundwater monitoring data. The TVOC mass TL therefore represents a historical upper bound of <br />TVOC mass in impacted groundwater. An exceedance of the TVOC mass TL or four consecutive increases in <br />TVOC mass would be suggestive of potential increasing VOC concentrations on a plume-wide basis. Similarly, <br />the Evaluation Procedure Report also specifies TLs for TVOC concentrations at individual corrective action <br />monitoring wells. An exceedance of a TVOC concentration TL would be suggestive of potential increasing VOC <br />concentrations at that specific well. The TVOC mass TL and individual well TVOC concentration TLs are <br />summarized on Table 1. <br />In order to evaluate the effectiveness of corrective action at the ARU, this 2023 Annual Corrective Action <br />Evaluation Report evaluates groundwater monitoring results from the third quarter of 2022, the fourth quarter of <br />2022, the first of quarter 2023, and the second quarter of 2023 (the monitoring period), using the criteria listed <br />above. Analytical data from the Evaluation Monitoring Program (EMP)/Corrective Action Program (CAP) wells <br />were used in the TVOC mass calculation. <br />Six new monitoring wells, designated as AMW-50S, AMW-50M, AMW-51M, AMW-52S, and AMW-52M, were <br />installed between November 2022 and April 2023. These wells were added to the monitoring program beginning <br />in the second quarter of 2023. The results from these new wells were used to refine the TVOC mass calculation <br />for the second quarter of 2023, and will be used in future evaluations.