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2015 Annual Corrective Action Evaluation Report Augstin Road UWL Fonvard Landfill - ManLecA CaliLomig PaLe 6 7.0 Summary During the past four quarters, there have been no exceedances of the TVOC mass TL, and TVOC mass did not exhibit four consecutive quarters of increases. There was only one exceedance of the individual well TVOC concentration TLs during the past four quarters: domestic supply well 8106-A in the third quarter 2014. This exceedance was due primarily to detections that were not confirmed in the subsequent monitoring event. Comparison of the May/June 2015 results to computer modeling simulations indicates that in the immediate vicinity of the facility, groundwater quality improvements are generally occurring at a rate consistent with predictions. However, the May/June 2015 results indicate that reductions in VOC concentrations are occuning less quickly than had been projected at the following wells: tetrachloroethene at AMW-1, AMWA AMW-1 3, and 8106-A; trichloroethene at AMW-1, AMW-1 3, and 8106-A; and cis-1,2-dichlorothene at AMW-1. Groundwater pumping at two additional extraction wells, EW -3R and EW -4, was initiated in 2009 in order to improve groundwater quality near the northern boundary of the facility, with the former targeting AMW-1 specifically. Overall, the groundwater quality at the site is improving, likely due to the performance of the landfill gas collection system and groundwater extraction treatment system. This report represents the thirteen annual evaluation of the effectiveness of corrective action measures at the ARU. Subsequent annual reports will be submitted following each second quarter groundwater sampling event. The revised Engineering Feasibility Study that the facility is preparing may include revisions to the corrective action evaluation procedures previously described in the Evaluation Procedures Report. In particular, any updated groundwater computer simulation modeling is likely to incorporate the evaluation monitoring wells installed since 2001, in order to better evaluate groundwater quality improvements to the north and northeast of the facility. Should you have any questions or concerns, please contact the undersigned at your earliest convenience. 9E= HERST & ASSOCIATES, INC. Ward E. Herst, RG Andrew Wyatt Managing Director Senior Environmental Scientist M' 7-im Bannister — Andrews Environmental Engineering, Inc. Locklin Caffey — Republic Sen4ces Din Fanning — Republic Services Rick- Jaime — Northern California Youth Center Bill Lope-- — GeoLogic Associates Victoria Warren — Republic Services Attachments: Table 1- TVOC Tolerance Limits Table 2 - 77fird Quarter 2014 Groundivater VOCResults