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AUG 25 2016 N Appendix A HE.1_T, ; T Monitoring Well Abandonment Workplan City of Lathrop Consolidated Treatment Facility 1. General Information The City of Lathrop's Consolidated Treatment Facility(CTF)treats and disposes domestic wastewater generated within the City of Lathrop. On February 5,2015,thE Regional Water Quality Control Board approved new Waste Discharge Requirements (WDRs) (Or(er No. 115-2015-2006). This Monitoring Well Abandonment Plan describes the proposed abandonr ient procedures for wells identified in the WDRs or identified as damaged or dry during the Septem er to October 2015 well reconnaissance outlined in the Well Condition Survey Report. 1.1. Purpose The WDRs slated six monitoring wells for abandonment to simplify the mnitoring network(CLSP- 2,CLSP-3,CLSP-4,MWM-14,MWM-16,and MWM-26).1 However,field rec nnaissance revealed that grading activities around one of these wells (CLSP-3) increased land surface level adjacent to the well,and excavation will be required to expose the buried concrete well pad in order to properly abandon the well.Because the well is accessible to the City,it is secure and functional, provides water level data adjacent to the San Joaquin River,and there is u certainty in the timing and extent of future land use plans for the site,the City recommends keepi ng CLSP-3 as an active well within the current network. Additionally,the well inspections during September and October 2015,idl ntified three damaged wells (MWR-6,MWR-13,and CLSP-10)and two low-yielding wells (MWR 15 and MWR-20) recommended for abandonment. The well locations are shown in Figure 1 (two wells are located within CLSP,three are located within Mossdale,and four are located on River Islands).This workplan outlines the general procedure to abandon and seal the monitoring wells consistent with Calif rnia Well Standards Bulletin 74-90 and San Joaquin County Well Standards. 1.2. Local Hydrogeologic Conditions The Lathrop area is located in the basin-trough geologic zone of the San Ic aquin Valley,which consists of continental Pleistocene and Holocene stream-laid and still-wal er depositsz.These 'Recommended Groundwater Monitoring Well Network and Sampling and Analysis I Ilan.City of Lathrop.March 19,2014.Prepared by Hydro Focus, Inc. P Jennings,C.W.and Strand,R.G.,1958,"Geologic map of California,Santa Cruz Sh et",California Division of Mines and Geology,Sacramento,California.