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WORK PLAN AND TIME SCHEDULE FOR ANALYSES OF BACKGROUND GROUNDWATER QUALITY City of Stockton Regional Wastewater Control Facility 1.0 INTRODUCTION This Work Plan has been prepared by Condor Earth Technologies,Inc. (Condor)at the request of the City of Stockton Municipal Utilities District(MUD)to comply with Provision VI.C.2.c of California Regional Quality Control Board, Central Valley Region (Regional Water Board) Order No. 115-2008-0154 for municipal sewage discharges at the Stockton Regional Wastewater Control Facility (RWCF). This work plan and time schedule describes the installation of additional monitoring wells and other testing needed to effectively and fully characterize background groundwater quality conditions to evaluate compliance with Groundwater Limitations V.B.I.b and c. Sections 2.0 through 8.0 include introductory and background information, the theoretical basis of the approach taken with respect to the use of the background concept and a needs assessment. Descriptions of the work proposed begin in Section 9.0.The Time Schedule is included in Section 13.0. 2.0 FACILITY DESCRIPTION The location of the RWCF is shown on Figure 1. Effluent treatment and disposal practices at the facility have been on-going for decades. The RWCF consists of a primary and secondary treatment facility on the east side of the San Joaquin River(SJR)including primary treatment screening,grit removal, and primary sedimentation with enhanced treatment through injection of polymer and ferric chloride into the primary clarifiers. The secondary treatment consists of high rate trickling filters and secondary clarifiers. Treated effluent is piped under the SJR to the tertiary treatment facilities west of the river. Tertiary treatment facilities west of the SJR include oxidation ponds, recirculation canals and interceptor ditches, a constructed wetland treatment area,treatment plants, chlorination facilities and the river outfall discharge system.A Flow Schematic is provided in Appendix 6. Groundwater monitoring at the facility was initiated in 2003 and has continued on a quarterly basis. MUD maintains a network of 17 active monitoring wells around the RWCF that are sampled quarterly or semi- annually. The locations of the facility's monitoring wells east and west of the SJR are shown on the topographic map on Figure 2. Also shown on Figure 2 are December 2008 groundwater surface contours with groundwater flow direction indicated by arrows. Table 1 lists completion details of the monitoring wells. Of particular note is the well screen submergence in 16 of 18 monitoring wells. The tops of well screens range from 2.87 feet above the mean static water level at well MW-18 to 15.08 feet below the mean static water level at MW-5. The average screen submergence of all wells is 6.81 feet below the respective mean static water level in the wells. Typically the wells were constructed with sand pack extending 1.5 to two(2)feet above the top of screens. 3.0 PHYSICAL AND HYDROLOGICAL SETTING The RWCF site is located in the SJR delta. The oxidation ponds are located at sea level on flat ground west of the SJR and the primary and secondary treatment facilities are located in a similar setting east of the river. The Bums Cutoff and the former U.S. Naval Facilities on Rough and Ready Island are located to the North, a Stockton industrial area is located to the east, and agricultural lands are located to the west and south. The SJR is subject to daily tidal fluctuations of three (3) feet or more which, periodically, i.�i1 t;ON�/)R