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Kennedy/Jenks Consultants Section 8: Phase 11 Groundwater Investigation Work Plan This section presents the proposed Phase II Groundwater Investigation Work Plan. The discussions herein summarize the proposed monitoring well Incations and their rationale. This section also includes a brief summary of the Site hydrogeology and description of existing monitoring wells. 8.1 Site Hydrogeology The Site lies in the portions of a complex alluvial fan where braided stream channels coalesce along the foothills to form an alluvial fan apron or flood plain. The Neroly Formation, of marine origin, has been mapped to the south and southwest of the Site. In the floodplain, groundwater of different depths or different braided stream channel deposits merge in more uniform-sized and finer-grained depositional materials than those in the uplands. In this type of geologic zone and as interpreted from groundwater data collected at the Site, groundwater can flow in multi- directional flow paths influenced by both natural recharge from the uplands (upgradient of the Site) and regional groundwater flow in the lowlands and flatter portions of the Site (downgradient areas). The groundwater flow directions at the Site are summarized in Sections 5.1 and 5.2 of this Report. A more detailed description of the regional and Site geology and hydrogeology is provided in Section 2 of this Report. 8.2 Existing and Proposed Groundwater Monitoring Wells A detailed description of the existing Site groundwater monitoring well network was included in Section 1.3.2 and Section 4.3 of this Report. The proposed monitoring well locations shown on Figure 19 are based on discussions with RWQCB staff in a meeting on 24 August 2007 in Fresno, California, and a follow-up meeting on 12 September 2007 in Modesto, California, and on the results of the Phase I groundwater investigations. The CDO also specifies three study locations as identified during the meetings with RWQCB staff, in which either borings or wells are to be installed, referred to as Area 1, Area 2, and Area 3 (Figure 19). 8.2.1 Study Area 1 As shown on Figure 19, proposed Well Cluster 1 of shallow and deep monitoring wells is located generally to the east of the Site. The objective of these wells is to compare regional groundwater quality with onsite groundwater quality as monitored in Wells MW-10R, MW-17, and MW-18. Access agreements for installation and monitoring of wells at this location have been secured by Musco (Musco 2008). Proposed Well Cluster 2 comprised of one shallow and one deep groundwater monitoring well is to be located northeast of the Title 27 surface impoundments on the Safeway distribution center property. This well pair will be located in an area that is crossgradient of deep groundwater flow and downgradient of shallow groundwater flow, if present, for the purpose of comparing water quality onsite and regional water quality offsite. The primary objective of Well Cluster 2 is to compare TDS concentrations in the shallow groundwater zone between onsite monitoring wells —i.e. Well MW-17 and a newly proposed Well Cluster 1. Well Cluster 2 includes a companion deep monitoring well if groundwater is encountered at no deeper than 130 feet bgs. Phase I Groundwater Investigation Report and Work Plan for Phase 11 Investigation Page 25 Musco Family Olive Company, Tracy, California g:Yagouplatlmn`joh'p2lglgig4.�mumplNe`Ag+epalsk4oVaWi3lpheee t gwlnvegry(phase II inveA vrh pNlsxttloc