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Eastern San Joaquin Groundwater Basin Groundwater Management Plan Mokelumne River to the Lower Farmington Canal would cost approximately $15 to $20 million (SEWD, 2000). 8.2.7 Gill Creek and Woodbridge Road Flood Control Improvements The Gill Creek and Woodbridge Road watersheds are located approximately four miles north of the City of Lodi and cover about 14.4 square-miles of relatively flat terrain. The area has a history of drainage deficiencies resulting in long-duration shallow flooding including infill or disking of natural drainage ways, changes in land use, rural residential development, and undersized culvert crossings and pump stations. Historically, the proposed solution focused on increased channel capacities along Gill Creek; however, current regulations regarding down stream impacts, stormwater quality, and permitting present challenges to a diversion focused project. In 2004 the San Joaquin County Department of Public Works Stormwater Management Division completed the Gill Creek and Woodbridge Road Watersheds Reconnaissance Study (Gill Creek Study) to identify and recommend a project that would provide a 100-year level of protection to structures and a 25-year level of protection to agriculture in the study area. The Gill Creek Study explored three alternatives with the following focuses: channel enlargement, detention, and diversion into the Lower Mokelumne River. The Gill Creek Study identified detention as the preferred alternative which includes minor channel improvements and the construction of up to 15 detention basins covering a total area of 65 acres spread throughout the watersheds. A map of the preferred alternative can be seen in Figure 8-17. The preferred alternative also has the potential to provide addition benefits as the channels and detention basins could be used to convey Mokelumne River Water for irrigation and direct recharge. The NSJWCD owns an existing 30 cfs irrigation system near Tretheway Road extending west along Acampo Road. Improvements to the NSJWCD North Irrigation System or an additional system could serve the conjunctive water management needs of the area. The preferred alternative is expected to cost approximately $25 million with an expected benefit of close to $30 million in prevented structural and agricultural damages. The next step is to perform a feasibility study where the conjunctive use and flood control operation can be explored further and the benefits quantified (San Joaquin County Department of Public Works, 2004). 8.2.8 South Gulch Reservoir In 1984, SEWD completed the South Gulch Water Conservation Project Technical Reconnaissance Report to evaluate the feasibility of the proposed South Gulch Reservoir. South Gulch Reservoir is located approximately 22 miles east of Stockton, California, and approximately seven miles southwest of New Hogan Dam. The proposed dam location is six- tenths of a mile upstream from the South Gulch and Calaveras River confluence. The South Gulch Reservoir surface area is approximately 3,000 acres with a storage capacity of 130,000 to 180,000 af. In conjunction with the construction of the South Gulch Dam, the Upper Farmington Canal would be completed to supply excess water from the Stanislaus River. Additionally, a diversion structure on the Calaveras River just down stream of New Hogan Reservoir would convey excess water to the proposed South Gulch Reservoir in wet years. A map of the proposed reservoir can be seen in Figure 8-18. The project is one of the key proposed facilities of the Eastern Water Alliance. (Aqua Resources, Inc. et al, 1984) 8.2.9 Lyon's Dam The Tuolumne Utilities District (TUD) obtains the majority of its water supply from the South Fork of the Stanislaus River. In 1983 TUD entered into an agreement with PG&E for the use of Northeastern San Joaquin County Section 8 Groundwater Banking Authority 130 Integrated Conjunctive Use Program