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Work Plan Test Well 2 Background An aquifer storage and recovery(ASR) well has been proposed in Lathrop, CA.To evaluate subsurface conditions and identify zones suitable for recharge, a second test hole/monitoring well (TW2) is to be constructed.The first test hole/monitoring well (TW1) was drilled to a total depth of 800 feet and converted to a triple completion monitoring well with a total depth of 760 feet.TW2 is intended to provide additional information at depth below 800 feet to a possible total depth of 1,250 feet in order to improve the understanding of local hydrogeology to inform ASR well design and to provide long-term monitoring of ASR operations. Project Information The proposed drilling site is located at 950 Stewart Road, Lathrop, CA (Figure 1). Additional info: o Drilling contractor: Bradley and Sons Drilling and Pump System o Subcontractor/Engineer: Luhdorff&Scalmanini, Consulting Engineers o Project Location Address: 950 Stewart Road, Lathrop, CA 95330 o APN: 21-21-001 o Property is owned by the City of Lathrop. Property was deeded to the city in September 2023 (Attachment A) o Work is to be completed in the summer of 2023. Work Sequence and Conceptual Design Specifications for the TW2 are included in Attachment B.The following is a general description of the work sequence and conceptual design of the test well. A 1,250-foot test hole is to be drilled where drill cuttings will be collected every 10 feet and at every formation change. Drilled cuttings from several 10-foot intervals will be submitted to a geotechnical laboratory for sieve analyses. The results of the sieve analyses will be included in the final well installation report. Sieve analysis can play an important role in filter pack selection when designing a well. The analysis involves passing a sediment sample through a series of calibrated screens to quantify sorting and grain size. The filter pack selection generally involves identifying the screen mesh size that retains 70 percent of the sediment by weight and multiplying that grain size value by 3 to 10 (depending on specific sediment characteristics),yielding the optimum filter pack grain size. However, the process of filter pack selection is subjective, and is influenced by local hydrogeologic conditions. A geophysical survey will also be conducted to determine additional subsurface properties. Analysis of the drill cuttings and geophysical survey will be used to finalize the monitoring well design. The monitoring well will likely consist of two monitoring zones below the Corcoran Clay (E-Clay).A conceptual well design is presented in Figure 2.The proposed construction details for the monitoring zones are included in Table 1.The design presented is preliminary and will be finalized after drill cuttings and geophysical data area analyzed. Water quality will be tested in each of the monitoring zones.These well completion reports, geophysical log, and a list of the water quality analytes are included in Attachment C.