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California Regional Water Quality Control Board-Central Valley Region 23 February 2022 Page 2 Background The Site history, hydrostratigraphy,groundwater investigations in the North Area, and development of the IRA are described in previous reports (Haley&Aldrich, 2020 and 2021). In a letter dated 2 August 2021,the California Regional Water Quality Control Board—Central Valley Region (Water Board) concurred with the conceptual design of the recommended IRA as presented in the Draft North Area Groundwater Interim Remedial Action Plan (TRAP; Haley&Aldrich, 2021). The IRA will consist of groundwater extraction from former irrigation well RPS-1 and a new proposed extraction well (RPS-3), a groundwater treatment system,two injection wells for treated water(IW-1 and IW-2), and subsurface conveyance piping connecting the wells to the treatment system, which will be located at the northern end of the Ripon Public School property(Figure 2).The treated water will be made available on demand for irrigation by the Ripon Public School.The IRAP proposed redrilling and deepening well RPS-1(screened in the C1 Zone from 135 to 148 feet below ground surface [bgs])for use as a combined Cl-and C2-Zone IRA extraction well.The two injection wells for replenishing the aquifer with treated water will be located along the northern property boundary of the Ripon Public School.This work plan describes the methods for installing the new extraction well RPS-3 and the two injection wells IW-1 and IW-2. Extraction and Injection Well Installation FIELD PREPARATION AND PERMITTING Prior to the start of field activities, Haley&Aldrich will prepare a Site-specific Health and Safety Plan; obtain well installation permits from San Joaquin County Environmental Health Department; coordinate access with the property owner(Ripon Public School);and contract with a private utility location subcontractor and a drilling subcontractor. Haley&Aldrich will mark each drilling location and notify Underground Service Alert at least 48 hours prior to the start of fieldwork. Each location will be screened for utilities by a private utility locator prior to any ground disturbance and will be manually cleared to a minimum depth of 5 feet bgs using a hand auger. DRILLING AND WELL CONSTRUCTION METHODS Haley&Aldrich will subcontract a California C-57 licensed drilling contractor to advance the proposed borings using sonic drilling methods. Each location will be continuously cored, and soil will be logged by a field geologist under the supervision of a California Professional Geologist in general accordance with ASTM International Standard D2488 (Standard Practice for Description and Identification of Soil, Visual-Manual Procedure). Soil cores will also be screened for organic vapors using a photoionization detector. Upon reaching the target depth for each well (discussed below),the wells will be constructed as follows: • Extraction well RPS-3 will be constructed of six-inch diameter,Schedule 80 polyvinyl chloride (PVC),with approximately 20 feet of six-inch diameter, stainless steel,wire-wrapped screen (with 0.030-inch slots).The target screen interval is approximately 160 to 180 feet bgs, which corresponds to the C2 Zone of the Intermediate Aquifer in this area.A four-feet long section of '%EKICH