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2019 Groundwater Interim Remedial Action Work Plan—Revision 2 UniFirst Facility, Stockton, California location will be cleared of utilities to a minimum depth of 5 feet bgs using a hand auger. Based on depth to water measurements collected in monitoring well MW-5A in September 2019, groundwater at this portion of the site is at about 17 feet bgs. Drilling will be performed using a direct push drilling rig to a depth of about 15 feet bgs (about 2 feet above groundwater). A 1.5-inch sintered stainless-steel sampling probe connected to the surface by 1/4 inch Teflon tubing will be installed at the base of the borehole. The bottom 1-foot of the borehole will be filled with sand. A 6-inch layer of dry bentonite pellets will be placed on top of the sand and the remainder of the boring will be filled with a bentonite cement mix. A GPS unit will be used to collect and record the X, Y, and Z coordinates of each probe location. Following sampling, the 1/4 inch tubing will be removed and any open space in the borehole will be filled with additional bentonite cement mix. The sidewalk surface above the borehole will be repaired in accordance with City of Stockton requirements. Based on previous boring installations, it is anticipated that the City will require cutting away affected sidewalk with a diamond saw and replacing it with new sidewalk that meets City specifications. 5.3 Soil Vapor Sampling A sample will be collected from each soil vapor probe in general accordance with the DTSC Advisory using the methodology described in Appendix D. Quality control procedures, including a shut-in test and a leak testing using propanol as a tracer, will be conducted prior to/during sample collection to confirm the integrity of the above-ground sampling equipment. Each sample will be analyzed by a National Environmental Laboratory Accreditation Program—certified analytical laboratory for site COCs using U.S. Environmental Protection Agency (EPA) Method TO-15 for target analytes. 5.4 Injection Well Installation Injection well installation will be conducted in the sidewalk area adjacent to the MW-5 well cluster (Figure 7). The wells will be installed at locations hydraulically upgradient of the MW-5 well cluster. As the area where the MW-5 well cluster is installed contains underground utilities and has tree cover, the injection well locations will be adjusted as needed to prevent damage to these features. One injection well will be installed for each monitoring well, with a screened interval at approximately the same depth as the corresponding monitoring well, as shown on Figure 8. For example, well IW-5A will be screened across the same interval as well MW-5A. Prior to commencing subsurface work, Wood will obtain drilling permits from the SJCEHD. Wood will obtain encroachment and traffic permits from the City of Stockton to work in the city right of way on North Hunter Street. In the intervening years since the last injection, a tree belonging to the City of Stockton has overgrown the drilling area. Wood will obtain an agreement with the City of Stockton to prune the tree to allow vehicle access to the drilling site. At least two business days before the injection borings are advanced, Wood will mark the boring locations and notify Underground Services Alert. The injection boring locations will also be cleared by private underground utility locating service. Additionally, each location will be cleared to a minimum depth of 5 feet bgs using a hand auger prior to drilling. I Based on data collected in September 2019, the depth to groundwater in the vicinity of the MW-5 well cluster should be about 17 feet bgs. Wood will install three injection wells at the locations shown on Figure 7. A preliminary well construction design is presented on Figure 8. The final well construction will be r0r • wood.