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Groundwater samples from the wells will be submitted to a California-certified analytical laboratory for the following analyses: Constituent Method' Total Dissolved Solids SM 2540C Dissolved Iron and Manganese EPA 200.8 Dissolved Organic Carbon SM 5310C Alkalinity as Calcium Carbonate (CaCO3), SM 2320B Bicarbonate as CaCO3, Carbonate as CaCO3, and Hydroxide as CaCO3 Chlorinated Volatile Organic Compounds EPA 8260B 1 EPA=U.S. Environmental Protection Agency and SM=standard method. Groundwater samples will be collected in accordance with the methods approved for semiannual monitoring at the site. The constituents listed above are the same as for a semiannual event, with the additional of dissolved iron. Samples will also be collected for microorganisms using the QuantArray method from Microbial Insights. The sampling method will involve suspending Microbial Insights's proprietary Bio-Trap samplers at the approximate centers of the screened interval for each well and leaving them in place for approximately 30 days. Leaving the samplers in place for an extended period reduces the variability in sampling results and increases the sensitivity. Sampler installation, collection, chain-of- custody documentation, and transportation will be conducted in general accordance with procedures provided by the laboratory (Appendix D). 5.4 Injection Well Installation Injection well installation will be conducted in the sidewalk area adjacent to the site; the final location will be determined following evaluation of well MW-11 data. The wells will be installed at locations hydraulically upgradient of the MW-5 and MW-10 well clusters. As the area where the wells will be 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 6. For example, well IW-5A will be screened across the same interval as well MW-5A. Prior to commencing subsurface work, WSP will obtain drilling permits from the SJCEHD. WSP will obtain encroachment and traffic permits from the City of Stockton to work in the city right of way on North Hunter Street and/or East Poplar Street. WSP will obtain an agreement with the City of Stockton to prune the trees to allow vehicle access to the drilling site, if possible. The trees along East Poplar Street are not considered heritage trees and can be trimmed. The status of the trees along North Hunter Street is currently unknown. At least 2 business days before the injection borings are advanced, WSP 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. Based on recent historical data, the depth to groundwater in the vicinity of the MW-5 and MW-10 well clusters should be between 17 and 20 feet bgs. Figure 5 shows the preliminary location of the three injections wells that will be installed by WSP. A preliminary well construction design is presented on Figure 6. The final well construction will be adjusted in the field depending on the actual depth to first-encountered groundwater and lithologies at the drilling locations. WSP will contract with a California-licensed C-57 drilling contractor and fieldwork will be conducted under the supervision of a WSP professional engineer or geologist. The monitoring wells will be installed in conformance with California and San Joaquin County well standards. 2019 Groundwater Interim Remedial Action Work Plan—Revision 3 Page 6 UniFirst Facility,Stockton,California Project No.0132902023 IM 3000s\13290\Archive\13290-177.docx