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Composite samples for waste characterization will be collected from waste soil and water generated by well installation and development. These materials will be analyzed for volatile organic chemicals using U.S. Environmental Protection Agency (EPA) Method 8260 and metals using EPA Method 6010. Based on results from previous site investigations, it is anticipated that the waste materials generated by this phase of the investigation will prove to be non-hazardous. Accumulated waste will be disposed of off-site at disposal facilities authorized to accept them, based on the results of the characterization. 5.2 Injection Well Placement Evaluation Previous revisions of this work plan called for three injection wells to be installed hydraulically upgradient of the MW-5 well cluster(Figure 5). Monitoring data from the new MW-10 well cluster shows the plume beneath the site extents further northwest than earlier investigative studies concluded. Monitoring data from the MW-5 and MW-10 well clusters, as wells as data from the new well MW-11, will be used to refine placement of the injection well cluster. Previous experience at other sites has shown that sometimes the initial monitoring results from wells installed in relatively fine textured soils may not be representative of longer-term results. As such, UniFirst proposes to evaluate the results of at least three semiannual monitoring events for well MW-11 prior to proposing the final location of the new well cluster. The proposed well cluster location will be provided in the monitoring report submitted following three MW-11 monitoring events.. 5.3 Pre-Injection Monitoring Pre-injection monitoring will be used to establish groundwater quality conditions prior to injection of amendments and to measure populations of dechlorinating microorganisms. Dechlorinating microorganisms were detected in a soil sample collected from deeper soil in 2007. However, analytical methods available at that time were far less sensitive than current methods and distinguished just one type of microbe (dehalococcoides ethanogenes). Current methods can detect a variety of dehalogenating organisms. Depending on the results, these data can be used to identify which organisms are most prevalent and; therefore, which chlorinated compounds may be most readily degraded dechlorination or the absence of organisms likely to degrade select compounds, which could result in incomplete dechlorination. It is anticipated that adjustments to the amounts of each amendment described below may be made to the injection program described below depending on the evaluation of the pre-injection monitoring data. The selected method for the analysis is the QuantArray method from Microbial Insights, Inc. (Microbial Insights), in Knoxville Tennessee. A sample analytical report for dechlorinating microorganisms is provided in Appendix C. The results include the estimated number of each type of organism and charts showing the relative proportion of organisms capable of dechlorinating various CVOCs. An initial sampling event will be conducted on the MW-5 and MW-10 well clusters prior to well installation and will include field parameters and laboratory analyses. Before sampling, each monitoring well will be purged using a portable Grundfos stainless-steel electric submersible pump. Purging with the Grundfos pump will consist of removing at least four casing volumes or until the field parameters of the purge water(temperature, pH, and electrical conductance) have stabilized and the water is relatively clear and free of sediment. Other measured field parameters of the purge water will include oxidation reduction potential (ORP), dissolved oxygen, and a qualitative assessment of turbidity. This monitoring may be conducted as part of a semiannual monitoring event. Following purging and completion of the field measurements, groundwater samples will be collected in laboratory-prepared containers, labeled, and placed in an ice-cooled chest for delivery to the laboratory using chain-of-custody procedures. The Grundfos pump and associated tubing will be decontaminated before collecting samples from each monitoring well by washing with a Liquinox solution, rinsing with clean water, and rinsing again with deionized water. Water generated from groundwater sampling activities will be placed in 55-gallon drums for characterization and subsequent disposal. 2019 Groundwater Interim Remedial Action Work Plan—Revision 3 Page 5 UniFirst Facility,Stockton,California Project No.0132902023 I:\13000s\13290\Arch ive\13290-177.docx