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Drilling equipment will be decontaminated before drilling and between wells. A diamond core drill bit or concrete saw will be used to remove sections of the sidewalk to permit drilling. Each well boring will be drilled using a hollow-stem auger drilling rig to the approximate depths shown on Figure 6. The borings will be continuously cored, and soil cores will be logged for lithology using ASTM International Test Method D2488. The wells will be installed with well screens over the approximate interval shown on Figure 6. A WSP field geologist will log the soil core from each well boring at approximately 5-foot intervals except for the base of well IW-5C, which will be continuously cored. Drill cuttings will be stored in drums or bins for disposal pending waste characterization. The wells will be sealed to about 0.5 feet bgs with cement-bentonite grout and completed with a locking traffic-rated flush-mount cover set in concrete. Upon completion, the monitoring wells will be surveyed for location and elevation consistent with the GeoTracker survey standard. A minimum of 48 hours after drilling and installation, each well will be developed to remove sediments and stagnant water. Well development water will be placed in bins or drums pending waste characterization. Well development will consist of surging and bailing until groundwater field parameters (turbidity, pH, electrical conductance, and temperature) stabilize. Composite samples for waste characterization will be collected from waste soil and water generated by well installation. These materials will be analyzed for volatile organic chemicals using 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. 5.5 Injection A plan to inject amendments into the subsurface using the injection wells has been developed with input from representatives of Regenesis Bioremediation Products, Inc. (Regenesis), in San Clemente, California. Regenesis is a producer of in-situ bioremediation amendments with experience in remedial actions at numerous sites with CVOCs in groundwater and was the provider of the HRC used for the 2011 pilot study. Injection of three amendments (3-D Microemusion [3-DME], Chemical Reducing Solution [CRS], and Bio-Dechlor Inocculum Plus [BDI]) are proposed. HRC also was considered for the proposed injection; however, newer amendments more suited to the Iithology of the site have since become available. One of the chief drawbacks of HRC is its viscosity, which tends to limit the volume of effect of the HRC at sites with predominately fine grained Iithologies such as are present at the UniFirst site. The newer version of HRC (3-DME) has a lower viscosity, allowing it to diffuse over a greater volume of effect than HRC in fine grained Iithologies. 3-DME breaks down in water to release both lactate and vegetable-based oil molecules. The lactate and oil-based compounds released are electron receptors that act as an energy source for dechlorinating microbes. One of the advantages of 3-DME over HRC is that it contains non-petroleum oil-based compounds in addition to lactate. The oil-based compounds are broken down by microbes more slowly than lactate, which lengthens the effective treatment life of the amendment. 3-DME contains no hazardous materials, and a safety data sheet and product information literature for 3-DME is provided in Appendix C. CRS is an amendment containing ferrous gluconate solution. The ferrous iron in the solution forms precipitates that can degrade CVOCs via chemical reduction. Groundwater quality results from well MW-5B indicate an increase in reducing conditions (the ORP became more negative) and a significant increase in dissolved iron concentration for approximately 2 years following the HRC injection in 2011 (Wood, 2019). These data indicate degradation via iron reduction may have been stimulated by the HRC injection. Injection of CRS should promote additional CVOC degradation via this mechanism. CRS contains only food-grade materials, and a safety data sheet and product information literature for CRS is included in Appendix C. Injection of the amendment BDI also is proposed. This amendment contains a mix of microorganisms proven to degrade CVOCs. As described in the introduction, dehalogenating microorganisms were detected only in the deeper soil samples from borings installed during the site assessment. Groundwater monitoring results indicate dechlorination daughter products are present in wells 2019 Groundwater Interim Remedial Action Work Plan—Revision 3 Page 7 UniFirst Facility,Stockton,California Project No.0132902023 I:\13000s\13290\Arch ive\13290-177.docx