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installed in shallow, medium, and deep intervals. Nevertheless, it may be that the shallow and medium intervals either do not contain sufficient numbers of organisms or the right types for complete dechlorination. For example, the vinyl chloride concentrations in well MW-513 remain at a level that is significantly higher than before the pilot test(Appendix A), indicating incomplete dechlorination. Injection of the amendment materials in the injection wells will be performed after the wells have been developed. Well development introduces oxygen into the subsurface. Since the microorganisms that promote degradation of chlorinated chemicals are predominantly anaerobic in nature, the aquifer will be given time, at least 1 week following development, to reestablish the relatively anoxic conditions normally present in the MW-5 well cluster groundwater(Wood, 2019). The amendments will be mixed with water obtained from the City of Stockton for dilution prior to injection. One sample will be collected from the dilution water and one sample from each of the three amendments for analysis of CVOCs using EPA Method 8260. The purpose of these samples is to evaluate the potential for cross-contamination from the injection process. The proposed amount of each amendment to be injected in the wells at each depth was calculated based on the CVOC concentrations in groundwater, the length of the screened interval in the corresponding MW-5 well cluster, and application experience at other similar sites affected by CVOCs. The following dosage rates are proposed for each well: • 3-DME: 2,400, 1,200, and 1,200 pounds for wells MW-5A, MW-5B, and MW-5C, respectively. The 3-DME will be mixed with approximately 2,300 gallons of water obtained from the City of Stockton prior to injection. • CRS: 1,000, 500, and 500 pounds for wells MW-5A, MW-5B, and MW-5C, respectively. • BDI: 18.5, 9.3, and 9.3 liters of BDI for wells MW-5A, MW-5B, and MW-5C, respectively. The BDI will be mixed with approximately 333 gallons of water obtained from the City of Stockton prior to injection. These amounts assume similar conditions are detected in each well based on the results of the pre- injection monitoring. However, depending on the results of the pre-injection monitoring, they may be adjusted to optimize the dosage of each amendment for each well. Pumping equipment will be attached to each wellhead, and the amendments will be injected under pressure. Based on experience with HRC injections, it will likely require several hours of injection per well for the aquifer to accept the amendments due to the relatively fine-grained lithology. 5.6 Post-Injection Monitoring Groundwater monitoring of the on-site monitoring wells will be performed on a semiannual basis in accordance with the Monitoring and Reporting Program, except samples from the MW-5 and MW-10 well clusters and well MW-11 also will be monitored for dissolved iron by EPA Method 200.8 for up to 2 years. 6 Reporting Following the injection and receipt of the analytical results of the samples collected from the dilution water and the amendments, a report summarizing the results of the sampling, well installation, and injection will be prepared and submitted to the RWQCB. Groundwater monitoring reports will be prepared and submitted to the RWQCB following each semiannual monitoring event. These reports will include a section evaluating the performance of the 2019 interim remedial action for events conducted after the injections are complete. 7 Schedule A preliminary schedule has been prepared for the scope of work included in this work plan. The schedule assumes RWQCB approval of this work plan within 2 months of submission and timely approval of boring and well installation permits by SJCEHD. The schedule also assumes availability of 2019 Groundwater Interim Remedial Action Work Plan—Revision 3 Page 8 UniFirst Facility,Stockton,California Project No.0132902023 I:\13000s\13290\Arch ive\13290-177.docx