WORK PLANS - Laserfiche WebLink

Home Browse Search

�I 2019 Groundwater Interim Remedial Action Work Plan—Revision 2 UniFirst Facility, Stockton, California 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 B. 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 B. 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 dechorination daughter products are present in wells 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-5B 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-SA, 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. . • wood.