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Privileged and Confidential-Attorney Client Communication Geosyntec Ij <br /> consultants <br /> be added upstream of MWP or within the pond to improve treatment <br /> performance (this may include the installation of chemical feed systems). <br /> Supplemental feed systems are also an option for the back end of the MWP to <br /> enhance the performance of downstream biological treatment systems. <br /> • Pond#2: existing bioreactor system will be removed and replaced with a <br /> modified gravel-filled bioreactor. As part of the reconstruction of Pond#2, a <br /> clay liner will be installed so the water does not seep into groundwater. <br /> • Pond#3: the existing stormwater pond will be converted to an additional <br /> biological treatment step for the new water treatment system. A new Outfall <br /> 002A will be constructed at the end of Pond#3 with discharge into Sneffels <br /> Creek. <br /> 2.2 Passive Treatment Technology Review <br /> Geosyntec conducted a passive treatment technology review to identify the most <br /> appropriate passive hybrid water treatment system for the Mine given the current state <br /> of knowledge for passive biological treatment systems and the driving site constraints, <br /> such as seasonal weather variation, flow ranges through the system, and pond <br /> capacities. For this evaluation we collected and reviewed peer reviewed articles, case <br /> studies, and EPA guidance manuals specifically for the design of passive treatment <br /> systems at high altitude and cold climate mines. We also applied our internal experience <br /> resulting from the completion of numerous projects involving the design, construction, <br /> and troubleshooting of various wetlands and bioreactors. As a final component of our <br /> analysis we engaged with the Colorado School of Mines(CSM)to consult with <br /> Professor Dr. Linda Figueroa, a seasoned expert in biological treatment systems in <br /> Colorado with over thirty years of experience. Dr. Figueroa will serve as a technical <br /> advisor through the treatability testing and the development of the basis of design at the <br /> completion of the testing. <br /> There are a variety of passive treatment technologies available for treating mine water. <br /> Four options were evaluated as the most likely candidate options for the Mine and each <br /> are briefly described below: <br /> • Aerobic Wetland: shallow basin with native wetland vegetation planted in loose <br /> substrate to promote slow flow and attachment sites for metal precipitates. Used <br /> primarily for oxidation and filtration of iron and manganese, as well as <br /> hydrolysis and settling(Skousen, et al., 2017). <br /> • Sulfate Reducing Bioreactor(SRB): basin filled with a mixture of organic <br /> matter, limestone, and strong particles such as gravel or course sand to minimize <br /> compaction and plugging. Capable of treating acidic and metal-rich water <br /> (Zagury, Neculita, & Bussiere, 2007). Addition of a liquid organic supplement is <br /> sometimes necessary for inoculation of bacteria and during upset conditions <br /> Treatability Study Work Plan 8 February 8,2018 <br />