2019-12-27_INSPECTION - M1977300

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PERMIT#:M-1977-300 INSPECTOR'S INITIALS:AME INSPECTION DATE:November 7,2019 The wetland and biochemical reactor(BCR)pilot-scale study continues on top of the mesa, in an area east of the water treatment plant. The primary focus of the study is to evaluate whether uranium can be treated biologically. The study is operated seasonally(May—October) and monitored for inflow and outflow metals concentrations. The wetland treatment system consists of four cells in a series with local plants. Two series are built with bulrush and the other two series are built with aquatic sedge. The operator indicated they observed promising results with the bulrush plants over the summer. The BCR system consists of five separate columns, two of which have a solid carbon source(food for microbes), two of which have a liquid ethanol carbon source, and one of which is a control with no carbon added. A small greenhouse structure has been constructed around the BCRs to keep them above 50°F over the winter. The operator anticipates running the BCRs until about mid- December, at which time, the system will be put into hibernation for the winter. If,based on the results of this study, the operator decides to incorporate passive treatment methods into the reclamation plan for the site, these changes could be proposed through the appropriate permit revision. The Division inspected the upgradient cutoff wall and observed that all flows in Ralston Creek were being routed through the bypass pipeline. According to the operator, the creek was not flowing above the cutoff wall just a few weeks ago, prior to significant snowmelt occurring in the valley. The Division also inspected the areas adjacent to Glencoe Valley Road (near the toe of the NWRP) located upstream from the cutoff wall, where red- and green-colored ponded water (believed to be seep water from the NWRP)was observed during the inspection conducted on March 22, 2019. These areas were dry during the current inspection. The Division inspected the top of the NWRP, where saturated conditions were observed during the Division's March 22, 2019 inspection. Saturated conditions were not observed on top of the pile during the current inspection. The Division is currently reviewing Technical Revision No. 28 (TR-28; submitted on May 9, 2019) to revise the stormwater control plan for the NWRP that was approved in 2017 (through Technical Revision No. 23). The decision date for TR-28 is currently set for January 10, 2020. The operator believes that installation of the revised stormwater control structure(s) will address any seep issues with the NWRP by diverting water from the above drainage around the pile, and discharging the water to the creek below. The operator initially expected to install the revised stormwater control structure(s) during the 2019 construction season. However, due to the extensions needed for addressing the Division's concerns in TR-28, the operator now expects the system will be installed during the 2020 construction season. In the meantime, the operator has cleaned out the ditch along the northern edge of the top of the NWRP to allow stormwater to flow more easily around the pile until the revised structures can be approved and installed next spring/summer. The operator indicated the affected lands boundary may need to be slightly expanded around the NWRP to accommodate disturbances associated with installation of the stormwater control structures. Any proposed increase to the approved affected area could be included in the same Amendment application submittal to propose disposing of excavated valley fill material inside the Black Forest Mine. No problems were observed during the inspection. This concludes the report. Airy questions or comments regarding this inspection report should be forwarded to Amy Eschberger at the Colorado Division of Reclamation, Mining and Safety, 1313 Sherman Street, Room 215, Deriver, CO 80203, via telephone at 303-866-3567, ext. 8129, or via email at its. Page 3 of 9