2020-12-09_REVISION - M1977300 - Laserfiche WebLink

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Schwartzwalder Completed Scope Included in Current Bond—2020 Initial In Situ Treatment There were three previous _ in situ treatments of the mine pool in 2013, 2015, and 2017. These in situ treatments are discussed in 4 the following paragraphs. In situ mine pool treatment was initiated in May 2013 as a pre-treatment step to ,•x,n A( _d 4 the RO system in which '_: molasses and methanol N, F were injected into the mine pool. Molasses was first Figure 1. FormerSchwaruwalder Mine Site injected in the#1 Shaft (-800 ft deep),the#2 Shaft 1,160 ft deep), and the open stope behind the bulkhead. Three subsequent monthly injections of methanol followed, and a second injection of molasses and methanol was made six months after the start of treatment. Water quality of the mine pool was monitored biweekly at a sample port in the WTP just before the RO units. Within three months of injection of molasses and methanol into the mine pool, the uranium concentration dropped by 90%, from 22.8 milligrams per liter(mg/L)to 1.8 mg/L. This decrease in uranium concentration was accompanied by a decline in the concentration of sulfate and sulfide mineral-forming elements such as molybdenum, indicating that a sulfate-reducing environment was rapidly established in the mine pool. The in-situ treatment of the mine pool was interrupted by a 1,000-year rainfall event that prohibited access to the Schwartzwalder Mine from after the event in September 2013 until the summer of 2015. In December 2017, another in situ treatment of the mine pool was conducted. Phosphoric acid was injected into the#2 Shaft on December 19, 2017. The phosphoric acid was added as a microbial nutrient. Molasses was then injected into the#2 Shaft on December 20, 2017, and December 29, 2017. A 25 horsepower(hp)pump installed at 210 ft below the Steve Level was operating and the mine pool was reinjected into the#2 Shaft after being processed through the RO units. The operation of the pump allowed for a mechanical mixing of the mine pool to distribute the molasses and phosphoric acid. The work required for the"Initial In Situ Treatment" scope has long been completed. Consequently, CLL is requesting that the $350,000 included in the current bond be released.