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COLORADO LEGACY LAND <br /> SCHWARTZWALDER MINE <br /> soil was identified in Technical Revision 14 as having the potential to leach uranium to shallow <br /> groundwater and adversely affect Ralston Creek.Upon the completion of the alluvial valley excavation <br /> project, Ralston Creek will be allowed to flow through its natural channel (the bypass pipeline will <br /> remain adjacent to Ralston Creek as a contingency system). <br /> • Historical sources, e.g., waste rock dumps and alluvial waste rock fill, have contributed to a limited <br /> amount of mass loading of Ralston Creek with uranium and metals, and has affected the alluvial <br /> groundwater quality. <br /> o Waste rock dumps: In 2020, CLL constructed a diversion channel on the North Waste Rock <br /> Pile (NWRP). This channel diverts run-on water around the NWRP. Subsequent to the <br /> installation of this diversion, mass loading from the NWRP into Ralston Creek is now <br /> considered de minimus as observed seeps in the area of the NWRP have been largely <br /> eliminated. <br /> o Alluvial waste rock: As described above,a bypass pipeline now prevents Ralston Creek from <br /> interacting with the contaminated alluvial valley soil. Similarly, alluvial groundwater in the <br /> permit area has historically been captured by a sump system and sent back into the mine.As <br /> alluvial waste rock has been removed throughout the valley,the alluvium around the sumps <br /> has been removed so that the sumps are now above the surrounding soil and are thereby <br /> becoming redundant. These engineering controls shall be removed once the onsite source is <br /> addressed. <br /> o The historical solid phase sources have largely been reclaimed with limited materials around <br /> the Site access road still in the process of being removed,and then the valley will be reclaimed <br /> by establishing native vegetation. The reclamation activities combined with the upstream <br /> diversion have essentially eliminated mass loading to Ralston Creek. <br /> • The mine pool is seasonally pumped to a water treatment plant (WTP), treated, clean water is <br /> discharged to Ralston Creek, and reject brine is sent back to the mine. The WTP includes a reverse <br /> osmosis (RO) and ion exchange (IX) system that removes uranium and metals from the mine pool <br /> water. <br /> • Since CLL purchased the Site in March 2018,pumping of the mine pool has consistently maintained <br /> the mine pool elevation below the regulatory limit of 150 feet (ft) below the Steve Level (hereafter <br /> referred to as the"regulatory limit")even during consecutive months of no pumping. <br /> o Maintaining the mine pool below the regulatory limit has led to (i) establishing a hydraulic <br /> gradient away from Ralston Creek in the permit area,and(ii) closing the mine has resulted in <br /> reducing the exposure of wall rock to oxygen, which minimizes uranium oxidation in the <br /> workings and translates to less mobile uranium to treat. <br /> o The regulatory limit was established as the permit level in 2012 by the Mine Land Reclamation <br /> Board.This elevation is agreed to establish a hydraulic gradient away from Ralston Creek in <br /> the permit area. <br /> • In-situ treatment of the mine pool with molasses and alcohol (carbon and nutrient sources for the <br /> indigenous population of sulfate reducing bacteria [SRBJ), has shown promising results in reducing <br /> uranium concentrations to below 10 milligrams per liter (mg/L). These results indicate that in-situ <br /> treatment of the mine pool may be a viable feature of a long-term strategy to manage the mine pool. <br /> MAY 2022 10 AMENDMENT 6 <br />