2019-01-03_REVISION - M1977300 (2)

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N.COLORADO LEGACY LAND TECHCNIAL REVESION 27.RESPONSE TO COMMENTS 1. The Operator is proposing to submit a single quarterly sampling report which provides the results of the quarterly sampling event.Please confirm the quarterly sampling report will continue to include the laboratory analytical results and the chain of custody forms. Response: Confirmed. The quarterly report will include a copy of the analytical laboratory report and chain of custody. For clarity the example report included as AttachmentA of Technical Revision 27 has been revised with the following text: "The analytical laboratory data report and the chain of custody are attached to this report". 2. The Operator did not include the sumps in the groundwater sample locations.Please provide a list of all sumps which are being sampled and confirm the proposed changes to the sampling methodology and reporting include the sump locations. Response: The text of Technical Revision 27 and Attachment A Table 2 have been revised to include sampling the sumps. CLL proposes sampling all of the sump water that is collected and combined prior to piping it underground. This new sample location will be a spigot within the water treatment plant and will replace individually sampling the sumps. This new sample location will be call"Sumps". 3. The Operator is proposing to relocate the submersible pump to a new location utilizing the Jeffrey air shaft.Please describe what steps will be taken to ensure the new pump and associated infrastructure are working properly before the current pump and infrastructure are taken off-line. Response: All infrastructure that is associated with the current pump(25 Horse Power[HP])will remain in place. All infrastructure associated with the new pump(60 HP)will be incorporated into the existing Water Treatment Plant plumbing design. Modifications will be made to the plant piping to allow the water treatment plant operator the ability to alternate between the two different source streams. The valve setup is shown in the attached piping and instrument diagrams. The capability to alternate between the two source streams will aid in the initial commissioning and transition of the 60 HP pump to full operation. The performance of the 25 HP pump is effective up to 200 feet of head and is intended to be used while the mine pool is within the 25 HP pump effective range. The 60 HP pump will be used to continue to dewater the mine pool to an elevation of 6202 feet above mean sea level(FAMSL)or 400 feet below the Steve Adit. 4. As noted above,the new submersible pump will be installed within the Jeffrey air shaft.The Operator removed an existing closure from the Jeffrey air shaft to gain access to the underground workings.Please confirm,that upon final closure of the site,the air shaft will be sealed in the manner approved under Technical Revision No.8. If an alternate closure method will be utilized,then provide the Division with the design details of the proposed closure. Response: Due to the size of the pump assembly the foam plug will need to be removed. The head frame structure is designed to create a steal barrier to eliminate access into the ventilation shaft.An access panel will be installed in the center of the head frame to allow for equipment maintenance and replacement. The panel will be secured in place using a pad lock. Following successful closure of the site and the removal of the pumping equipment,the Jeffrey air shaft seal will be replaced using the same design specifications. The current seal consists of a 12-foot-deep foam plug supported by 1-beam cross members and ply-wood. The surface completion will also be reconstructed to the original state,which was 6 feet of amended top soil on top of the foam plug. PAGE 2 OF 16