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Permit Modification and East Waste Rock Extension UGW350010:
Kennecott Utah Copper LLC

Project Summary

Kennecott Utah Copper (KUC) is proposing to extend the footprint of the East Waste Rock Dumps to accommodate additional waste rock from mining operations. This project will require the relocation and reconstruction of the Eastside Collection System (ECS), the water collection and capture system for the dumps. The East Waste Rock Extension (EWRE) project proposes to relocate the existing ECS and replace or upgrade portions of the system as described in the permit modification application currently permitted under UGW350010. As part of the extension project, KUC will remove soil in stages from approximately 338 acres to prepare a base for the placement of waste rock. Previously constructed cut-off walls in the project area will be removed or breached, then replaced at the furthest eastern extent of the waste rock extension. The primary toe drain system used to collect and convey seepage from the dumps embankments will be replaced and upgraded at the projected toe of the extended dumps.

Ground water monitoring will continue mostly unchanged during and after the extension. Currently, it is anticipated that only two wells will be impacted by the extension, and depending on the final configuration of the dumps and the realignment of a new mine access road, possibly two others (Appendix I, Attachment 3: Compliance Monitoring Plan). KUC has proposed to replace any wells impacted by the EWRE project or new mine road. The remaining compliance wells are located east of the final extended dump toe and will be unaffected by the extension. Following removal of the soil and replacement of impacted cut-off walls, KUC will dump waste rock into the new waste rock extension area. The new waste rock will be placed in a configuration that is more stable than current dump surfaces and will allow for reclamation of the final dump surfaces. The reclaimed dumps will have a store-and-release cover system designed to minimize infiltration into the underlying waste rock and segregate any storm water surface flows into a separate conveyance pipeline to minimize any potential contamination. The reclaimed dumps will tie into and overlie the existing dump surfaces. The goal of reclamation is to minimize infiltration, thus lowering the amount of waste rock contact water generated by the old and new waste rock dumps.

It is important to note that KUC will not be leaching the extended dump area or any of the existing waste rock dumps. KUC ceased all active leaching operations in 2000. This measure significantly reduces the volume of water which has the potential to infiltrate and cycle through the waste rock dumps.

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