2018-08-16_REVISION - M2012032 - Laserfiche WebLink

Home Browse Search

Ouray Silver Mines Inc. Technical Revision 10 August 14, 2018 In November 2016, OSMI submitted a termination request for discharge Permit. In June 2017, the termination request was denied. On August 4th, 2017 the CDPHE requested a Permit Modification to CO0000003 in addition to the permitting completed through DRMS, that included a sampling point before commingling with other waters. As a result, GW-3R replaced failed-well GW-3A and was located directly within the infiltration mound of the bioreactive bed to facilitate evaluation of infiltrating water. Water quality at GW-3R has consistently met groundwater quality standards. CDPHE has not accepted GW-3R as an interim compliance point. A new five-stage passive treatment system with Sneffels Creek discharge via a second outfall (Outfall 002A) was approved as Modification 4 to CDPS permit CO0000003 on July 31, 2018 and is effective on August 31, 2018. The new system is consistent with OSMI's commitment to a passive treatment system that will function into closure. Prior to discharge, the mine water would pass through a five-stage passive treatment system that incorporates sediment ponds 2 and 3 before discharging to Sneffels Creek(Map 1). OSMI will bring the system into full functionality under a Compliance Order on Consent with the Enforcement side of the Division following CDPS permit renewal. TR 10 requests DRMS approval for construction of the five-stage passive treatment system with surface water discharge. 2.2 Groundwater Monitoring Well Installation OSMI proposes an additional monitoring well, GW-4, be located between Pond 3 of the five- stage system and Sneffels Creek to monitor for potential water quality impacts associated with the passive treatment system. 2.3 Re-Locate Diesel Tank The C-1 (see SWMP) diesel tank is located at the entrance to the Mill Building. OSMI proposes to move it to a less congested area on the western edge of the Administrative area, improving traffic flow and safety(Map 1). 3 Project Rationale The rationale for each of the requested changes is presented in this section. 3.1 Five Stage Passive Treatment System The purpose of this project is to construct a passive water treatment system that will meet both DRMS and CDPHE requirements for water quality and function into closure with minimal maintenance, low waste production, limited power requirements, and strong aesthetic value. The system and new Outfa11002A was approved as Modification 4 to CDPS permit CO0000003 on July 31,2018. A five-stage passive treatment system is currently being pilot tested underground, following a Treatability Study crafted by Geosyntec Consultants (Appendix B). The five stages are: • Settling • Aerobic wetlands • Sulfate reducing bioreactor • Anaerobic wetlands and/or Aeration 2