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Amendment 4 should also be revised to incorporate clear benchmarks that identify what the final <br />acceptable result is for remediation of the south waste rock pile, alluvial fill, and mine pool. Without <br />clearly identifiable goals, it will be difficult to measure the success or failure of the activities described in <br />Amendment 4. Cotter must also describe alternatives should it fail to meet the target result. For example, <br />Cotter proposes to eventually remove the temporary bypass structure after remediation of the alluvial fill <br />material and south waste rock pile. Removal of the bypass structure, however, should be conditioned on <br />Cotter's ability to demonstrate that it has attained long term sustainable remediation of the site, and /or <br />that it will pursue other alternatives subject to DRMS' approval, such as installation of a permanent <br />bypass structure or continued operation of the current sump /ion exchange water treatment system. <br />Amendment 4 should also include terms and conditions for monitoring of the mine pool and <br />Ralston Creek, and reporting of data. For instance, monitoring data obtained from the mine pool and <br />Ralston Creek should be shared with Denver Water and other stakeholders. <br />In addition, Cotter must provide an adequate financial warranty sufficient to cover activities <br />described in any final version of Amendment 4 approved by DRMS. Release of portions of the financial <br />warranty should be conditioned upon the successful completion of the benchmarks as determined by <br />DRMS in subsequent public hearings, and upon notice to interested stakeholders, including Denver <br />Water. <br />Again, additional comments prepared by Arcadis on behalf of Denver Water are attached to this <br />letter. If you have any questions regarding these comments or would like to discuss them further, please <br />do not hesitate to contact me. <br />Attachments: Arcadis Memorandum dated June 20, 2012 <br />Cc: Charlotte Neitzel, Attorney <br />Sabrina Forest, EPA <br />Steven H. Gunderson, WQCD <br />Jim McCarthy, City of Arvada <br />James Petrock, Attorney <br />Mary A. Boardman, CDPHE <br />Sincerelly, Z--- <br />Tom Roode <br />Director of Operations and Maintenance <br />Denver Water <br />Page 3 of 3 <br />Denver Water Comments /Schwartzwalder Mine Permit - Amendment 4 <br />M -1977 -300 <br />