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ARCADIS o Mine Dewatering with Ex -situ Water Treatment o In -situ Mine Pool Treatment o Long -term Stabilization of the Mine Pool Water Level • Section 6: Water Quality Monitoring Plan • Section 7: References and Information Considered Particular emphasis is placed on the adequacy of the supporting information and data upon which to base decisions that are critical for the success of reclamation at the Schwartzwalder Mine (the site). The primary sources of data and information considered and relied upon for this review included: • Reclamation Plan (Cotter 2012). • DRMS letters to Cotter dated January 30, 2012 (DRMS 2012a) and March 28 2012 (DRMS 2012b). • Information previously cited in ARCADIS 2011a and 2011b. 2.0 GENERAL REVIEW COMMENTS General comments pertaining to the Reclamation Plan review include: • The Reclamation Plan identifies three sources of water quality impacts at the site. These include: 1) the mine pool, 2) historic low -grade mineralized mine spoils and waste rock (alluvial fill) near the mine in the alluvium, and 3) alluvial fill in or under the South Waste Rock Pile. It is of note that the South Waste Rock Pile was not considered a source in the EPP, but is now targeted for additional characterization, which is consistent with previous recommendations provided by ARCADIS. • Overall, the Reclamation Plan addresses the mine pool and its relationship with the alluvial groundwater and Ralston Creek (creek). This relationship was initially identified as a data gap during the EPP review and has been addressed in the Reclamation Plan. • The Reclamation Plan requires additional details with respect to performance criteria, specifically for the following aspects of the Reclamation Plan: 1) treatment concentration targets for uranium and other constituents of concern (COCs) within the mine pool (these targets should be set so that re- contamination of the alluvium is prevented, and concentrations at Ralston Creek remain in compliance with public water supply concentration limits); and 2) in -situ mine pool treatment (establish performance criteria for the in -situ trial [acceptance criteria]). • The sequence of reclamation activities that is most protective of public health and the environment is as follows: 1) excavate alluvial fill; 2) seal coreholes, faults, and fractures (with concurrent bench tests of in -situ mine pool treatment); 3) pump down the mine pool to 500 feet below the Steve Level; 4) begin in -situ trial and evaluate results; 5) conduct full -scale in -situ mine pool treatment (if bench and trial results are acceptable); 6) evaluate mine pool treatment results, concentrations achieved in the mine pool, and resultant concentrations in the alluvium; 7) verify that COC concentrations in Ralston Creek meet public water supply concentration limits for a time period that includes multiple seasons (high -flow and low -flow conditions); and 8) based upon site data and concentrations in Ralston Creek, evaluate removal of the diversion pipeline. Page 2116