2011-01-25_REVISION - M1977300

• Permit No: M1977300
• IBM Index Class Name: REVISION
• Doc Date: 1/25/2011
• Doc Name: Review of EPP
• From: ARCADIS
• To: Denver Water
• Type & Sequence: AM2
• Email Name: DB2
• Media Type: D
• Archive: No

Daniel Arnold, Esq. January 25, 2011
Denver Water Page 20 of 21
values averaging 0.003 mg /L, to MW -0, which is downgradient of the rock piles and has
values averaging 0.167 mg/L. Uranium values in downgradient well MW -0 have always
been above the MCL and there is evidence of an increasing trend in recent years. The
waste rock piles require additional mitigation, otherwise groundwater with elevated
uranium concentrations will continue to enter the central mine area.
Uranium Mobility in Alluvium
DRMS states that the contaminants in alluvium are geologically unstable and easily
mobilized by minor fluctuations in groundwater levels, pH, or redox conditions. This
may be true, but the data to assess this are not contained in the EPP; groundwater levels
in monitoring wells and redox potentials are not provided. We found that the major factor
for uranium mobility in the alluvial aquifer is the degree of pumping from the sumps.
Reactive surfaces of the alluvium and fill may contribute uranium, but the pumping of the
sumps and degree of "dilution water" pulled into the aquifer from the creek is the
dominant factor. This is evidenced in 2009 when uranium concentrations in the
groundwater increased in response to stoppage of pumping in Sump 1. Concentrations
increased because dilution water from the creek stopped.
5.0 REFERENCES
Whetstone Associates. Inc. 2010. Schwartzwalder Mine Environmental Protection Plan.
Prepared for Cotter Corporation (N.S.L.). July 31.
Cotter Corporation (N.S.L.). 2010a. Letter to the Division of Reclamation, Mining and
Safety regarding Schwartzwalder Mine, Permit No. M- 1977 -300 and the September 2,
2010 notification of a discharging pipe. September 3.
Cotter Corporation (N.S.L.). 2010b. Personal communications with Cotter representatives
during site tour; November 5.
Cotter Corporation (N.S.L.). 2010c. Personal communications with Cotter representatives
relative to the November 22, 2010 Technical Memorandum summarizing the November
5, 2010 site tour.
Division of Reclamation, Mining and Safety. 2009. Letter to Cotter regarding the
Schwartzwalder Mine Permit No. M -1977 -300, Environmental Protection Plan,
Technical Revision TR -11, Adequacy Review #1, October 21.
Division of Reclamation, Mining and Safety. 2010. Letter to Cotter regarding the
Schwartzwalder Mine Permit No. M -1977 -300, Environmental Protection Plan,
Technical Revision TR -11, Adequacy Review #1, May 19.