BOARD02441

• Board Meeting Date: 3/26/2001
• Description: ISF Section - Donation Water Division 7 - Carbon Lake Ditch
• Board Meetings - Doc Type: Memo

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Rod Kuharich, Director
Dan Merriman, Section Chief
March 15, 2001
Page 2

Background

Serious metals contamination from historic mining practices in the Red Mountain and Silverton
Mining districts has been identified, characterized, and analyzed for remediation feasibility by
ARSG. Mineral Creek, from which the Carbon Lake Ditch diverts, is currently on the State of
Colorado's 303 (d) list of non-complying stream segments and has been designated as having the
highest priority for cleanup. The Carbon Lake Ditch transports irrigation water trans-basin to the
Uncompahgre Basin, ARSG has sampled water quality and mine waste sites in the Carbon Lake
area and determined that the Kohler Tunnel drainage contributes the largest amounts of
aluminum, cadmium, copper, and zinc to the Animas watershed of any single source.
Accordingly, ARSO has given the Kohler Tunnel drainage the highest priority for remediation.

The Kohler Tunnel drains water believed to be entering the workings of the San Antonio Mine.
Recent geophysical investigations indicate a high potential that the Ditch is leaking water into
the mine workings. Mine maps show that open stopes exist directly under the Ditch. Because of
ice build-up and periodic heavy monsoon rains, the dikes of the Ditch have frequently breached,
causing serious erosion of soils and requiring expensive maintenance, when the area is
accessible. Once willer enters a mine, the process of acid rock drainage begins. Metals and acids
are leached out of the rock, enhanced by a bio-catalytic process in an aerobic environment.

The treatment of acid mine drainage is extremely expensive and must be continued in perpetuity.
Studies conducted by Sunnyside Gold Corporation in the Silverton area indicate that although
passive wetland treatment may be successful, renewal of the medium and the disposal of
accumulated wastes would cost over one half million dollars per year. Active treatment,
requiring a power supply, and the additional costs of infrastructure, power, and maintenance,
would also produce a large amount of waste which would need to be disposed.

Rather than treating the water discharged from the Kohler Tunnel, a more practical approach
would be to eliminate the source of the water that infiltrates the mine, making perpetual
treatment unnecessary or greatly reducing the extent of required treatment. Although the Carbon
Lake Ditch is operated for a short period each year, standing water and ice remain in the ditch
year round. Containing of the entire 15 c.f.s. of water rights decreed to the Ditch in a pipeline
would be very costly and mechanically difficult at best, given the extreme environmental
conditions ofthis high elevation, alpine ditch,

Proposed Purchase and Donation

The Council, in cooperation with ARSG, therefore, proposes to purchase at least 80%, but
preferably all, ofthe water rights in the Carbon Lake Ditch to reduce water infiltration into the
mine workings, provide enhanced flows to preserve the natural environment in Big Horn and
Mineral Creeks and restore the natural hydrological regime of the area. All the owners of the
water rights in the Carbon Lake Ditch except one have verbally agreed to sell their water and