Tract Plats for Animas Substation and Access Road

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The northern parcel also contairis slag from a lead smelter which operated on the site prior to the
construction of the uranium mill. Approximately 200,000 cubic yards of slag remain on the site,
covered by 18 to 24 inches of clean backfill and 6 inches of topsoil. The location of the slag is
shown on the attached figure. The slag was not removed during. remedial action because the
material was not included under the UMTRA authority (it did not meet the definition of residual
radioactive material).
The EPA regulations also allow for contaminated materials to be left in place where removal
would pose a clear and present risk of injury to workers or would produce environmental harm
that is excessive compared to the health benefit achieved. These cases are called Supplemental
Standards. Supplemental standards were applied to areas on the slope of Smelter Mountain, the
banks of the Animas River, and to an area beneath the lead slag. The Supplemental Standards .
areas are identified on the attached map. ' .
The groundwater beneath both parcels remains contaminated and will be addressed during Phase
II of the uranium mill tailings remedial action project. Several groundwater monitor wells are
present on each parcel and will remain in place until the U.S. Department of Energy determines
that they can be removed. _
Additional information concerning the remedial action, groundwater conditions, lead smelter slag
and supplemental standards is available from the Colorado Department of Public Health and
- Environment; Hazardous Materials and Waste Management Division.