8.4
SPECIFIC CLOSURE AND RECLAMATION OF AFFECTED AREAS
8.4.1 Tailings Storage Facility
A closure cover will be placed over the TSF surface. Directly on top of the TSF surface a
geotextile (similar to BX geonet from Tensar) will be installed to provide stability for the heavy
equipment to backfill and place the soil cover layers. The total geotextile surface area is
estimated at 892,641 SY. A fill layer will be placed directly over the geotextile. The thickness of
the fill will vary and it will be regraded with negative slope towards to northeastern embankment.
This will eliminate ponding on top of the reclaimed tailings surface. The fill material will be
excavated from the stockpiles, loaded, hauled, and compacted as part of placement. The
quantity of fill is estimated at 2,801,650 CY. A 24-inch layer of rock fill will be placed on top of
the fill layer. The rock fill will be excavated from the onsite borrow source, loaded, hauled, and
compacted as part of placement. The quantity of rock fill is estimated at 729,700 cubic yards
(CY). Finally, a 12-inch layer of topsoil will cap the TSF cover. The topsoil will be excavated
from the onsite stockpiles, loaded, hauled, and placed. The quantity of topsoil is estimated at
483,200 CY and will cover the TSF surface and the embankment slope. Figures 2 and 3 in
Appendix D depict the TSF cover and details.
The TSF embankment slope will be ripped to loosen the surface in order to propagate
revegetation before the topsoil is placed. Seed and mulch will be placed to include the TSF
surface and embankment slope.
Fiber rolls (also called fiber logs or straw wattles), tube-shaped erosion-control devices filled
with straw, flax, rice, coconut fiber material, or composted material will be placed along the
western edge of the tailings surface, at the crest, on the slope face of the embankment and
along the toe of the embankment to reduce erosion and rilling. Each roll is wrapped with UV-
degradable polypropylene netting for longevity or with 100 percent biodegradable materials like
burlap, jute, or coir. The rolls are typically 8-inch minimum diameter, staked on four-feet
spacing. Approximately 35,562 square feet of fiber rolls will be placed.
Infiltration through the TSF into the undertrain pond is assumed to continue for 30 years, at
which time the pond will be reclaimed.
8.4.2 Underdrain Pond
After the TSF is no longer draining into the pond, any remaining pond sludge will be excavated
and hauled to a hazardous waste landfill in Deer Trail, Colorado. It is assumed that there will be
sludge in the bottom of the pond and 930 tons will be trucked to landfill. Once the sludge has
been removed, the double liner will be cut and folded by hand by laborers. Approximately
14,579 CY of material will be cut and filled to bury the liner and return the pond the pre-
construction ground conditions.
The pipe from the TSF to the Underdrain Pond will be closed to ensure no further drainage into
the pond. Termination of the pipe at the TSF will be completed over 2 days by excavating into
the TSF embankment to expose the pipe; cutting, grouting and capping the end; and replacing
the excavated material back into the embankment. The remaining 3 tons of pipe and soils will
be removed and disposed of in the city landfill.
The filled-in pond area as well as any other minor surface disturbances will be covered with 12
inches of topsoil (2,300 CY), and revegetated using seed and mulch.
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