NEPA--Environmental Assessment

Silverton Grazing Risk Assessment
There is evidence that the S33 Pole Mountain/Upper Lake Fork Herd experienced a
significant and widespread die-off in the late 1980’s. However, there is no evidence
suggesting contact with domestic sheep in the Picayne/Mineral Point Allotment was
related to the incident. There has been no indication that domestic sheep grazing in this
allotment have contacted bighorn sheep or been related to disease events in the S33
bighorn herd.
Under Alternative 2, the permittee has the option of accessing the south half of the
allotment by trailing from Engineer Pass south and west around the Animas Forks
townsite, then tailing down the Animas River road (State Highway 110) to Picayne Gulch,
then up the road (County Road 9) to the head of Picayne Gulch. Or, the permittee could
access the same area by trailing around the west side of the Animas Forks townsite, then
trailing up steep avalanche chutes to the basins east and south of Treasure Mountain.
Under Alternative 3, the permittee would trail around the west side of the Animas Forks
townsite, then trail up the steep avalanche chutes to the alpine the basins east and south
of Treasure Mountain.
Surveys for bighorn were conducted by BLM employees in the area of overlap over the
past four summer seasons and no bighorn sheep have been detected in the allotment. The
domestic sheep permittee has reported no sightings of bighorn sheep in the allotment.
The allotment is also heavily used by the public for motorized recreation with an extensive
network of heavily traveled 4x4 roads and no bighorn sheep have been reported to CDOW
in the area of overlap.
BLM staff surveys have detected bighorn sheep in four of the last five summer seasons in
Grouse Gulch and Burns Gulch, two side canyons directly across the Animas River from
the allotment on the east side of the Animas River canyon. Bighorn sheep have been
detected each summer in Grouse Gulch, only about 0.25 miles east of the Animas River
road, near the mouth of the gulch. The Animas River road has been used for decades by
the Picayne/Mineral Point Allotment permittee as a trailing route to access the south half
of the allotment. This trailing route would continue to be permitted under Alternative 2.
The trailing route most likely used by the permittee under Alternative 3 would be about 1
air mile west of the Grouse Gulch bighorn use area and on the west side of the Animas
River canyon. Portions of Burns Gulch where bighorn sheep have been detected are about
1 air mile east of the allotment’s active grazing areas, but across the Animas River
canyon. Crown Mountain and Niagara Peak are about 2.0 air miles east of the allotment
and are believed to be summering areas regularly used by bighorn sheep.
Summary of Risk Rating for Picayne/Mineral Point Allotment:
Risk Rating: Alternative 2 – High
Alternative 3 – Moderate
Under Alternative 2, the close proximity of domestic sheep to known bighorn use areas
(about 1 mile), very close proximity of a domestic sheep driveway to bighorn use areas
(about 0.25 mile), and proximity of grazed portions of the allotment to bighorn use areas
(about 2 miles), and the potentially expanding nature of the S33 bighorn sheep herd,
together result in a rating of “High Risk” for contact throughout the south half of the
Picayne/Mineral Point Allotment.
Under Alternative 3, the application of additional herding techniques and project design
criteria described below (Table 3), the use of a more westerly driveway to access the south
half of the allotment, the lack of bighorn occurrences in the allotment, the lack of bighorn
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