NEPA--Environmental Assessment
NEPA--Environmental Assessment
NEPA--Environmental Assessment
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Silverton Grazing Risk <strong>Assessment</strong><br />
popular summer recreation trail and is the main access route for hikers and horseback<br />
riders into the central Weminuche Wilderness and the Pine River basin. Re-opening the<br />
Pine-Piedra Stock Driveway for use by sheep would require a significant amount of<br />
mechanical work, including moving large amounts of downed logs that were placed across<br />
the trail as fireline mitigation after the 2002 Missionary Ridge wildfire.<br />
To prevent having to trail domestic sheep up the Pine River trail and through the heart of<br />
the S28 Vallecito Creek bighorn sheep herd’s summer range and summer concentration<br />
area, or up the lengthy Pine Piedra Stock Driveway, it was proposed to access the Pine<br />
River Allotment from the north via Rio Grande Reservoir. The proposal was to truck<br />
domestic sheep to Rio Grande Reservoir, then trail sheep up the Weminuche Trail, south<br />
over Weminuche Pass, and into Rincon La Vaca and Rincon La Osa. Sheep would then be<br />
trailed back out via the Pine River Trail, over Weminuche Pass and back down to Rio<br />
Grande Reservoir. We were unable to obtain permission from the Rio Grande National<br />
Forest to use this access route. This route would take sheep through and very close to<br />
mapped summer range for the S16 Cimmarona/Hossick herd.<br />
If the Pine River Allotment were to be restocked with domestic sheep, potential for contact<br />
with bighorn sheep from the S16 Cimmarona/Hossick herd and the S28 Vallecito Creek<br />
herd appears to be high. Moving domestic sheep from a “High Risk” allotment in the<br />
Silverton Landscape to the upper Pine River Allotment would be moving sheep to an area<br />
of equal or greater risk for contact with bighorn sheep, thereby maintaining the same<br />
problem, just moving it to a different location. We recommend not stocking any portion of<br />
the Pine River Allotment due to its lengthy wilderness access route, lack of permission for<br />
access from Rio Grande Reservoir, substantial overlap with mapped summer range for the<br />
S16 Cimmarona/Hossick bighorn sheep herd, and need to trail through mapped summer<br />
range of the S28 Vallecito Creek bighorn sheep herd.<br />
RISK ASSESSMENT PROCESS<br />
This “Risk <strong>Assessment</strong>” process involved the participation by FS/BLM wildlife biologists,<br />
FS/BLM rangeland management specialists, FS/BLM decision makers, Colorado Division<br />
of Wildlife terrestrial biologists and District Wildlife Managers, and domestic livestock<br />
permittees. A series of meetings were held to review maps of the affected bighorn sheep<br />
herds and grazing allotments.<br />
The focus of the risk assessment process was on active and vacant domestic sheep<br />
allotments (see Figures 2 and 3, below). Because vacant allotments could be restocked<br />
administratively at any time, it is important to provide a risk rating in the event the<br />
allotment was to be restocked. Allotments that have already been closed were not<br />
specifically reviewed but would have received a rating of low risk.<br />
The risk of physical contact between domestic sheep and bighorn sheep, with the<br />
potential for subsequent disease transmission, was given a rating of “High’, “Moderate”, or<br />
“Low”. Disease transmission however, is considered a correlate of contact, not an effect.<br />
And, although disease transmission is discussed in this assessment, these ratings are not<br />
intended to be an estimate of disease transmission probability, only an estimate of<br />
relative level of risk for physical contact between domestic and bighorn sheep.<br />
A risk rating of “High” indicates that contact between domestic sheep and bighorn sheep<br />
is thought to be likely in the immediate future, although disease transmission resulting in<br />
a bighorn sheep mortality event is by no means certain. If allotments have been operated<br />
for many years without apparent disease transmission, we do not use this observation to<br />
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