3.6.2.2 Project Effects on Noxious Weeds and Invasive Species

Table 3.6-4. Vegetation Communities Permanently Impacted by Proposed Upper Reservoir Vegetation Community Acres

Inter-Mountain Basins Big Sagebrush Steppe Northwestern Great Plains Mixedgrass Prairie Rocky Mountain Foothill Limber Pine-Juniper Woodland Western Great Plains Saline Depression Wetland Wyoming Basins Dwarf Sagebrush Shrubland and Steppe 84.3

1.8

35.6

0.5

17.5

Total 139.7

3.6.2.2 Project Effects on Noxious Weeds and Invasive Species

Non-native invasive plant species can impact human and other environmental resources. Areas where vegetation and soils have been disturbed are more susceptible to invasion by invasive weeds than undisturbed environments. Aggressive invasive weeds crowd out native vegetation and alter the natural environment and habitat for wildlife species, as well as affecting agricultural water-use efficiency and recreational land values. They can adversely affect native plant species, plant communities, and wildlife habitat through competition.

Noxious weeds and invasive species were documented during the 2021 and 2022 field seasons. During the field studies, the occurrence and distribution of eight State of Wyoming noxious weeds and four Carbon County noxious weeds were observed in the botanical study area. Wyeth lupine, Canada thistle, hoary cress, Russian knapweed, bull thistle, and diffuse knapweed were all primarily found along the two-track road leading to the proposed upper reservoir. Halogeton, perennial pepperweed, hoary cress, plumeless thistle, and Russian olive were all found along Hanna Leo Draw Road and/or in the vicinity of Difficulty Creek. The remaining species, cheatgrass and plains pricklypear, are not restricted in their distribution in the botanical study area.

The invasive plant species found in the botanical study area are known to occur throughout the western U.S. and are spread by various land uses. The combination of past and present land use activities in the Project vicinity has contributed to and likely will continue to facilitate the creation of disturbed and weedy habitats. It is well known that many types of land uses contribute to the invasion and spread of non-native invasive species including all ground-disturbing activities as well as any activities that promote the dispersal of weed seed. Roads, agriculture, farming/ranching, recreation, and residential and commercial developments all can contribute to the spread of invasive botanical species.

Black Canyon intends to minimize and control the spread of invasive botanical species that could result from construction and operation of the Project through development of a Noxious Weed Management Plan. Given adequate and appropriate weed management and site restoration activities, the Project should have minimal effects on plant communities and could provide a net benefit by reducing weed infestations in the botanical study area and vicinity. Thus, the Project is not expected to have significant impacts to the landscape from the spread of noxious weed species.