Plants

3.6.2.3 Project Effects on Rare, Threatened, and Endangered Plants

Black Canyon consulted with the USFWS and BLM to identify RTE plant species in the Project vicinity. Black Canyon also conducted specific studies and incidental field observations to identify these resources in conjunction with other field activities conducted in 2021 in support of the Project licensing. The field surveys identified 23.54 acres of suitable habitat for Ute ladies’-tresses, an ESA-threatened species but no individual of Ute ladies’-tresses was found in the botanical study area. Two BLM sensitive plant species, limber pine and persistent sepal yellowcress, were also identified during field surveys in the botanical study area.

Habitat for Ute ladies’-tresses was primarily found along the margins of perennially flowing streams in the botanical study area, generally in areas not expected to be affected by Project construction (e.g., because Project transmission will span these areas). A total of 23.54 acres were identified as potential suitable habitat for Ute ladies’-tresses within the botanical study area. As described in the Special-Status Plants and Noxious Weeds Study Report, the data collected for the Aquatic Resources Inventory was used to determine suitable habitat for this species. Information was gathered during the aquatic resources delineation, as it directly correlates to Ute ladies’-tresses habitat. Most of the identified Ute ladies’-tresses suitable habitat has experienced some level of disturbance, including livestock grazing and trampling as well as hay production in wet meadow areas. Most of the suitable habitat occurs in irrigated hay pastures that were inundated during the August 2022 surveys. Of the 23.54 acres of Ute ladies’-tresses suitable habitat, 21.44 acres occur on private property, with the remaining 2.34 acres occurring on BLM-managed lands. In 2021, one potential Ute ladies’-tresses individual was observed in the study area but was extremely desiccated, and a positive identification was not possible. In 2022 the specimen was relocated and determined to not be Ute ladies’-tresses. Because marginal to suitable habitat for this species does occur in the study area, protocol surveys for Ute ladies’tresses will be required prior to Project construction. Per USFWS protocol for this species, preconstruction surveys will be conducted for three consecutive years during the known Ute ladies’-tresses flowering period between late July and the end of August, in areas where impacts cannot be avoided. Survey methodology and locations will be determined in consultation with USFWS. These surveys will be conducted by trained botanists in areas that will be disturbed by the Project. If the final configuration of the Project impacts mapped habitat for Ute ladies’-tresses, then the results of the protocol focused survey for Ute ladies’-tresses that would be conducted prior to construction would determine if and how many individual plants would be affected by the Project. Impacts to Ute ladies’-tresses habitat could take the form of direct impacts through construction of the Project, and indirect impacts through degradation of habitat by construction of the Project near Ute ladies’-tresses habitat. Because no Ute ladies’-tresses are currently known to occur in the botanical study area, it is not likely that the Project would jeopardize the continued existence of this species.

Persistent sepal yellowcress was found along the western and northeastern shorelines of Seminoe Reservoir. Along the western edge of the Reservoir there are nine occurrences that were documented during the 2022 survey efforts that could be temporarily and permanently affected by construction of a temporary laydown yard and/or marine works

areas, and the construction and use of these temporary Project components could impact persistent sepal yellowcress through direct impacts on individuals and indirect impacts through disruption of habitat that could contain a seed bank for this species. Because this species was found within 300 feet of the shoreline of Seminoe Reservoir, and at least 14 occurrences of this species occur in the immediate vicinity of different proposed components of the Project (Intermountain Region Herbarium Network 2022), the entire Seminoe Reservoir shoreline should be considered suitable habitat for persistent sepal yellowcress.

Potential threats to these occurrences include herbivory from ungulates such as bighorn sheep (Ovis canadensis), which were observed grazing in one of the occurrences along the eastern edge of the reservoir, drought and associated low reservoir water levels, encroachment of invasive and noxious plant species, and recreation in Seminoe Reservoir.

Potential Project effects on persistent sepal yellowcress could include fluctuations in water levels associated with Project pumping and generating operations, encroachment of noxious weeds into suitable habitat, as well as potential trampling and mortality of individuals during construction of the marine works areas. Impacts on persistent sepal yellowcress are considered negligible as occurrences documented during the 2021 and 2022 surveys are mostly outside of the construction footprint for most facilities.

As discussed in Section 2.1.1.2, Project operations are predicated to have a daily surface water fluctuation of 6.4 inches under normal operating headwater elevation of 6,357 feet. Any change in Seminoe Reservoir elevation due to Project operations will be within the historic range of Seminoe Reservoir water levels and, therefore, any impacts to shoreline habitats would occur withing areas where Seminoe Reservoir has operated historically. Project effects on Seminoe Reservoir water level and surface area will occur within a band where wave action has historically altered water levels and impacted shoreline habitat conditions on an intra-day and even intra-hour scale. Specifically, persistent sepal yellowcress populations were observed within 300 feet of the water’s edge. Because persistent sepal yellowcress typically occupies shoreline habitat with sparse vegetation, daily fluctuations of approximately 6.4 inches are unlikely to adversely impact this species.

Limber pine was found throughout the botanical study area and occurring as a primary constituent of the Limber Pine-Juniper Woodland community around the proposed upper reservoir area, and as isolated occurrences. Some areas of Rocky Mountain Foothill Limber Pine-Juniper Woodland are expected to be directly impacted by the Project through the construction of the proposed upper reservoir and proposed access roads as well as along the transmission line. According to GIS projections, 109.05 acres of Limber Pine habitat will be permanently disturbed because of construction activities planned for the Project (Table 3.6-5). Of the 109.05 acres of permanently disturbed habitat, 84.83 acres will be from surface level events. Similarly, 102.63 acres of temporary construction disturbance areas will be impacted from construction activities. Important to note, these areas are likely to be disturbed during construction but will be revegetated after construction activities are complete.

It is possible that the isolated limber pine occurrences along the access roads and transmission line corridor could be entirely avoided by the Project. If the final configuration