2.1.2 2013 Phase I Pumped Storage Evaluation Study

In 2013, Reclamation performed a preliminary screening study (Phase I Study) to assess the viability of adding additional pumping and generating capacity at four existing conventional hydropower stations: Yellowtail, Pathfinder-Alcova, Seminoe-Kortes, and Trinity-Lewiston (Reclamation 2013a). Five concepts to add additional pump-generation capacity were explored for the four sites:

• Concept 1 – Replace existing conventional units with new pump-generating sets. • Concept 2 – Replace existing conventional units with new pumping sets. • Concept 3 – Add adjacent new pumping sets. • Concept 4 – Add adjacent new pump-generating sets. • Concept 5 – New upper reservoir and new pump-generating sets.

Concepts 1 and 2 were eliminated from consideration due to requiring existing generating units to be taken offline for a significant amount of time, impacting Reclamation’s ability to produce power and potentially adhere to downstream flow requirements. Additionally, the conversion of existing conventional units to pump turbines requires a significant amount of costly (and typically not economically viable) civil work to lower the unit centerline for the required pump submergence.

For the Seminoe-Kortes site, one type 3 concept (3SK), one type 4 concept (4SK), and six type 5 concepts (5A1, 5A2, 5B, 5C, 5D1, and 5D2) were explored in the Phase I Study. One screening criterion for the alternatives was the conveyance length to head ratio (L/H Ratio) of less than 12 for pumped storage facilities utilizing a new upper reservoir, and less than 5 for the addition of new pumping/pump-generating units. The Type 3 and 4 concepts (3SK and 4SK) were eliminated due to their excessively high L/H Ratios and related capital costs. Only pumped storage alternatives (type 5 concepts), specifically 5A1, 5A2, 5C, and 5D1, were deemed to have potential to be further investigated in the Phase II Study. Alternative 5B was eliminated as an option due to its small generation capacity relative to its volume. Alternative 5D2 was eliminated because a similar alternative (5D1) appeared to be a strictly better alternative.

Reclamation qualitatively screened alternatives for environmental impacts to identify potential fatal flaws for the proposed alternatives. Examined environmental impacts included:

• Impacts to water storage and water supply; • Impacts to meeting minimum flow release requirements; • Impacts to water quality or temperature; • Changes to existing system operations; • Impacts to reservoir or riverine fisheries; • Impacts to special-status species and critical habitat (non-fish species);

• Impacts to existing reservoir or in-river recreation; • Impacts to cultural or historic resources; • Impacts to Native American resources; • Impacts to land uses or regulatory designations; • Other project construction impacts; and • Stakeholder conflicts, including irrigation, flood control, water quality, fishery needs, tribal needs, recreation, and hydropower, all represented by different stakeholders with varying interests.

A three-level rating scale was used to evaluate options and their potential impacts and any fatal flaws relative to each criterion:

• Green, indicating that the alternative would not have substantial effects that could yield a fatal flaw, potentially with mitigation efforts; • Yellow, indicating that the alternative could have substantial effects, but are not expected to result in fatal flaws; and • Red, a fatal flaw was identified for the alternative.

None of the environmental criterion indicated a fatal flaw for any of the Seminoe alternatives proposed in the Phase I Study. Impacts given a yellow rating were to be quantified in the Phase II Study to evaluate the presence of a fatal flaw.

Alternatives 5A1 and 5D1, which utilize Kortes Reservoir as a lower reservoir, were expected to have substantial impacts on water levels, reservoir storage, and project operations. The proposed pumped storage impacts to the Kortes Reservoir operations, reservoir storage, and flow releases would impact water temperature which would likely have impacts on fish habitat and populations. This would impact Miracle Mile, which is downstream of Kortes Reservoir and a premier recreational fishing area for Wyoming.

Alternatives 5A2 and 5C utilize Seminoe Reservoir as the lower reservoir and were not anticipated to have substantial impacts on water levels, reservoir storage, or otherwise impact project operations. As such, these alternatives would be more favorable from an environmental impact standpoint for reduced impacts to water quality, water temperature, and impacts to downstream flow requirements.

No potential cultural or Native American resources issues were identified in the Phase I Study for any of the Seminoe site alternatives. Land use impacts for the Seminoe site alternatives include the reservoirs being located in either the Bennett Mountains Wilderness Study Area (WSA) or in the Morgan Creek Wildlife Habitat Management Area. Neither designation would rule out development from a regulatory standpoint and, therefore, was not identified as a fatal flaw and given a yellow rating. Construction impacts for the alternatives were considered substantial, but not considered a fatal flaw and given a yellow rating. Impacts considered included land disturbance, vehicle access, construction footprint, and air pollutant emissions. The installation of permanent Project features and construction footprint would remove habitat from wildlife thatcould be specialstatus species habitat or designated critical habitat. Special-status species have been

documented in the vicinity of Seminoe Reservoir. Required consultation with the U.S. Fish and Wildlife Service could identify appropriate conservation measures, so a green designation was given for the Seminoe alternatives. The Seminoe alternatives were given a yellow rating for the stakeholder issues criterion due to the complexity of coordinating with the states of Wyoming, Nebraska, and Colorado along with Federal and local agencies.

Characteristics for the alternatives are summarized in Table 2.1-2. The configurations for the six pumped storage alternatives from the Phase I Study are shown in Figure 2.1-3. All upper reservoirs were assumed to be concrete-faced, rockfill dams with a 30-foot-wide crest with a maximum allowable dam height of 400 feet and a freeboard of 10 feet. The range of energy storage options varied from approximately 10 to 40 hours of storage with corresponding generation capacities.