Application

2.2.3 Concept Study Alternatives and 2019 Successive Preliminary Permit Application

In 2019, Black Canyon submitted to FERC a Successive Preliminary Permit Application to the 2016 Preliminary Permit Application. A new design supported by a conceptstudy (HDR 2019) was described in the 2019 Successive Preliminary Permit Application. The concept of the West forebay from the 2016 Preliminary Permit Application was eliminated since the inlet/outlet location was deemed infeasible due to its proximity to the Seminoe waterretaining structures. Instead, the concept study utilized the East forebay as the sole upper reservoir as the basis of refinements. The concept study examined five alternatives for the East forebay:

1. Alternative 1, a 500 MW (3 x 166 MW variable-speed units) pumped storage facility with a 10-hour operating time. 2. Alternative 2, a 500 MW (3 x 166 MW variable-speed units) pumped storage facility with a 14-hour operating time. 3. Alternative 3, a 600 MW (3 x 200 MW variable-speed units) pumped storage facility with a 10-hour operating time. 4. Alternative 4, a 600 MW (3 x 200 MW variable-speed units) pumped storage facility with a 14-hour operating time. 5. Alternative 5, a 750 MW (3 x 250 MW variable-speed units) pumped storage facility with a 10-hour operating time.

Five different reservoir configurations were considered, one for each of the alternatives. All alternative upper reservoirs were assumed to be earthfill embankment dams with emergency spillways to prevent overtopping during a hypothetical over-pumping event. A surge tank was recommended for all alternatives with diameter sizing ranging from 35 feet (Alternatives 1 and 2) to 45 feet (Alternative 5). Differences among the five alternatives were primarily with reservoir and conveyance system sizing.

Alternatives 4 and 5 share the same upper reservoir configuration but differ in the specifics of the conveyance system sizing. Alternative 5 was determined to capture improved economy of scale when compared to the alternatives identified in the 2016 Preliminary Permit Application. Alternative 5 was the Project configuration presented in the 2019 Preliminary Permit Application and in 2020 in the PAD (Figure 2.2-3). Additionally, refinements of the upper reservoir location resulted in the avoidance of the Bennett Mountains WSA as shown in Figure 2.2-3. Table 2.2-3 provides a description of the five alternatives.