Exhibit A (Seminoe FLA)

FERC Project No. 14787 Black Canyon Hydro, LLC January 2023

2.1. Upper Dam and Reservoir 5 2.2. Lower Reservoir and Seminoe Dam ..........................................................................8

2.3. Hydraulic Conveyance Between Reservoirs ............................................................ 10

2.4. Dam Safety 12

2.5. Powerhouse and Transformer Caverns 13

2.5.1. General 13 2.5.2. Machine Hall 13 2.5.3. Transformer Gallery 13 2.5.4. Busbar Galleries 14 2.5.5. Ventilation and Fire Safety 14 2.5.6. Power Facilities Access 14 2.5.7. Evacuation of Power to the Surface 15

2.6. Pump-Turbines 16 2.6.1. Turbine Inlet Valve .......................................................................................16 2.6.2. Pump-Turbines ............................................................................................16 2.6.3. Pump-Turbine Components ......................................................................... 17

Tables

Table 1.0-1. Summary of Lands Within the Proposed FERC Project Boundary 1

Table 2.2-1. Water Level Variation in Seminoe Reservoir due to a Complete Project Pumping or Generating Cycle (10,800 acre-ft) 9

Table 2.3-1. Pumping and Generating Times, at Full Capacity 12

Table 2.11-1. Summary of Project Features .............................................................................. 22

Table 4.0-1. Federal Lands Within the Proposed FERC Project Boundary 29

Figures

Figure 1.0-1. Proposed Seminoe Pumped Storage Project Location 2

Figure 2.0-1. General Site Plan 4

Figure 2.8-1. Single-Line Diagram for proposed Seminoe Pumped Storage Project. ................ 19

Seminoe Pumped Storage Project

List of Acronyms and Abbreviations

AASHTO American Association of State Highway and Transportation Officials

ASR alkali-silica reaction

Black Canyon Black Canyon Hydro, LLC BLM U.S. Bureau of Land Management DFIM double-fed induction machines

FERC Federal Energy Regulatory Commission GSU generator step-up LV low voltage MAT main access tunnel Project Seminoe Pumped Storage Project RCC roller-compacted concrete Reclamation U.S. Bureau of Reclamation

WAPA Western Area Power Administration WSA Wilderness Study Area

Units of Measure

°C degrees Celsius AC alternating current ac-ft acre feet amp amperes cfs cubic feet per second fps feet per second ft feet K horizontal distance in feet needed to make 1 percent change in grade kV kilovolt kW kilowatt mph miles per hour MVA megavolt ampere MW megawatt(s) MWh megawatt-hour(s) rpm rotations per minute

Final License Application

Seminoe Pumped Storage Project

1.0 Proposed Project Location and Overview

Black Canyon Hydro, LLC’s (Black Canyon) proposed Seminoe Pumped Storage Project (Project) will utilize the existing U.S. Bureau of Reclamation (Reclamation) Seminoe Reservoir as the lower reservoir and create a new upper reservoir The two reservoirs will provide a static head of approximately 1,000 feet for a 972-megawatt (MW) pumped storage facility Associated proposed features include a low-pressure headrace tunnel; a vertical pressure shaft; underground high-pressure hydraulic conveyance tunnels; underground power facilities including a main cavern, a transformer cavern containing generator step-up (GSU) transformers, and a gas-insulated switchgear switchyard; a cable tunnel and shaft; two 500 kilovolt (kV) transmission line circuits; an outdoor grid connection; access roads and tunnels; and other appurtenant facilities. The Project will be located in Carbon County, Wyoming, at and near the existing Reclamation Seminoe Reservoir, approximately 35 miles northeast of Rawlins, Wyoming, on the North Platte River (Figure 1.0-1) Although the existing Seminoe Reservoir will be utilized as the lower reservoir for the Project, neither Seminoe Reservoir nor the existing Seminoe Dam is part of the proposed Project for this license application Black Canyon will work with Reclamation on ensuring operations of Seminoe Dam and Reservoir and associated facilities will not be adversely impacted by the proposed Project.

The waterways and generating facilities will be located on lands administered by the U.S. Bureau of Land Management (BLM), Reclamation, and private lands in and around the existing Seminoe Reservoir. (Figure 1.0-1).

The area within the Federal Energy Regulatory Commission (FERC) proposed Project Boundary will contain the completed Project facilities necessary for operation and maintenance purposes which will be located on both private and Federal lands The private lands are situated along the proposed transmission corridor Federal land predominates in the main Project facility areas. The transmission line will also traverse some Federal lands The total amount of Federal land impacted will be approximately 879 acres Table 1.0-1 presents a summary of lands by ownership classification within the proposed FERC Project Boundary Maps detailing the individual parcels and a summary of the acreage of lands of the United States within the FERC Project Boundary are included in Exhibit G-2 through G-8. A tabulation of Federal lands within the proposed FERC Project Boundary by legal subdivision of the Public Land Survey is presented in Section 4.0 of this Exhibit.

Table 1.0-1. Summary of Lands Within the Proposed FERC Project Boundary

Ownership/Administration

Acres

Bureau of Land Management 826.16

Bureau of Reclamation 52.88

Private 642.96

TOTALS 1,522

Figure 1.0-1. Proposed Seminoe Pumped Storage Project Location

Existing Facilities

The Project will use Reclamation’s existing Seminoe Reservoir as the lower reservoir Neither the reservoir nor the existing Seminoe Dam will be part of the FERC-licensed facilities Seminoe Reservoir, impounded by Seminoe Dam on the North Platte River, has a total capacity of 1,017,280 acre feet (ac-ft) (Reclamation 2022) The existing Seminoe Reservoir has an active conservation storage volume of 985,600 ac-ft between elevations 6,239 feet and the normal headwater elevation of 6,357 feet. The crest of the Seminoe Dam is at elevation 6,361 feet Seminoe Dam features a powerhouse with an installed capacity of 45,000 kilowatts (kW).

2.0 Proposed Project Facilities

The proposed Project facilities will create an “open loop” hydraulic arrangement. The facilities will include a new upper reservoir constructed to the west of the Bennett Mountain Wilderness Study Area (WSA); an upper intake structure; isolating gates in a separate gate shaft; a near-horizontal headrace tunnel including a steel conduit over a gulley; a vertical shaft and surge facility; a horizontal, low-level, high-pressure tunnel connected to a manifold and penstocks; underground power facilities containing three pump turbines and three variable-speed generator-motors; GSU transformers; gas-insulated switchgear; draft tube extensions and manifold; a tailrace surge shaft; tailrace; gates and gate shaft; and a lower intake within the existing Seminoe Reservoir Access tunnels will provide access and egress from the underground works, and a vertical cable shaft will contain high-voltage transmission cables from the gas-insulated switchgear to the (surface) overhead transmission lines to the Aeolus interconnection. Figure 2.0-1 shows the general arrangement of the main Project components discussed herein.

Seminoe Pumped Storage Project

2.1. Upper Dam and Reservoir

The new upper reservoir, to be constructed to the west of the Bennett Mountain WSA, will be located within an area of rolling terrain and occasional small rock outcrops at a minimum existing ground elevation of 7,280 feet.

The upper reservoir will be formed by constructing a roller-compacted concrete (RCC), water-retaining perimeter structure using aggregate processed from excavated material from within the reservoir area The crest of the RCC water-retaining structure will be at elevation 7,455 feet and the crest width will be 20 feet.

The storage between the normal maximum operating pool of elevation 7,445 feet and the normal minimum operating pool level of elevation 7,350 feet will be approximately 10,800 ac-ft. The normal maximum operating pool level allows for a freeboard of 10 feet to the dam crest, which will be enhanced by a 3-foot-high wave wall. The over-pumping emergency spillway crest elevation is 7,446 feet, one foot above the normal maximum operating pool elevation. Incidental wave overtopping spillage at the over-pumping emergency spillway is anticipated to be infrequent and nominal, which will be attenuated by the spillway stilling basin at the toe of the dam and subsequent downstream protection.

The adopted cross section of the RCC water-retaining structure will be typical for such structures and will include a vertical upstream face and a stepped downstream face averaging 0.8 H to 1 V. Aggregate materials for RCC construction will be primarily processed from the headrace tunneling, from excavations within the reservoir footprint, and from dam foundation excavation activities. Sand, cement, pozzolans, and admixtures will be imported from local and regional commercial sources The upstream face will incorporate grout-enriched, vibrated RCC to ensure impermeability. The crest will incorporate a road delineated by raised curbs, the 3-foot-high parapet and wave wall on the upstream side, and a steel vehicle barrier on the downstream side.

Preparing the foundation of the RCC structure is necessary for dam construction. Vegetation, overburden, waste material, and weathered rock will be removed to expose firm, un-weathered bedrock Where required, dental and leveling concrete may be placed.

If geologic features (such as joints, lineaments, etc.) are encountered during foundation preparation, each will be excavated, cleaned, filled with concrete, and (if needed) treated with remedial grouting before any required consolidation grouting is performed. It is currently assumed that an average of 10 feet of excavation will be required over the whole dam (structure) foundation to reach acceptable bedrock quality, although this will be verified during site investigations.

Vehicles will access the crest of the RCC water-retaining structure near the intake and gate shaft and also close to the over-pumping emergency spillway, in both cases by 20foot-wide ramps These ramps will be formed by extending the RCC placement downstream of the downstream stepped face of the structure.

Vehicles will access the interior of the reservoir by a similar, 20-foot-wide, RCC ramp forming an extension upstream of the water-retaining structure near the intake.

Seminoe Pumped Storage Project

The floor of the reservoir will be covered by an impermeable geomembrane attached to, and sealed to, the upstream face of the RCC water-retaining structure This membrane will consist of a layer of geotextile, supported by geomembrane and a geospacer all founded on a crushed granular bedding The excavated rock surface forming the floor of the reservoir will be shaped to avoid incidence of high stresses in the geomembrane, and as appropriate, concrete infill will be placed on the floor for shaping The geomembrane will be anchored to the rock floor at regular intervals. Appropriate underdrainage will be incorporated, discharging in galleries at the low spots of the perimeter where the RCC water-retaining structure is highest.

The proposed site of the upper reservoir is currently traversed by two existing Western Area Power Administration (WAPA) transmission lines, the Miracle Mile-Snowy Range 1 115 kV (MM-SNG-1) and Miracle Mile-Snowy Range 2 230 kV (MM-SNG-2). These WAPA transmission lines extend from the Project site to the Aeolus Substation The Project will utilize this existing alignment to the maximum extent possible to establish the corridor for the Seminoe interconnection transmission lines, as described below Prior to the implementation of construction at the upper reservoir site or even before a contractor has been mobilized the section of these existing WAPA lines extending over the footprint of the new upper reservoir will be relocated to accommodate the new upper reservoir.

To prevent any access by individuals or animals to the RCC structure, the reservoir will be surrounded by a 10-foot-high chain and rail security fence, approximately 25 feet from the toe of the RCC Lockable gates will be installed where the access road to the RCC structure passes through the fence. Cameras mounted at intervals on the downstream RCC slope will monitor any attempts to climb or damage the fence.

Over-Pumping Emergency Spillway

The upper reservoir will have no natural water inflow (except rain and snow), but an overpumping emergency spillway will be included, sized for the simultaneous over-pumping discharge condition of the three units at maximum water elevation (i.e., if the motors fail to trip at the maximum water level) The over-pumping emergency spillway will be a 200-footlong, ungated, ogee crest formed by conventional concrete on the top of the RCC section, with a weir crest elevation of 7,446 feet, one foot above the maximum normal water level of 7,445 feet.

Discharges over the over-pumping emergency spillway will be minimized or eliminated by redundant data sensors linked to the pumping controls A Level Control System will be used for normal plant operation and a completely independent Level Protection System will be a fail-safe backup system to the Level Control System Multiple types of instrumentation equipment will be used for both systems to avoid faults specific to one manufacturer. Redundancy, alternative cable routes and types, and battery back-up packs at the upper reservoir will also be incorporated to mitigate the consequences of equipment failure or power supply interruptions. The independent Level Protection System will consist of, at a minimum, three sets of two electrical sensing devices, which will be set at least three inches higher than the normal shutdown level of the pump cycle. Each set will be connected to one of the units If either of the pairs of sensors is activated, a hard-wired

shutdown of the pump cycle will occur At least two other sensors located remotely from each other will be included to back up the electrical switches and will be set at least 3 inches higher than the unit electrical sensors Each of these extra sensors will trip all three pumps Two additional electrical switches will be located within the over pumping emergency spillway – but separately from each other - to trip all pumps if any significant water volumes flow over the spillway crest Actuation of either switch in the over-pumping emergency spillway will trip all the pump cycles and initiate an alarm. In summary the independent emergency Level Protection System will include at least eight discrete water level sensors physically separated from each other, plus two spillway sensors.

A literature review has been made of the reliability of water level sensors. A study by Idaho National Engineering Laboratory in 1995 indicated an average failure rate of water level sensors of between 2.2 to 6 E-7 per hour, while other selected references indicated a worst case of 2.1 E-6 per hour. The IEEE Standard of 2007 indicates a failure rate of 2.88813E7 per hour of a pressure sensor based on a rate of 0.00253 per year. From the available data and using a conservative value of failure rate of 2.0E-6, the proposed system of sensors would exhibit a combined failure rate of 1.6E-23 per hour which implies that water could be inadvertently discharged over the emergency spillway once every 7.13E+18 years.

Including the spillway sensors in the calculation (i.e., assuming that the spillway sensors fail to register the initial discharge from over pumping, and thus allow continuous over pumping), implies a failure rate of 5.606E-31 per hour (or uncontrolled release once every 1.78E+30 years).

These failure rates will be investigated and confirmed in a Potential Failure Modes Analysis (PFMA) during detailed design but can be categorized as very low probability. To further enhance the safety – and reduce the possibility of spillway discharge – cameras will be installed to allow plant operators to visually monitor the water level in the upper reservoir 24 hours per day – particularly at the spillway crest. Redundant cameras will monitor a fixed staff gauge in a stilling well located in an Instrumentation Building cantilevered over the water. Additional cameras will provide a view of the reservoir.

If units were to continue pumping in excess of the maximum water level (elevation 7,445 feet), the excess water would be discharged through the engineered spillway in a controlled manner Given the volume and size of the lower reservoir, there is a potential for a significant water transfer well in excess of the volume of the upper reservoir This excess would be limited by the pumping capacity flow rate If all three units were to continue pumping when the normal maximum water elevation had been reached, the consequent pumping flow would be approximately 8,298 cubic feet per second (cfs) This pumping flow is much greater than the peak flow of 93 cfs resulting from a probable maximum precipitation event at the upper reservoir (which would be the criteria for spillway design if there were a limitation on the available water for pumping) The over pumping flow which could pass over the spillway is not, however, in excess of the spillway capacity of the Kortes dam ungated spillway.

2.2.

Seminoe Pumped Storage Project

The ogee crest will direct the spilling water down a stepped spillway located on the face of the RCC dam into a stilling basin A significant amount of energy from the discharging water will be dissipated on the stepped spillway with the balance being dissipated in a Reclamation Type I basin at elevation 7,378 feet The stilling basin will discharge into a natural gulley downslope of the northwest corner of the reservoir site and thence into the Kortes Reservoir Riprap erosion protection is envisioned for 50 feet downstream of the stilling basin to protect the upper part of the gulley and mitigate erosion below the overpumping emergency spillway During the detailed design site investigations, an examination of the gulley will be performed to determine if any further riprap or protection of the gulley is needed, such as further riprap or grouting of existing rocks in the gulley. The provision of a catch basin close to the top water level of Kortes Reservoir will be considered as a mitigation to reduce the sediment entering Kortes Reservoir

WAPA Transmission Line Rerouting

Two existing WAPA transmission lines, the Miracle Mile-Snowy Range 1 115 kV and Miracle Mile-Snowy Range 2 230 kV, traverse the footprint of the proposed new upper reservoir. These are the same lines that extend past the Aeolus Substation, establishing the proposed corridor for the Seminoe interconnection transmission line to follow, as described below. As part of this Project construction – or before – the existing WAPA lines above the proposed footprint of the upper reservoir would be rerouted to avoid traversing the footprint of the upper reservoir.

WAPA has been consulted and is considering two alternatives – one northwest of the reservoir, and one southeast of the reservoir along the existing track. In either case, WAPA is amenable to co-locating the two lines on to one series of poles, and thus will accept a right of way of 150 feet. The drawings show both potential routes for the WAPA lines around the upper reservoir.

Lower Reservoir and Seminoe Dam

The lower reservoir for the pumped storage Project will be the existing Seminoe Reservoir on the North Platte River. Seminoe Reservoir, with a total capacity of 1,017,280 ac-ft, is formed by a concrete-arch dam structure containing 210,000 cubic yards of concrete and rising 295 feet above the rock foundation.

Reclamation operates Seminoe Reservoir such that the normal minimum water level is elevation 6,290 feet, but a lower minimum water level of elevation 6,239 feet (the Active Conservation Level) is possible during extreme drought events or to facilitate repair work on the dam During a full pumping or generating cycle of the Project, the variation in the water level of Seminoe Reservoir at its normal operating headwater elevation of 6,357 feet, will be less than 6.4 inches.

The variation of the water level in Seminoe Reservoir due to a full Project pumping or generating cycle is shown for various Seminoe Reservoir water levels below in Table 2.2-1.

Table 2.2-1. Water Level Variation in Seminoe Reservoir due to a Complete Project Pumping or Generating Cycle (10,800 acre-ft)

Seminoe Reservoir Water Level (elevation in feet)

Water Level Variation (inches)

6,290 20.8 6,300 17.0 6,310 14.2 6,320 11.8 6,330 9.8 6,340 8.3 6,350 7.0 6,357 6.4

Seminoe Dam, which is a Federal facility operated by Reclamation, is a part of the Kendrick Project, which was authorized pursuant to Section 4 of the Act of June 25, 1910 (36 Stat. 836), and Subsection B of the Act of December 5, 1924 (43 Stat. 702) The Seminoe Dam and Powerplant is a multiple-purpose structure that provides benefits of irrigation, power, and flood control. Its construction was completed in August 1939 The power plant at the downstream base of the dam with a rated head of 166 feet generates electric power as the water is released for irrigation and other purposes.

As noted in the prior sections, the crest of the Seminoe Dam is at elevation 6,361 feet, with a normal headwater elevation of 6,357 feet. Water is normally released from the reservoir through penstocks to the Seminoe Power Plant, which includes three units, each composed of a 13,500 KW generator driven by a 20,800-horsepower turbine Water can also be released through a low-level outlet works or over a controlled spillway and outlet tunnel with a capacity of 48,500 cfs at a water level of elevation 6,357 feet.

Seminoe Dam exhibits some deterioration from alkali-aggregate reaction and is experiencing ongoing alkali-silica reaction (ASR) that has affected the durability and integrity of concrete in the dam Studies of this phenomena at Seminoe have been underway since the 1950s and various cores extracted from the dam have indicated deterioration in the top 35 feet of the dam structure, with most of the damage within the top 10 feet. Reclamation continues to study the dam structure but has not yet decided upon a mitigation strategy.

A solution to the ASR deterioration may require a medium-term drawdown of water while repairs are implemented Despite this potential variation in the dam’s operation, the operation of the pumped storage facilities will likely be unaffected by ASR-related construction, except in extreme drought years.

2.3. Hydraulic Conveyance Between Reservoirs

The hydraulic conveyance system between the upper and lower reservoirs and through the power generating facilities will be predominately comprised of underground tunnels The sole exception will be an approximately 615-foot-long section of the upper waterway across a gulley close to the upper reservoir, which will be formed by a steel conduit supported on concrete piers.

Near the southwestern edge of the upper reservoir will be an intake in the form of a covered bell-mouth set at a weir elevation of 7,295 feet The setting will avoid deleterious vortexes and air entrainment, and will prevent frazil ice, but does allow if necessary for a considerable drawdown below the normal minimum water level of elevation 7,350 feet An excavated channel from the intake to the northeast corner of the reservoir will be included to facilitate this extra drawdown The diameter of the bell mouth entrance will be 75 feet The upper reservoir floor elevation around the intake will be at elevation 7,290 feet A 400foot-wide channel will connect the intake to the lowest part of the reservoir. There will be no gates on the intake and the coarse screens will be such as to prevent the entry of major debris. Additionally, a floating trash boom will be anchored around the intake to prevent floating debris from being drawn into the intake Debris caught on the screen will be dislodged during pumping. Security cameras will be installed to monitor the intake for debris If any debris accumulates, it will be removed in a timely manner.

The intake will discharge into a short, concrete-lined, vertical shaft with an internal diameter of 36 feet At the base of this shaft will be a 90-degree bend and a near-horizontal, concrete-lined tunnel below the RCC water-retaining structure.

Immediately downstream of the foundations of the RCC water-retaining structure will be a headrace gate shaft with an excavated diameter of approximately 46 feet The waterway will be divided into two sluiceways through the gate structure in which two identical wheeled operating gates, 13 feet wide by 36 feet high, will be mounted in gate guides Upstream of the wheeled gates (i.e., the reservoir side) will be slots in which bulkheads can be placed for maintenance of the wheeled gates or during maintenance of the headrace tunnel.

The excavated gate shaft will daylight downstream of the RCC water-retaining structure and so will be extended using structural concrete to the crest level of the RCC waterretaining structure The area between the gate shaft and the RCC water-retaining structure will form part of the road access to the crest of the dam structure.

From the headrace gate shaft to the vertical shaft, the tunnel will be horseshoe shaped, fully lined in concrete, and 32 feet wide finished by 32 feet high finished The tunnel will slope downstream at approximately 1: 100 (0.0025) and the routing will require a steel penstock section over the gulley close to the upper reservoir The gulley enables access to create construction portals on the upstream and downstream side of the gulley area. The gulley will be crossed by an approximately 24-foot-diameter steel penstock supported on concrete columns at approximately 50-foot centers At the downstream end of the steel

section, close to the portal, an access hatch will be included for inspection of the headrace tunnel and penstock.

The hydraulic conduits have been sized to maintain maximum flow velocities of approximately 15 feet per second (fps) for concrete-lined tunnels and approximately 24 fps for steel-lined penstocks The large-diameter, low-pressure steel pipe in the headrace tunnel is estimated to permit a slightly higher flow velocity of 28 fps.

At the downstream end of the headrace tunnel, a vertical, concrete-lined shaft will be constructed with an internal finished diameter of 30 feet For surge mitigation and for ease of construction, the vertical shaft will be extended upwards to the surface. The initial portion of this surge shaft will be 15 feet in diameter; at an approximate elevation of 7,190 feet, the diameter will increase to 30 feet The 15-foot and 30-foot portions of the surge shaft will be concrete lined Near the existing ground surface, the top 50 feet of the surge shaft will be steel lined, with a steel pressure cover at ground level to form a pressure chamber

Two small compressors may be located on the surface next to the pressure chamber (one for redundancy) to maintain sufficient air pressure within the surge shaft to address potential surge conditions. Alternatively, the compressors may be located within the transmission take-off building at the top of the cable shaft with compressed air piping conducted from there to the surge shaft through buried ducts.

At the bottom of the vertical shaft, the hydraulic conduit will include a 90-degree bend into a fully concrete-lined, high-pressure tunnel that is 30 feet in diameter This tunnel will extend to a concrete-lined manifold and three penstock tunnels. The concrete penstock tunnels will be 17 feet in diameter and steel lined within 165 feet of the power facilities The amount of steel lining for the penstocks will be re-evaluated based on the completion of additional data gathering on the rock quality at the power facilities.

The penstocks connect the hydraulic conduit to the pump-turbines located in the underground machine hall Downstream of the pump-turbines, the draft tube extension tunnels will be steel lined to the draft tube gate valves located below the transformer gallery Downstream of the gate valve, the draft tube will be 17.5 feet in diameter, concrete lined, and will intersect the concrete-lined manifold extending to the downstream surge shaft The downstream surge shaft is proposed to be 30 feet in diameter and concrete lined. It will extend to a level of elevation 6,360 feet to accommodate all surge events without loss of water The top of the shaft will be a cavern, sized adequately for shaft construction.

From the downstream surge shaft, the tailrace will be circular and concrete lined with a diameter of 31 feet.

The access tunnel to the surge shaft will be 15 feet wide by 16 feet high and will be lined with shotcrete.

At the downstream end of the tailrace, a gate shaft with an excavated diameter of approximately 46 feet will be constructed This gate shaft will be configured identically to the upper reservoir gate shaft and house a waterway divided into two sluiceways in which

two identical wheeled operating gates, 13 feet wide by 36 feet high, will be mounted in gate guides Downstream (reservoir side) of the wheeled gates will be slots in which bulkheads can be placed for maintenance of the wheeled gates or for maintenance of the headrace tunnel Access to the gate shaft will be from the existing road at the lower intake and the road will be accessed via a tunnel from the main access tunnel.

The lower reservoir intake will be a precast structure at the outlet of the tailrace tunnel. The planned construction methodology envisages that the lower reservoir intake will be pre-cast and floated into place and sunk on to a pre-excavated rock ledge. The lower reservoir intake will be horizontal at an invert level of elevation 6,230 feet It will include bar racks that are cleanable and removeable. The slots into which the bar racks fit will be engineered for bulkheads that allow the water intake structure to be drained for maintenance. A gantry crane will be located at the deck level of elevation 6,360 feet to facilitate cleaning and the handling of both the bar racks and bulkheads.

The power and control cabling for the lower reservoir intake cranes and gates will be routed through the main access tunnel (MAT) and the lower reservoir intake and gate shaft access tunnel.

The elevation of the lower reservoir intake and the size of the bar racks are based on Reclamation data of historical water levels and assume a bar rack velocity during pumping of 2 fps, at 1 foot in front of the racks, is applicable. Further studies may result in reevaluation of the intake velocity criteria and a redesign of the lower intake Computational fluid dynamic modelling may also be performed to finalize the shape and geometry.

Pumping and generating times are given below in Table 2.3-1

Table 2.3-1. Pumping and Generating Times, at Full Capacity Operation

Total pumping time from maximum Seminoe elevation (6,357 ft) 15.1 hours

Total pumping time from minimum Seminoe elevation (6,290 ft) 19.0 hours

Generating time maximum capacity 9.7 hours

Maximum energy stored 10,600 MWh

Computational fluid dynamic analysis has been used to check water velocities in the reservoir in front of the intake during generation at low Seminoe levels, and a small hot spot has been discovered where velocities may be slightly higher than 2 fps At this location a 100-foot by 100-foot clean rock blanket may be placed to mitigate any sediment pick up.

2.4. Dam Safety

Black Canyon places its highest priority on the public safety aspects of its projects. The Project will be designed, constructed, and monitored during operations in accordance with

all regulatory requirements The key design criteria relating to dam safety will be avoidance of an uncontrolled release of water from the upper reservoir Project features such as the upper reservoir, hydraulic conveyance facilities, and control works will be designed and constructed to meet the requirements of the FERC Engineering Guidelines for the Evaluation of Hydropower Projects. During operation, periodic inspections and performance reviews will contribute to the continued safety of the Project water-retaining structures.

An emergency condition resulting in an uncontrolled release of water from the upper reservoir is highly unlikely; however, an emergency action plan to any such condition will be developed. As a pumped storage plant, in the event of the prospect of an uncontrolled release of water, the facility will be able to generate using all three units down to a minimum level upper reservoir elevation of 7,290 feet. An emergency action plan will be developed to notify public authorities and the local populace about any incident and to guide the Project operator, the local populace, and public authorities as to appropriate actions.

2.5. Powerhouse and Transformer Caverns

2.5.1. General

The proposed underground power facilities are typical of a pumped storage plant of this size and capacity The underground power facilities will consist of two caverns the machine hall and the transformer gallery connected by three busbar galleries and a connecting access tunnel.

2.5.2. Machine Hall

The machine hall will contain the three pump-turbines, three generator-motors, and unit spherical shut-off valves upstream of the pump-turbines. The machine hall will also contain the powerhouse bridge crane and a substantial number of systems supporting the operation of the units and the general functioning of the plant (balance of plant systems). A control room, workshops, and stores will also be in the machine hall and the various floors will be serviced by two elevators and at least two isolated stairwells. Hatches in the floors associated with each unit will provide for moving heavy equipment and parts between the floors and the main floor level which will incorporate an erection bay.

The MAT will connect to the machine hall at the southwest end to facilitate direct entry to the assembly bay At the other end of the machine hall and at the far end of the transformer gallery, emergency egress tunnels will be located and routed to connect with the downstream surge shaft access tunnel at a higher level.

2.5.3. Transformer Gallery

The transformer gallery will contain a three-phase, GSU transformer for each unit and other plant rooms, as well as – on a lower floor – draft tube bonneted gate valves on the draft tube extensions Provision for storing a spare, three-phase, GSU transformer has not

been included, but could be incorporated later in the design process In the crown of the transformer gallery will be gas-insulated switchgear arrangement described later

Access to the transformer gallery will be via a connecting gallery from the assembly bay in the machine hall. Rails will be set in the floor of the connecting gallery and the transformer hall for the movement of the GSU transformers

2.5.4. Busbar Galleries

There will be three busbar galleries approximately 170 feet long between the machine hall and the transformer gallery containing the low-voltage (LV) bus, reversing switches, breakers, etc., as well as the electrical equipment for the variable-speed generator-motors

2.5.5. Ventilation and Fire Safety

The internal floors and sections of the machine hall and the transformer gallery will be divided by fireproof walls into fire zones and redundant sealed stairwells so that emergency egress routes are available into the emergency egress tunnel and the MAT

Ventilation ducts and fans will be installed to ensure that both normal ventilation and smoke venting are routed to the emergency evacuation routes In general, normal air circulation and smoke and air evacuation during a fire will be directed up the cable shaft, so that fresh air is always entering the underground complex via the MAT and the emergency egress route.

The MAT will function as the main conduit for ventilation air to enter the cavern complex so that under conditions of emergency egress, fresh air will always be entering and smoke cannot engulf personnel exiting

The surge shaft access tunnel will be connected to the rest of the underground cavern complex directly by a 20-foot-diameter shaft and a 10-foot by 10-foot emergency egress tunnel from the end of the power cavern opposite of the MAT. This connecting tunnel and shaft will be an alternative emergency egress from the cavern complex in the event of fire or other emergency.

The vertical cable shaft will also have steel stairs as an alternative emergency egress.

2.5.6. Power Facilities Access

The access to the underground facilities will be through the MAT This will be a vehicular tunnel, sized for the largest item to be transported during construction (which is expected to be the three-phase, GSU transformer) For the purposes of design development, the tunnel is shown as 32 feet wide by 32 feet high and unlined but with a concrete floor slab.

The portal for the MAT will be approximately 1,350 feet downstream of the existing Seminoe Dam, with a road grade at elevation 6,250 feet on the east abutment This is approximately 92 feet above the normal maximum reservoir level (elevation 6,158 feet) of the Kortes Reservoir – although when spilling Kortes level can reach elevation 6,165.70

feet. This configuration will provide sufficient separation at the point where the access tunnel crosses the tailrace tunnel The location is a sufficient distance downstream from Seminoe Dam and its access road to ensure Reclamation operations are not affected and also offers maximum flexibility for Reclamation in any design development to mitigate the impact of any potential future structural improvements relating to the ASR deterioration of Seminoe Dam

It is preferable that the access tunnel portal be at the lowest elevation possible commensurate with Reclamation plans so that the bridge configuration is not overly complex in design or construction requirements

The proposed access tunnel will be aligned near horizontally to the bridge crossing of the Seminoe Dam tailrace but the tunnel portal elevation and location may be adjusted after further discussion with Reclamation to ensure that the final configuration is best suited to Reclamation operations and potential ASR mitigation plans for Seminoe Dam

A bridge will be constructed across the Seminoe tailrace, from the existing road on the left side of the tailrace to the portal. The bridge will support a 40-foot-wide road and will be designed for the largest delivered load during construction of the Project, which is expected to be the GSU transformers.

Two additional secondary access tunnels will be constructed: i) an access tunnel for the construction of, and maintenance of, the lower reservoir intake and, ii) a downstream surge shaft access tunnel The surge shaft access tunnel will be connected to the rest of the underground cavern complex directly by a 20-foot-diameter shaft and a 10-foot by 10-foot emergency egress tunnel from the end of the power cavern remote from the MAT This connecting tunnel and shaft will form a second (emergency) egress from the cavern complex in the event of fire or other emergency Fans or other arrangements will be included to ensure that, like the MAT, air is always drawn in through the emergency egress, facilitating safe escape The following sections outline further emergency egress stairs routes in the cable shaft.

For construction, several connecting tunnels will be created by, and for the convenience of, the construction contractor depending on the method of excavation of the underground works These tunnels will be incorporated into the overall ventilation scheme of the Project and may be used to create safety refuges, with emergency air, supplies, and communication

2.5.7. Evacuation of Power to the Surface

Power will be evacuated from the transformer gallery through a horizontal tunnel with an approximate length of 765 feet to a vertical cable shaft The GSU transformers will be connected to the outgoing circuits via 500 kV, gas-insulated switchgear configured as a breaker and a half arrangement and located in the crown of the transformer gallery Within the cable shaft will be an elevator, separate fireproof compartments for each of the two sets of three cables, and a set of steel stairs The cable tunnel and shaft will be incorporated into the ventilation system as the conduit to draw air out of the underground

Seminoe Pumped Storage Project

complex, with fans at the top of the shaft and within the horizontal cable tunnel at the transformer gallery level The proposed size of the cable tunnel is 18 feet wide and 20 feet high and is not expected to require a concrete lining or floor The tunnel will have a full shotcrete lining Similarly, the cable shaft is only lined with shotcrete

2.6. Pump-Turbines

2.6.1. Turbine Inlet Valve

Each of the three pump-turbines will be provided with a spherical inlet valve at the entrance to the unit’s spiral case Valve sizing is expected to be between 8 to 10 feet, with the final diameter determined by the supplier of the pump-turbine, in accordance with the spiral case intake diameter The spherical valve will be operated by a high-pressure, doubleacting servomotor, served from a hydraulic power unit and a valve counterweight for emergency closure. Pressurized oil may be provided by the governor hydraulic power unit, or separately by a dedicated valve hydraulic power unit

Functions of the spherical valve include the following:

• Isolating an individual pump-turbine from the penstock (in conjunction with the draft tube gate) so its spiral case can be emptied for maintenance work without draining the penstock;

• Normal shut-off for reducing pressure in the spiral case to minimize leakage through the closed wicket gates when the unit is shut down or is being started as a pump; and

• Secondary independent means of emergency shut-off of flow in the event the wicket gates are unable to close

2.6.2. Pump-Turbines

The three, identical, proposed pump-turbines will operate at a synchronous speed of 300 rotations per minute (rpm) and are nominally rated at 324 MW.

Each pump-turbine will be a vertical-shaft, single-runner, reversible, reaction-type with movable wicket gates, fixed stay vanes, steel-plate spiral cases, and elbow-type suction draft tubes

The movable wicket gates are for regulation of power output and for control of speed during starting, synchronizing, and shutting down in the turbine mode The moveable wicket gates also serve for control of starting and stopping during pump operation and are regulated to obtain the maximum pump efficiency under varying head conditions

The initial operation of the first pump-turbine will be in pumping mode and water must be available to provide head against which the pump will start. Therefore, the construction sequence of the RCC water-retaining structure will be organized so that the RCC placement on the east side up to a level of approximately elevation 7,305 feet will be

completed first, together with the reservoir lining In this way, snow melt and rain can be collected during the construction period so that up to 96 ac-ft is available to be pumped into the headrace tunnel at the appropriate time

2.6.3. Pump-Turbine Components

The embedded pump-turbine components consist of the draft tube liner, discharge ring, stay ring, spiral case, and pit liner. Access to the water passages is provided by watertight man doors on the spiral casing and the draft tube liner

Pump-turbine rotating parts consist of the runner (impeller) and the pump-turbine shaft The runner is bolted directly to the lower end of the flanged shaft, with connection to the generator shaft at the upper end The assembly is typically supported by the combined thrust and guide bearing located immediately below (or above) the generator-motor, a generator guide bearing, and by a turbine guide bearing close to the headcover, just above the shaft seal

The distributor assembly includes the headcover and bottom ring, the wicket gates, and their operating mechanism consisting of levers, links, and an operating ring with connection to the distributor servomotors

The pump-turbine headcover also supports the shaft seal and miscellaneous piping for air, water, pressure equalizing, tailwater depression, and bearing oil systems

A water depression system will be provided for start-up in pumping mode This system consists of a compressor and sufficiently large pressure accumulators with the relevant piping, sensors, and control When applied, the system will depress the water in the runner chamber down the draft tube cone to ensure the runner spins completely in air during startup The spiral casing remains filled with water and partially pressurized, with the wicket gates completely closed and the runner band drain valve open. Separate water lines will be provided to the upper and lower runner seals for cooling while the runner spins in air

Each pump-turbine will be provided with an electro-hydraulic digital governing system with speed and acceleration sensing, speed regulation, stabilizing, and diagnostic functions All control and diagnostic functions are accomplished through a digital processor The processor provides a control signal to an electro-hydraulic transducer that controls positioning of the main oil-distributing valve directing pressure oil to the gate servomotors to position the wicket gates The governing system is also designed and equipped to provide the control features required for pumping, including optimization of wicket gate opening during pumping Each governing system includes electrical speed sensing, an actuator, restoring connection, an oil pump set, sump tank, high-pressure tank, oil piping to the pump-turbine servomotors, and all controls, instruments, and accessories necessary for a complete governing system.

2.7. Generator-Motors

The generator-motors will be sized to match the ratings of the pump-turbines for pumping and generating The generator-motors will be double-fed induction machines (DFIM) that are capable of variable-speed operation. The machine rating is 360 megavolt ampere (MVA) at 0.90 power factor Synchronous speed will be 300 rpm to match that of the pumpturbine. Nominal voltage will be 18 kV, although the final voltage selection will be made by the suppliers within 10 percent of this rated voltage

The pump-turbines are sized for a maximum pump-input power of approximately 309 MW, allowing for a motor rating of 330 MVA at 0.95 power factor, to respect a potential 999 MVA interconnect agreement (also considering all other loads and losses). Depending on the chosen vendor for a variable-speed unit, the speed is typically adjustable within +/- 5 to 10 percent of the synchronous speed for increased operating range and to optimize efficiency given the head range

The resulting equipment selection provides a machine represented by a pumping ‘K-factor’ between 606 and 725 at maximum and minimum total dynamic head, respectively where K = nq*H^0.5.

Unlike conventional synchronous machines, the rotor has an alternating current (AC) winding to which variable frequency power is applied The stator is identical in function to a comparable synchronous machine, although there is a tendency for the core height to be increased

The generator-motor will be indirect cooled via air-to-water surface air coolers to maintain ambient temperature in the generator housing at not greater than 40 degrees Celsius (°C). Cooling water will be taken from the penstock or draft tube of the unit and returned to a different point. The same cooling water circuits will be used to provide cooling for other components in the power station as well

The generator-motors will be high-impedance grounded, limiting the ground fault current to not more than 20 amperes (amps). Between this feature and the main circuits being comprised of isolated phase bus, high current faults are eliminated except in the generator itself or other components that are not of isolated phase construction, mostly transformers and reactors.

A DFIM unit does not require a separate starting bus and static frequency converter because the generator-motor can be started as a motor using the variable-speed drive Black-start capability can be provided by supply of a low voltage AC circuit to the AC excitation system from station service to temporarily build up the voltage on the unit when the AC supply to the excitation transformer is not available.

2.8. Configuration and Ratings

A single-line diagram is provided in Figure 2.8-1 and also in Exhibit F, Sheet 21, identifying the configuration of equipment needed to support the DFIM machines.

Figure 2.8-1. Single-Line Diagram for proposed Seminoe Pumped Storage Project.

Final License Application – Exhibit A Seminoe Pumped Storage Project

2.9.

Switchyard

2.9.1. General

GSU transformers for each unit will be provided rated at 360 MVA, with 18 kV, deltaconnected, LV windings, and 500 kV, grounded wye, high-voltage windings located in the transformer gallery of the underground complex Appropriate basic insulation level and surge-arrester ratings will be selected based on technical standards for these ratings.

Transformers will be 3-phase construction, oil-filled, water-cooled type oil directed water forced or oil forced water forced, but use natural, ester oil-type FR-3 or equal with 600°C flashpoint instead of the 300°C flashpoint of mineral type insulating oil GSUs will be provided with oil-capture basins that guide oil to closed tanks so that any potential fire hazard is transferred away from the transformer A low-volume, nitrogen-injected fire protection system similar to a Victaulic Vortex system is envisioned to be provided with each GSU Each transformer will be contained in a vault with a 4-hour fire rating A singleline diagram for the transmission system is shown in Figure 2.8-1.

2.9.2. Switchgear

The underground facilities will incorporate a 500 kV, gas-insulated switchgear arrangement in the crown of the transformer gallery above the GSU transformers.

The underground, 500 kV, gas-insulated switchgear will be configured as a breaker and a half arrangement SF6 is currently used for such applications, but alternate gases are under development for active components and are expected to be available by the year 2024 Wherever possible, gas-insulated buses or lines will use compressed air instead of SF6 to reduce the carbon potential This could be accomplished by selection of an 800 kV, gas-insulated bus to account for the lower dielectric strength of compressed air.

To avoid issues with transformer energization and de-energization, point-on-wave circuit breakers will be provided for all 500 kV breakers Transmission line feeders will be supplied with high-speed ground switches. Surge arresters are provided at both ends of the underground transmission line feeders and at the terminals of each GSU.

2.10. Transmission Lines

2.10.1. General

Power input and evacuation will be by two, 500 kV circuits from the underground gasinsulated switchgear through the low-level cable tunnel, up the cable shaft to a take-off structure at the surface, and thence via two separate, 500 kV, overhead primary transmission lines extending to the 500 kV interconnection at Aeolus Substation, approximately 30 miles to the southeast of the Project (Sheets 32-40 of Exhibit F)

The proposed design for transmission lines from the transformer hall to the surface provides for the use of either solid dielectric cables (separated in the tunnels and shafts)

or a gas-insulated bus with no combustible materials Either option provides acceptable fireproofing The 28-foot-diameter vertical shaft, which will also function as the air and smoke evacuation conduit, will include an elevator for maintenance access to the cables or bus in the shaft as well as access to the outdoor cable terminations and disconnect switches. The vertical shaft will include steel grating platforms every 30 feet. Steel stairs will also be included for emergency egress from all landings Stairs and platforms will use gratings to maximize airflow capability of the system.

To interconnect the Project to the existing electrical grid, approximately 30 miles of BLM and private lands will be traversed by an overhead transmission system The power delivery will be split into two self-supporting or separate circuits, at the request of the interconnecting utility 500 kV is the preferred transmission voltage It should be noted that negotiations for transmission right-of-way with private landowners are ongoing, and the final routing of the Project transmission line in particular areas will depend on the results of those negotiations.

The proposed 500 kV transmission line corridor from the Seminoe gas-insulated switchgear to the Aeolus Substation follows the existing WAPA transmission line and is located based on construction, maintenance, and engineering requirements; land use; and potential impact to landowners in the area.

The initial routing of the transmission lines from the take-off structure will be on the south side of the existing WAPA 230 kV and 115 kV lines At the bottom of the initial slope, the 500 kV lines from the Project will cross the WAPA lines and will be to the north of these lines for the remainder of the transmission route The 500 kV lines will be on steel lattice towers approximately 100 feet tall and spaced evenly across a 450-foot-wide right-of-way.

At certain locations, to avoid stringing lines directly above buildings, a slight line diversion will be proposed away from the WAPA lines (See Exhibit G).

The 500 kV Aeolus Substation at the terminus of the primary 500 kV lines will require the addition of two feeders, assumed as one full new bay of breaker and a half This will require the addition of civil works to expand the 500 kV substation, including the ground mat and fencing New dead-end towers will be required to terminate the incoming transmission lines from the Project

Transmission line protection of the 500 kV transmission circuits will be determined in later design phases and likely consist of transfer trip, carrier blocking, and/or line differential arrangements It will incorporate high-speed differential protection of the underground circuits that will block reclosing of both ends of the line and close a high-speed ground switch No automatic reclose of these circuits should occur until they have been proven to be unaffected and functional.

2.10.2. Towers, Foundations, and Conductors

Drilled pier foundations will be utilized as the primary foundation solution along the transmission line If upon detailed design, drilled piers are deemed unsuitable due to

access, subsurface strata, or topography, micro pile foundations are an alternative due to the nature and ease of installation in difficult terrain

Aluminum conductor, steel-reinforced cable will be used on this Project Aluminum conductor, steel-reinforced cable is the most common and economical conductor used in high-voltage transmission projects During detailed design, alternative conductors may be evaluated, especially in environmentally sensitive areas or for particularly long spans where a customized, low-sag conductor may be a more suitable and less invasive option

The use of optical ground wire is also anticipated This cable serves as an overhead lightning protection wire, as well as a means of communication between Project facilities and the interconnecting grid facilities Optical ground wire requires a splice box to be placed on structures at fixed intervals, controlled by the maximum reel length available

Opposite of the optical ground wire will be a steel or alumoweld overhead ground wire, which is simply for lightning protection of the phases not covered by the optical ground wire

2.11. Summary of Project Features

Table 2.11-1 summarizes the Project features.

Table 2.11-1. Summary of Project Features

Project Feature Feature Data

Hydroelectric Plant

Number of Units 3

Operating Speed Nominal 300 rpm

Total Rated Capacity in generating mode (@M-G Terminals) 972 MW

Unit rated Capacity in generating mode (@M-G Terminals) 324 MW

Unit firm power (max output at minimum net head, @M-G Terminals) ~265 MW

Maximum Plant Discharge in generating mode ~12,500 cfs

Maximum Turbine unit Flow ~4,200 cfs

Unit maximum motor input power (@M-G Terminals) ~314 MW

Maximum pump flow ~3,500 cfs

Maximum pump flow at TWL in upper reservoir 2,766 cfs

Generator Rating 360 MVA, 0.90 power factor

Motor Rating 330 MVA, 0.95 power factor

Seminoe Pumped Storage Project

Project Feature Feature Data

Low Pressure Headrace Waterway

Tunnel Internal Width/Height, D shape, concrete lined 32 ft by 32 ft

Tunnel Length 2,756 ft

Steel gulley crossing diameter 24 ft

Steel Pipe Length ~615 ft Shaft

Internal Diameter, concrete lined 30 ft Length 1,225 ft

High Pressure Tunnel

Internal Diameter – concrete lined 30 ft Length 123 ft

Penstock

Internal Diameter - concrete and steel lined 17 ft Length 330 ft, 247 ft, and 165 ft

Draft Tube extension

Internal Diameter - concrete and steel lined 17.5 ft Length 140 ft, 103 ft, and 85 ft

Downstream Surge Chamber

Internal Diameter 36 ft Length 232 ft

Tailrace Tunnel

Internal Diameter 31 ft Length 4,070 ft

Powerhouse Cavern

Height 142 ft Length 460 ft Width 80 ft

Transformer Cavern

Height 113 ft Length 413 ft Width 71 ft

Project Feature Feature Data

ISO Phase Bus galleries (3)

Height 43.5 ft

Length 170 ft

Width 31 ft

Upper Reservoir

Water-retaining structure type RCC

Storage

Total Reservoir Capacity (below spillway crest) 13,300 ac-ft

Inactive storage 2,500 ac-ft

Active Storage 10,800 ac-ft

Operating Levels

Maximum Normal Water Level 7,445 ft

Minimum Normal Water Level 7,350 ft

Water Surface Area

Surface Area at Normal Maximum Water Level 114 acres

Surface Area at Normal Minimum Water Level 111 acres

Dam Structural Dimensions

Maximum Structural Height 180 ft

Minimum Structural Height 65 ft

Top Width 20 ft

Length 8,498 ft

Crest Elevation 7,455 ft

Over-pumping emergency spillway Ungated Ogee Weir

Length 200 ft

Crest Elevation 7,446 ft

Capacity (max pumping flow at normal max level) ~8,298 cfs

Lower Reservoir1

Retaining structure Seminoe Dam

Project Feature Feature Data

Operating Levels

Maximum Normal Water Level 6,357 ft

Minimum Normal Water Level (typical) 6,290 ft

Minimum Normal Water Level (active conservation level) 6,239 ft

Storage 1,016,717 ac-ft

Water Surface Area at Normal Maximum Water Level 20,291 acres

Transmission Line

No of Circuits 2

Structure Type Single Circuit Lattice Tower

Voltage 500 kV Length ~30 Miles

1. The Project’s lower reservoir is Reclamation’s existing Seminoe Reservoir and is not a proposed Project facility for purposes of the FERC license See Section 1.0 of this Exhibit for more information on the relationship of the Project to Reclamation’s Seminoe Dam and Reservoir.

3.0 Project Access

Access to the Project area for construction, equipment, supplies, and eventual operations and maintenance functions will be on public roads. From Casper, Wyoming, road access is via Wyoming State Highway 220, connecting to Kortes Road in Alcova, and onto Bennett Mountain Road where the Project road leading to the upper reservoir site begins. Alternatively, from Casper, some construction or operations-related traffic will cross the North Platte River on the Miracle Mile bridge and follow Seminoe Road to Seminoe Reservoir’s western shoreline areas or to the MAT portal situated just downstream of Seminoe Dam

Access from Rawlins, Wyoming, can be from public roads off Interstate 80 at Sinclair, Wyoming (Seminoe Road). Also, public roads off Interstate 80 near Hanna, Wyoming, provide access to the northeast side of Seminoe Reservoir and the proposed lower reservoir intake location, via Hanna Draw and Powerline Roads. Powerline Road has private land sections that will likely require negotiated access agreements with landowners.

Improvements to Seminoe Road or other public roads are not proposed or anticipated at this time except for bridge or culvert upgrading which will be determined when a contractor is selected and the requirement for bringing heavy or oversize loads is determined These public roadways are operated and maintained in good condition by the State, County, and Reclamation.

Seminoe Pumped Storage Project

3.1. Access to Upper Dam and Reservoir

The existing access BLM Bennett Mountain Road (sometimes called Dry Lake Road) that accesses the high plateau area where the upper reservoir is proposed, is a rough road that is currently unpassable for most street vehicles. The existing road does not have the capacity to support construction or ongoing maintenance activities with a reasonable level of service, and will, therefore, require significant improvements to support the construction of the upper reservoir To reach the upper reservoir site, there is a 900-foot gain in elevation, rising from elevation 6,400 feet to elevation 7,300 feet.

The existing single-lane Bennett Mountain Road leading up to these higher-elevation BLM lands in the Seminoe Mountains was created for the construction and upgrade of the 230 kV WAPA transmission line Portions of Bennett Mountain Road are steep in places and show signs of significant erosion and rutting In addition to several very sharp radii corners, the existing road exceeds 30 percent grade in isolated locations and 20 percent for much of the climb. Therefore, it is proposed that most of the existing road be upgraded and, in some places, relocated Additionally, there are wetlands in the lower portion of the existing road along Number One Gulch Stream course which constrains the ability to make significant improvements through that segment

To facilitate the creation of an access roadway which can support long-term construction and maintenance activities while maintaining an appropriate level of safety the existing alignment will be utilized as much as possible and necessary diversions from the existing road to reduce grades and avoid wetlands will be introduced American Association of State Highway and Transportation Officials (AASHTO) design standards will be used, in particular:

• AASHTO Standards from the Guidelines for Geometric Design of Low-Volume Roads 2019 Edition

• AASHTO Standards from the Guidelines for Geometric Design of Highways and Streets 2018 Edition.

The existing BLM road will be upgraded and realigned based on a design using the following criteria:

Design Speed

Desired Design Speed = 25 miles per hour (mph)

Minimum Design Speed = 15mph (posted if needed)

Cross Section

Lanes - 12-ft

Shoulder - Berm - 5-ft width (2-ft high)

Max Cross Sectional Width = 34-ft

Min Cross Sectional Width = 24-ft

Horizontal

Minimum Radii = 100-ft (at 15 mph)

Desired Radii = 140-ft (at 25 mph) Stopping Sight = 125-ft

Vertical

Maximum Grade = 18% (100-ft)

Maximum Sustained Grade = 15% (500-ft)

Desired Maximum Grade = 8%

Minimum Grade = 2%

Minimum Vertical Crest K = 8 (13 desired) Minimum Sag Crest K = 26 (37 desired)

The proposed 24-foot-wide upgraded roadbed provides for two-way traffic while allowing sufficient additional width for longer equipment around relatively tight corners.

There will be no work or disturbance to any lands in the adjoining Bennett Mountain WSA, and the final design shall ensure all work is outside this boundary.

3.2. Access to Lower Reservoir

Access to the top of the downstream surge chamber which will be above Seminoe Reservoir normal maximum water level elevation of 6,357 feet will be from the north bank of Seminoe Reservoir (the Project’s proposed lower reservoir)

Access for construction and operations will not be via the crest of Seminoe Dam, rather the powerline road from Hanna can be used for access to the lower intake and gate shaft area A small section of an existing, single-track, rough road leading up from the proposed gate shaft location to the exit of the surge chamber access tunnel will be upgraded.

The existing powerline roads to this area are mostly a single-lane track used for the construction and maintenance of the WAPA transmission line and access to private ranch lands northeast of Seminoe Reservoir While this road can be used for some light-vehicle access and for construction of the new transmission line, it is not considered suitable for significant or extensive hauling of materials and supplies to the lower reservoir intake Additionally, as noted previously, the main lower reservoir intake facilities will be floated into place across Seminoe Reservoir

Therefore, a gate shaft access tunnel will be constructed from the MAT to the lower reservoir intake area and its gate shaft This tunnel will be used for primary vehicular and general equipment access to those lower Project facilities during construction and thereafter for periodic operations and maintenance uses The tunnel has been sized smaller than the MAT as large or bulk materials or supplies are not anticipated to be passed through Both secondary access tunnels will be 15 feet wide by 16 feet high and a maximum grade of 12.5 percent has been assumed.

Seminoe Pumped Storage Project

The secondary access tunnels will be lined with shotcrete In later design phases, the proposed tunnel sizing may change depending on the construction equipment and final construction methods.

3.3. Access to the Main Access Tunnel Portal

The MAT leads into the underground powerhouse facilities. Connecting the MAT portal to the existing road network will require constructing a new bridge over the North Platte River, approximately 1,000 feet downstream of Seminoe Dam The bridge will connect to Morgan Creek Road, that connects to Seminoe Road, both of which are existing gravel-surfaced roadways used by the public and Reclamation operations staff The Morgan Creek roadway leads to a public river access facility on the North Platte River

The proposed bridge will support a road 40 feet wide and will be designed for the largest load during construction of the Project The bridge structure will be comprised of precast beams and a cast-concrete deck, and will consist of six, 50-foot spans supported on sets of 3 columns with capping beams at either end of the bridge The approach slab will be supported by an embankment confined by concrete “reinforced earth walls.”

The MAT will be used as the principal access for construction of the power facilities complex; and it is envisaged that most of the excavated material will be removed through the tunnel using dump trucks The MAT will also serve as the only access during delivery of all permanent electrical, mechanical, and hydromechanical equipment, including the pump–turbines, generator-motors, GSU transformers, cranes, and penstock steel liners.

The largest permanent equipment that will be transported through the MAT will be the core of the three-phase GSU transformers usually transported on a multi-steerable-axle lowboy This GSU transport weight is expected to be in excess of 250 tons and approximately 21 feet wide by 40 feet long and 26 feet high. The MAT has been sized for this purpose It is possible that the selected construction contractor will use dump trucks that are of such size that the MAT needs to be slightly larger.

Given the continuous use in construction and operation, the MAT grade will be limited to 8 percent grade and the floor (roadbed) will be reinforced concrete. The MAT will intersect the power facility in the main machine hall at the main floor level A cross gallery will provide access to the transformer hall from the main machine hall and will also be sized for transport of the GSU transformer core on rails.

By orienting the MAT to a portal downstream of the Seminoe Dam at elevation 6,250 feet, the average grade of the MAT will have reasonable grades for vehicular and equipment movements

During construction, air ducting will be installed in the crown of the MAT, but the permanent ventilation system will likely be further configured to draw air into the complex through the whole cross section of the MAT for operations. This feature will also be applied to the other tunnel selected as the emergency egress tunnel, so that, in the event of a fire underground,

there are always two routes for egress which are directly and continuously supplied with fresh air.

4.0 Lands of the United States

Table 4.0-1 identifies each section, or portion thereof, within the proposed FERC Project Boundary that is Federal land, per the Public Land Survey System.

Table 4.0-1. Federal Lands Within the Proposed FERC Project Boundary Administered by Township Range Section Acres

Bureau Of Land Management T24N R80W 20 38.78 21 0.48 27 0.54 28 40.68 34 31.82 R81W 19 0.53 20 41.71 21 0.01 R82W 19 0.31 20 41.82 21 0.26 22 42.31 24 42.19

R83W 01 0.34 02 43.05 12 21.76 13 0.24 24 11.85

T25N 18 14.93 19 35.37 20 39.26 28 49.91 29 0.01 35 0.16 R84W 02 3.08 03 165.91

Seminoe Pumped Storage Project

Administered by Township Range Section Acres 04 6.21 09 20.70 10 28.50 13 48.47 14 44.36

T26N 35 10.59

Bureau Of Reclamation T25N R84W 04 2.82 05 3.36 08 1.93 09 6.86 10 28.44 15 9.48

Total 873.51

5.0 Literature Cited

Reclamation, U.S. Bureau of (Reclamation). 2022. Seminoe Dam Overview. https://www.usbr.gov/projects/index.php?id=233 Accessed April 4, 2022