Pathfinder Dam
| Pathfinder Dam | |
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Pathfinder Dam
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| Location | Natrona County, Wyoming, USA |
| Coordinates | 42°28′05″N 106°51′14″W / 42.46806°N 106.85389°WCoordinates: 42°28′05″N 106°51′14″W / 42.46806°N 106.85389°W |
| Construction began | 1905 |
| Opening date | 1909 |
| Operator(s) | U.S. Bureau of Reclamation |
| Dam and spillways | |
| Type of dam | Cyclopean masonry gravity arch |
| Impounds | North Platte River |
| Height | 214 feet (65 m) |
| Length | 432 feet (132 m) |
| Width (crest) | 10.5 feet (3.2 m) |
| Width (base) | 96.5 feet (29.4 m) |
| Dam volume | 65,700 cu yd (50,200 m3) |
| Spillway type | Uncontrolled natural channel |
| Spillway capacity | 33,940 cu ft/s (961 m3/s) |
| Reservoir | |
| Creates | Pathfinder Reservoir |
| Total capacity | 1,016,500 acre feet (1.2538 km3) |
| Catchment area | 14,600 sq mi (38,000 km2) |
| Power station | |
| Hydraulic head | 300 ft (91 m) |
| Turbines | 2 x 33.4 MW Francis-type at Fremont Canyon Powerplant |
| Installed capacity | 66.8 MW |
| Annual generation | 172,606,300 KWh (2007) |
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Pathfinder Dam
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| NRHP Reference # | 71000888 |
| Added to NRHP | August 12, 1971 |
Pathfinder Dam is a cyclopean masonry dam, located on the North Platte River, approximately 47 miles (76 km) southwest of Casper, Wyoming. It was originally constructed between 1905 and 1909 as part of the North Platte Project and has been modified several times since then. It is included on the National Register of Historic Places. Construction of the dam created Pathfinder Reservoir which provides water storage for 226,000 acres (910 km2) of irrigation in Wyoming and Nebraska. The dam is named for General John Charles Fremont, who had explored the area in 1842 and was nicknamed the "Pathfinder of the West."
Pathfinder Dam is composed of granite blocks, quarried from the same stone that forms the river's canyon. With Buffalo Bill Dam, its contemporary, Pathfinder Dam was intended to irrigate semi-arid lands in Wyoming. Buffalo Bill Dam, however, is of concrete construction, owing to its location within 7 miles (11 km) from the railroad, while Pathfinder Dam is about 45 miles (72 km) from the nearest railroad. Freight took at least three days to cover the distance, and once took 76 days. Transportation of cement in barrels was not feasible by horse-drawn wagon, so the dam was built of quarried stone. The dam was faced with stones between 24 inches (61 cm) and 36 inches (91 cm) thick, laid in a 2-inch (5.1 cm) thick mortar bed. Between these facings was a core of irregularly-shaped granite blocks of up to ten tons in weight, bedded in mortar and quarry tailings. The diversion tunnel was adapted to become the dam's outlet works. Construction costs were $2.5 million in 1909. An auxiliary dike, 38 feet (12 m) high, extends to the south of the dam. It is an earthfill structure with a concrete corewall. A natural channel was enlarged and straightened to form an uncontrolled spillway on the north side of the dam.
The original diversion tunnel became the north outlet works, abandoned and sealed in 1958 with bulkheads. From 1958 the tunnel was modified to feed the power outlet works, an 18 feet (5.5 m) tunnel extending 3 miles (4.8 km) to the Fremont Canyon Powerplant at the upper end of Alcova Reservoir. The Fremont Canyon Powerplant has a capacity of 66.8 MW with two turbines, upgraded from 48 MW between 1986 and 1990. A low-flow outlet was completed at the dam in 1997 to allow water flow in the four river miles between the dam and the powerplant.
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