Rampart Dam - Site

Site

From its headwaters in the Coast Mountains, the Yukon River flows northwest, across the Yukon–Alaska border, until it intersects the Porcupine River at the settlement of Fort Yukon. At that point, the river turns west and southwest, flowing through the Yukon Flats, a low-lying wetland area containing thousands of ponds, streams, and other small bodies of water. As the river flows southwest, it intersects the Tanana and Koyukuk rivers before looping south, then north into Norton Sound in the Bering Sea.

During the river's flow through eastern Alaska, and before it intersects the Tanana River, the Yukon flows through the Central Plateau region of Alaska. During the millions of years of its flow, it has cut through ridges, forming canyons in some places near its juncture with the Tanana. One of the deepest of these canyons is known as Rampart Gorge, or Rampart Canyon. The gorge is located 31 miles (50 km) downstream of the village of Rampart, 36 miles (58 km) upstream of the village of Tanana, and immediately downstream from the mouth of Texas Creek. It is named for the nearby village of Rampart, Alaska, a former gold-mining community now home to subsistence fishermen.

At the proposed dam site, the river is 1,300 feet (396 m) wide and has an elevation of 183 feet (56 m) above sea level. On the south bank, the land rises sharply to a ridge 1,500 feet (457 m) high. North of the river, the bank rises to 1,200 feet (366 m) before ascending gradually northwest to the Ray Mountains. Below the surface of the ground are patches of permafrost, and the area is seismically active. An earthquake measuring 6.8 on the Richter Scale struck the region in 1968, and a 5.0 earthquake hit the area in 2003. Geologically, igneous rock predominates, and quartz can be seen in places.

Hydrologically, the portion of the river upstream of the proposed dam drains about 200,000 square miles (517,998 km2). On average, the Yukon flows at a rate of 118,000 cubic feet per second (3,341 m3/s) through the canyon, with the fastest flow occurring in the later part of May and the first part of June, and the slowest flow occurring after the river has frozen over. This occurs no later than early November and lasts until mid April.