Morrow Point Dam is a 468 feet (142.6 m) concrete

Concrete

Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 double-arch dam

Arch dam

An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes...

 on the Gunnison River

Gunnison River

The Gunnison River is a tributary of the Colorado River, long, in the Southwest state of Colorado. It is the fifth largest tributary of the Colorado River, with a mean flow of 4320 ft³/s .-Description:...

 located in Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

, the first dam of its type built by the U.S. Bureau of Reclamation. Located in the upper Black Canyon of the Gunnison, it creates Morrow Point Reservoir

Morrow Point Reservoir

Morrow Point Reservoir is an artificial reservoir on the Gunnison River in southwestern Colorado operated by the U.S. Bureau of Reclamation. Located in the upper Black Canyon of the Gunnison, it is impounded by tall Morrow Point Dam, and is within the National Park Service-operated Curecanti...

, and is within the National Park Service

National Park Service

The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...

-operated Curecanti National Recreation Area

Curecanti National Recreation Area

Curecanti National Recreation Area, in Colorado, is formed by three reservoirs, named for corresponding dams on the Gunnison River. The national recreation area borders Black Canyon of the Gunnison National Park on the west...

. The dam is between the Blue Mesa Dam

Blue Mesa Dam

Blue Mesa Dam is a zoned earthfill dam on the Gunnison River in Colorado. It creates Blue Mesa Reservoir, and is within Curecanti National Recreation Area just before the river enters the Black Canyon of the Gunnison. The dam is upstream of the Morrow Point Dam. Blue Mesa Dam and reservoir are...

 (upstream) and the Crystal Dam

Crystal Dam

Crystal Dam is a double curvature, concrete thin arch dam located six miles downstream from Morrow Point Dam on the Gunnison River in Colorado, USA. Crystal Dam is the newest of the three dams in Curecanti National Recreation Area; construction on the dam was finished in 1976. The dam impounds...

 (downstream). Morrow Point Dam and reservoir are part of the Bureau of Reclamation's Wayne N. Aspinall Unit of the Colorado River Storage Project

Colorado River Storage Project

The Colorado River Storage Project is a United States Bureau of Reclamation project designed to oversee the development of the upper Colorado River basin...

, which retains the waters of the Colorado River

Colorado River

The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...

 and its tributaries for agricultural and municipal use in the American Southwest. The dam's primary purpose is hydroelectric power generation.

Description

The dam, powerplant and reservoir are contained in pre-Cambrian metamorphic rocks, primarily micaceous quartzite

Quartzite

Quartzite is a hard metamorphic rock which was originally sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to gray, though quartzites often occur in various shades of pink...

, quartz-mica, mica

Mica

The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...

 and biotite

Biotite

Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...

 schist

Schist

The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...

s, with granitic

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

 veining. The dam site is in a narrow canyon about 200 feet (61 m) wide at the river and 550 feet (167.6 m) wide at the top. The spillway discharge falls 350 feet (106.7 m) into a stilling basin whose waters are retained by a weir below the dam. Intake structures near the south abutment feed two 18 feet (5.5 m) diameter penstock tunnels with 13.5 feet (4.1 m) steel linings leading to the powerplant. A streamflow of 100 ft3/s is maintained at all times, equivalent to 200 acre.ft per day.

History

The Curecanti Project (later renamed the Wayne N. Aspinall Project) was conceived in 1955, initially with four dams. It was approved by the Secretary of the Interior in 1959, comprising Blue Mesa Dam and Morrow Point Dam. Crystal Dam's design was unfinished and was approved in 1962. Plans for a fourth dam were dropped as uneconomical. The project was restricted to the stretch of the Gunnison above Black Canyon of the Gunnison National Monument (later designated a national park), a 40 miles (64.4 km) length of the river. Work began at the damsite in 1961 with foundation drilling. In 1962 the power plant exploratory tunnel was excavated. The construction contract for the dam was awarded to a joint venture between the Al Johnson Construction Company and Morrison-Knudsen, with notice to proceed given on June 13, 1963. Access roads and a diversion tunnel were begun that year, with the diversion tunnel complete by May 1964. Keyway excavation on either side of the dam continued through 1964. In in 1965 work got underway on the powerplant, with several tunnels started. Concrete for the dam was first placed on September 3, 1965. The powerplant was excavated by April 1966. Final concrete placement on the dam took place on September 14, 1967. The diversion tunnel was closed on January 24, 1968, with releases through the outlet structures the next day. Final completion was achieved for the dam on October 7, 1968, while work continued on the powerplant. The plant was accepted and a visitor center was completed in 1971, with final completion on May 12, 1972.

The dam's grout curtain was extended in 1970 after leakage into the power plant reached 429 gallons per minute, using asphaltic emulsion and cement grout, reducing leakage to 37 gpm.

Powerplant

Morrow Point Dam's powerplant is tunneled into the canyon wall 400 feet (121.9 m) below the surface at the dam's left abutment. It houses two 86.667 MW generators, uprated from 60 MW each in 1992-1993. The generating hall measures 231 feet (70.4 m) by 57 feet (17.4 m), with between 64 metres (210 ft) and 134 feet (40.8 m) of height. First operating in 1970, it is operated as a peaking plant. An exploratory tunnel became a ventilation tunnel, while initial access during construction was made through the cable tunnel, with two headings raising the head of the tunnel arch. An access tunnel intersects the generating hall at a right angle, with two draft tubes excavated below. In irrigation season the powerplant is operated as a base load plant, providing peaking power in other seasons.

External links

• Morrow Point Dam at the Bureau of Reclamation
• Morrow Point Powerplant at the Bureau of Reclamation
• Wayne N. Aspinall Storage Unit at Curecanti National Recreation Area