Mountain Dell Dam
Encyclopedia
The Mountain Dell Dam provides a water equalizing and storage reservoir for Salt Lake City, Utah
located 10 miles (16.1 km) east of the city in northeastern Salt Lake County
, near Interstate 80
in Parley's Canyon
.
Designed by John S. Eastwood
, and constructed between 1914 and 1925, the dam is an example of a mixed buttress dam
and multiple arch dam
construction. At the time the plans were made, the city was in need of a sufficient supply of water, especially during late summer and the middle of winter.
With the completion of the dam, the city had an available storage capacity of 850 million USgals (3,217,600.2 m³), and distributing or equalizing capacity of 24 million USgals (90,849.9 m³) compared to 9 million USgals (34,068.7 m³) previously.
The dam was listed on the National Register of Historic Places
in 1980.
After consideration, the multiple arch type was chosen. One of the factors influencing this decision was the bedrock
condition at the site. The bedrock is a calcareous
shale
not entirely watertight and of a nature to decompose somewhat under exposure to air and water. The advantages of the multiple arch type in this connection were considered to be the practical elimination of upward pressure, the practical impossibility of overturning or sliding on its base and the ready facilities for internal inspection of the dam at any time.
The cost of the structure was considerably increased because of the necessity of going 43 feet (13 m) below ground level in the bottom of the canyon to secure the bedrock foundation. The spillway
level is 4 feet (1.2 m) below the top of the dam, so that the maximum depth of the reservoir is 58 feet (18 m) to the crest of the spillway.
The dam as planned and as constructed consists of 11 buttress
es and 11 arch
es in the first stage and an additional 5 buttresses and 5 arches in the second stage. The maximum base width of the dam is 132 feet (40 m) from the face of the arch to the downstream end of the buttresses. The maximum thickness of the buttresses is 8 feet (2.4 m). The maximum thickness of the arch rings is 4.1 feet (1.2 m). The thickness at the present top of the dam is 15 inches (381 mm). The arch rings are 120 degree
arcs of circles. The spacing between buttress centers is 35 feet (10.7 m). The two sets of outlet gates each consist of two 24 inch (610 mm) pipes with a suitable grating entrance, and with a butterfly
and a double-disc gate
valve
on each pipe.
The total quantity of concrete in the dam is 8,271 cubic yards (6,323 m³). The total cost of the dam was $90,000. The storage capacity at the present height is slightly over 300 million USgals (1,135,623.6 m³). The general design and supervision was handled under the direction of Sylvester Q. Cannon
, City Engineer
of Salt Lake City and John S. Eastwood acting as consulting engineer. Parrott Bros. Co. were the contractors.
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
located 10 miles (16.1 km) east of the city in northeastern Salt Lake County
Salt Lake County, Utah
Salt Lake County is a county located in the U.S. state of Utah. It had a population of 1,029,655 at the 2010 census. Its county seat and largest city is Salt Lake City, the state capital. It occupies Salt Lake Valley, as well as parts of the surrounding mountains, the Oquirrh Mountains to the west...
, near Interstate 80
Interstate 80
Interstate 80 is the second-longest Interstate Highway in the United States, following Interstate 90. It is a transcontinental artery running from downtown San Francisco, California to Teaneck, New Jersey in the New York City Metropolitan Area...
in Parley's Canyon
Parley's Canyon
Parley's Canyon is a canyon located in the U.S. state of Utah. The canyon provides the route of Interstate 80 up the western slope of the Wasatch Mountains and is a relatively wide, straight canyon. The lower part of the canyon, however, is relatively twisty and had to be dynamited to make way for...
.
Designed by John S. Eastwood
John S. Eastwood
John S. Eastwood was an American engineer who built the world's first reinforced concrete multiple-arch dam on bedrock foundation at Hume Lake, California, in 1908. Mr...
, and constructed between 1914 and 1925, the dam is an example of a mixed buttress dam
Buttress dam
A buttress dam or hollow dam is a dam with a solid, water-tight upstream side that is supported at intervals on the downstream side by a series of buttresses or supports. The dam wall may be flat or curved. Most buttress dams are made of reinforced concrete and are heavy, pushing the dam into the...
and multiple 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...
construction. At the time the plans were made, the city was in need of a sufficient supply of water, especially during late summer and the middle of winter.
With the completion of the dam, the city had an available storage capacity of 850 million USgals (3,217,600.2 m³), and distributing or equalizing capacity of 24 million USgals (90,849.9 m³) compared to 9 million USgals (34,068.7 m³) previously.
The dam was listed on the National Register of Historic Places
National Register of Historic Places
The National Register of Historic Places is the United States government's official list of districts, sites, buildings, structures, and objects deemed worthy of preservation...
in 1980.
Design
Plans were made for three types of dam:- Arched solid dam, gravity type
- Reinforced concrete dam of the Ambursen type
- Multiple arch reinforced concrete dam of the Eastwood design
After consideration, the multiple arch type was chosen. One of the factors influencing this decision was the bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
condition at the site. The bedrock is a calcareous
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
not entirely watertight and of a nature to decompose somewhat under exposure to air and water. The advantages of the multiple arch type in this connection were considered to be the practical elimination of upward pressure, the practical impossibility of overturning or sliding on its base and the ready facilities for internal inspection of the dam at any time.
Construction
The dam was built in two stages, the first stage completed in 1917 with a height of 105 feet (32 m) above the foundation and the second stage, completed 1925, added 40 feet (12 m) to the height of the dam.The cost of the structure was considerably increased because of the necessity of going 43 feet (13 m) below ground level in the bottom of the canyon to secure the bedrock foundation. The spillway
Spillway
A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...
level is 4 feet (1.2 m) below the top of the dam, so that the maximum depth of the reservoir is 58 feet (18 m) to the crest of the spillway.
The dam as planned and as constructed consists of 11 buttress
Buttress
A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall...
es and 11 arch
Arch
An arch is a structure that spans a space and supports a load. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.-Technical aspects:The...
es in the first stage and an additional 5 buttresses and 5 arches in the second stage. The maximum base width of the dam is 132 feet (40 m) from the face of the arch to the downstream end of the buttresses. The maximum thickness of the buttresses is 8 feet (2.4 m). The maximum thickness of the arch rings is 4.1 feet (1.2 m). The thickness at the present top of the dam is 15 inches (381 mm). The arch rings are 120 degree
Degree (angle)
A degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...
arcs of circles. The spacing between buttress centers is 35 feet (10.7 m). The two sets of outlet gates each consist of two 24 inch (610 mm) pipes with a suitable grating entrance, and with a butterfly
Butterfly valve
A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve...
and a double-disc gate
Gate valve
The gate valve, also known as a sluice valve, is a valve that opens by lifting a round or rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow...
valve
Valve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...
on each pipe.
The total quantity of concrete in the dam is 8,271 cubic yards (6,323 m³). The total cost of the dam was $90,000. The storage capacity at the present height is slightly over 300 million USgals (1,135,623.6 m³). The general design and supervision was handled under the direction of Sylvester Q. Cannon
Sylvester Q. Cannon
Sylvester Quayle Cannon was the sixth presiding bishop of The Church of Jesus Christ of Latter-day Saints between 1925 and 1938 and a member of church's Quorum of the Twelve Apostles from October 6, 1939 until his death. He was the son of George Q...
, City Engineer
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...
of Salt Lake City and John S. Eastwood acting as consulting engineer. Parrott Bros. Co. were the contractors.