Seneca Dam | |
---|---|
Country | United States |
Coordinates | 39°03′27.65″N77°19′05.054″W / 39.0576806°N 77.31807056°W |
Status | Unbuilt |
Construction cost | $101,789,000 (1963) |
Owner(s) | U.S. Army Corps of Engineers |
Dam and spillways | |
Type of dam | Concrete gravity |
Impounds | Potomac River |
Height | 87 ft (27 m) |
Length | 2,880 feet (880 m) |
Width (crest) | 28 feet (8.5 m) |
Spillways | 27 |
Spillway type | Gated overflow at dam crest |
Reservoir | |
Total capacity | 1,193,000 acre-feet (1.472 km3) |
Surface area | 24,000 acres (9,700 ha) |
Normal elevation | 226 ft (69 m) |
Seneca Dam was the last in a series of dams proposed on the Potomac River in the area of the Great Falls of the Potomac. Apart from small-scale dams intended to divert water for municipal use in the District of Columbia and into the Chesapeake and Ohio Canal, no version of any scheme was ever built. In most cases the proposed reservoir would have extended upriver to Harpers Ferry, West Virginia. The project was part of a program of as many as sixteen major dams in the Potomac watershed, most of which were never built.
The earliest proposals for exploitation of hydropower on the Potomac were made in the 1880s. By the 1920s the U.S. Army Corps of Engineers reviewed the possibilities for hydroelectric power.
After a new study mandated by Congress in 1936-37, the Corps of Engineers in 1938 proposed a dam for flood control, power generation and water quality improvement, to be located above Great Falls at Riverbend. The scheme was revived following World War II. Opposition to the flooding of the entire river to Cumberland by a chain of dams, and to the inundation of the Chesapeake and Ohio Canal doomed the Riverbend proposal. However, in 1963 the Corps proposed a new plan to improve water quality on the Potomac, which moved water storage off the main stem of the Potomac to its upper tributaries and scaled the Riverbend dam back to a lower dam at Blockhouse Point, near the mouth of Little Seneca Creek, to be called Seneca Dam. This proposal was debated through the 1960s until it was finally abandoned in 1969.
Beginning in the 1880s a series of proposals were made to use the Potomac River's hydropower potential, which arises from the steep drop of the river at Great Falls as it crosses the Atlantic Seaboard fall line, dropping to sea level over about 10 miles (16 km). Frequent flooding and a desire to secure a reliable water supply for Washington, D.C. increased the attractiveness of a major dam on the Potomac.
A detailed plan for a major dam on the Potomac at Great Falls was first advanced by the Corps of Engineers in a 1921 report, which proposed a concrete gravity dam which would include a hydroelectric powerplant. Reservoir capacity was projected at 300,000 acre-feet (0.37 km3) for a 24,000-acre (9,700 ha) reservoir with a reservoir at 215 feet above sea level. [1] Power generation capacity was planned at 105 MW [2] and total cost was projected at $18,616,000 in 1921. [3]
By direction of Congress in 1936 and 1937 the Army Corps of Engineers, which manages Washington D.C.'s water supply system, examined possibilities for flood control along the Potomac. The Corps returned with an ambitious agenda for 14 dams on the main stem of the Potomac, its branches and its major tributaries. Beginning at tidewater, a dam at Chain Bridge would extend to Bear Island, where another dam would back a reservoir up to Great Falls. Just above Great Falls the Riverbend Dam would create a reservoir up to Sandy Hook, just below Harpers Ferry. Dams at Sandy Hook, Rocky Marsh Run, Pinesburg and Little Orleans would convert the main stem of the river to a series of slackwater reservoirs. More dams on the North and South Forks of the Potomac, the North River and the Shenandoah River would complete the scheme. The Corps suggested that the discharge from the Riverbend Dam could enhance flow over Great Falls during daylight hours. Locks were to be provided to allow small craft to reach Harpers Ferry. [4] The cost of this program was estimated at $235 million in 1945. [5]
The Corps plan, which would have inundated nearly all of the defunct Chesapeake and Ohio Canal was opposed by the National Park Service, which had acquired the canal property in 1938. A 1954 hearing at the Department of the Interior was attended by more than 1000 people, only three of whom spoke in favor of the Corps plan. In the meantime the Park Service had proposed its own plan for a parkway on the canal right-of-way from Cumberland to Washington. Opposition to this plan gained force during the 1950s and culminated in a 1954 letter to the Washington Post by U.S. Supreme Court Justice William O. Douglas blasting the plan and urging the canal's preservation as a wild park, and challenging Post editors to walk the 185-mile (298 km) length of the canal towpath. Joined by conservation leaders and supported by the Park Service, the hike was accomplished in seven days and brought the preservationist cause extensive publicity. [4]
In 1958 the Corps again was directed by Congress to study dams, this time to improve water quality in addition to flood control. Tension between legislation for park use and water management use increased, until President Dwight D. Eisenhower proclaimed Chesapeake and Ohio Canal National Monument under the authority of the Antiquities Act on January 18, 1961. The proclamation earned the enmity of House Interior and Insular Affairs Committee Chairman Wayne Aspinall. Later in 1961 a park authorization bill was proposed with Aspinall's support that would allow dam construction on the Potomac. In May 1962 the Corps proposed a new scheme for 16 dams on the Potomac and its tributaries. This version scrapped most of the mainstem dams in favor of more tributary dams, and moved the Riverbend Dam to a site at Seneca, 4.5 miles (7.2 km) upstream. The Seneca Dam was to be lower than Riverbend. Douglas immediately attacked the proposal, as did Maryland Representative Charles Mathias. A task force review in 1966 opposed the Seneca Dam. In 1968 draft legislation proposed the Potomac National River, eliminating the possibility of a Seneca Dam in favor of more tributary dams. However, this proposal was opposed by landowners and other interests in the areas earmarked for dams on the Monocacy, Cacapon and upper Potomac rivers. In 1968 Congress converted the national monument into Chesapeake and Ohio Canal National Historical Park, effectively precluding dam construction anywhere along the length of the park. By 1969 the Seneca Dam proposal had been publicly abandoned by the Corps of Engineers. [6]
Water quality and supply concerns that had previously been cited as reasons for dam building were addressed by new Federal requirements for stringent sewage treatment, which greatly improved water quality on the lower Potomac, eliminating the need to dilute effluent in reservoirs. Mine waste discharge was also regulated, with dilution provided by the eventual construction of Jennings Randolph Lake on the North Branch of the Potomac by the Corps of Engineers. [7]
The Riverbend Dam was to be a 119-foot (36 m) dam at the westward bend of the Potomac just above Great Falls. Its reservoir was to extend nearly to Harpers Ferry, with branches extending up the Monocacy River past Frederick and major branches on streams in Loudoun County, Virginia. The dam was to incorporate small locks to allow pleasure boats to reach Harpers Ferry. After intense public opposition the Riverbend project was shelved in favor of less ambitious proposals [4]
The final proposal for a lower Potomac dam was Seneca Dam. The concept developed in the 1950s and was proposed by the Corps of Engineers in its final form in the 1963 Potomac River Basin Report. Answering objections to the visual intrusion of the Riverbend Dam at Great Falls, Seneca Dam was placed at Blockhouse Point, about 1.6 miles (2.6 km) downstream from the mouth of Seneca Creek, about 4.5 miles (7.2 km) upstream from the Riverbend site and just downstream from the Chesapeake and Ohio Canal's Dam Number 2. No immediate hydroelectric development was planned, the dam was meant to provide a water source, to control floods, and to provide recreation. The Corps of Engineers assumed that water quality would continue to decline under the effects of upstream sewage discharge, especially during periods of low river flow, and opined that unless sewage was diverted by pipeline to the Chesapeake Bay, a dam would be necessary to dilute the effluent to an acceptable level. [8] However, the Corps projected that the Seneca reservoir would not be able to assure sufficient water flow and quality without support from upstream dams on tributaries. [9]
The dam was planned as a straight-crested concrete gravity dam with a central overflow spillway regulated by 27 gates. Provision for future power generation was to be included in the south abutment, with water supply provisions on either end of the dam. No lock was to be provided for small craft. [10] For flood control the project was designed to pass 150,000 cu ft/s (4,200 m3/s) of a 400,000 cu ft/s (11,000 m3/s) flood to minimize damage downstream. Drawdown from May to September was expected to be about 5 feet (1.5 m), with another 7 feet (2.1 m) for the rest of the year. The pool would have varied from 38,700 acres (15,700 ha) at maximum flood pool to 24,000 acres (9,700 ha) at full conservation pool, and 9,100 acres (3,700 ha) at minimum pool. Construction was expected to take six years. The reservoir was planned to store 550,000 acre-feet (0.68 km3), of which 50,000 acre-feet (0.062 km3) were allocated for sedimentation. An additional 643,000 acre-feet (0.793 km3) were available for flood storage. [8]
The reservoir was projected to cost more than $100 million in 1962 dollars. The project was opposed by Maryland and Virginia, as well as by conservation organizations and fell out of favor with the Corps of Engineers in 1969. [6] As with the Riverbend proposal, the reservoir was to spread along tributary creeks and reservoirs, in some cases considerable distances. On the Virginia side, Sugarland Run would have been flooded to Herndon, Broad Run to Sterling, Goose Creek to Evergreen Mill and Catoctin Creek to Taylorstown. On the Maryland side, Seneca Creek would have been flooded past Dawsonville, and the Monocacy River would have been flooded past Frederick to Ceresville. The main river pool would have extended to Sandy Hook, Maryland. Maps of the reservoir show that portions of Point of Rocks and Buckeystown, Maryland would have been flooded by the full flood pool, and most or all of Lilypons and Seneca in Maryland, Limestone School and Fairview in Virginia and White's Ferry in Maryland and Virginia. The lower portion of the Ball's Bluff battlefield would have been submerged, as well as the Monocacy Aqueduct. [11]
Roads and railroads were expected to be flooded by the reservoir and would have had to be replaced. The 1963 report described the relocations as "extensive." Road relocations were budgeted at $8,500,000 and railroads at $10,040,000. About 21,000 acres (8,500 ha) of wildlife habitat was expected to be inundated, including the McKee-Beshers and Dierssen wildlife management areas. 13,120 acres (5,310 ha) of replacement habitat was expected to be required to mitigate habitat loss. The project was judged to have little effect on agriculture and forestry. 460 families were expected to be displaced. [8]
The Potomac River is a major river in the Mid-Atlantic region of the United States that flows from the Potomac Highlands in West Virginia to the Chesapeake Bay in Maryland. It is 405 miles (652 km) long, with a drainage area of 14,700 square miles (38,000 km2), and is the fourth-largest river along the East Coast of the United States and the 21st-largest in the United States. More than 5 million people live within its watershed.
The Chesapeake and Ohio Canal, abbreviated as the C&O Canal and occasionally called the Grand Old Ditch, operated from 1831 until 1924 along the Potomac River between Washington, D.C. and Cumberland, Maryland. It replaced the Potomac Canal, which shut down completely in 1828, and could operate during months in which the water level was too low for the former canal. The canal's principal cargo was coal from the Allegheny Mountains.
The Potomac Company was created in 1785 to make improvements to the Potomac River and improve its navigability for commerce. The project is perhaps the first conceptual seed planted in the minds of the new American capitalists in what became a flurry of transportation infrastructure projects, most privately funded, that drove wagon road turnpikes, navigations, and canals, and then as the technology developed, investment funds for railroads across the rough country of the Appalachian Mountains.
The Chesapeake and Ohio Canal National Historical Park is located in the District of Columbia and the state of Maryland. The park was established in 1961 as a National Monument by President Dwight D. Eisenhower to preserve the neglected remains of the Chesapeake and Ohio Canal and many of its original structures.
The Monocacy River is a free-flowing left tributary to the Potomac River, which empties into the Atlantic Ocean via the Chesapeake Bay. The river is 58.5 miles (94.1 km) long, with a drainage area of about 970 square miles (2,500 km2). It is the largest Maryland tributary to the Potomac.
The Patowmack Canal, sometimes called the Potomac Canal, is a series of five inoperative canals located in Maryland and Virginia, United States, that was designed to bypass rapids in the Potomac River upstream of the present Washington, D.C., area. The most well known of them is the Great Falls skirting canal, whose remains are managed by the National Park Service since it is within Great Falls Park, an integral part of the George Washington Memorial Parkway.
Great Falls Park is a small National Park Service (NPS) site in Virginia, United States. Situated on 800 acres (3.2 km2) along the banks of the Potomac River in northern Fairfax County, the park is a disconnected but integral part of the George Washington Memorial Parkway. The Great Falls of the Potomac River are near the northern boundary of the park, as are the remains of the Patowmack Canal, the first canal in the United States that used locks to raise and lower boats.
Seneca Creek is a 5.8-mile-long (9.3 km) stream in Montgomery County, Maryland, USA, roughly 16 miles (26 km) northwest of Washington, D.C. It drains into the Potomac River.
The California State Water Project, commonly known as the SWP, is a state water management project in the U.S. state of California under the supervision of the California Department of Water Resources. The SWP is one of the largest public water and power utilities in the world, providing drinking water for more than 27 million people and generating an average of 6,500 GWh of hydroelectricity annually. However, as it is the largest single consumer of power in the state itself, it has a net usage of 5,100 GWh.
Auburn Dam was a proposed concrete arch dam on the North Fork of the American River east of the town of Auburn, California, in the United States, on the border of Placer and El Dorado Counties. Slated to be completed in the 1970s by the U.S. Bureau of Reclamation, it would have been the tallest concrete dam in California and one of the tallest in the United States, at a height of 680 feet (210 m) and storing 2,300,000 acre-feet (2.8 km3) of water. Straddling a gorge downstream of the confluence of the North and Middle Forks of the American River and upstream of Folsom Lake, it would have regulated water flow and provided flood control in the American River basin as part of Reclamation's immense Central Valley Project.
The Bear River is a tributary of the Feather River in the Sierra Nevada, winding through four California counties: Yuba, Sutter, Placer, and Nevada. About 73 miles (117 km) long, the river flows generally southwest through the Sierra then west through the Central Valley, draining a narrow, rugged watershed of 295 square miles (760 km2).
Little Falls Branch, a 3.8-mile-long (6.1 km) tributary stream of the Potomac River, is located in Montgomery County, Maryland. In the 19th century, the stream was also called Powder Mill Branch. It drains portions of Bethesda, Somerset, Friendship Heights, and Washington, D.C., flows under the Chesapeake and Ohio Canal (C&O), and empties into the Potomac at Little Falls rapids, which marks the upper end of the tidal Potomac.
A series of projects in the 18th and 19th centuries attempted to make the Potomac River navigable and connect the Ohio River valley and the East Coast. The first project was started by the Potomac Company, but it was the Chesapeake and Ohio Canal Company (C&O) that finished the project in the 1830s and 1840s.
Glacier View Dam was proposed in 1943 on the North Fork of the Flathead River, on the western border of Glacier National Park in Montana. The 416-foot (127 m) tall dam, to be designed and constructed by the U.S. Army Corps of Engineers in the canyon between Huckleberry Mountain and Glacier View Mountain, would have flooded in excess of 10,000 acres (4,000 ha) of the park. In the face of determined opposition from the National Park Service and conservation groups, the dam was never built.
Paradise Dam was a proposed dam on the Clark Fork River in Montana. It was proposed by the U.S. Army Corps of Engineers as an alternative to the construction of Glacier View Dam on the western boundary of Glacier National Park, to capture the flow of the Flathead River. The earth embankment dam was planned to be about 250 feet (76 m) high, impounding a reservoir of 4,080,000 acre-feet (5.03 km3). While it was viewed as a desirable power generation and water storage project by the Corps of Engineers, it was opposed by those it would displace from towns and productive agricultural lands, and was never built.
Brocks Gap Dam was a never-built proposal for a water storage dam on the North Fork of the Shenandoah River at Brocks Gap in northwest Virginia. The proposal by the U.S. Army Corps of Engineers encountered opposition from local residents and was withdrawn in 1967.
The Potomac River basin reservoir projects were U.S. Army Corps of Engineers programs that sought to regulate the flow of the Potomac River to control flooding, to assure a reliable water supply for Washington, D.C., and to provide recreational opportunities. Beginning in 1921 the Corps studied a variety of proposals for an ambitious program of dam construction on the Potomac and its tributaries, which proposed as many as sixteen major dam and reservoir projects. The most ambitious proposals would have created a nearly continuous chain of reservoirs from tidewater to Cumberland, Maryland. The 1938 program was focused on flood control, on the heels of a major flood in 1936. The reformulated 1963 program focused on water supply and quality, mitigating upstream pollution from sewage and coal mine waste.
Riley's Lock (Lock 24) and lock house are part of the 184.5-mile (296.9 km) Chesapeake and Ohio Canal that operated in the United States along the Potomac River from the 1830s through 1923. They are located at towpath mile-marker 22.7 adjacent to Seneca Creek, in Montgomery County, Maryland. The lock is sometimes identified as Seneca because of the Seneca Aqueduct that carried the canal over the creek to the lift lock. The name Riley comes from John C. Riley, who was lock keeper from 1892 until the canal closed permanently in 1924.
Violette's Lock is part of the 184.5-mile (296.9 km) Chesapeake and Ohio Canal that operated in the United States along the Potomac River from the 1830s through 1923. It is located at towpath mile-marker 22.1, in Montgomery County, Maryland. The name Violette comes from Alfred L. "Ap" Violette and his wife Kate, who were lock keepers from the beginning of the 20th century through the permanent closure of the canal in 1924.
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