{{Use mdy dates|date=February 2025}} {{Use American English|date=January 2025}}{{For|the unincorporated community in Cherokee County|Hiwassee, North Carolina}} {{Infobox dam | name = Hiwassee Dam | image = Hiwassee Dam.jpg | image_caption = | name_official = Hiwassee Dam | dam_crosses = [[Hiwassee River]] | res_name = [[Hiwassee Lake]] | location = [[Cherokee County, North Carolina]], U.S. | operator = [[Tennessee Valley Authority]] | dam_length = {{convert|1376|ft|m|abbr=on}} | dam_height = {{convert|307|ft|m|abbr=on}} | dam_width_base = | construction_began = July 15, 1936 | opening = February 8, 1940 | res_capacity_total = {{convert|434000|acre feet|dam3|abbr=on|lk=in}} | res_catchment = {{convert|968|mi2|km2|abbr=on}} | plant_capacity = 185 MW | coordinates = {{coord|35|9|5|N|84|10|39|W|type:landmark|display=inline,title}} | extra = }} '''Hiwassee Dam''' is a [[hydroelectric dam]] on the [[Hiwassee River]] in [[Cherokee County, North Carolina|Cherokee County]], in the U.S. state of [[North Carolina]]. It is one of three dams on the river owned and operated by the [[Tennessee Valley Authority]], which built the dam in the late 1930s to bring [[flood control]] and electricity to the region.<ref name=report1>Tennessee Valley Authority, ''The Hiwassee Project: A Comprehensive Report on the Planning, Design, Construction, and Initial Operations of the Hiwassee Project'' (Hiwassee Valley Projects Volume 1), Technical Report No. 5 (Washington, D.C.: U.S. Government Printing Office, 1946), pp. 1-8, 39-40, 211, 230, 242, 248.</ref> The dam impounds the [[Hiwassee Lake]] of {{convert|6000|acre|ha}}, and its tailwaters are part of [[Apalachia Reservoir]]. At {{convert|307|ft|m}}, Hiwassee Dam is the highest overspill dam east of the Mississippi River and is second only to [[Grand Coulee Dam|Grand Coulee]] dam in the nation.<ref>{{Cite web |date=2024-01-23 |title=Hiwassee Dam (Q-54) {{!}} NC DNCR |url=https://www.dncr.nc.gov/blog/2024/01/23/hiwassee-dam-q-54 |access-date=2024-04-14 |website=www.dncr.nc.gov |language=en}}</ref> At the time it was completed, it was the highest overspill dam in the world.<ref name="NC Markers 2023-08-05">{{cite web |url=http://www.ncmarkers.com/Markers.aspx?MarkerId=Q-54 |title=Hiawassee Dam |work=North Carolina Highway Historical Marker Program |publisher=North Carolina Department of Cultural Resources |accessdate=2023-08-06 }}</ref><ref name=":0">{{Cite news |last=McKeever |first=Mrs. Hobart |date=1961-01-29 |title=Cherokee County Shows Greatest Progress During 1950-60 Decade |url=https://www.newspapers.com/image/201809295/?terms=cherokee%20county&match=1 |access-date=2024-03-21 |work=[[Asheville Citizen-Times]] |page=77}}</ref>
Hiwassee Dam is the third highest dam in the TVA system, behind only [[Fontana Dam|Fontana]] and [[Watauga Dam|Watauga]].<ref name=nickajack1>Tennessee Valley Authority, ''The Nickajack Project: A Report on the Planning, Design, Construction, Initial Operations, and Costs'', Technical Report No. 16 (Knoxville, Tenn.: Tennessee Valley Authority, 1972), pp. 10-11.</ref> The dam and associated infrastructure was listed on the [[National Register of Historic Places]] in 2017.<ref>{{Cite web |title=National Register Database and Research - National Register of Historic Places (U.S. National Park Service) |url=https://www.nps.gov/subjects/nationalregister/database-research.htm |access-date=2024-03-15 |website=www.nps.gov |language=en}}</ref> Hiwassee Dam is classified by the [[United States Army Corps of Engineers|U.S. Army Corps of Engineers]] as a high-hazard dam, meaning a [[dam failure]] may pose a deadly threat to nearby residents. The dam's condition is not made available to the public due to security concerns.<ref>{{Cite web |date=2021-06-15 |title=Hiwassee Dam |url=https://nid.sec.usace.army.mil/#/dams/system/NC00419/inspections |access-date=2024-10-25 |website=National Inventory of Dams}}</ref><ref>{{Cite news |last=LIEB |first=David A. |date=2022-05-05 |title=Condition of some US dams kept secret in national database |url=https://apnews.com/article/technology-dams-ac3d7561181d622b29983c15de84520b |access-date=2024-10-25 |work=[[Associated Press]]}}</ref>
Hiwassee Dam is named after the Hiwassee River.<ref name=report1 /> The river's name is derived from the [[Cherokee language|Cherokee]] word for [[savanna]], or large meadow. Two of the tribe's towns along the river in the 18th century were also called Hiwassee.<ref>James Mooney, ''Myths of the Cherokee and Sacred Formulas of the Cherokee'' (Nashville, Tenn.: C and R Elder, 1972), p. 512.</ref>
==Location== The Hiwassee River flows northwestward from its source in [[Towns County, Georgia]] through Western North Carolina, where it proceeds to slice a scenic valley through the southern [[Appalachian Mountains]] en route to its mouth along [[Chickamauga Lake]] in [[Tennessee]].
Hiwassee Dam was constructed nearly {{convert|76|mi|km}} above the river's mouth, at the downstream end of a large bend in the river known as Fowler Bend. The dam is {{convert|10|mi|km}} upstream from [[Apalachia Dam]] (which is near the Tennessee-North Carolina state line) and {{convert|45|mi|km}} downstream from [[Chatuge Dam]]. Hiwassee Dam and its reservoir are surrounded by the [[Nantahala National Forest]].
[[Hiwassee, North Carolina|Hiwassee Village]], a small community that developed alongside the dam and reservoir, is located immediately south of Hiwassee Dam. North Carolina Secondary Road 1314 (Hiwassee Dam Access Road) crosses the top of the dam.
==Capacity== Hiwassee Dam is a concrete, gravity-overflow dam {{convert|307|ft|m}} high and {{convert|1376|ft|m}} long, and has a generating capacity of 185,000 [[kilowatt]]s.<ref name=web1>Tennessee Valley Authority, [https://web.archive.org/web/20021121160900/http://www.tva.com/sites/hiwassee.htm Hiwassee Reservoir]. Retrieved: 25 January 2009.</ref> The dam's spillway is controlled by seven radial gates, which, along with four regulating conduits at the bottom of the dam, give the dam a total maximum discharge of {{convert|112000|cuft/s}}.<ref name=report1 /><ref name=nickajack1 />
Hiwassee Lake stretches along the river for approximately {{convert|22|mi|km}} to the town of [[Murphy, North Carolina]]. It has {{convert|180|mi|km}} of shoreline, a storage capacity of {{convert|434000|acre feet|dam3|abbr=on}}, and {{convert|205590|acre feet|dam3|abbr=on}} of flood storage.<ref name=report1 /><ref name=web1 /> The reservoir's operating level varies by roughly {{convert|38|ft|m}} in a typical year.<ref name=web1 />
==Pumped storage== In the 1950s, TVA began experiments with [[Pumped-storage hydroelectricity|pumped storage]] at Hiwassee Dam. It used an energy-generating turbine that was run in reverse during low-demand hours to pump water from below the dam into the upper reservoir. This integration of pump and turbine was the first of its kind in the United States; further, at the time it was the largest and most powerful pump in the world, capable of pumping 1,750,000 gallons of water per minute.<ref name=":0" /> The "pump-turbine" at Hiwassee is designated as a "[[National Historic Mechanical Engineering Landmark]]" by the [[American Society of Mechanical Engineers]] (ASME).<ref name="files.asme.org">[http://files.asme.org/asmeorg/Communities/History/Landmarks/5567.pdf Hiwassee Dam Unit 2 Reversible Pump-Turbine (1956)] {{Webarchive|url=https://web.archive.org/web/20131004221010/http://files.asme.org/asmeorg/Communities/History/Landmarks/5567.pdf |date=2013-10-04 }}, National Historic Mechanical Engineering Landmark report, 14 July 1981. Retrieved: 2 October 2013.</ref><ref name="tva.gov">[http://www.tva.gov/heritage/mountaintop/ The Mountaintop Marvel], TVA.gov. Retrieved: 2 October 2013.</ref>
==Background and construction== [[File:Hiwassee-dam-design-tva1.jpg|right|250px|thumb|TVA's design plan for Hiwassee Dam, circa 1936]]
The hydroelectric potential of the Hiwassee River has been recognized since the early 1900s. The cities of [[Andrews, North Carolina|Andrews]] and Murphy in North Carolina had already established minor dams with generating capacities along the river when major power companies began planning large-scale hydro projects in the valley in the 1920s. The Carolina-Tennessee Power Company (later reorganized as the [[Southern States Power Company]]) purchased {{convert|10000|acre|ha}} of land and flowage rights along the river in 1924 in hopes of building a large dam just above the present dam site, but the project was never fully developed.
The [[Tennessee Valley Authority]], created as a [[New Deal]] measure in 1933 during the Franklin D. Roosevelt administration, was given oversight of flood control operations in the Tennessee River watershed, which included the Hiwassee. It also intended to develop hydroelectric projects to generate electricity for the rural region. One of TVA's first initiatives was to control flooding on the Hiwassee River, the waters of which contributed to regular seasonal flooding in the city of [[Chattanooga, Tennessee|Chattanooga]]. Congress authorized the construction of Hiwassee Dam in 1935, and work began the following year.<ref name=report1 /> TVA also considered two sites in Tennessee for constructing Hiwassee Dam. Original plans called for a $13 million dam {{convert|185|ft|m}} high with a {{convert|4000|foot|m}} tunnel.<ref>{{cite news |last=Robertson, Jr. |first=A.T. |url=https://newspapers.digitalnc.org/lccn/sn83004710/1934-09-27/ed-1/seq-9/ |format=PDF |title=TVA Co-operating In Brasstown Program |work=The Cherokee Scout |location=Murphy, N.C. |date=1934-09-27 |pages=8–9 }}</ref> Southern States Power agreed to sell its Hiwassee tract to TVA, although the two entities bickered over the land's value in federal court until 1944, when TVA agreed to a final price of $250,000.<ref name=report1 />
The construction of Hiwassee Dam and its reservoir required the purchase of {{convert|24102|acre|ha}} (including the {{convert|10000|acre|ha}} purchased from Southern States Power), {{convert|3836|acre|ha}} of which had to be cleared. 261 families, 462 graves, and {{convert|25|mi|km}} of roads had to be relocated. Eight new bridges were constructed, and a Southern Railway trestle required modification. Several changes were necessary to protect the city of Murphy's riverfront, mainly at its main bridge and filtering plant.<ref name=report1 />
[[Image:Hiwassee-dam-construction-tva1.jpg|thumb|left|250px|Construction of Hiwassee Dam's powerhouse and switchyard]]
Hiwassee Dam's height required a large mass of concrete which engineers feared would trap heat during its setting, making the dam more vulnerable to cracks. To help heat escape, the dam's concrete sections were divided into blocks no more than {{convert|50|ft|m}} in length. The blocks' joints were formed with shear keys, and pipes were installed to allow future grouting should it become necessary. Several practices were employed to avoid trapping heat in the setting of the concrete, including the use of low-heat cement.<ref name=report1 />
Hiwassee Dam's gates were closed on February 8, 1940, although minor construction work continued until later that same year. The first generator went online May 21, 1940.<ref name=report1 /> The dam's final price tag was just over $24 million.<ref name=nickajack1 /> Shortly after the project's completion, TVA transferred {{convert|17000|acre|ha}} of its Hiwassee property reservation to the [[U.S. Forest Service]] for inclusion in the Nantahala National Forest.<ref name=report1 />
In 1952 unit 2 was added, an integration of pump and turbine built by Allis-Chalmers Company. After the electrical system for the pump failed in 2011, it remained offline until being repaired in 2016.<ref>{{cite web| url = https://www.tva.gov/Newsroom/Hiwassee-Dam%E2%80%99s-Unit-2-Pumps-It-Up| url-status = dead| archive-url = https://web.archive.org/web/20160712194541/https://www.tva.gov/Newsroom/Hiwassee-Dam%E2%80%99s-Unit-2-Pumps-It-Up| archive-date = 2016-07-12| title = TVA - Hiwassee Dam's Unit 2 Pumps It Up}}</ref>
==References== {{Reflist}}
==External links== {{stack|{{Portal|United States|Water|Renewable energy}}}} {{Commons category|Hiwassee Dam}} *[https://www.tva.com/energy/our-power-system/hydroelectric/hiwassee Hiwassee Reservoir] — official TVA site *[http://newdeal.feri.org/attic/002.htm Scrapbooks of Edgar F. Pohlmann, Engineering Aide, Hiwassee Dam, TVA]
{{Tennessee Valley Authority Facilities}}
[[Category:Dams on the Hiwassee River]] [[Category:Tennessee Valley Authority dams]] [[Category:Buildings and structures in Cherokee County, North Carolina]] [[Category:Dams in North Carolina]] [[Category:Hydroelectric power plants in North Carolina]] [[Category:Dams completed in 1940]] [[Category:Energy infrastructure completed in 1940]] [[Category:National Register of Historic Places in Cherokee County, North Carolina]] [[Category:Dams on the National Register of Historic Places in North Carolina]] [[Category:Historic districts in North Carolina]] [[Category:Pumped-storage hydroelectric power stations]] [[Category:1940 establishments in North Carolina]]