Trinity Dam

In response to the Great Depression and drought conditions in California during the early 20th century, the United States Congress passed the 1935 Rivers and Harbors Act, which authorized the Central Valley Project (CVP) – a system of dams and canals to provide a stable supply of irrigation water to California's Central Valley.{{cite web

|url=http://www.usbr.gov/projects/Project.jsp?proj_Name=Central+Valley+Project

|title=Central Valley Project

|publisher=U.S. Bureau of Reclamation

|date=2011-04-21

|access-date=2012-02-12}} Among the project works was a 1942 proposal to divert water from the Trinity River in northwestern California to augment water supplies in the CVP service area, known as the Trinity River Division. However, the state dropped the Trinity River project from the CVP in 1945.{{cite web

|author = Stene, Eric A.

|url = http://www.usbr.gov/projects/Project.jsp?proj_Name=Shasta/Trinity%20River%20Division%20Project

|title = Trinity Division: Central Valley Project

|publisher = U.S. Bureau of Reclamation

|year = 1996

|access-date = 2012-02-12

|url-status = dead

|archive-url = https://web.archive.org/web/20130222212059/http://www.usbr.gov/projects/Project.jsp?proj_Name=Shasta/Trinity%20River%20Division%20Project

|archive-date = 2013-02-22

}}

Six years later, however, the U.S. Bureau of Reclamation (USBR), which was responsible for the construction and operations of most CVP facilities, revived the division, which comprised a system of four dams and two tunnels to capture and store the flow of the Trinity and transport it to the Sacramento River, generating a net surplus of hydroelectric power along the way. Trinity Dam was to be the main storage feature of the division, providing a stable flow to the Lewiston Dam, the diversion point for Trinity River waters into the Central Valley.{{cite web

|url = http://www.usbr.gov/projects/Project.jsp?proj_Name=Shasta/Trinity%20River%20Division%20Project

|title = Shasta/Trinity River Division Project

|publisher = U.S. Bureau of Reclamation

|work = Central Valley Project

|date = 2011-04-21

|access-date = 2012-02-12

|url-status = dead

|archive-url = https://web.archive.org/web/20130222212059/http://www.usbr.gov/projects/Project.jsp?proj_Name=Shasta/Trinity%20River%20Division%20Project

|archive-date = 2013-02-22

}}

Construction at Trinity Dam began on June 4, 1956 with preliminary excavation and the river was diverted around the dam site on July 8, 1957. Work was bogged down in late 1957 when the river flooded and took out the cofferdam that protected the construction site. However, workers cleared out the dam site by the summer of 1958, and the hiatus also allowed them time to line the diversion tunnel with concrete.

Rock placement began on the main structure as early as 1957, but it was not until 1959 when an {{convert|11000|ft|m|abbr=on}} conveyor belt was incorporated, allowing much faster transport of fill to the dam site. The spillway tunnel was completed in October 1959 and the embankment was topped out in late 1960. The dam's power plant, however, was not finished until December 1963. Trinity stood as the highest earthfill dam in the world until eclipsed by the Oroville Dam, also in California, in 1968. The latter remains the tallest dam in the United States.{{cite web

|url=http://www.water.ca.gov/swp/facilities/Oroville/LakeDam.cfm

|title=Oroville Dam and Lake Oroville

|publisher=California Department of Water Resources

|work=California State Water Project

|date=2009-06-17

|access-date=2012-02-12}}

As the reservoir filled, it submerged the pioneer towns of Trinity Center, Stringtown and Minersville as well as parts of a historic Northern California stagecoach route.{{cite news

|author=Jones, Carolyn

|url=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/09/11/BAO71L2JBO.DTL

|title=Anger lingers over towns flooded by Trinity Dam

|work=San Francisco Chronicle

|date=2011-09-12

|access-date=2012-02-12}} The reservoir was originally named Clair Engle Lake after Clair Engle, a United States senator and major proponent of the CVP. This name was unpopular among local residents, many of whom had watched their homes inundated by the rising waters. By 1995, it had been renamed Trinity Lake.{{cite web

|url=http://origin.www.gpo.gov/fdsys/pkg/CRPT-104hrpt134/pdf/CRPT-104hrpt134.pdf

|title=Designation of Trinity Lake

|publisher=U.S. Government Printing Office

|work=104th Congress, 1st Session

|date=1995-06-07

|access-date=2012-02-12}}

File:TrinityDam3.jpg

Trinity Dam is an earth and rock-filled dam composed mainly of river gravel and local rock, rising {{convert|538|ft|m|abbr=on}} from its foundations and {{convert|440|ft|m|abbr=on}} above the riverbed. The dam's crest is {{convert|2450|ft|m|abbr=on}} long and {{convert|2395|ft|m|abbr=on}} above sea level.{{cite web|url=http://www.usbr.gov/projects/Facility.jsp?fac_Name=Trinity+Dam&groupName=Dimensions|title=Trinity Dam: Dimensions|publisher=U.S. Bureau of Reclamation|work=Shasta/Trinity River Division Project|date=2009-06-04|access-date=2012-02-12}} High water releases are controlled by three different sets of gates. The outlet works have a capacity of {{convert|24000|cuft/s|m3/s|abbr=on}}, and the service spillway, a morning-glory (bell-mouth) design, can take {{convert|22400|cuft/s|m3/s|abbr=on}} of water. The dam's auxiliary spillway has a capacity of {{convert|2250|cuft/s|m3/s|abbr=on}}.{{cite web|url=http://www.usbr.gov/projects/Facility.jsp?fac_Name=Trinity+Dam&groupName=Hydraulics+%26+Hydrology|title=Trinity Dam: Hydraulics & Hydrology|publisher=U.S. Bureau of Reclamation|work=Shasta/Trinity River Division Project|date=2009-06-04|access-date=2012-02-12}}

Trinity Lake can hold up to {{convert|2447650|acre feet|dam3|lk=on}} at full pool, and encompasses up to {{convert|17722|acre|ha|abbr=on}} of water.{{cite web|url=http://npdp.stanford.edu/DamDirectory/DamDetail.jsp?npdp_id=CA10196|title=Trinity Dam|publisher=Stanford University

|work=National Performance of Dams Program|access-date=2012-02-12}} Trinity Powerplant, located at the base of the dam, has two Francis turbines with a capacity of 140 megawatts (MW) combined, uprated from an original capacity of 100 MW. The plant generates an average of 358.97 million kilowatt hours (kWh) and has a low capacity factor, which means it operates mainly on a peaking basis.{{cite web|url=http://www.usbr.gov/projects/Powerplant.jsp?fac_Name=Trinity%20Powerplant|title=Trinity Powerplant|publisher=U.S. Bureau of Reclamation|work=Shasta/Trinity River Division Project|date=2001-04-04|access-date=2012-02-12|url-status=dead|archive-url=https://web.archive.org/web/20120925124913/http://www.usbr.gov/projects/Powerplant.jsp?fac_Name=Trinity%20Powerplant|archive-date=2012-09-25}}

Trinity Dam forms an impassable barrier for migrating salmon in the Trinity River, but along with other division facilities has also had adverse impacts on salmon habitat in the lower reaches of the river. Within ten years of the dam's completion, more than three-quarters of Trinity River water was being diverted to the Central Valley each year, and the little flow left in the river was warm, shallow and less suitable for spawning salmon. In addition, the dam blocks the Trinity River's annual floods and sediment loads, leading to degradation in the gravel bars that are vital for salmon habitat.{{cite web

|url=http://swr.nmfs.noaa.gov/recovery/soncc_draft/Chapter_39_Upper_Trinity_River_Population.pdf|title=Upper Trinity River Population|work=SONCC Coho Salmon Recovery Plan|publisher=National Oceanic and Atmospheric Administration|date=January 2012|access-date=2012-02-12}}{{cite web|url=http://www.trrp.net/?page_id=23|title=Background|publisher=Trinity River Restoration Program|access-date=2012-02-12}}

In response to declining salmon populations, the USBR built the Trinity River Fish Hatchery. The hatchery is operated by the California Department of Fish and Game and has a capacity of 40 million eggs. In 1992, Congress passed the Central Valley Project Improvement Act, which established a minimum annual release of {{convert|340000|acre feet|dam3|lk=on}} into the lower Trinity River.{{cite web|url=http://www.usbr.gov/mp/cvpia/docs_reports/meetings/2011/Trinity_Briefing_CVPIA_Feb%202011.pdf|title=Trinity River Restoration Program Overview|publisher=U.S. Bureau of Reclamation|work=CVPIA Annual Work Plan|date=2011-02-17|access-date=2012-02-12}}

Also, below the Trinity Dam, is the Lewiston Dam (California) in which that water is sent to other water customers that live throughout the State.{{cite web|author1=Aaron J. Douglas|author2=Jonathan G. Taylor|title=The Economic Value of Trinity River Water|url=http://www.uwsp.edu/cnr-ap/UWEXLAKES/Documents/people/economics/45_trinityRiverWater_douglas_paper.pdf|access-date=31 March 2016}} This is important because this requires the help of two dams just to move water from the reservoir to the customers that require water for either Agriculture or Urban uses.

With {{convert|145|mi|km}} of shoreline,{{cite web|url=http://www.recreation.gov/recAreaDetails.do?contractCode=NRSO&recAreaId=32&agencyCode=129

|title=Trinity Lake – Bureau of Reclamation|publisher=Recreation.gov|access-date=2012-02-12}} Trinity Lake is a popular summer destination for Northern California residents. Since 1965, the lake has been part of the Trinity Unit of the Whiskeytown-Shasta-Trinity National Recreation Area. The lake has been developed with boat ramps and marinas, most of which are concentrated in the Stuart Fork arm in the southwest and around the resort town of Trinity Center near the north end of the reservoir.{{cite web|url=http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5130544.pdf|title=Trinity Unit|publisher=U.S. Forest Service|work=Whiskeytown-Shasta-Trinity National Recreation Area|year=2003|access-date=2012-02-12}}

{{stack|{{Portal|California|Water|Renewable energy}}}}

• List of dams and reservoirs in California
• List of largest reservoirs of California
• List of power stations in California
• List of the tallest dams in the United States

{{Reflist|30em}}

{{commons category|Trinity Dam}}

• [http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5130538.pdf Bathymetric map and navigation safety on Trinity Lake]
• [http://cdec.water.ca.gov/river/res_CLE.html California Department of Water Resources: Trinity Lake Reservoir Up-to-Date Data]
• [http://www.trrp.net/ Trinity River Restoration Program]
• [http://www.usbr.gov/mp/cvo/ USBR Central Valley Operations Office] {{Webarchive|url=https://web.archive.org/web/20040209001614/http://www.usbr.gov/mp/cvo/ |date=2004-02-09 }}

{{Central Valley Project infrastructure}}

{{Generating stations in California|state=autocollapse}}

Category:Dams on the Trinity River (California)

Category:Embankment dams

Category:Hydroelectric power plants in California

Category:Buildings and structures in Trinity County, California

Category:Central Valley Project

Category:Weaverville, California

Category:United States Bureau of Reclamation dams

Category:Dams in California

Category:Dams completed in 1962

Category:Energy infrastructure completed in 1962