Seven Oaks Dam
{{Infobox dam
| name = Seven Oaks Dam
| name_official =
| image = Seven_Oaks_Dam.jpg
| image_size =
| image_caption =
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| location_map =
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| coordinates = {{coord|34|07|02|N|117|06|00|W|type:landmark|display=inline,title}}
| country = United States
| location = San Bernardino National Forest, San Bernardino County, near Mentone, California
| status =
| construction_began = {{start date and age|1993}}
| opening = {{start date and age|2000}}
| demolished =
| cost = $450 million{{cite web|url=http://www.sbcounty.gov/dpw/floodcontrol/sevenOaks.asp|title=Seven Oaks Dam|publisher=County of San Bernardino Department of Public Works|date=|accessdate=2012-03-24}}
| owner = Orange County Flood Control District,
San Bernardino County Flood Control District
| dam_type = Embankment
| dam_height = {{convert|550|ft|m|abbr=on}}
| dam_height_thalweg =
| dam_height_foundation=
| dam_length = {{convert|2980|ft|m|abbr=on}}
| dam_width_base =
| dam_volume =
| dam_crosses = Santa Ana River
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| spillway_capacity =
| res_name = Seven Oaks Reservoir
| res_capacity_total = {{convert|145600|acre feet|km3|abbr=on}}
| res_capacity_active =
| res_capacity_inactive=
| res_catchment = {{convert|176|mi2|km2|abbr=on}}
| res_surface = {{convert|780|acre|ha|abbr=on}} (max)
| res_elevation ={{convert|2604.4|ft|m|abbr=on}} (max)
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Seven Oaks Dam is a {{convert|550|ft|m|adj=on}} high earth and rock fill embankment dam across the Santa Ana River in the San Bernardino Mountains, about {{convert|4|mi|km}} northeast of Redlands in San Bernardino County, southern California. It impounds Seven Oaks Reservoir in the San Bernardino National Forest.
The dam was proposed in response to major floods in the mid–20th century, and was constructed between 1993 and 2000. Seven Oaks is a dry dam that serves mainly for flood protection to Orange, Riverside and San Bernardino Counties, although it also used to impound water for groundwater recharge. One of the largest embankment dams in the United States, the dam was built under contract from the U.S. Army Corps of Engineers (USACE) by Odebrecht Corporation of California, a subsidiary of the Brazilian firm Contructora Norberto Odebrecht,.Odebrecht The dam is now owned and operated by local flood control districts.
History
The USACE began an ambitious effort to improve levees and dams on the Santa Ana River system known as the Santa Ana River Mainstem Project.{{cite web
|url = http://www.ocflood.com/SARP_Projects.aspx
|title = OC Flood Santa Ana River Project (SARP)
|publisher = Orange County Department of Public Works
|work = Flood Control District
|accessdate = 2012-03-24
|url-status = dead
|archiveurl = https://web.archive.org/web/20120224131545/http://www.ocflood.com/SARP_Projects.aspx
|archivedate = 2012-02-24
}} Among the works proposed under the project were an expansion of the massive Prado Dam, which despite filling to capacity did not fully prevent heavy flooding damages in Orange County,{{cite news
|author1=Kim, Rose |author2=Dunbar, Donnette
|title=Prado Dam's Floodgates Open, River Comes Alive: Runoff: As rain pummels the Southland, Santa Ana channel receives up to 3,000 cubic feet per second
|url=https://www.latimes.com/archives/la-xpm-1992-02-13-me-3207-story.html
|work=Los Angeles Times
|date=1992-02-13
|access-date=2012-03-24}} and the construction of the $530 million "Mentone Dam" across the Santa Ana north of Mentone in San Bernardino County.{{cite news
|author=Lindgren, Kristina
|title=Alternative to Mentone Dam Aimed at Objections to River Flood Control Work
|url=https://www.latimes.com/archives/la-xpm-1985-10-01-me-19211-story.html
|work=Los Angeles Times
|date=1985-10-01
|access-date=2012-03-24}} However, the Mentone Dam site was controversial because it would affect groundwater recharge, was aesthetically unpleasing and lay on unstable sediment deposits directly above the San Andreas Fault. In response to public opposition, the USACE replaced the Mentone proposal with the $304 million Upper Santa Ana River Dam, later to be called Seven Oaks Dam, in a bedrock canyon one mile (1.6 km) upstream in the southern San Bernardino Mountains.{{cite news
|author=Lindgren, Kristina
|title=Taming the Santa Ana River: $1.1–Billion Plan to Avert Disastrous Flooding Still Awaits Action in Congress
|work=Los Angeles Times
|date=1985-11-24
|url=https://www.latimes.com/archives/la-xpm-1985-11-24-me-1694-story.html
|access-date=2012-03-24}}
The contract for Seven Oaks Dam was awarded in 1994 and construction work began in May.{{cite web
|url = http://www.ocflood.com/SARP_SevenOaksDam.aspx
|title = OC Flood: Seven Oaks Dam
|publisher = Orange County Department of Public Works
|work = Flood Control District
|accessdate = 2012-03-24
|url-status = dead
|archiveurl = https://web.archive.org/web/20120224131656/http://www.ocflood.com/SARP_SevenOaksDam.aspx
|archivedate = 2012-02-24
}} A system of conveyor belts totaling {{convert|3.5|mi|km}}, with a capacity of 3,400 short tons (3,080 t) per hour, was built to transport materials to the dam site. Fill used in the embankment was excavated from the Santa Ana River canyon directly below the dam, the alluvial fan of the river north of Mentone, and a cut in a ridge directly southeast of the dam that now serves as the dam's spillway. The dam was built in ten alternating zones of dirt, rock and clay that ultimately totaled {{convert|38000000|yd3|m3}}.{{cite web
|url=http://www.co.san-bernardino.ca.us/flood/dampage.htm
|title=Seven Oaks Dam Project
|publisher=County of San Bernardino
|date=
|accessdate=2012-03-24}} When completed and dedicated in January 2000, the Seven Oaks Dam was the 12th highest dam in the world and was one of the last major dams built in the United States.{{sfn|Blatt|2005|p=41}} At $450 million, the final cost of the dam significantly exceeded the USACE's projected cost. The federal government shouldered 70.47% of the total cost, while Orange County paid 27.09%, San Bernardino County 1.71%, and Riverside County 0.73%.{{cite web
|url=http://www.ocflood.com/SARP_CostSch.aspx
|title=OC Flood: Project Cost and Schedule
|publisher=Orange County Department of Public Works
|work=Flood Control District
|date=
|accessdate=2012-03-24}}
Design and operations
File:Santa Ana River, Seven Oaks Dam, Mill Creek, and Slide Peak.jpg
Seven Oaks Dam is a {{convert|2980|ft|m|adj=on}} long arched embankment structure standing {{convert|550|ft|m}} high above the Santa Ana River and {{convert|650|ft|m}} above its deepest foundations. The dam is {{convert|40|ft|m}} wide at the crest and over {{convert|2200|ft|m}} wide at the base. Situated close to the San Andreas Fault, Seven Oaks is designed to withstand an 8.0 ML earthquake.{{cite web
|url=http://www.ocpublicworks.com/ocoandm/dams.aspx
|title=Dams: Seven Oaks Dam
|publisher=Orange County Department of Public Works
|work=OC Operations & Maintenance
|date=
|accessdate=2012-03-24}} The reservoir has a gross storage capacity of {{convert|145600|acre feet|km3}}, with {{Convert|113600|acre feet|km3}} reserved for flood control and the remainder for sediment accumulation. At full pool, the reservoir lies at an elevation of {{Convert|2604.4|ft|m}} and has an area of {{convert|780|acre|ha}}.{{cite web|url=http://cdec.water.ca.gov/cgi-progs/profile?s=SVO&type=dam|title=Seven Oaks Dam (SVO)|publisher=California Department of Water Resources|work=California Data Exchange Center|date=|accessdate=2012-03-24}} Water releases are controlled by a {{convert|1623|ft|m|adj=on}} long tunnel outlet that runs through the base of the structure, and a {{convert|500|ft|m|adj=on}} wide ungated overflow spillway located just southeast of the dam. The dam controls runoff from an area of {{convert|176|mi2|km2}} or {{convert|209|mi2|km2}} including the drainage area of Baldwin Lake, which overflows into the Santa Ana River system during periods of heavy runoff.
In tandem with Prado Dam, Seven Oaks prevents about $140 million of flood–related damages each year in Orange, Riverside and San Bernardino Counties and provides flood protection to more than two million people. During flood events, Seven Oaks Dam will store runoff as long as the reservoir of Prado Dam is rising, then release the captured water as quickly as downstream channel conditions allow.{{cite web
|url=http://www.rcip.org/Documents/general_plan/appendix_h/pdf/03_05.pdf
|title=County Flood Control and Reservoir Projects
|publisher=Riverside County Integrated Project
|work=Flood Hazards–County of Riverside
|date=2000-08-01
|accessdate=2012-03-24}} Seven Oaks is designed to completely contain a "Reservoir Design Flood" of {{convert|85000|cuft/s|m3/s}}, corresponding to a 350-year flood event, reducing it to a peak outflow of {{convert|7000|cuft/s|m3/s}}.{{cite web
|url=http://www.waterboards.ca.gov/waterrights/water_issues/programs/hearings/santa_ana_river/exhibits/local_sponsors/ls1_0.pdf
|title=Testimony of Vana Olson, Director, San Bernardino County Flood Control District; Jim Borcuk, Chief, San Bernardino County Flood Control District, Federal Projects Division; and Lance Natsuhara, Manager, Orange County Flood Control District, Santa Ana River Project Section, on behalf of the Santa Ana River Mainstem Project Local Sponsors in the SWRCB Hearing on Santa Ana River Water Rights Applications
|publisher=California Environmental Protection Agency
|work=State Water Resources Control Board
|date=
|accessdate=2012-03-24}} The dam is capable of withstanding an inflow of up to {{convert|180000|cuft/s|m3/s}}, or the "Probable Maximum Flood". In addition, controlled releases from the dam allow about {{convert|10000|acre feet|km3}} of additional groundwater recharge in the upper Santa Ana River basin each year. Captured floodwater from the Seven Oaks Dam benefits local water districts, as river water costs only a fraction of water imported through the State Water Project, which supplies most agricultural and municipal needs in the area.{{cite news
|author=Zimmerman, Janet
|title=San Bernardino County: Seven Oaks Dam holds back a muddy lake
|url=http://www.pe.com/local-news/riverside-county/riverside/riverside-headlines-index/20110129-san-bernardino-county-seven-oaks-dam-holds-back-a-muddy-lake.ece
|work=The Press–Enterprise
|date=2011-01-28
|accessdate=2012-03-24}}
Since its construction, Seven Oaks Dam has not yet been filled to capacity. The highest lake level on record was about {{convert|43000|acre feet|km3}}, or less than a third of capacity, on March 8, 2005.{{cite web
|url=http://rcflood.org/Documents/PublicNotices/Agencies_Will%20_Test_Seven_Oaks_Dam_Outlet_Works.pdf
|title=Agencies Will Test Seven Oaks Dam Outlet Works
|work=U.S. Army Corps of Engineers
|publisher=Riverside County Flood Control and Water Conservation District
|date=2010-07-08
|accessdate=2012-03-24}} The high water presented an opportunity to test large water releases through the dam's outlet works, but the trial had to be cancelled because the high flows destroyed sections of the concrete tunnel lining. The tunnel was repaired and later tested successfully in 2011.{{cite news
|author=Zimmerman, Janet
|title=Region: Seven Oaks Dam testing goes smoothly
|work=The Press-Enterprise
|url=http://www.pe.com/local-news/riverside-county/riverside/riverside-headlines-index/20110216-region-seven-oaks-dam-testing-goes-smoothly.ece?ssimg=304072#ssStory279102
|date=2011-02-15
|accessdate=2012-03-24}}
Environmental impacts
In March 1999, as the dam neared completion, environmental groups filed a lawsuit against the USACE because construction activity at the Seven Oaks site had affected the habitats of two endangered plants, the Santa Ana River woolly star and slender-horned spineflower, and the endangered San Bernardino kangaroo rat.{{cite news
|url=https://www.latimes.com/archives/la-xpm-1999-sep-12-me-9354-story.html
|title=Hole in the Dam: If Not for 3 Endangered Species, Seven Oaks Would Be Set to Operate
|author=Reyes, David
|work=Los Angeles Times
|date=1999-09-12
|access-date=2012-03-24}} The USACE responded by purchasing {{convert|1547|acre|ha}} of land adjoining the dam and reservoir to use in conservation of these species. The Seven Oaks Dam has also damaged the habitat of native fish species including the Santa Ana sucker, which is endemic to a handful of river systems of Southern California.{{cite web
|url=http://www.biologicaldiversity.org/species/fish/Santa_Ana_sucker/index.html
|title=Saving the Santa Ana Sucker
|publisher=Center for Biological Diversity
|date=
|accessdate=2012-03-24}}
See also
References
{{Reflist|30em}}
Works cited
- {{cite book
|last=Blatt |first=Harvey
|title=America's environmental report card: are we making the grade?
|publisher=MIT Press
|year=2005
|isbn=0-262-02572-8
|url-access=registration
|url=https://archive.org/details/americasenvironm0000blat_a8f4
}}
External links
- [http://www.redlandsfortnightly.org/papers/7oaksdam.htm Fortnightly Club of Redlands – Seven Oaks Dam]
- [http://cdec.water.ca.gov/cgi-progs/stationInfo?station_id=SVO Seven Oaks Dam Live Hydrologic Data]
- [https://web.archive.org/web/20120405234723/http://www.ocflood.com/SAR_Seven_Oaks_Dam_2.aspx Seven Oaks Dam Construction Photos]
Category:Buildings and structures in San Bernardino County, California
Category:San Bernardino Mountains