Difference between revisions of "San Clemente Dam"

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(Geology and Sedimentation)
(Geology and Sedimentation)
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===Geology and Sedimentation===  
 
===Geology and Sedimentation===  
 
[[Image:sanclementedam_2_NOAA.jpg|300px|thumb|right|Image 2. San Clemente Dam being overtopped by highly sedimented flow during a rain storm. Image: NOAA]]
 
[[Image:sanclementedam_2_NOAA.jpg|300px|thumb|right|Image 2. San Clemente Dam being overtopped by highly sedimented flow during a rain storm. Image: NOAA]]
Parts of the the Carmel River are surrounded by steep slopes of fractured granite that are subject to serious erosion during heavy precipitation events (Image 2). The steep slopes and arid climate of the [[Santa Lucia Range|Santa Lucia Mountains]] make [[History of Major Wildfires in the Central Coast Region|wildland fires]] more difficult to suppress and more destructive when they occur. The “Marble Cone Fire” in 1977 led to serious erosion issues and a large influx of sediment into the river. Although the dam was built in 1921, by 1947 it was 25% silted  and by 2012 was 98% silted. <ref name="CVAHistory"> Carmel Vally Association [http://www.carmelvalleyassociation.org/assetts/docs/CV_Voices/Carmel_River_History.pdf "Carmel River History"] </ref> <ref>The Carmel Watershed Conservancy [http://carmelriverwatershed.org/wp-content/uploads/2012/09/Active_Projects_in_the_Carmel_River_Watershed.pdf Active Projects in the Carmel River Watershed] </ref>
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Parts of the the Carmel River are surrounded by steep slopes of fractured granite that are subject to serious erosion during heavy precipitation events (Image 2). The steep slopes and arid climate of the [[Santa Lucia Range|Santa Lucia Mountains]] make [[History of Major Wildfires in the Central Coast Region|wildland fires]] more difficult to suppress and more destructive when they occur. The [[Marble Cone Fire]] in 1977 led to serious erosion issues and a large influx of sediment into the river. Although the dam was built in 1921, by 1947 it was 25% silted  and by 2012 was 98% silted. <ref name="CVAHistory"> Carmel Vally Association [http://www.carmelvalleyassociation.org/assetts/docs/CV_Voices/Carmel_River_History.pdf "Carmel River History"] </ref> <ref>The Carmel Watershed Conservancy [http://carmelriverwatershed.org/wp-content/uploads/2012/09/Active_Projects_in_the_Carmel_River_Watershed.pdf Active Projects in the Carmel River Watershed] </ref>
  
 
===Seismic Considerations===
 
===Seismic Considerations===

Revision as of 20:24, 29 March 2017

Image 1. San Clemente Dam during normal flows.

This page gives a short history of the San Clemente Dam and a description of the completed dam removal project, its environmental impact, and related issues and controversies.

History

The San Clemente Dam was built in 1921 by a local businessman Samuel Morse on the Carmel River to supply the water needs of Monterey's growing population and tourism industry. Later the dam was purchased by Chester Loveland who owned the California Water and Telephone Company (CW&T). To meet the needs of the growing population and increasing demand from the sardine processing industry in Monterey, CW&T built the Los Padres Dam upstream from San Clemente Dam in 1948. In 1966 CW&T sold the dam to California American Water Company (CalAm) for $42 million. [1] [2] [3].

Geology and Ecology of Carmel River Watershed

Geology and Sedimentation

Image 2. San Clemente Dam being overtopped by highly sedimented flow during a rain storm. Image: NOAA

Parts of the the Carmel River are surrounded by steep slopes of fractured granite that are subject to serious erosion during heavy precipitation events (Image 2). The steep slopes and arid climate of the Santa Lucia Mountains make wildland fires more difficult to suppress and more destructive when they occur. The Marble Cone Fire in 1977 led to serious erosion issues and a large influx of sediment into the river. Although the dam was built in 1921, by 1947 it was 25% silted and by 2012 was 98% silted. [3] [4]

Seismic Considerations

Located near the Cachagua and Tularcitos faultlines, the San Clemente Dam was vulnerable to a catastrophic failure due to an earthquake. With the dam having reached the end of its expected useful life and 1500 homes and other structures below the dam under threat, in 2006 the California Department of Water Resources decided that action had to be taken to mitigate the danger by either removing or reinforcing the dam. While CalAm proposed reinforcing the dam, other stakeholders including NOAA advocated removal. In 2013 the San Clemente Dam was commissioned to be removed. (CITATION MISSING)

Threatened Species

There are two threatened species in the Carmel River and Watershed that will be impacted by the dam removal process.

  • The Central Coast steelhead trout population endemic to the Carmel River are within the South-Central California Coast (SCCC) Evolutionarily Significant Unit (ESU). The SCCC ESU has been classified as "threatened". The California Department of Fish and Game (CDFW) is responsible for managing and maintaining a healthy steelhead population and are working on restoration of the population to historic levels on the Carmel River. [5]
  • The California red-legged frog was listed as threatened in 1996 by the U.S. Fish and Wildlife Service. The red-legged frog is found in different parts of the watershed and the health of the population is unclear and development and water extraction activities have required additional review to ensure compliance with the Endangered Species Act.[6]

Dam Removal

The San Clemente Dam was removed from in 2015 due to flood and earthquake hazards. Granite Construction took on the task of removing and restoring the San Clemente Dam. In the summer of 2015 the dam was removed and the Carmel River was released to freely flow through the reroute site [7].

Reasons for Dam Removal

In the 1990s, California Department of Water Resources (DWR) Division of the Safety of Dams(DSOD) issued a safety order which determined that in the event of the maximum credible earthquake or probable maximum flood the dam would potentially fail creating a public safetly issue [8]. After this report the San Clemente Dam was listed as a high priority public safety issue. An Environmental Impact Report was undertaken to explore the best method for addressing the public safety issues. In 2006 the DWR released a Draft Environmental Impact Report/Environmental Impact Statement (EIR/EIS). The EIR explored CalAm's preferred option of strengthening the Dam and four alternative projects, including the Carmel River Reroute and Dam Removal (CRRDR) option. The CRRDR option had several ecological benefits that the Dam Strengthening option did not have. In 2008 the DSOD stated the CRRDR project would address the dam's public safety issues and other environmental impacts caused by the dam making it the best option for all stakeholders. [8]

Carmel River Reroute and Dam Removal (CRRDR) Project:

The Carmel River Reroute and Dam Removal (CRRDR) will provide several benefits for the Carmel River including:

  • Permanent resolution to the dam safety concern
  • Access for endangered steelhead trout to 25+ miles of spawning and rearing habitat
  • Improve California red-legged frog habitat
  • Restoration of sediment to the downstream reach of the river and Carmel River State Beach
  • Restored ecological connectivity for riparian and aquatic habitats

Project

Image 3. Proposed layout for the Carmel River Reroute and Dam Removal (CRRDR).
In order to carry out the CRRDR in 2013, access roads were constructed off of Carmel Valley Road after Carmel Valley Village and before the Sleepy Hollow turn-off.

The Carmel river was rerouted into the adjacent San Clemente Creek a half mile upstream of the dam by cutting a diversion channel through a narrow ridge separating the two channels. The rock created by the diversion channel was used to block the sedimented reach of Carmel and diverted the river into the San Clemente reach. This rock barrier, known as a diversion dike, created a new ridge along the valley floor cutting off the Upper Carmel reach that is full of sediment. Sediment that has accumulated in the San Clemente reach was excavated and moved to the Upper Carmel reach. The sediment that accumulated directly behind the dam was excavated and transferred to the Upper Carmel reach. After the sediment was excavated and placed upstream of the dam, the sediment slope was stabilized to prevent erosion during high flows.

After the sediment was excavated and stabilized, the San Clemente reach of the river downstream of the diversion dike was converted to a system of step pools. The restoration was intended to create a riparian corridor and seasonal ponds that can be used as habitat for California red-legged frogs.

In 2014, the San Clemente Dam and fish ladder was removed. Once removed, the Old San Clemente Dam (1800 ft downstream) was notched to improve steelhead passage and the overall river stability [8] [7].

As of March 2016, final touches are still being made on the reroute channel. The eventual plan is for CalAm to transfer the completed project to the Monterey Peninsula Regional Park District. Adding this portion of land to the Park District will link Garland Regional Park and the San Clemente Open Space, which. The property use will be restricted for watershed conservation and compatible public access [9].

The total cost of the project was 83 million dollars. California American Water Company (CalAm) contributed 49 million dollars, the original cost to stabilize the dam in-place. The remaining funds were contributed by numerous other agencies such as California State Coastal Conservancy (Conservancy), National Marine Fisheries Service (NMFS), and the Planning and Conservation League Foundation [7].

Timeline

Below is the key project goals from 2013 to 2016. The project is projected to be completed in October 2016. [7]

2013

  • Access road design and construct
  • Finalized diversion system design
  • Obtain permits and government approval
  • Wildlife relocation along new Access Road and Project Site
  • Site preparation including clearing, fencing, and construction access roads
  • Geotechnical investigations111
  • Partial construction of Diversion System

2014

  • Site earthwork design
  • Complete construction of Diversion System
  • Construct Diversion Dike
  • Construct the Re-Route Channel
  • Construct the Sediment Stockpile
  • Partial excavation of the Combined Flow Reach
  • Partial San Clemente Dam removal
  • Additional geotechnical investigation

2015

  • Construct the Stabilized Sediment Slope
  • Finalize Channel and Habitat restoration design
  • Complete demolition of the San Clemente Dam
  • Construction of the Combined Flow Reach Channel
  • Initial habitat restoration
  • Construct permanent bridge over Carmel River

2016

  • Completion of habitat restoration & irrigation system
  • Removal of the Old Carmel River Dam
  • Construct the Sleepy Hollow Ford Bridge
  • Start of monitoring and habitat establishment periods

Post Removal Monitoring

Several post-dam removal monitoring projects to quantify the channel and fish impacts are planned or underway [10]:

Stakeholders

Various private and public organizations have interests in the dam removal project. Some of these are:

References

  1. California American Water Company (CalAm) http://www.amwater.com/caaw/customer-service/rates-information/monterey-san-clemente-dam-removal-project.html
  2. Keith Vandevere Water Over the Dam
  3. 3.0 3.1 Carmel Vally Association "Carmel River History"
  4. The Carmel Watershed Conservancy Active Projects in the Carmel River Watershed
  5. Final Supplement to the Environmental Impact Report: San Clemente Dam Seismic Safety Project
  6. Resource Conservation District of Monterey County& members of the Carmel River Task Force Watershed Stewardship Manual
  7. 7.0 7.1 7.2 7.3 SanClementeDamRemoval.org
  8. 8.0 8.1 8.2 San Clemente Dam Removal Project Summary
  9. San Clemente Removal Project Description
  10. Mitigation Monitoring and Reporting Program for the San Clemente Dam Seismic Safety Project by the Department of Water Resources
  11. Monterey Penninsula Water Management District Meeting Notes
  12. Centeral Coast Watershed Studies: 2015 Pre-San Clemente Dam Removal Morphological Monitoring of the Carmel River Channel in Monterey County, California
  13. Centeral Coast Watershed Studies: Large Woody Debris on the Carmel River From Camp Steffani To Carmel Lagoon

Links

Disclaimer

This page may contain students work completed as part of assigned coursework. It may not be accurate. It does not necessarily reflect the opinion or policy of CSUMB, its staff, or students.