Difference between revisions of "San Clemente Dam"

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[[Image:SCdam.JPG|300px|thumb|right|Image 1. San Clemente Dam during normal flows.]]
[[Image:SCdam.JPG|300px|thumb|right|Image 1. San Clemente Dam during normal flows.]]
A [[Watershed Issues]] summary by the [[ENVS 560/L Watershed Systems]] class at [[California State University Monterey Bay|CSUMB]].
A [[Summaries of Environmental Topics in California's Central Coast Region|Environmental Topics]] summary by the [[ENVS 560/L Watershed Systems]] class at [[California State University Monterey Bay|CSUMB]].

Revision as of 18:22, 8 April 2019

Image 1. San Clemente Dam during normal flows.

A Environmental Topics summary by the ENVS 560/L Watershed Systems class at CSUMB.

This page gives a short history of the former San Clemente Dam and a description of the completed dam removal project, its environmental impact, and post-construction monitoring efforts. As of 2017, the project ranked as the largest dam removal project in California history.[1]


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. When it was first built, the dam had a reservoir storage capacity of approximately 1,425 acre-feet. [2]

In 1930, Morse sold the dam to 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.[3] In 1966 CW&T sold the San Clemente Dam to California American Water Company (CalAm) for $42 million. [4].

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 severe erosion during heavy precipitation events (Image 2). The rugged terrain and arid climate of the Santa Lucia Mountains make wildfires difficult to control, leading to a range of land and water management challenges in the wake of fire. In specific, numerous local wildfires contributed substantially to a decrease in reservoir capacity at the former San Clemente Dam site. [5] Although the dam was built in 1921, by 1947 it was 25% silted and by 2012 it was 98% silted. [4]

Seismic Considerations

Located near the Cachagua and Tularcitos faults, [6] the San Clemente Dam was deemed vulnerable to a catastrophic failure in the event of a "maximum credible earthquake" by the California Department of Water Resources (DWR) Division of the Safety of Dams. 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 DWR 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 the NOAA Marine Fisheries Service (NMFS) advocated removal in order to benefit local species subject to population decline: the California Red-legged frog and coastal steelhead. In 2013 the San Clemente Dam was commissioned to be removed. [2]

Threatened Species

There are two, federally-listed species in the Carmel River Watershed that would likely benefit from a restored river in place of the dam.

  • 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. [7]

Dam Removal

Granite Construction, a locally-based construction management firm, served as the general contractor for the dam removal. Before the dam was taken down, they worked for two years to prepare the site by rerouting the river and relocating reservoir sediments. The San Clemente Dam was removed in the summer of 2015. [9]

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. After this report the San Clemente Dam was listed as a high priority public safety issue. An Environmental Impact Report was prepared 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. In 2008, the DSOD stated that the CRRDR project would address the dam's public safety and environmental impact issues, making it the best option for all stakeholders.

Carmel River Reroute and Dam Removal (CRRDR) Project:

The Carmel River Reroute and Dam Removal (CRRDR) was expected to 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
  • California red-legged frog habitat improvement
  • Restoration of sediment to the downstream reach of the river and Carmel River State Beach
  • Restored ecological connectivity for riparian and aquatic habitats.[1]

Project Details

Image 3. Proposed layout for the Carmel River Reroute and Dam Removal (CRRDR).

Before any work on the project was performed, the County of Monterey drafted a document for CalAm that covered all requirements for the dam removal project, including sediment, vegetation, municipal, and biological monitoring[10].

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 excavated during construction of the diversion channel was used to block off the sedimented reach of the Carmel above the dam and is referred to as the diversion dike (Image 3). The sediment that had accumulated in the channel directly behind the dam was excavated and transferred to the upper portion of the Carmel reach and stabilized to prevent erosion during high flows.[1]

The reach of the San Clemente 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 California red-legged frogs can use as habitat.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.

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. The property use will be restricted for watershed conservation and compatible public access [11].

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), NMFS, and the Planning and Conservation League Foundation [12].

Project Details from Agreements

CalAm was adhered to standards and timelines set by an agreement for the CRDDR written by the CDFW in 2013[13]. The agreement was amended in 2015[14] and 2016[15] to allow more habitat restoration in and around the dam removal site in all seasons. Amendments were valued at approximately $560 each[16]. The 2013 standards included:

  • Notifying the CDFW of any special status species that were present during construction or prior to construction[13]
  • Removing of any invasive species, such as American Bullfrog and Red Swamp Crawfish[13]
  • Replenishing the local tree species (i.e., Willows, White Alder, etc.) with exact numbers specified by the CDFW agreement[13]
  • Reporting sightings of the nests from Bald Eagles and Dusky-Footed Woodrats along with surveys of nesting birds and roosting bats within 30 days of the sightings and surveys[13]
  • Following all permitted standards and regulations

Removal Timeline

Below are the key project goals from 2013 to 2016. The project was completed on schedule in 2016. [17]


  • 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


  • 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


  • 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


  • 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

Project Status

Heavy precipitation events in the wake of the Soberanes Fire, during the winter of water-year 2017, caused extreme flood events that completely rearranged the 54 engineered step pools in the San Clemente River reroute channel.[18] The step-pool system has not been reconstructed. These high flows also resulted in sediment from the former San Clemente Dam reservoir being transported throughout the course of the Carmel River, with significant aggradation and pool filling found as far downstream as the river mouth. [19]


Post-Construction Monitoring

Several post-dam removal monitoring criteria are established in the Mitigation Monitoring and Reporting Program (MMRP).[20] These monitoring and mitigation criteria are the responsibility of Cal-Am Water and their contractors, and fall into the categories of:

  • Geology and soils
  • Hydrology and water resources
  • Water quality
  • Fisheries
  • Vegetation and wildlife
  • Wetlands
  • Air quality
  • Greenhouse gas emissions
  • Noise
  • Traffic and circulation
  • Cultural resources
  • Visual Resources
  • Recreation.

Some scientists involved gave more detailed information on the processes of post-construction monitoring[21]. These include:

Broad themes of post-construction monitoring efforts were made known to the public, but most was kept private until recently. Some of these broad themes included:

Permitting for Post-Removal Monitoring

Recently, documents such as agreements, permits, and post-monitoring reports were made public. The remaining information is a summary of these documents[28]:

Cal-Am had to adhere to guidelines and restrictions in geotechnical, vegetation, biological, and hydrological permits[28] distributed in 2013 by:[29]

  • The United States Army Corps of Engineers (USACE)
  • The California Department of Fish and Wildlife (CDFW)
  • The Regional Water Quality Control Board (RWQCB)
  • The United States Fish and Widlife Services (USFWS)
  • The National Marine Fisheries Service (NMFS)
  • The United States Environmental Protection Agency
  • The Department of Water Resources
  • Monterey County

Permits[28] granted for the dam removal stated that geomorphological, California Red-legged frog, Steelhead, and vegetation monitoring would have to be conducted 1, 2, 3, and 5[30] years after the removal of the dam (10 years was also stated in the project description "if needed")[29]. Permits also stated that annual reports must be written for every year of monitoring, and the final year (5 or 10) must include all information to that date, and describe how all permitting processes were met[30]. Granite construction also underwent a permitting process for removal of concrete and alteration of the geomorphology of the Carmel River, most of which were distributed in 2014[31]. The State Coastal Conservancy Executive Officer, Samuel Shuchat, granted Cal-Am a total of $32,827,403.64 for the implementation of the San Clemente Dam Removal, by the via a formal agreement (appended nine times) [32].

Post-Construction Efforts

AECOM released its "Year 1" post-construction monitoring report of geomorphological and Steelhead surveys[33], California Red-legged frog surveys[34], for Cal-Am in February 2019. AECOM's "Year 1" reports for geotechnological[35] and "re-vegetation"[36] monitoring were prepared for Cal-Am in December 2018. The reports can be found here.[37] Some of the post-construction monitoring efforts, which were defined in the agreements and permits[28], included:

  • No net loss of wetland habitat (set by the United States Army Corps of Engineers Section 404 permit signed by AECOM)[29]
  • Ensuring survival rates no less than 70% and 50% (stated in the Habitat MMRP and the California Department of Fish and Wildlife (CDFW) permits, respectively) of protected tree species in the riparian and upland areas [29]
  • Replace permit-specified numbers of protected tree species in the riparian and upland areas [29]

Trends of MPWMD Monitoring

MPWMD focused on mainly biologic surveys (Steelhead and riparian vegetation). They have monitored the Carmel River for over a decade. All MPWMD monitoring reports (including the most recent public post-construction monitoring report) with summaries of results can be found here[38].

These are the trends for some of the reports:

  • The 2000-2001 annual report stated that adult Steelhead populations had increased from "a handful" to almost 900 recorded individuals[39] and that riparian corridor vegetation improved[39]
  • In 2002-2003, adult Steelhead were counted, while 16,238 juveniles were rescued from drying areas. Six hundred tons of gravel were set to create suitable breeding grounds for Steelhead[40]
  • in 2003-2004, 388 adult Steelhead were counted and 50,277 smolts were rescued. Cal-Am and MPWMD experimented new ways to plant riparian vegetation to efficiently use irrigation. Effects of woody debris were also inspected in the Carmel River[41]
  • Fewer adults and juvenile Steelhead were counted (328 and 6,124, respectively) in 2004-2005. Bioassessment protocols were performed at 6 locations in the Carmel River. Riparian vegetation was reported to be healthy, which was thought to be caused by the decrease in fine sediments upstream[42]
  • Steelhead were recovering from their low numbers, but the recovery was only increasing slightly (368 adults). The channel was recorded to be recovering from its widened state after floods in the late 1990s, likely due to riparian and channel vegetation stabilizing the banks[43]
  • Flows dropped to 0cfs near the Highway 1 bridge and stayed below 10cfs until May of 2007. Steelhead numbers were very low and small numbers of smolts were let out to the ocean via the river mouth, which was manually opened after going dry. The monitoring program continued its efforts to plant riparian and channel vegetation in a way to reduce its reliance on irrigation and filled exposed banks with vegetation to mitigate erosion. Two property owners were also charged for "serious violations" of standards set in 2003[44]
  • Steelhead numbers were higher in 2007-2008 than the previous year's report, resulting in 17 adults, approximately 12,000 juveniles, 38 of which died upon rescue. The two property owners from 2006-2007 were continually prosecuted. The rip-rap they installed was removed and they were no longer allowed to perform work without a proper permit [45]
  • The most recent public post-construction monitoring report (2016-2017) stated that flow was extremely low in some areas (less than 10cfs), which forced daily monitoring to occur. A total of 670 Steelhead were counted, including 425 juveniles. Additional vegetation was planted to account for erosion, which was a main protocol for this annual monitoring[46]


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


  1. 1.0 1.1 1.2 San Clemente Dam Removal & Carmel River Reroute Project Website Project Overview
  2. 2.0 2.1 San Clemente Dam Removal & Carmel River Reroute Project Website Background & History
  3. Keith Vandevere, Visual Voices Threat of the Dam. Water Over the Dam
  4. 4.0 4.1 Carmel River Watershed Council, 2010. Carmel River History.
  5. Alberola GJ. 2012. Active Projects in the Carmel River Watershed, prepared for The Carmel River Watershed Conservancy.
  6. (USGS) Kapple GW, Mitten HT, Durbin TJ, and Johnson MJ. 1984. Analysis of the Carmel Valley Alluvial Ground-Water Basin, Monterey County, CA, Water-Resources Investigations Report 83-4280.
  7. Final Supplement to the Environmental Impact Report: San Clemente Dam Seismic Safety Project
  8. Resource Conservation District of Monterey County& members of the Carmel River Task Force Watershed Stewardship Manual
  9. San Clemente Dam Removal & Carmel River Reroute Project Website Home
  10. https://app.luminpdf.com/viewer/tr52FxGiiLEA6EPFD
  11. California State Coastal Conservancy. Date unknown. San Clemente Removal Project Description
  12. San Clemente Dam Removal & Carmel River Reroute Project Website Project Funding
  13. 13.0 13.1 13.2 13.3 13.4 https://app.luminpdf.com/viewer/79fxo7jmXLKWkcuNZ
  14. https://app.luminpdf.com/viewer/hkSEqZedtzBQmkN4c
  15. https://app.luminpdf.com/viewer/sf3Bwv6xsiargTpkZ
  16. https://app.luminpdf.com/viewer/4BDeyx6oTSGvi6AxQ
  17. San Clemente Dam Removal & Carmel River Reroute Project Website Schedule
  18. Schmalz D. 2017. High winter flows remade the new Carmel River channel, that might be a good thing. Monterey County Weekly Online.
  19. 19.0 19.1 Harrison LR, East AE, Smith DP, Logan JB, Bond RM, Nicol CL, Williams TH, Boughton DA, Chow K, Luna L. 2018. River response to large-dam removal in a Mediterranean hydroclimatic setting: Carmel River, California, USA: River response to large-dam removal. Earth Surface Processes and Landforms. 10.1002/esp.4464.
  20. DWR Division of Safety Dams. 2012. Mitigation Monitoring and Reporting Program for the San Clemente Dam Seismic Safety Project.
  21. https://www.psmfc.org/steelhead/2016/Urquhart__TUES_PM_SCDRRPFinalCopy4Talk.pdf
  22. Smith D., Bogdan, M., Klein J., Terzoli, A., and McNeely S. 2018. Carmel River Reroute and Dam Removal Fish Passage Assessment (Summer 2018). Watershed Institute, California State University Monterey Bay, Publication No. WI-2018-07
  23. Chow K, Luna L, Delorge A, and Smith D. 2016. 2015 Pre-San Clemente Dam Removal Morphological Monitoring of the Carmel River Channel in Monterey County, California. The Watershed Institute, California State University Monterey Bay, Publication No. WI-2016-01, 50 pp.
  24. Steinmetz C. and Smith D. 2018. 2017 Post-San Clemente Dam Removal Morphological Monitoring of the Carmel River Channel in Monterey County, California. The Watershed Institute, California State University Monterey Bay, Publication No. WI-2018-03, 47 pp.
  25. Klein J, Bogdan M, Steinmetz C, Kwan-Davis R, Price M, and Smith D. 2019. 2018 Post-San Clemente Dam Removal Morphological Monitoring of the Carmel River Channel in Monterey County, California. The Watershed Institute, California State University Monterey Bay, Publication No. WI-2019-02, 68 pp.
  26. Carter L, Fields J, Smith DP. 2016. Large Woody Debris on the Carmel River from Camp Steffani to the Carmel Lagoon, Fall 2015: Watershed Institute, California State University Monterey Bay, Publication No. WI-2016-05, 25 pp.
  27. Steinmetz, C. and Smith DP. 2018. Large Woody Debris on the Carmel River from the Former Dam Keeper's House to Carmel Lagoon, Fall 2017: Watershed Institute, California State University Monterey Bay, Publication No. WI-2018-02, 27 pp.
  28. 28.0 28.1 28.2 28.3 https://drive.google.com/drive/u/0/folders/1gltPb-uCmOQ2vxhryRDpEBo2O3MS9zMW
  29. 29.0 29.1 29.2 29.3 29.4 https://app.luminpdf.com/viewer/rrSPdtcFpY6MZ5a8C
  30. 30.0 30.1 https://app.luminpdf.com/viewer/GJs8abswX2o3g3SKQ
  31. https://drive.google.com/drive/u/0/folders/1UTfH1M6vVzKtreVdqEOWxCdxtRFuy9RR
  32. https://app.luminpdf.com/viewer/wr7YrJQ7ZT7tMLp6j
  33. https://app.luminpdf.com/viewer/K5vpERpJWyaW6giGp
  34. https://app.luminpdf.com/viewer/wbQCT8LCXfQKcmTv5
  35. https://app.luminpdf.com/viewer/iWujuEuYsZaNiAXg6
  36. https://app.luminpdf.com/viewer/Nt4Gxodt6gHJmSKMj
  37. https://drive.google.com/drive/u/0/folders/1GJd3YXao560rVX2-CX3m65Fary8PxdhB
  38. https://www.mpwmd.net/environmental-stewardship/mitigation-program/
  39. 39.0 39.1 https://www.mpwmd.net/wp-content/uploads/2015/08/Executive-Summary-for-Reporting-Year-2000-2001.pdf
  40. https://www.mpwmd.net/wp-content/uploads/2015/08/Executive-Summary-for-Reporting-Year-2002-2003.pdf
  41. https://www.mpwmd.net/wp-content/uploads/2015/08/Executive-Summary-for-Reporting-Year-2003-2004.pdf
  42. https://www.mpwmd.net/wp-content/uploads/2015/08/Executive-Summary-for-Reporting-Year-2004-2005.pdf
  43. https://www.mpwmd.net/wp-content/uploads/2015/08/Executive-Summary-for-Reporting-Year-2005-2006.pdf
  44. https://www.mpwmd.net/wp-content/uploads/MPWMD-Annual-Mitigation-Report-2006-2007.pdf
  45. https://www.mpwmd.net/wp-content/uploads/MPWMD-Annual-Mitigation-Report-2007-2008.pdf
  46. https://www.mpwmd.net/programs/mitigation_program/annual_report/2016-2017/MPWMD_MitigationReport_FinalRY2017.pdf
  47. https://www.ksbw.com/article/several-homes-flooded-in-the-paso-hondo-neighborhood-in-carmel-valley/26362252



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