The Matilija Dam Ecosystem Restoration Project is intended to restore the Ventura River watershed through the removal of the obsolete Matilija Dam. Constructed in 1948, the dam has trapped 6 million cubic yards of sediment and contributed to the decline of the endangered southern steelhead.
The primary technical issue is management of the sediment that has accumulated upstream of the dam.
The Feasiblity Study resulted in a plan to remove the dam and allow controlled release of sediment through natural transport. However, downstream development requires additional work to ensure secure water supply and flood protection. The project components are illustrated below and include:
- Slurry Disposal - 2 million cubic yards of fine sediment downstream of Robles Diversion
- Stabilize remaining 4 million cubic yards of sediment (from small fines to large boulders) behind the dam
- Desilting basin - construct a sediment basin along the Robles Water Diversion Canal
- Meiners Oaks - new levee downstream of Robles Diversion
- Live Oak levee reconstruction (just upstream of Santa Ana Blvd bridge)
- Camino Cielo bridge
- Santa Ana bridge
- (Robles Diversion) Modifications - High flow bypass will flush sediment past diversion
- Wells - drill 2 new water wells at Foster Park for the City of Ventura.
Arundo (giant reed) ManagementYou may also download a poster that describes the project components (1MB)
The Feasibility Study determined that “Full Dam Removal with Short-Term Sediment Stabilization” was determined to be the best overall concept, given the watershed hydrology and constraints. The primary design constraint is floodplain development downstream of the dam. Residences, roads and bridges, and water supply facilities all need to be protected under any project alternative. Approximately 2 million cubic yards of fine sediments currently trapped in the reservoir area will be slurried downstream (see Slurry Disposal below) The remaining 4 million cubic yards will be stored upstream of the dam site as illustrated below.
The Matilija Dam Ecosystem Restoration project plan will allow for full dam removal with controlled sediment release. Environmental benefits are maximized, including renewed public access to Matilija Canyon, while the potential downstream impacts are minimized.
- Private property: residents have concerns over privacy and security
- Public trails: plan should mesh with existing/planned OVLC facilities
- Geographic Constraints: bottleneck at confluence and Camino Cielo
References: See "Draft Slurry Pipeline and Recreation Trail Alignments" at www.matilijadam.org
The Feasibility Study 'Recommended Plan' identified 5 disposal sites, now known as Baldwin Road Disposal Areas (BRDA) downstream sites. (Left hand figure) a single site identified as the Meiners Oaks Disposal Area (MODA.) The figure on the right is from the Draft Recommended Plan from February 2004 describingthe Meiners Oaks DisposalArea (MODA). This was originally a 90 acre/15-20 ft deep disposal site below the bluff along Rice Rd. Recent and ongoing studies by the Corps of Engineers, Bureau of Reclamation, and Ventura County are aimed at determining the preferred site (or sites) for slurry disposal.
For most recent news please see: http://venturaecosystem.blogspot.com/search/label/Matilija%20Dam
The Matilija Dam Project includes modification or construction of three levees downstream of the dam site. These are located at Meiners Oaks, Live Oak (Oak View) and Casitas Springs.
- Impacts to recreation and public access
- Combined with the proposed levee the MODA site may induce flooding and subsequent urbanization of the adjacent neighborhood (i.e. escalating flood control measures including channelization of creeks within the floodplain.)
These figures show the existing 100-year flooding threat, worst-case flooding with dam removal, and intended flood mitigation with proposed levee (which is shown for reference on each image.) Inflow from upland tributaries was not included in this analysis. Ref: Hydrology, Hydraulics, and Sediment Studies for the Meiners Oaks and Live Oak Levees - DRAFT Report (July 2007), http://matilijadam.org/
Meiners Oaks Levee
These figures show the historical river channel migration since 1947 and location of tributary inflows. The alignment of proposed levee is shown in the figure on the left. Green lines represent existing flood control channels.
Bridge modifications will be required at Camino Cielo and Santa Ana Rd. At Camino Cielo a new bridge will be designed and constructed. Downstream at Santa Ana Rd the bridge will be widened by adding a new passage on the left (Oak View) bank.
Robles High Flow Sediment Bypass:
The intent of the high flow bypass modification to the Robles Diversion Dam is to solve the problem of sediment accumulation. The Feasibility Study included a proposed new radial gate structure that would open during high flow events to flush sediment downstream. The figure below shows a variation on this from the Value Engineering Study on the ROBLES DIVERSION PROJECT Ventura River Basin, CA June 2007. Physical modeling was showcased in Denver on Feb 11, 2008.
Some concerns with this project component include providing for fish passage and adequate integration with the existing facility and the proposed levee. Successful design should achieve the project objectives, most importantly restored natural sediment transport and fish passage. See also: http://venturaecosystem.blogspot.com/2008/10/casitas-lawsuit-threatens-steelhead.html
Arundo (Giant Reed) management
The habitat assessment (HEP) analysis predicted that without management the non-native Arundo donax, or giant reed, would invade the floodplain, forcing out native habitat and wasting the valuable water supply.
Comunity concerns regarding the large quantities of herbicide (glyphosate) that have been used to remove the mass of plants.
References: see the arundo management plan at www.matilijadam.org
Matilija Coalition Comments on Final Design components of the Matilija Dam Ecosystem Restoration Project:
Matilija VCWPD+CCC letter 8-10-2010
Matilija Coalition letter 6-30-2010
Matilija Coalition Sediment Management and Restoration Opportunities
2010-04-01 EDC to ACE-VC-DFG re Matilija Project.pdf
Cooper Letter on USA-Matilija Dam Removal.pdf
Initial Response to Paul J Re Fine Sed in MC - 2.26.10.pdf
Comments on Matilija Dam Sediment VE Study.pdf (10-11-07)
BRDA concept description.pdf (12-16-2008)
Matilia Coalition Slurry Comments 10-20-08.pdf