Ventura River Ecosystem: Matilija Technical Advisory Committee

Monday, January 23, 2012

Matilija Technical Advisory Committee

January 12-13, 2012 - Matilija Technical Advisory Committee meeting

The Matilija Technical Advisory Committee (TAC) met for two days to familiarize the members with the project and kick off discussions on moving forward with the next steps. (See Matilija Dam - Next Steps)

Matilija TAC field trip - Foster Park

The TAC was formed following the recommendations of last year's Fine Sediment Study Group Report. The goals are to:

(1) Assess key recommendations and major data gaps shown in the Fine Sediment Study Group’s Final Report (August 2011), and make any recommendations for additions.

(2) Identify and prioritize a limited number of focused studies to address the key recommendations and major data gaps and develop a cost-effective scope of work and proposed budget for each study.

The two-day meeting included a field visit on day 1 and a meeting on day 2. The field tour included stops at the Ventura River estuary and levee, Grant Park, Foster Park, Santa Ana Bridge, Hwy 150 bridge (Baldwin Rd), OVLC Rice Rd Trailhead, Matilija Canyon, and Matilija Dam. The day concluded with a short presentation of recent dam removals in the Pacific Northwest including the Marmot, Condit, and Elwha projects. (See dam removal)

Matilija TAC field trip - Robles Diversion

Goals of Proposed Sediment Management Project:

1. Restore effective fish passage, minimize impacts and restore aquatic/riparian/upland habitats in reservoir area
2. Minimize cost/maximize cost-effectiveness
3. Maximize mobilization of fine material to high flow events, minimize mobilization during low flows
4. Minimize the impact of nutrients and turbidity in Casitas Reservoir as the result of the Project
5. Not significantly increase water supply risk to customers of water districts
6. Minimize permanent structures/artificial features within environmental sensitive areas such as the riparian corridor and upland habitats
7. Minimize artificial or permanent stabilization material (i.e. riprap or soil cement) in reservoir area

The main goal of the TAC committee is to develop a Scope of Work for the following:

1. Hybrid Analysis: Assume that the dam removal notching and sediment excavation period is extended beyond a single year. Take advantage of natural sediment transporting flows. Reservoir sediment could still be dredged prior to each notch and placed either upstream of the dam or at the BRDA sites. The scope would include analysis of several different notching scenarios, upstream disposal, and downstream disposal scenarios to develop the most cost effective method of notching and sediment handling. Other components of the project could be a flow bypass around the reservoir area, a desilting basing, changing Robles operations, etc…

Matilija TAC - pondering the question

2. Interim Notching Analysis and Design: The dam would be notched to the silt level or slightly below the silt level. Detail the impacts associated with notching of the dam and develop a preliminary design. The same team that analyzes the interim notching could perform the hybrid analysis. Intensive monitoring would be part of the project so that the design of the remaining dam removal would be improved.
The breadth of the scopes should include:
• Develop detailed descriptions of the entire construction process, assuming the general phasing adopted by project management
• Identify significant unknowns and recommended studies to reduce the same
• Develop a cost estimate, identifying the estimated range of the unknowns on the costs
• Identify potential NEPA related-impacts