Photo by Mike Wier
All stakeholders involved agree that the Matilija Dam needs to come down. But removal will cost millions of dollars, and lack of funding has been a major impediment to action. Other factors, such as determining the best way to manage sediment release, the eventual need to modify downstream roads, levees and bridges, all add to the challenges of the undertaking.
Matilija Dam was notched twice in the 1960s and 1970s. Ventura County made the decision in 1998 to remove the dam altogether. Congressional approval for a preferred preliminary design was obtained in 2007, through the Water Resources Development Act of 2007, but was not funded. For almost 20 years a broad coalition of community groups and resource agencies have been working together to develop a comprehensive strategy to remove the dam and restore the river to its natural health.
This year stakeholders agreed to a plan that will create two uncontrolled orifices (with optional gates)on the lower wall of the dam, allowing sediment to be released and effectively transported. It is anticipated that a single ten-year event/storm could erode sufficient sediment from the upstream side of the dam so that dam removal would then proceed in a single phase during the dry season. Smaller flood events may require additional intervals to move the sediment, which may take 2-9 years longer.