Monday, October 13, 2008

Matilija Dam Meeting - October 2, 2008

Matilija Dam Ecosystem Restoration Project
Design Oversight Group Coordination Meeting
October 2, 2008 9:00 AM – 12:00

The primary focus of this meeting was the Potential Slurry Disposal Area(s). Other features and related issues will be tabled for future DOG meetings.

The meeting was well attended, and included several local residents, water district representatives, and other local stakeholders. It is interesting to note that this has now elevated itself to an election campaign issue: "candidates running for two board seats in the Meiners Oaks County Water District...oppose a proposed dumping site for sludge to be removed from behind Matilija Dam. The site is near two of the district's best producing wells."

The Slurry Disposal has been divided into 2 separate alternatives: MODA and BRDA. MODA is a 75 acre site below the Rice Rd bluff at Meiners Oaks, and BRDA consists of several sites near and downstream of the Hwy 150 bridge, or Baldwin Rd. These are described here:

Ventura County engineer Peter Sheydey provided an introduction, stating that the reason for the slurry is to protect CMWD water diversions. As part of the Matilija Dam removal plan, approximately 2 million cubic yards of fine silt and clay will be dredged and slurried downstream of the Robles Diversion to prevent the suspended sediments from entering Lake Casitas. The purpose of this meeting was to solicit comments and suggestions for selection/evaluation criteria.

Blair Greimann provided an overview of the Bureau of Reclamation's Hydraulic Analysis of sediment disposal sites:
•Because of the levee to be constructed upstream, most of the MODA site will not erode from river flows
• They modeled a 2,000 cfs design storm @ Cozy Dell (includes McDonald drainage) thru MODA – need a channel 50 ft wide to convey flood flows – shown in contour plan for sediment disposal
• Alternate channel straight to river, would discharge near existing bedrock pools.
• BRDA – has the potential benefit of allowing erosion of sediment which removes fines from the river system during a high flow event (greater than 10 year flood)

ASPEN environmental consultants provided a summary of their Biological Information Studies.
• Oak tree counts have increased because they included toe of slope at MODA - 132 oak and 31 black walnut – large and old trees
• Pipeline habitat acreage impacts were also looked at in more detail
These studies are on the internet at

Discussion of Evaluation Criteria for selection of slurry disposal site(s):

• Environmental impacts
• Constructability
• Footprint
• Height of stockpile
• Cost

• Short term vs. long term impacts/benefits
• High flow mobility
• Community acceptance/resident impacts
• Groundwater quality
• Water supply
• Safeguard existing infrastructure
• Recreation
• Land availability
• Upland disposal
• Optimize by combining MODA and BRDA 1&2

The Army Corps of Engineers is accepting COMMENTS until OCT 20, 2008 – e-mail to Doug Chitwood:

Next Meeting: December 4, 2008