Parking is available just across the street from the
coordinates. Damage to the road has turned a portion into a single
lane. An Adventure Pass may be required for parking, but you
shouldn't be gone that long.
This
earthcach quickly looks at a couple of the effects of dam
construction. It also touches on issues that will soon be affecting
many older dams across the world.
The Matilia Dam was completed in 1948 by the County of Ventura
to provide water supply and flood control for the area. At its
completion, the reservoir behind the dam had a capacity of 7,018
acre feet (an acre of land filled to a depth of 1 foot). It was
originally estimated that it would take 39 years before the dam
would be filled with sediment.
Prior to the dam construction, there was a thriving population
of steelhead living in the creek. The dam blocked steelhead
migration to approximately 20 miles of habitat in the Matilija
Creek upstream of the dam. A year after the dam's completion, a
large number of fish were killed behind the dam due to stagnant hot
water.
Additionally, The Matilija Dam traps sediment and prevents it
from being transported to the Ventura beaches. Along the Ventura
Coastline, beach sand is constantly moving southward. Without a
constant re-supply of sand from the rivers, the beaches are
gradually eroded. See related sand movement on Ventura Beaches
Earthcache .
As it turns out the materials used in the construction of the
dam makes it potentially unsound. The aggregate (large filler rock
in concrete) is alkali-reactive. This means that the cement used in
the dam chemically reacts with the aggregate and forms a gel. That
gel then absorbs water and expands causing cracking and failure.
This problem was brought up by the architect during
construction.
In 1964, a safety study condemned the dam and suggest removal.
However, the County chose to notch (remove the top part of the dam)
and removed the top 30 feet of the dam. This reduced the reservoir
capacity by 65%.
In 1969, 21 years after its completion, a 100-year flood event
occurred. That single event deposited approximately 27% of the
sediment that fills the reservoir (calculated in 2001). As a
result, the dam was no longer able to effectively control future
floods.
In 1978, the dam was notched again. As a result of the notching
and filling up by sediment, the dam currently has a capacity of
less than 500 acre feet.
As a result of the reduced capacity and concerns regarding the
structural integrity of the dam, the County began plans to remove
the dam in 1998. The US Army Corp of Engineers became involved as
much of the funding will come from the federal government. This
began with a series of studies to evaluate the potential costs of
various plans to remove the dam. At the time, it was the largest
dam ever proposed for removal. In 2000, Secretary of the Interior
Bruce Babbitt symbolically removed a portion of the dam as the
start of a demonstration project to determine the most effective
way to remove the Metilija Dam. Through this project and other
studies, the final feasibility report was issued in September 2004.
While funding has yet to be obtained, News reports suggest that
work could begin in 2006 and take two years.
I walked down the road to the dam and saw people fishing in the
lake. I took the "No Trespassing" signs as meaning we couldn't walk
down to the lake and swim in it or climb on the dam.
Logging requirements:
Send me a note with :
- The text "GCPRZ0 Matilija Dam Removal" on the first line
- The number of people in your group.
- What evidence can you can see indicating that the dam is no
longer useful for flood control
- Alternately, post your thoughts on the various options you can
think of for safely demolishing the dam and restoring the
creek to a natural flow (any logs with off the wall or sarcastic
suggestions will be deleted).
As always posted pictures are welcome, especially when they begin
the demolition. It will be interesting to see when they finally
start the demolition.
I will only respond if you have incomplete
logging requirements. Go ahead and log your cache
The following sources were used to generate the
information in this cache:
- http://www.matilijadam.org (It
has historic pictures and pictures of recent flood events. It also
has a more detailed history)
- http://www.doi.gov/news/archives/001012.html
- http://ca.water.usgs.gov/cgi-bin/influx/projectsapp.pl?preview=57
- http://pages.sbcglobal.net/pjenkin/matilija/spilling.htm
- September 23, 2004. Feasibility Report for
Matilija Dam Ecosystem Restoration Feasibility Study, Ventura
County, Ventura, California, US Army Corps of Engineers.
http://www.matilijadam.org/final/notice.pdf
- March 27, 2004, Matilija Dam Removal Project
Backed Up, Los Angeles Times
http://www.nrmbc.org/News/0005-MatilijaDam/NewsPage.htm
- Sherman, Douglas J., Karmon M. Barron, and Jean
T. Ellis, Retention of Beach Sands by Dams and Debris Basisns in
Southern California, Journal of Coastal Research, Spcial Issue 36,
2002