Los Ranchitos Improvement Association

How Safe Are Marin's Dams,by Jack Gibson, MMWD Board Member

By Jack Gibson
MMWD Board Member
February 12, 2018
It has been one year since the newspaper headlines reported the crisis at Oroville, with pictures
depicting water cascading through and over the giant spillway of the huge Oroville Dam. In
February 2017, Oroville Dam, the highest in the country at 770 feet high, presented the
immediate threat of a potential catastrophe. The threat of a 30-foot wall of water heading down
on the town of 8,000 people, its many Gold-Country tourists, and the downstream residents,
required the immediate evacuation of nearly 200,000 people. A year later the newspapers are still
reporting on the near disaster.

It brings us all to raise the question: How safe are Marin’s dams?

The water district manages and maintains seven reservoirs and dams capturing and storing 75%
of our water supply. Each year, the District inspects each dam and spillway jointly with an
inspector from the Division of Safety of Dams (DSOD) under the California Department of
Water Resources. The most recent DSOD inspection determined that all of the dams are in good
condition. In addition to the annual DSOD inspections, our district has a comprehensive Dam
Safety Program to make sure that all of our dams and spillways are safe and functioning
properly. The program has three parts: monitoring, frequent inspections and maintenance, and
preparation for emergencies.

The District monitors conditions at the dams and spillways to ensure they are
functioning as intended. Instruments placed on and in the dams track and record
parameters such as water seepage, dam movement, and water pressure. Monthly visual
inspections of each dam are carried out by District engineers. District rangers tour the dams even
more often, as MMWD rangers live on-site at Phoenix, Alpine and Soulajule dams.
Through ongoing maintenance, the District is able to protect the dams from deterioration and
prolong their lifespans. In addition to the joint annual inspection with DSOD, the District sends
an instrumentation report to the Division of Dam Safety. After each site inspection, DSOD
provides written reports of field observations and findings for each dam. These reports are
available on the District website, marinwater.org.

The water District’s post-earthquake evaluation team is core to the Dam Safety Program. After
significant earthquakes, trained personnel inspect the dams for any signs of damage, and the dam
monuments are surveyed by the District surveyor to check for any vertical or horizontal
movement. In addition, MMWD works with other agencies and public safety personnel on
emergency action planning and training exercises.

Posted by Los Ranchitos on 03/07/2018
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