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Chapter 10: A Long-term Commitment to Reliability
collaboration between the Water Authority and
one of its member agencies, the Olivenhain
Municipal
Water District, which had considered
building a dam at the site for decades because
it’s away from development and the topogra-
phy would allow for a relatively small lake sur-
face area to mini
mize evaporation. "This is truly
an excellent example of interagency coopera-
tion," former Olivenhain General
Manager David
McCollom told
The
San Diego Union-
Tribune
when the
project wrapped
up.
2
To complete the
dam, more than
1.4 million cubic
yards of concrete
were placed at
rates as high as
16,000 cubic
yards per day dur-
ing round-the-clock construction. The resulting
structure stands nearly 320 feet tall and rough-
ly a half-mile long. It holds back 24,000 acre-
feet of
water – 18,000 acre-feet for use in
regional emergencies and another 6,000 acre-
feet for operational use. As part of the
Emergency Storage Project, Olivenhain Dam
was designed to remain fully functional during
and after a magnitude 7.25 earthquake. The
reservoir is connected to the Water Authority’s
Second Aqueduct, allowing its stored water to
be used around the county.
The next really big piece of the CIP to take
shape was the Twin Oaks Valley Water
Treatment Plant near the city of San Marcos.
By the early 2000s, it became clear that grow-
ing demands for
treated water would
soon outstrip the
region’s treatment
capacity and
become a threat to
regional
water relia-
bility, particularly
during the hot sum-
mer months. This
spurred develop-
ment of a regional
water treatment
facility to alleviate the bottleneck. The need for
the new plant became obvious to everyone by
the mid-2000s, when peak demands bumped
up against treatment capacity and led to urgent
calls for conservation.
When completed in 2008, the Twin Oaks facili-
ty was the largest “submerged membrane”
The Twin Oaks Valley community members provide input on
plans for treatment plant
The Twin Oaks Valley Water Treatment Plant was complet-
ed in 2008
–
solar panels generate about one-third of the
plant’s energy needs