Officials of the East Bay Municipal Utility District said that it will begin the seismic renovations to the Lafayette Reservoir outlet tower in 2020 once the project is approved by the California Division of Safety of Dams and the district completes its planning, design and community outreach. The DSOD found that the tower was vulnerable to a major seismic event and though EBMUD had planned to retrofit the tower by 2022, the state agency said the proposed timeline was unacceptable, with continued delays "increasing the potential risk to public safety."
According to Xavier Irias, EBMUD director of engineering and construction, the district and its consultants came up with three options for the tower renovation. Option No. 1 would be to cut off the top of the tower, which would reduce the tower weight and prevent it from overstress. An alternative was to strengthen the tower with external rods and tendons.
The third option, and the one under review by the DSOD, was to install a base isolation device within the tower; in short, to separate the tower from its foundation, which would absorb the energy and minimize the earthquake force transmitted to the tower. Think of riding in a car over a rough, rocky road. The suspension absorbs the shock of the rocks and the potholes and cushions the blows inside the vehicle. San Francisco and Oakland city halls are constructed on base isolators.
As the district and the DSOD analyze the base isolator alternative, Irias said EBMUD is lowering the reservoir water level 5 feet from its current depth of 445 feet.
The base isolator option would preserve the visual appearance of the tower, a consideration for the city. "Because it is a community icon ... it would be ideal if the existing tower could either be retrofitted or rebuilt to bring it up to an excellent rating while retaining our beloved tower's architectural form," said City Manager Steve Falk, though John Coleman, EBMUD board member, emphasized that design is less important than the safety of those who live downstream of the reservoir.
Alison Kastama, EBMUD manager of public affairs, said the district intends to be conscious of community concerns over the planned modifications and she promised plenty of community outreach before any tower construction begins.
Lafayette Council Member and EBMUD liaison Cameron Burks met with Coleman and requested that EBMUD provide a Lafayette Reservoir construction fact sheet for residents. The district complied and posted information on the city of Lafayette website.
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Lamorinda Weekly, Moraga CA