Technical difficulties at Tuesday’s special City Council meeting prevented residents from hearing a presentation by City Manager Eric Wier regarding a big change in Crescent City’s water system, and a request for extra funding to pay for it.
Engineering Project Manager Nicole Sutterfield explained later that in 2016, the city originally was to seismically retrofit the existing elevated water tank off Wonder Stump Road. The tank was installed in 1958, has a capacity of 50,000 gallons, and is raised to 210 feet above sea level.
Repair or reroute
“Due to its age and appearance, the City hired Pittsburg Tank and Tower Maintenance Co. to complete a tank inspection and seismic assessment,” said staff reports. “...the tank was found to vulnerable to damage and potential collapse during a strong earthquake.”
Funded by a Prop 84 grant, a project was to retrofit the 21-story tank with braces and a new foundation, which would take it out of service for several months.
In the meantime, Wier, who was director of the city’s Public Works Department, and then-Interim City Manager Mike Young — both professional engineers — decided in spring 2016 to use a pressure control valve to regulate the water pressure while the retrofit was to take place.
Before, water was pumped from underground wells into the elevated tank and gravity from the tank provided the necessary pressure to deliver water. Now, a pressure relief valve regulates the water between the source pumps and the city.
“Once installed, it was put through operational tests,” said staff reports. “It worked better than expected.” It was also determined that the valve would withstand an earthquake and other emergency conditions, so staff investigated whether it could be a permanent solution. After opting to keep the new valve system, a small emergency storage tank was installed, along with a small building to house the plumbing.
Sutterfield said the rest of the project started in July 2017 and was completed in May.
“The full scope of the proposed revised project is to dismantle the existing tank and install the pressure control valve system,” said staff reports. “To operate this new system will require a more robust control strategy, for which the new (Supervisory Control and Data Acquisition) system will be required.” The new SCADA system will replace the city’s old one, which was installed in 1999.
However, to budget the changed project, the city will need to provide an additional $34,755 for the $623,377 project, said reports.
City council approved the change order and additional funding.
Sutterfield said a request for proposals will go out in the next couple weeks. Once all the newly installed equipment is tested and online, the old tank will be dismantled, she said.
“The demolition of the old tank should happen in a year or so,” Sutterfield said.