The Carlsbad Municipal Water District has 11 concrete and nine steel tank reservoirs, ranging in size from 1.5 million to 9 million gallons. Concrete reservoirs are larger and cheaper to maintain than steel ones, but more expensive to build.
“The useful life of welded steel tanks should be 100 years as long as they are properly maintained to keep them from rusting and corroding,” said David Ahles, senior civil engineer in the City of Carlsbad Utilities Department. The tanks undergo annual inspections, which involve divers immersing themselves in the water and inspecting major features like welds to detect any obvious flaws.
The steel tanks vary in size, but can be three stories high, 200 feet across and hold 8.5 million gallons, which is enough to fill 1,275 average backyard swimming pools.
Last year work crews began a program of draining the tanks, rigorously inspecting them inside and out, and rehabilitating them. The water district rehabs the tanks during cooler months, when water demand is low.
Repairs on two tanks at Black Rail Road and Poinsettia Lane are nearly complete, and the water district will rehabilitate three other steel tanks later this year. It will work on two other active steel tanks in 2014. It has two other steel tanks that have been retired from service. After the district has rehabbed the steel tanks, it will turn its attention to the concrete ones.
“In addition to our annual inspections, every three years we drain, clean and inspect them. Every 10 or 12 years we repaint the steel tanks inside and out with an epoxy coating, repair anything that needs to be repaired and bring them up to current safety standards,” Ahles said. For example, he said, the latest Occupational Safety and Hazard Administration standards require that the tanks have two side openings, rather than one, which was the previous standard, so crews will cut a second opening into the shell of every tank. Sometimes the inspections reveal more damage than the engineers anticipated.
One tank at Black Rail Road and Poinsettia Lane, “D2,” had more corrosion than inspectors anticipated, so the district replaced beams and repaired other damage. That tank, built in 1969, holds recycled water. Its twin, “D1,” built in 1958, also contains recycled water. In the upcoming year the district will rehabilitate three tanks in northwestern Carlsbad, all of which were built in 1972. They are in relatively good condition. They are:
- Ellery, 5 million gallons, at the end of Janis Way.
- Elm, near Carlsbad Village and Donna drives, 1.5 million gallons.
- Skyline, near Tamarack Avenue and Cay Drive, 1.5 million gallons.
The City of Carlsbad operates the district’s water system. The Carlsbad Municipal Water District, a subsidiary district of the City of Carlsbad, provides water service to about 85 percent of the city. Members of the Carlsbad City Council also serve as board members of CMWD. The southeastern part of the city is served by the Olivenhain Municipal Water District and theVallecitos Water District.
–City of Carlsbad Press Release