Officials overseeing Portland's water supply want to delay federally mandated reservoir projects until at least 2020 -- years beyond the original schedule.

from the Portland Water Bureau, which is on the hook to spend hundreds of millions for reservoir projects at Kelly Butte, Mt. Tabor and Washington Park. The latter two reservoir systems are not covered and open to the air, prompting the projects.

Portland's extension request will be submitted to the Oregon Health Authority for consideration.

The first round of so-called "LT2" requirements had been scheduled for completion by 2014 with all projects completed by 2020. But after city officials learned there may be wiggle room, they are now seeking to complete the first project by 2020 and wrap up all work by 2025.

Some ratepayer advocates have suggested the city should ask for an extension past 2030.

Separately, the Water Bureau also had been expected to avoid another federal mandate -- building an ultraviolet treatment plant at the Bull Run watershed. A decision by state regulators had been expected by Jan. 31 but

.

According to the city, delaying reservoir projects and eliminating the treatment-plant would save about $500 million over the next five years. Even so, much of those costs would eventually hit ratepayers if and when the projects are built.

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