Once Morro Bay opens a new, $141 million sewage treatment plant in 2021, the city intends to achieve total “water independence” from state supplies by processing 800 acre-feet of treated wastewater, injecting it into the local aquifer and eventually pumping it back out of the ground to use as drinking water, under a plan released this month.
The proposal would save the city — and ratepayers — more than $1 million per year in state water costs, officials estimate, although the city is calculating how the cost of the new facility will affect water rates for Morro Bay residents.
“I think it’s vital that the city become 100 percent water independent, and that’s what we’re shooting for with this project,” Councilman Robert “Red” Davis said in a statement. “We don’t know how expensive state water will become in the future, and we don’t know what climate change will do to us. We have to be able to produce our own clean drinking water.”
Details of how the future water recycling system would work are laid out in a new Master Water Reclamation Plan. The plan depends on the city buying 30 acres at South Bay Boulevard and Highway 1 to build the sewage treatment and water reclamation plant, which would replace an aging facility near the beach that dumps 1 million gallons of treated sewage into the ocean every day.
The city has a memorandum of understanding to buy the 30 acres, pending completion of an environmental impact report.
Under the master plan created by Arroyo Grande engineering consultant Michael K. Nunley and Associates, the new plant would treat about 1,000 acre-feet of sewage per year. Of that amount, about 800 acre-feet could be reused as potable water after multiple treatments and groundwater injection.
About 1,150 acre-feet of water is used in the city now, City Manager Dave Buckingham said. The city intends to combine an existing right to pump 580 acre-feet per year from the Morro Valley aquifer with the additional 800 acre-feet per year from groundwater injection to boost the city’s water supply to 1,380 acre-feet per year.
The city now pays $2.4 million annually for 1,313 acre-feet of state water at a fixed cost no matter how much it elects to take or the state provides.
The new plant would reduce the city’s water costs by about $1.2 million per year, or $36 million over 30 years, Buckingham said.
“The key finding of the study is that the city can achieve indirect potable reuse of all the highly-treated water coming out of the (water reclamation facility) and then — following strict regulating guidelines and relying on the aquifer as an environmental buffer — can reuse this water as a source of drinking water,” Buckingham said.
Here’s how the process would work:
Wastewater entering the plant would undergo extensive treatment using membrane bio reactor technology, ultraviolet disinfection, reverse osmosis and advanced oxidation processes. The purified water coming out of the new facility would be piped to Morro Valley and injected into a sub-aquifer. That water would seep through the ground for at least two to six months into an aquifer where it would be pumped out and sent to the city’s existing water treatment plant for final processing and then made available for public use.
Similar systems are used in Orange County, Oxnard and San Diego, Buckingham said.
In order to pay for the new treatment plant, the city is conducting a rate study to analyze costs. That study will be reviewed by several citizen advisory committees in April and then by the City Council on April 25, giving residents a sense of how much they’ll be paying for the new plant.
The city’s agreement for state water is open-ended, but the first point at which the city can renegotiate any terms is in 2021 when the local facility bond is paid off, city public works Director Rob Livick said.
In the near term, however, the city could lease its state water allocation to a neighboring community, Buckingham said.