Amid California’s drought and future uncertainty over the state’s water supply, the city of Morro Bay will soon apply to the state Coastal Commission to more consistently operate its used desalination plant.
The city let its operating permit expire in 2000, and the plant has sat idle since, except for occasional emergency use.
But the desalination plant won’t be put online on a regular basis any time soon.
Morro Bay has a 20-year contract to buy water from the state, paying about $1.82 million annually. This year, that state water made up 97 percent of the city’s water supply, with the rest coming from groundwater and reserves.
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The contract expires in seven years and the city won’t restart the desal plant until it renegotiates that contract to purchase less water, City Engineer Rob Livick said.
Still, the city expects to start planning for its future water supply within the next year. And the desal plant will play a role.
“Even though it’s years out, the planning for a transition like this needs to start happening well in advance,” Livick said.
Morro Bay’s City Council will ultimately decide how to structure its water supply portfolio. “In the long term, the permit is important to what will likely be part of our long-term water supply strategy,” City Manager Dave Buckingham said.
The desalination plant — next to the city’s aging sewage treatment facility at 160 Atascadero Road — was turned on for nine days in June to clean the distribution system.
It was the first time the plant had been switched on since November. The system produced treated water — 850 gallons per minute — during that time for community use.
The plant can treat seawater and brackish groundwater and has the capability to produce enough to meet all of the city’s needs.
The cost for Morro Bay to produce desalinated water is cheaper than buying water from the state.
Seawater costs about $1,550 per acre-foot to treat, while treating brackish groundwater costs about $1,000 per acre-foot, Livick said.
The city pays $1,600 per acre-foot to buy state water.
But boosting desal production now would be too expensive, because the city has to pay for its state contracted water whether it uses it or not.
Under the state contract, the city is entitled to 1,313 acre-feet of state water per year at a fixed cost no matter how much it elects to take or the state provides.
The city chose to take 1,140 acre-feet of state water this year and banked the rest in the San Luis Reservoir.
And in the long term, the city may not be able to use desal as a primary supply because of complications with groundwater and seawater.
The city has rights to draw 581 acre-feet per year of groundwater in Morro Valley, which is about half of what it needs each year. The groundwater also has a high nitrate content.
Seawater desalination has other problems, including high concentrations of naturally occurring iron in the water that clogs the desal system. One of its five saltwater wells is especially impacted with iron.
The city is looking into newer filtration devices for its seawater treatment component that don’t require as much maintenance and extensive backwashing — pumping water backward through the filters so they can be reused.
Use of the plant
The city only uses the desalination plant as an emergency supply — typically when the state water system shuts down temporarily.
The city expects to increase the plant’s usage in future years because it provides a more reliable water source.
That can’t be said for the state water supply.
Deliveries can’t be guaranteed, particularly in drought years.
Last year, Morro Bay received 5 percent of its state water allocation, and this year it collected 15 percent.
As a safeguard, the city stores some reserve water in the San Luis Reservoir, which it has used during the current drought. The city has about 2,200 acre-feet of stored water. “I envision at some point in the future, splitting up our water sourcing differently,” Livick said. “One possibility might be one-third reclaimed water from our new water reclamation facility, one-third state water and one-third desalination.”
Buckingham said he’s optimistic the city’s future water reclamation facility, which will be built in conjunction with a new sewage treatment plant, will offer a steady recharge of Morro Creek well water.
He said a possibility is using a relatively small amount of state water as emergency backup, given the possibilities for increased use of well water and desal.
The amount of water the city may yield from the new reclamation facility per year hasn’t been determined. But it could be significant if laws are passed to allow treated wastewater for potable use.
“As our water reclamation facility comes online, we hope to recycle some or all of that water into the Morro Valley aquifer,” Buckingham said.
History of the desalination plant
Morro Bay’s desalination plant was built in 1992 to treat seawater during a drought emergency.
The facility was expanded in 2009 to treat brackish groundwater, according to the city’s Urban Water Management Plan.
Now, the plant can treat both.
The desal plant was used as the city’s primary water supplier for a few months in 2010 when state water deliveries were curtailed — and the city faced a shortage.
The sources of the water for desalination treatment are five saltwater wells along the Embarcadero and seven wells used to treat brackish water in the lower Morro Valley using reverse osmosis.
The saltwater system uses reverse osmosis membranes to produce potable water, discharging brine (salty water) into the ocean through the Morro Bay Power Plant cooling water outfall and sending drinking water into the city’s distribution pipes.
Production problems arose with seawater desalination in the mid-1990s when it was used as a supplementary source of water and iron oxides fouled the membranes, Livick said. The plant was shut down.
The city let the plant’s permit with the Coastal Commission lapse over the past 15 years. The city will soon be applying with the agency to operate the plant on a nonemergency basis.
The update of the permit is a city priority in the next few months, and it has hired the firm RFB Consulting, an entity of Michael Baker International, to see the process through.
The city’s contract is for $45,000, of which $7,200 has been spent, Buckingham said. “Basically, we only use our desal for emergencies, and we notify the Coastal Commission beforehand,” Livick said. “We only operate when we need to.”
The plant is turned on for regular testing each week for about an hour, and that water is channeled into the distribution system as city officials take samples.
Future regional plant?
Buckingham also said the city is in the “very, very early stage” of exploring a partnership with private companies to build and operate a regional desalination facility at the old Morro Bay Power Plant site. This would be a new facility.
Buckingham said the coastal location is ideal and some of the infrastructure already is in place, including an ocean intake and outfall, as well as proximity to the state water pipeline, about a mile away.
“This is just a concept,” Buckingham said. “I definitely wouldn’t want desal to be the only thing on that 100 acres (of the old power plant site), and am not even sure that would be the best use of that property. … There may be a good business case, especially as the cost of state water increases, and Morro could be an ideal location.”