The tab to build a bay desalination plant to make Marin "drought proof" has skyrocketed, with costs that could be more than double original estimates, a new engineering report discloses.
Initial estimates from the Marin Municipal Water District put the cost to build a plant at about $70 million, but the range has shot up to between $111 million and $173 million, depending on what type of facility is built, according to consultants Kennedy/Jenks and CH2M Hill.
The water produced by a desalination plant would cost two to three times as much as standard water, consultants said.
"We have been worried about a high number, but we can't be daunted by it," said Jack Gibson, water district board member. "Quite frankly, it is a big deal. It's something people in Marin will be talking about 75 years from now. We are talking about stabilizing our water supply. Do we want to think little or think big? This is buying into our future. I'm optimistic."
It is unclear how a plant would be financed, but a voter-approved bond measure is an option, officials said.
Desalinated water would cost up to three times more than standard water, or from $2,023 to $2,996 per acre-foot, according to the report. Presently, the district charges about $1,000 per acre foot for water. An acre-foot can supply about three single-family homes with water for a year.
That does not mean water rates for users would necessarily double or triple, because desalinated water would only make up part of the water supply, officials said.
Specifically how water rates would be affected is under review. The district is planning a meeting to discuss the water rate issue Feb. 21.
"The thing that people are most interested in are the different scenarios we have looked at and the costs associated with them," said Paul Helliker, water district general manager. "So that's the main thing we will be discussing with the board. The principal factor in the higher cost is construction costs increasing."
The report outlines four water plant options:
- A 5 million-gallon-a-day facility that would never expand for $111 million;
- A 5 million-gallon-a-day facility that could expand to provide 10 million or 15 million gallons a day for $116 million;
- A 5 million-gallon-a-day facility that could rapidly expand to 10 million gallons a day in case of drought, and eventually go to 15 million gallons a day for $159 million;
- A 10 million-gallon-a-day facility that could expand to provide 15 million gallons a day for $173 million.
Costs aside, the report said "seawater desalination can be a viable, reliable and drought-proof drinking water source for Marin."
The report found desalinated water is safe, and meets or is better than all state and federal drinking water standards.
The report says the desalination process does not adversely impact marine life, even though brine would be pumped back into the bay. An environmental impact report is due this summer.
The engineering report was based on results culled from a $1 million pilot water desalination plant the water district operated in 2005 and 2006 at the Marin Rod and Gun Club in San Rafael.
During the operation, three treatment technologies and four desalination filters were tested. Drinking water and environmental tests were conducted.
Now the water board must determine what to do.
Marin faces a "dire" water situation, and a drought could bring conditions worse than those in 1976 and 1977, officials contend.
Officials say water demand in Marin is greater than the supply, although the situation has been masked by recent wet years. The district supplies water to 190,000 people in a 147-square-mile area between Sausalito and San Rafael.
Within 10 years, Marin's annual "water deficit" is expected to increase from the present 3,200 acre-feet to 7,060 acre-feet, as demand grows and less water flows south from the Russian River because of greater demand in Novato and Sonoma County.
The district receives 75 percent of its water from seven reservoirs, with the balance coming from the Russian River through a pipeline owned by the North Marin Water District.
If a drought hits and Mount Tamalpais reservoirs run dry, the district would have to impose rationing. In the second year of a drought, consumers would have to cut 65 percent of their water use, meaning they could only use 35 percent of what they use now, officials said.
The taste of the water from the desalination plant has seemingly passed muster. District officials said comments have been positive.
A full-scale plant could be built on district land at Pelican Way in San Rafael, with water from San Rafael Bay being pulled in at the end of a rebuilt Marin Rod and Gun Club pier.
The bay water would be piped west along existing roads to the plant. The salt extracted from the water would be piped to the Central Marin Sanitation Agency's wastewater treatment plant, blended with wasterwater and dumped back into the bay.
Sludge captured by filters in the process would be trucked to the Redwood Landfill.
"You can't have a desalination strategy in a vacuum," said Assemblyman Jared Huffman, D-San Rafael, who spoke about desalination last week. "You have to combine it with energy efficiency and renewable energy strategies and hopefully an operational scheme where you don't use it in wet years.
"Frankly, everyone takes step back when we see the pricetag for desalination, but we have to think about the pricetag of running out of water."
Contact Mark Prado via e-mail at firstname.lastname@example.org