A MARIN Municipal Water District desalination plant could process 5 million gallons of water a day, cost $115 million to build and supply a large part of the county with a drought-proof source of water, according to a draft environmental analysis.
Now water district officials want to hear from the public. A final decision from the board on the project won't come until 2008.
When the board meets Wednesday night it will determine the length of a public comment period on its draft environmental impact statement. The standard is 45 days, but because of the importance of the project, it's possible the period could last almost four months.
At least two public hearings and possibly a third will be held.
"Circulating the draft EIR for public comment does not mean MMWD has made a commitment to desalination," said Cynthia Koehler, board president. "It means we are committed to fully examining this alternative and to doing so in an open and inclusive public process. Regardless of the board's final decision on this issue, we will continue to aggressively pursue conservation, which is the most cost-effective measure we can take right now to ensure the reliability of our long-term water supply."
While most cost-effective, conservation probably won't be enough to supply 190,000 people in a 147-square-mile area of southern and central Marin County with enough water in case of a severe drought and as water use grows.
The district began to seriously examine desalination in 2003. The process takes water from the bay, removes salt and impurities and sends it to homes for drinking and other uses.
The desalination plant being proposed would be constructed in phases. The first phase would be construction of a 5-million-gallons-per-day facility, with the ability to expand to 15 million gallons per day, according to the report.
The desalination plant would take San Rafael Bay water and subject it to various forms of treatment to produce drinkable water through reverse osmosis technology.
The plant would be situated on MMWD-owned land near Pelican Way in San Rafael. Bay water would be piped from an intake at the end of a newly refurbished Marin Rod and Gun Club pier near the Richmond-San Rafael Bridge.
The desalination process would convert about half the volume of water taken from the bay into drinking water. The remaining water, or brine, would have a dissolved solids concentration about twice that of raw water. Brine would be blended and discharged back to the bay through an outfall operated by the Central Marin Sanitation Agency, which treats municipal and industrial wastewater generated in central Marin. Pretreatment of raw water to remove solids would generate sludge. This sludge would be hauled for disposal to the Redwood Landfill, according to the report.
The report said there were two issues that could not be avoided if the plant is built. One of the issues is temporary: the work would bring noise to the areas of construction.
A more permanent issue would be the visual character of San Quentin Ridge, where a large tank would have to be placed to hold water.
Cost estimates range from $111 million to $173 million, depending on what type of facility is finally built, according to the report.
Desalinated water would cost $2,023 to $2,996 per acre-foot. Presently, it costs the district about $1,000 per acre-foot for water. An acre-foot can supply about three single-family homes for a year.
"The options are to raise rates, or borrow money, which may be the better option," said Paul Helliker, MMWD general manager. "But all of that is subject to further deliberation by the board."
Marin faces a "dire" water situation, and a drought could bring conditions worse than those in 1976 and 1977, officials have warned.
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.
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.
The district receives 75 percent of its water from seven Mt. Tam reservoirs, with the balance coming from the Russian River through a pipeline owned by the North Marin Water District.
The Marin Municipal Water District can't raise dams at its reservoirs due to state regulations, and water from the Russian River is diminishing because of needs to the north in Novato and Sonoma County. Conservation has been pushed hard.
Despite the cost, an engineering report done earlier in the year said "seawater desalination can be a viable, reliable and drought-proof drinking water source for Marin."
AT A GLANCE
A proposed desalination plant would:
- Cost $115 million, producing 5 million gallons of water a day with the ability to expand to 15 million gallons per day.
- Raise the cost of treated water to $2,023 to $2,996 per acre-foot. Presently, it costs the district about $1,000 per acre-foot for water. An acre-foot can supply about three single-family homes for a year.
- Be built on water 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.
