MMWD’s desal plan (Point Reyes Light, 02.05.2009)

The gap between supply and demand for customers of the Marin Municipal Water District (MMWD) is expected to double in the next 15 years. In order to meet the needs of nearly 200,000 people, the district is considering desalinating water from the San Francisco Bay, an expensive but reliable alternative to increasing its supply from the Russian River.

“MMWD would not have adequate water supply to meet the needs of people and the environment during a sustained drought,” said MMWD General Manager Paul Helliker. “Even with the additional supplies developed and this mandatory ration, MMWD reservoirs would run out of water in the second year of a severe drought.”

The staff thinks desalination is a viable supplemental water supply especially in drought and emergency conditions, while others think the monetary and energy costs of a desalination plant may outweigh the benefits. The final environmental impact report for the desalination project was unanimously certified by the MMWD Board of Directors during a meeting on Wednesday.

MMWD, which serves south and central Marin County including the San Geronimo Valley, is also considering reservoir improvements, increased water recycling and conservation and additional Russian River supplies. The desalination plant could cost three times as much as the other alternatives and would take at least three to five years to implement.

According to MMWD’s records, which date back to 1879, January 2009 is the fifth driest January on record with only 1.08 inches of rain. These conditions might only worsen, and a long term water supply must be secured now.

The proposed desalination plant will take raw seawater from the San Francisco Bay and subject it to a series of treatments to produce drinkable water, a technology already being used in other parts of the country. There are two desalination proposals contained in the final environmental impact report, each with its own cost and timeline.

The 1-million-gallon-per-day (MGD) facility would supply water to San Quentin. It would supply 1,000 acre feet per year beginning 2013, and it would cost $3,600 per acre foot. A 5 MGD facility would supply water for all MMWD customers. This would supply 3,300 acre feet per year beginning in 2014, and this would cost $3,600 per acre foot.

MMWD’s proposed desalination facility would be constructed on Pelican Way, near the Home Depot in San Rafael. The plant will take saltwater from the San Francisco Bay through an intake pipe built at the end of a fishing pier owned by Marin Rod and Gun Club near the base of the Richmond Bridge.

The saltwater would be pre-treated to remove solids and then desalinated through a process called reverse osmosis—removing the freshwater from saltwater using pressure to push saltwater through a semi-permeable membrane to leave behind salt and contaminants. The brine waste would be disposed through an existing pipeline. The desalted water would then be post-treated to make it taste like the water that the district currently provides.

In 2005, MMWD operated a pilot desalination plant to test the viability of the desalinated water.

“We tested the technology, the environmental impacts and the drinking water quality,” said Libby Pischel of MMWD. “And they all proved to be viable.”

Technical staff who tasted the water from the pilot plant found it to be as tasteless as distilled water. “It had no flavor,” Pischel said, explaining that the desalination process removes everything that gives water its taste. So MMWD added minerals—sodium hypochlorite, ammonium chloride, calcium chloride and sodium carbonate—to make the water taste like the drinking water that the district currently provides. Blind taste tests were conducted during open houses for the district. “More often than not, people preferred the desalinated water—well more than half,” Pischel added.

MMWD used information learned from the Tampa Bay Seawater Desalination Plant, the nation’s largest plant of its kind, which was constructed in 2001 and has been fully operational since 2007 as a drought-proof alternative water supply. The plant can provide up to 10 percent of Tampa Bay’s water supply, providing up to 25 million gallons per day of drinkable water.

At present, MMWD gets 79 percent of its water from seven reservoirs—including Nicasio and Soulajule in West Marin—19 percent from the Russian River and 1 percent from recycling water. Together, these sources supply 40,400 acre feet of water per year. One acre foot can serve three families for one year.

Since 2007, MMWD has received more than 750 comments from governmental agencies, regional organizations and individuals on topics such as conservation programs, rainwater catchments, gray water use, energy use, greenhouse gas emissions, water quality, oil spills, impacts to aquatic habitat and encroachment permitting.

The 5 MGD plant would require 10,037,500 kilowatt hours a year. Californians can spend about 300,000 million kilowatt hours a year.

“If the requirement of energy is a huge environmental impact on this project, from what real sources can this energy be obtained and at what actual cost to the rate payers?” asked Sue Brown, a resident of Ross Valley.

Because of the high cost and energy requirements of desalination, other options are being considered. Increasing the supply from the Russian River is the least expensive of these, costing between $1,200 and $1,600. This option could be completed as early as 2011.

With the coordination of North Marin Water District and Caltrans, a North Marin pipeline could be enlarged along the Marin-Sonoma Narrows, and with the coordination of Sonoma County Water Agency, their pipeline could be improved. But the supply may be unreliable during drought years, and enlarging or improving the existing pipelines between Marin and the Russian River depends on environmental approval of other water districts.

MMWD currently uses up to two million gallons a day of recycled water for irrigation, toilet flushing, car washing and other non-agricultural purposes. Expanding the recycled water operation appears to be a simple system to implement, but environmental review and permitting for that option has not been completed.

MMWD has already spent $44 million on a conservation program for extra staffing, rebates, incentives and a more aggressive conservation education, but MMWD staff believe that the gap between supply and demand may not be met by conservation alone. Water conservation, which has the least environmental impact of the options, necessarily relies on thousands of customers to changing their behavior.

“We pour in a lot of energy and money for these types of projects. If the emphasis is on conservation and changing the price schedule to encourage doing more with less, in the long run, you have a viable and sustainable strategy,” said Norman Solomon, an author on politics who is currently working on a project called Green New Deal in North Bay. “Usually the dreams of a ‘techno-fix’ haven’t worked out very well. Efforts to improve on nature end up being setbacks for nature and human beings.”

The board of will listen to public comments and vote on a long-term project at a special board meeting on February 11.

~ by Janet Fang on February 8, 2009.

One Response to “MMWD’s desal plan (Point Reyes Light, 02.05.2009)”

  1. UV Water Purification…

    in a population already water stressed…

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