From Hot Tubs To Desalination, Marin County Has Come A Long Way, While California’s Quest For New Water Focuses On The Sea

By Wes Starratt, PE

More than just the land of hot tubs, Marin County may have the Bay Area’s first desalination plant. Yes, Marin is unique. Long ago, the growing City of San Francisco extended its water supplies from nearby reservoirs to the more reliable and abundant runoff of the Sierras, and the Peninsula cities tied into the Hetch Hetchy system to ensure reliable water supplies. The East Bay also built a water system to tap the Sierra runoff. Thus, a substantial part of the Bay Area has a relatively reliable water supply. Marin was different and too remote to tap into Sierra water, so it developed its own local water system based on runoff from the north slopes of Mt. Tamalpais.

Over the years, Marin’s water system has had its problems, and many residents remember the last drought, almost 20 years ago, when it was mandated that residents do everything possible to save water including taking quick showers together, using laundry rinse water to flush toilets, and letting lawns turn brown. Things got so bad that a pipeline was built across the Richmond-San Rafael Bridge to tap water from the East Bay’s more reliable system. Without that pipeline, Marin County would almost surely have run out of water.

 

Mt. Tam Watershed
Later, the venerable Marin Municipal Water District (MMWD), not wishing to repeat that near disaster, undertook an examination of its watersheds on the north slopes of Mt.Tamalpais, looking for additional dam sites. But there were none, although the district found that it could squeeze a bit more water from its watershed by raising the height of its newest dam, Kent, which it did in 1982.

The Tamalpais watershed had been extensively developed for over one hundred years, starting in 1872, when the Lagunitas Dam was built by a private company. It was followed by Phoenix Dam in 1905, prior to the formation of the Marin Municipal Water District in 1912. Watershed development didn’t end there, however. The concrete Alpine Dam was built in 1918 and twice enlarged. Next came the Bon Tempe Dam in 1948, and finally Kent in 1953. All of this watershed land, open to the public, created a vast green belt on the north slopes of Mt. Tam, which continues to be enjoyed by residents and visitors alike.

The West Marin Fiasco
Politically, water has always been an issue in Marin County, with some residents convinced that the county’s population should be limited by the ability to develop water supplies within county limits. With the Mt. Tam watershed almost completely drained, and the district facing lawsuits requiring the release of sufficient reservoir water to maintain a fish population in Lagunitas Creek, the district’s attention turned to West Marin.

A reservoir had been built in West Marin near Nicasio in 1960, but its water proved to be of poor quality, and has been used infrequently. Nevertheless, after the great drought of the 1970s, the district decided to explore the dairy farmland of West Marin for additional reservoir sites. Finally, they thought that they had found one, and in 1979 the district built a dam at a remote location in West Marin, called Soulajule. Some $15 million was spent for the dam, the water pipelines, and the pumps needed to connect it with the rest of the system. But to this day, water from that dam is almost never used. MMWD Board member, Jared Huffman, explained, “Water from the Soulajule is too expensive to use because of pumping cost and quality. The water is turbid and hard to treat; so we use it only in critical dry years. We have used Soulajule water only twice since we built it.” So it is obvious that somebody at the water district didn’t do his homework, and that $15 million, together with ongoing maintenance costs, has gone down the drain!

Desalination, A Shocking Discovery
For some time, Marin has had a keen interest in desalination (let’s call it “desal”) as a means of solving its perennial water problems. Thus, the district built a pilot desal plant near the Richmond-San Rafael Bridge and operated it for four months in the Fall of 1990.

We asked Huffman what was learned from that pilot plant. He responded, “We learned that we can desalinate Bay water. We can treat it to state and federal standards, a level where its quality and its taste are better than what we provide from our own reservoirs. In our taste tests, 95 out of 100 people chose desalinated water as tasting better.”

But cost studies done at the pilot plant came up with the shocking figure of $3,000 per acre ft of water (a unit that water suppliers use, in others one foot of water over an area of one acre or 325,900 gallons). That cost compares with the cost of water from the district’s local reservoirs of between $200 and $400 per acre ft and wholesale water from Sonoma at $425 per acre ft before it is piped into Marin. According to Huffman, the pilot plant’s “very sobering” cost estimate of desalinated water “led the district to consider Sonoma County and the Russian River as the preferred alternative for supplemental supplies.”

 

Looking Northward from Marin
MMWD began looking northward to what was perceived to be a never-ending source of supply, the Russian River. The North Marin Water District was augmenting its water supplies by piping water through a small pipeline from Petaluma to its reservoir near Novato. The MMWD made an agreement with North Marin and Sonoma to tap into that pipeline and began importing water from the Russian River in the mid-1970s. But the arrangement was not without its problems. The size of the pipeline restricted the amount of water that could be imported, and sufficient supplies were not always available during the dry summer months when they were needed most. Nevertheless, water from Sonoma County continues to make up 26 percent of Marin’s water supply. Huffman explained, “We have a long-term contract with the Sonoma County Water Agency to provide water, but we take that water from the excess capacity of existing facilities, and that excess capacity is dwindling. In addition, the availability is very constrained, especially in the peak summer period.”

The voters of Marin County were not satisfied with that arrangement, and in 1992 they approved a bond issue that could be used to build a major pipeline directly to the Russian River. The promise of unending water at a reasonable price from Sonoma County seemed too good to be true, and it was. The pipeline has yet to be built, and has become a focal point of considerable controversy.
We talked with Randy Poole, Executive Director of the Sonoma County Water Agency, who confirmed that Sonoma County is the nexus of all sorts of litigation, regulatory proceedings, etc., focusing on several species of endangered salmon, plus water diversion that has left the Eel River almost dry during summer months, plus increasing amounts of water demanded by the agricultural sector, “all of which is expected to take almost 10 years to sort out,” according to Poole. We also heard from a member of the Sonoma County Board of Supervisors, who commented that some of his constituents are becoming increasingly reluctant “to give away all of their water to Marin County.” The bottom line seems to be that increasing water supplies from the Russian River is very “iffy.”

With mounting problems in securing adequate water supplies from that source, the district is taking another look at desalination and considering a second pilot plant to test the most recent advances in the technology.

Desalination is Nothing New
Desalination has been used for decades in the Middle East where water is scarce and power is abundant. In fact, flash-distillation of seawater is probably the main source of water in much of that region. It requires a lot of energy, but energy is abundant in that region, and excess natural gas is even flared just to get rid of it. In other regions, flash distillation is used only where there is no alternative, such as at the Guantanamo Base in Cuba.

Some years ago, a process was developed that uses extremely fine tubular membranes to separate water from salt molecules. For every three gallons of seawater pumped through the membrane, approximately one gallon of potable water can be produced, leaving two gallons of salty brine behind, which can be discharged into the ocean. The process, called reverse-osmosis or RO (the reverse of the natural process found the plant world), requires considerable pressure, meaning electrical power, to force the water through the membrane. Thus, electrical energy is the number one cost of operating such plants; however, RO requires much less energy than flash distillation, and improvements continue to be made in membrane technology that reduce the pressure, hence energy, required to force the water through the membranes. RO plants comprise three distinct elements: a pretreatment step to remove sludge and other matter that would foul the membranes, followed by RO filtration, and a final step to adjust the chemical balance of the water.

In California, RO desalination has been used for a number of years to provide boiler feed water for coastal power plants. In the early 1990s, California’s largest desal plant was the 600,000 gallon per day (gpd) RO plant built and operated by Ionics at PG&E’s Diablo Canyon nuclear power plant. Later, Catalina Island put in operation the West Coast’s first plant to augment local supplies with desalinated water. That 200,000 gpd RO desal plant continues in operation by Southern California Edison at the island’s power generating station.

During California’s drought of the 1990s, a number of coastal communities faced severe water shortages. Santa Barbara was one of them. The city built and operated America’s largest RO plant, producing 10 to 12 million gallons of water per day (Mgd). Further up the coast, Morro Bay tapped the Ionics firm to design, build, and operate an RO plant similar to Diablo Canyon plant. Finally, the rains came, and Santa Barbara was able to tie into the California Water Project, which provided water at half the price of desalinated water. So, Santa Barbara put its RO plant into a “long-term storage mode,” while Morro Bay, without the benefit of imported water, retained its facility for operation “as needed.”

Desalination Continues to be of Growing Interest Throughout California
As California’s population continues to grow, as its agricultural industry continues to feed much of the nation, and as drought conditions continue in the Colorado River basin, and while politics dictate against developing new dams and expanding existing ones, the state’s demand for water outpaces supplies by an estimated 2 million acre-feet per year. Conservation and recycling are being pushed, even to the extent of discouraging green lawns in desert areas like Las Vegas. For all of these reasons, it is not surprising that there is a growing interest in seawater, as well as groundwater, desalination, especially in those areas with the most population and the least water, namely the coastal areas of southern California.

In September 2002, the State Assembly called upon the California State Dept. of Water Resources to establish a “Desalination Task Force” that would make recommendations on opportunities for seawater desalination. The task force concluded that desalination is “a proven, effective mechanism for providing a new source of water.” The report noted that the cost of desalination has dramatically reduced from about $2,000 per acre-foot to less than $1,000 as the membranes used for the RO process have been improved in efficiency and longevity.

When the report was issued late last year, there were “sixteen relatively small ocean desalination facilities in operation” in California, several of which provide water for coastal power plants. Today, “Nineteen new ocean and estuarine desalination facilities are in various stages of planning” in plant sizes ranging up to 50 million gallons per day (Mgd) for a state total of 213 Mgd. The Desalination Report stressed the importance of co-locating “desal” plants with existing coastal power plants, since such sites provide compatible industrial land use at a coastal site, offer the use of existing infrastructure for both feed water intake and brine discharge, and have the all-important potential of purchasing power at wholesale rates. Unfortunately, Marin County offers no coastal pilot-plant site.

Most of the Action is in Southern California
Southern California’s leading water wholesaler, the Metropolitan Water District (MWD), made up of 26 member water-supply agencies, stretching from Ventura County to the Mexican border, has embarked on a comprehensive program to stretch water supplies through a variety of programs including seawater desalination. MWD is offering to pay its member agencies an incentive of $250 per acre ft for up to 150,000 acre feet of desalinated water for a period of 25 years. That incentive should bring the cost of desalinated seawater down to about $750 00 per acre ft, which begins to approach the $500 to $600/acre foot for water imported from northern California by the California Water Project.

Thus far, five water agencies have signed on to MWD’s program…San Diego, Orange County, Long Beach, West Basin, and Los Angeles…for a combined capacity of 126,000 acre feet of desalinated water per year. The most ambitious project is proposed by the San Diego County Water Authority, which is holding discussions with Poseidon Resources Corp. to expand the firm’s pilot plant at Carlsbad to an operating plant of 50 Mgd capacity, which would make it the largest desal plant in the United States.

And in Northern California
Numerous California coastal communities are also facing water problems. In the Monterey Bay area, the City of Santa Cruz is busy writing an EIR in collaboration with the Soquel Creek Water District for a 2.5 to 4 Mgd desal plant. The plant not only can be expanded on an incremental basis, but can be operated when needed during the dry summers, thus offering something more flexible than a hydroelectric project. On the other side of Monterey Bay, Sand City is writing an EIR for a small desal plant using beach wells. Other local desal plants include a small unit at the Monterey Bay Aquarium and a larger plant to provide boiler feed water for the Moss Landing power plant.

A Red Flag at Tampa Bay
But RO seawater desalination is not without problems, among them is the fouling of membranes due to the inadequate pretreatment of intake water. Such is the case for what is currently the country’s largest desal plant, a 25 Mgd plant using cooling water from a power plant on Florida’s Tampa Bay. That desal plant was supposed to start up last year, but has only operated intermittently, driving the plant designer into bankruptcy and producing law suits that will keep attorneys busy for some time. Numerous solutions have been proposed, and it appears that the problem lies with the intake water and the pretreatment system. In any case, desalination enthusiasts are closely watching developments at Tampa Bay.

Back to Marin County
The Board of the Marin Municipal Water District, faced with a potentially unreliable source of future supplies from Sonoma County, is determined to learn more about whether or not desalination is the right answer to Marin’s future water needs, especially during extended droughts and long dry summers. The ultimate goal is a 10 Mgd plant that could be operated on an as-needed basis. But, first comes more pilot-plant testing, especially in light of the problems encountered at Tampa Bay. After all, Marin’s proposed desal plant would be the only other major desal plant not to utilize seawater, and San Francisco Bay water can be pretty brown with silt during wet winter months, although it does have the advantage of a lower salt content than ocean water. Thus, in October, the MMWD Board is scheduled to vote on whether to build a second pilot plant.

We asked Huffman, “Why do you need a second pilot plant?” He responded that, “We know that the economics have gotten a lot better from enhancements in membrane technology, but what we are really curious about is new pretreatment technology. That includes micro-filtration, which requires much smaller space. That is important for our proposed desal plant site, which will be located on the old San Rafael landfill. Also, micro-filters extend the life of the RO membranes and can be less energy intensive. We want to understand that technology and try different types of micro-filters so that we don’t make the mistakes that they made at Tampa Bay where they cut corners and didn’t properly brake-in and design the micro-filtration system.

“We will be looking for financial partners from the membrane industry and other agencies that are interested in this kind of pilot testing. So, the price tag for the pilot plant should be substantially less than $1 million. With approval at the October Board meeting, the pilot plant can be in operation before the end of the year so that we can test it during the rainy season and under varying conditions of salinity and sediments.

“We also hope to learn more about the removal of other toxics and turbidity from Bay water and test for everything that might be in the Bay water. And, by the way, all of those things are also in the Russian River water.

“From the pilot plant, we will be able to develop capital and operating costs for the full-scale plant. We want to move as fast as possible with the design and construction of that plant, and the EIR should be certified by the spring of 2005.” Marin’s full-scale plant will be based on a permit for a 15 Mgd plant, but it will likely be built in modules.” Huffman guesses that, “10 Mgd is the most effective size for the needs we face.”

We also asked Huffman how much he expects the water from that desal plant to cost. “Realistically between $1,000 and $1,500 per acre ft. It will be at least double the cost of water out of our reservoirs, but it will be similar to what we think the Russian River water will cost over time. We know that desal water will be high quality, and it will be there when we need it. Also, we can use it only when we need it, as contrasted with Sonoma water, which we must take whether or not we need it.”