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From Sewage to Artichokes

• August 25, 2009 • 12:00 PM

Wastewater recycling and other water-efficiency programs are saving aquifers and helping a famed produce industry thrive.

With a blue plaid button-up shirt tucked in his jeans and a pair of ballpoint pens protruding from his front pocket, Chris Drew doesn’t look much like a farmer until he puts on a pair of dirt-caked, orange leather gloves and begins trouncing through rows of 3-foot-tall artichoke plants. “Do you like big ones or small ones?” Drew, a production manager for Sea Mist Farms, shouts through a light mist.

“Doesn’t matter,” I call back to him, wriggling my black patent-leather heels from a suction cup of thick mud. “But the bigger the stem, the better. That’s the best part.”

Forging a path through thistle jungle, Drew retrieves a knife from his belt and slices two artichoke heads from their stems. “Watch the spines,” he says, carefully placing them in my hands.

The acres of fruit and vegetable fields Drew oversees don’t look much different than the average commercial agriculture area. Plots of artichokes commingle with rows of immature lettuce. Nearby, sprinklers rhythmically pulsate above freshly tilled ground; in the distance, white plastic carefully protects strawberry plants from the underlying dirt. But the fields around Castroville, Calif. — in all, nearly 12,000 acres of commercial cropland separating the Salinas Valley from Monterey Bay — are different from most other agricultural areas in one important way: They are irrigated with water recycled from urban sewage.

For most people — especially those not living in arid areas of the southwestern United States — the phrase “toilet to tap” elicits unpleasant images. Even in water-strapped California, only about 500,000 acre-feet of recycled water — just 1 percent of the total — are used each year. But population growth and other factors, including climate change, are dictating that California and other dry states become more efficient in their use of water. One water-treatment facility has found a way to really get the most out of its water, perhaps charting the course for other thirsty areas of California.

“Not only were we the first, but we’re the largest raw-food crop-water recycling project in the world [that] we know of,” says Keith Israel, general manager of the Monterey Regional Water Pollution Control Agency. The agency’s regional treatment facility, which blends into the flat agricultural terrain so completely that you might not know it existed unless you were told, intercepts 20 million gallons of sewage water from 12 communities dotting the Monterey Bay coastline every day, treating the wastewater and recycling it to 30 Castroville growers via a system of purple pipes. The recycled water supplies about two-thirds of the growers’ total water needs, greatly reducing the use of well water and slowing the intrusion of ocean water into the area’s freshwater aquifers.

An 11-year study — reviewed and approved by the U.S. Environmental Protection Agency, California Department of Public Health, the Centers for Disease Control and the U.S. Department of Agriculture — showed that water from the treatment facility poses no risk to farmworkers. The study also found no salmonella, E. coli or other viable pathogens of public health concern in the recycled water. As an added bonus, the recycled water contains more nitrogen, potassium and phosphorous — all beneficial nutrients commonly found in fertilizers — than well water.

“We’re confident that we are the safest growers,” Drew says. “And the people who thought of this were our saving grace.”

The reasoning behind Monterey County’s water-recycling program stretches back more than 30 years. In the 1970s, Castroville’s commercial agriculture community was at a crossroads. Farmers who had been growing artichokes, lettuce and broccoli in the area since the 1940s were watching their groundwater aquifers steadily being compromised. Instead of sinking like those in areas of California’s Central Valley, where water levels had declined as much as 30 feet, Monterey County’s freshwater aquifers were sucking in salty ocean water like a sponge.

The aquifers in Monterey County are stacked like a gigantic three-layer cake; as farmers drew water from the top two, they became heavily contaminated by seawater intrusion. By the time the treatment plant was completed in 1997, seawater had infiltrated the upper 180-foot-deep aquifer almost 6 miles inland and the second 400-foot-deep aquifer nearly 3 miles inland. At the time, the only other viable source for water was the lowest of the three aquifers. At 900 feet, it would have been a costly pumping operation for water whose quality was not only uncertain, but also the last untapped source in the region.

Without the regional treatment plant and its “tertiary” treatment facilities — which provide the third and final step in the water recycling process, making water finally “gulpable” — it would only have been a matter of time until the Castroville fields went fallow.

“A lot of the areas out here are multigenerational farms,” Israel says. “No one wanted to get to the point where the only use for this land is urban development. The agricultural land we have out here really adds to the ambience of the community.” Not to mention community pride: Each May, the annual Artichoke Festival celebrates the fact that 70 percent of the artichokes grown in United States come from the Castroville area, and 90 percent of them are irrigated with recycled water.

Actually, only two-thirds of the water flowing through the 45 miles of purple pipelines extending from the regional treatment plant to the farms is recycled; water is still being pumped from the aquifers. But because less groundwater comes from the supplemental wells, seawater intrusion has slowed 30 to 40 percent. “We’ve been in operation now for about 11 years,” Israel says. “That’s about 40 billion gallons of water that hasn’t been pumped out of the ground.”

But plans are afoot to make the water system in Monterey County even more efficient.

In a given year, only about 60 percent of the water entering the regional treatment plant is recycled and distributed to the Castroville farms. While urban sewage enters the facility at a steady pace throughout the year, a farmer’s demand for water is not so linear.

From October to February, when fewer crops are growing and winter storms pass through the region, the demand for recycled water is so low that the facility must release excess treated water to Monterey Bay through an outfall pipe that extends 2 miles offshore. During the summer, the opposite occurs. “In the summer time, the farmers use every drop of water we can produce,” Israel says. But since the growers need more water than the 12 contributing coastal municipalities can produce in sewage, the groundwater pumping continues — albeit to a smaller degree.

Israel does expect the amount of sewage water coming to the recycling plant to increase over time as Salinas and the other Monterey communities grow and the civilian redevelopment of Fort Ord, a former U.S. Army post closed in 1994, resumes. “Once the economy turns around and the developers believe they can sell houses again, I believe there’s going to be about 6,000 new homes built,” he says. “That’s going to mean more sewage, and we’ll be able to supply more water to the growers.” But the Monterey water pollution control agency knows this additional water won’t be sufficient for the growers’ summer needs. In fact, the growing municipal water use means more groundwater will be pumped.

So in an effort to become more sustainable, the Monterey County Water Resource Agency — a sister agency of the Monterey Regional Water Pollution Control Agency — decided to design and install a rubber dam on the Salinas River, which divides the Castroville farm region as it flows out to Monterey Bay. Approved by the Environmental Protection Agency, the California Department of Fish and Game, and the National Oceanic and Atmospheric Administration, the dam will be inflated from April through October; beginning next year, it will retain winter storm water released from the Nacimiento Dam upstream. Deflating the bladder in the winter will reduce negative environmental impacts, minimize sediment build up in its small retention reservoir and allow adult steelhead to migrate upstream from the ocean to spawn. (A fish ladder will allow steelhead to exit the reservoir when the dam is inflated.)

After treatment, the water stored behind the rubber dam will be mixed with recycled water and distributed to growers through the purple recycling pipes. Israel believes this additional water will supplement, if not fully replace, well water drawn during the dry, high-demand summer season and leave more water in the ground. “With the rubber dam, if you have several dry years in a row, there may be no water to release down the river,” he says, “but at least then you’ll have the backup wells and the groundwater they draw from.”

Although the dam will retain winter precipitation for summer use, the Monterey Regional Water Pollution Control Agency is already making plans, when funding becomes available, for another water-efficiency measure: a groundwater replenishment project that would inject secondarily treated wastewater back into the ground during the rainy season. The project would be similar to one instituted in Orange County, which has been injecting purified sewage water into its coastal aquifer since January 2008.

“A few years ago, people were saying, ‘You guys aren’t real smart. You don’t have any external water — state, federal or otherwise — coming in, and you have seawater intrusion,’” Israel remembers, but he hopes the regional treatment plant has created a water-use template other cities and agricultural areas can build on, even if they don’t produce 68 million pounds of artichokes a year. “From an energy perspective and a sustainability perspective, to be able to use all of our product and use it a second time makes a lot of sense.”

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Julia Griffin
Julia Griffin is a master's candidate in environmental science and management at the University of California, Santa Barbara. A fellow at the Miller-McCune Center in 2009, before that she worked as a film researcher for John-Michel Cousteau's Ocean Future Society and a producer/writer in CNN's Science and Technology Unit. She has a degree in marine biology from Duke University, and hopes to pursue a career in science and environmental journalism.

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