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San Diego, Ca. - By Tom Ewing, Special Projects Consultant-

Water, water everywhere, and still not enough to go around. With the costs of potable water increasing, and availability questionable during summer months, landscapers and commercial properties may be in a position to consider using recycled water as an irrigation alternative. For San Diegans it may be cheaper to buy and abundant.



San Diego imports nearly 90 percent of its water through the San Diego County Water Authority and the Metropolitan Water District of Southern California, which manage water coming from the Colorado River and the State Water Project. Even at an estimated 190 billion gallons per year, this has not been enough to meet growing population demands. To ensure a consistent water supply well into the future, the City of San Diego identified water saving alternatives, such as using reclaimed water, to help meet future needs.



“We have a network of pipelines in place to distribute recycled water throughout the City,” said Hossein Juybari, senior civil engineer with the San Diego Water Department. The City produces reclaimed water (also called recycled water) at the North City Water Reclamation Plant, located near the intersection of I-805 and Miramar Road. There, wastewater is processed until relatively clean. While not suitable to drink, it is excellent for secondary purposes, like watering plants. In fact, landscaping represents the single largest use of reclaimed water, which costs users from 10 to 50 percent less than potable water, depending on the municipality.



“This water is clean enough to swim in,” said Jim Ashcraft, senior project manager with Tetra Tech, an engineering firm that specializes in designing infrastructure for potable and reclaimed water. “The San Diego reclaimed water supply has the added benefit to landscapers of nitrogen. So when you irrigate with it, you apply nitrogen also.”



The City’s reclamation plant is a state-of-the-art facility that takes wastewater through a series of filters to screen out solid waste, sediment, minerals, and bacteria. “The plant currently produces about eight million gallons of recycled water a day,” Juybari said. “But it’s set up to produce up to 30 million gallons a day.” All that’s needed is the demand.



In April 2002, Miramar Wholesale Nurseries (MWN) initiated a reclaimed water retrofit plan which had been under development since the summer of 1998. Using reclaimed water has reduced the amount of potable water consumed by the facility’s day-to-day operations by 35 to 40 million gallons per year.



“A reclaimed water pipeline is the best way to ensure a guaranteed water supply for the nursery in case of potable water rationing during a drought,” said Joshua Dake, operations manager for the nursery. The facility didn’t have to wait for drought conditions to use the reclaimed water, however. Using reclaimed water on a regular basis saves potable water for the citizens of San Diego, and costs less too.



As part of the extensive retrofit of MWN’s irrigation system, a 21,000-gallon blending tank was installed to allow the nursery to store enough water for two days’ irrigation. The tank also blends reclaimed water with potable water for irrigation of ornamental plants that have specific watering requirements. With more than 250 acres of plant production area, the nursery’s demand for irrigation is high.



“Like many businesses, water is crucial to our survival and we use a lot of it,” Dake said. “Our decision to install a reclaimed water pipeline was largely based on our desire to do our part to help conserve water in San Diego.”



The nursery mixes potable and reclaimed water in the blending tank to reduce the mineral content of the reclaimed water, making it more suitable for the vast numbers of smaller plants grown on site. Two pipelines run the length of the center road of the facility – one for potable water and the other for reclaimed water. The potable water is used for human consumption; the reclaimed line transports water from the blending tank to the irrigation system. The ratio of potable to reclaimed water in the tank can be adjusted to accommodate the various plant types and mineral tolerances.



MWN’s Lake Forest site has used reclaimed water from the Los Alisos Water District exclusively since the nursery was built in 1996.



“The salt content in reclaimed water is higher than potable water in this area,” said Bob Seat, former owner and manager of the Lake Forest nursery facility. “As this site is almost exclusively a tree nursery, it can handle the salt content,” he said. Seat is a registered engineer who helped design the reclaimed water system for the San Diego MWN site.



Seat said because trees are large and sturdy, they are able to absorb the salt, while smaller plants are less able to tolerate it. “However, the remaining nutrients in reclaimed water are beneficial to nearly all plants,” he said.



Reclaimed water quality varies from city to city, so potential users should check out the standards set for their jurisdiction. According to the City of San Diego, the production of reclaimed water at the North City plant is monitored to ensure it meets all State Department of Health Services criteria. Stringent rules and regulations covering its use require all pipes, sprinkler heads, meter boxes and other irrigation equipment to be properly marked to avoid any potential for cross-connections and to distinguish them from potable supplies. Training classes are required for reclaimed water site supervisors, and site inspections are conducted regularly.



Businesses that take advantage of the reclaimed water option should be prepared to invest the time and effort into engineering a system that meets these requirements. “We design systems for municipal, commercial and industrial uses,” Ashcraft said. Consulting firms like his will prepare designs, plans, and handle the necessary health department issues. Golf courses are good candidates, as are parks and nurseries. Refineries use reclaimed water in their vast cooling systems.



Depending on the area, users pay to hook up to a network of reclaimed water pipes which is completely separate from potable water and sewer lines. This cost may be offset by savings in water rates over time. For MWN, it provides valuable insurance in the event of drought. The San Diego reclaimed water network extends from the North City facility west to the Torrey Pines biotech area to the La Jolla Village Drive and Colony area and to Governor Drive. To the east it follows Miramar Road to Sabre Springs, Scripps Ranch and Poway.



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Tom Ewing is a California Certified Nurseryman with more than 25 years of horticultural experience and managerial expertise. He has served as President and Chairman of the San Diego Chapter of the California Landscape Contractors Association, Chairman of the San Diego County Farm Bureau’s Water Committee, and is a board member of the San Diego Regional Chamber of Commerce. He is currently the special projects consultant for Miramar Wholesale Nurseries.



Captions:



Holding Tanks – Sewage is stored in these holding tanks to control the inflow of wastewater through the reclamation system. Levels of wastewater rise during the day and fall off at night.



Effluent Tanks – Once wastewater completes the cleaning process, it is distributed to the network of pipes from these purple tanks. Purple distinguishes recycled water from potable water throughout the network.

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