California city recycles runoff for school irrigation & toilet flushing
As drought continues to ravage Southern California, the quest to reduce demand for potable water has become paramount for many municipalities. The city of Santa Monica, Calif., has become a role model for communities seeking to implement water efficiency and conservation practices as it strives to meet the ultimate goal of its Sustainable Water Master Plan: to achieve water self sufficiency by 2020.
Image above: Storage for captured storm water and dry weather runoff was constructed under the park’s playing fields. Once complete, the system will treat 550,000 gal per year.
Already a veteran at water reuse projects—the Santa Monica Urban Runoff Recycling Facility has been treating storm water runoff for non-potable uses for approximately 10 years now—the city recently embarked on its latest water venture: the Los Amigos Stormwater Harvesting & Direct Use Demonstration Project.
A collaborative effort between the city of Santa Monica, the Santa Monica-Malibu Unified School Direct and the Metropolitan Water District of Southern California (MWD), the goal of the Los Amigos Park project is to “demonstrate the effectiveness of harvesting urban runoff for beneficial uses such as indoor flushing and park irrigation,” according to city documents. Once operational, the project will collect storm water and dry weather runoff from a 50-acre urbanized watershed and treat the water for reuse in irrigation of playing fields and toilet flushing at the park’s two restrooms.
According to Allan Sheth, civil engineering associate for the city of Santa Monica, the project not only will aid the city in reducing potable water demand, but also will go toward its Watershed Management Plan, which aims to reduce pollution in Santa Monica Bay, by reusing runoff that would otherwise have ended up in the bay. The project is funded, in part, with a $400,000 grant from MWD, the potable water supplier for Santa Monica. Sheth estimates the final project cost will total $1.7 million.
The captured runoff will be treated and reused to flush toilets in the park’s two restrooms and provide for approximately half of its irrigation needs, helping reduce demand for potable water. The treatment process includes pretreatment, filtration and UV treatment.
Recycling Urban Runoff
The 3.14-acre Los Amigos Park is owned by the Santa Monica-Malibu Unified School District and features soccer and baseballs fields, basketball and tennis courts, a playground and two restrooms. During the school day, the two adjacent schools—John Muir Elementary and the Santa Monica Alternative Schoolhouse—use the park. In evenings and on weekends, it is open to the public, and is utilized by various sports leagues.
Already completed project elements include a diversion structure that will divert runoff from an existing storm drain line and a pretreatment system installed in the public right-of-way; and a storage tank and wet well in the park. In construction as of December 2016 were the water treatment and pumping system, treated runoff supply lines and programmable logic controller equipment. The final step will be restoring the park to its original condition. Sheth estimates the project will be complete in January 2017.
According to Vik Bapna, cofounder of CWE and project designer, designing the treatment train was one of the more challenging aspects of the project—even though the contaminants encountered were those one would expect in this type of application. (“Bacteria is the biggest concern,” he said.) The design team was thrown a curve ball when it was partway through the design process. “[Los Angeles] County Department of Public Health had a certain set of guidelines for use of this water,” Bapna said. “They came up with revised and new guidelines, so we had to change our design a little bit to ensure we were meeting those criteria as well.”
The treatment train begins as soon as the water is diverted from the storm drain, with a “grate that screens the larger particles out,” Bapna said. The water then goes through a pretreatment system for removal of trash, oil and grease, and sediment, followed by storage to allow for additional fine particles to settle out.
Before it is used for toilet flushing or irrigation, the water also will go through a filtration system, followed by ultraviolet (UV) treatment to combat the bacteria concerns.
According to Sheth, the use of UV treatment also helped ease some of the school district’s concerns over the reuse of the storm water—not only does UV help ensure the water is safe and free from pathogens, it also does not require any potentially hazardous disinfection chemicals to be stored on site.
Once completed, the city predicts the system will be able to capture and treat approximately 550,000 gal of water per year, enough to irrigate half of the turf in the park and accommodate toilet flushing in the two restrooms.
The system collects runoff by tapping into an existing storm drain line that captures storm water and dry weather runoff from a 50-acre urbanized watershed.
Communication & Education
Ultimately, the project’s biggest hurdles came not from designing the treatment system, but from working with the various agencies and parties affected.
Because Los Amigos Park is located on a school property, the city had to work the California Div. of the State Architect (DSA), which oversees construction and design for schools and other state-owned facilities.
“We had to get [the DSA’s] buy-in, and they have a very rigorous process,” Bapna said, noting the agency’s “biggest concern was safety for the kids. But they’re not used to these types of projects,” so the project team worked to convince DSA of the project’s benefits. “There are definitely folks at [DSA who] are willing to hear and listen, and they did help us through the project once we got them on board,” he said.
Nonetheless, the project team found DSA’s review process to be one of the most difficult parts of the project. “That was one of the challenging aspects, just going through the entire plan review and getting some kind of definitive answer on what is needed to move the project forward,” Sheth said.
The project team also had to coordinate with the two affected schools themselves—an effort that required effective education and communication. Although construction began in the summer, it has continued into the school year, resulting in portions of the park being unavailable.
“There was a lot of impact on the school itself,” Sheth said. “We’re in construction now, and we fenced off about half the playground.”
The project team also provided education on the project to school administrators in an effort to address concerns and clear up any misunderstandings. “I think education is always key in ensuring everybody understand some of these things,” Bapna said. “No matter how much you do, it’s never enough.”
He noted that when the school administrators learned the goal of project was to capture pollution before it went into waterways, it sparked concern that the water that would be used to irrigate the fields would contain pollutants. Part of the educational process involved explaining how the treatment system would remove contaminants before the water was used for irrigation purposes.
The city also made an effort to ensure the baseball, softball and soccer leagues that used the park were aware of how construction would affect them. According to Sheth, meetings were held with the American Youth Soccer League and Pony League to alert them that certain fields would be closed during construction and that they would need to schedule games at other locations. These leagues often schedule games up to a year in advance, so city officials wanted to be sure they had plenty of advance notice.
Because the construction also would create some traffic and parking disruptions, residents in the surrounding neighborhood were notified of the project via several public outreach efforts. According to city officials, informational postcards and brochures were mailed to all residents and businesses located within a 500-ft radius to inform them of the park closures and project goals. A community meeting also was hosted prior to the start of construction. Additionally, the school sent notices to parents to make them aware of the impacts the project would have on the school. Officials said feedback from the community has been positive so far, and they plan to do further outreach to parents, teachers and students in the near future.
Water Reuse Role Model
Bapna predicts the Los Amigos Park project will have a positive impact on the environment, especially when it comes to dry weather runoff, such as that from irrigation or car washing. “We’re using that water back again, so it reduces the potable water demand,” he said. “Reusing that water is a huge benefit for the environment in that case—eliminating the pollutants that can go downstream, run off downstream, capturing some of those pollutants—same benefit to the environment.”
Sheth noted that the project also could have a long-term effect on other communities—he hopes it can be used as a model for other communities or water agencies that might be interested in a new approach to managing and reusing storm water. Because of its status as a demonstration project, the grant actually requires that the city “put together some challenges that we had and how we overcame those so that other agencies can then be encouraged to do the same thing,” Sheth said. “Obviously, we have a big drought in Southern California, so this is one of the ways we can help with offsetting the use of potable water.”
Other water agencies already have taken note of Santa Monica’s unique water reuse projects—Bapna already has had clients approach him about emulating some of the city’s projects. “Santa Monica has always been on the forefront of doing things outside the norm,” Bapna said. “People are looking at Santa Monica and what Santa Monica is doing; they also want to do similar things. That just adds more value to retaining and reusing water.”