For decades, the stormwater policy in Los Angeles for project designers was pretty simple—sweep runoff into the sewer drains and flood channels as quickly as possible. In response to a series of severe floods, the U.S. Army Corps of Engineers designed a system of concrete channels during the 1930s that became the foundation for the fast-growing city’s stormwater strategy for the following 75 years. Most of the water ended up in the Pacific Ocean, to the horror of environmentalists and conservationists alike.
“Stormwater was the last part of any development drawing,” says James Alamillo, urban program manager for Heal the Bay, a group that tracks water issues in the city. “It was almost always an afterthought.”
Today, Los Angeles is one of the many cities around the world facing the new paradigm of water management. No longer is it practical to simply let stormwater drain into the ocean. Problems as diverse as drought, overflowing sewer pipes, and beach closures due to pollution have prompted new regulations and the need for new approaches. Any developer wanting to build in Los Angeles nowadays needs to have a stormwater plan.
“Everyone is trying to find new and better ways to save water,” says Mike Meyers, senior principal at Lifescape International, a landscape architecture firm based in Orange County, south of Los Angeles. “Regulations have forced us to be more innovative.”
On a global scale, dealing with water has turned from a background issue to a top priority, especially for large-scale developments. Designers are exploring different methods for capturing and using stormwater and runoff. Instead of contributing to waste and inefficiency, developments can collect and distribute water to prevent flooding, cut usage, and increase supply, designers say. From new filtration technologies and intricate geological strategies, designers are trying to make water part of a holistic strategy for landscaping, engineering, and infrastructure.
“Now we’re seeing total water consciousness,” says Drew Gangnes, senior principal at Seattle-based Magnusson Klemencic Associates. “We’re going beyond just retaining rainwater.”
In many communities, designers no longer have a choice but to become more proactive about managing water. Many government agencies are mandating that developments capture stormwater. Aging infrastructure cannot handle the flow into sewer systems. In fast-growing Portland, Oregon, which receives more than 40 inches (100 cm) of rain annually, one-third of the sewer pipes are over 80 years old, says Tim Kurtz, senior engineer with the city’s stormwater system division. With a focus on keeping water out of the system, the city requires a stormwater abatement plan for any construction with more than 500 square feet (47 sq m) of impervious surface.
“Basically, anything larger than a small patio will trigger the process,” Kurtz says. The aggressive strategy has helped move developments forward, he adds. “As we plan, we don’t have to put in a larger infrastructure project to accommodate development. We can spread the burden of development a little more evenly.”
Most areas of the United States lag behind international trends. For years, countries in arid climates have been demanding that developments capture and reuse water. For these nations, drought conditions and the lack of available groundwater create constant pressures on supply. Desalination plants and residential water tank systems are necessities.
For example, in Bermuda, where little freshwater is available and hurricanes routinely batter the island, building codes require homes to include roof systems to capture water and funnel it to underground tanks. The distinctive whitewashed limestone roofs are typically terraced to slow the runoff and to buttress the homes against high winds. Reflection of sunlight off the white surface also helps disinfect water.
In other parts of the world, a new generation of violent storms and flooding is prompting the creation of more intricate runoff systems. In the past, planners were often satisfied to accommodate storms based on short-term rain averages, the regular storms that may batter a project. Today, in the wake of storms that have devastated cities around the world, designers are often called upon to prepare for dramatic events that may occur more often than once every 50 or 100 years.
Plans for Arboleda, a 26-acre (11 ha) mixed-use development in Monterrey, Mexico, were developed shortly after Hurricane Alex devastated the area in 2010. In response to the storm, developer One Development Group, which is based in Monterrey, wanted to create systems for the project, a Pelli Clarke Pelli–designed layout with residential towers, offices, hotels, and retail space, to handle the worst-case scenarios.
In addition to a 30,000-gallon (114,000 liters) underground stormwater collection tank, plans for Arboleda call for a network of retention ponds, bio-soil planters to capture water, and green roofs to serve as sponges to absorb water. “We could not rely on just the tank,” says Dillon Diers, a principal at the Office of James Burnett, a landscape architecture firm based in Solana Beach, California, that worked on the project. “Additional sitewide environmental strategies were needed.”
Project designers often talk of a more universal approach these days. Runoff is viewed as one part of a broader strategy to conserve water and energy, protect the local environment, and, in some cases, link to the culture of a place.
In San Antonio, designers have made water a key element in plans to redevelop Hemisfair, the city’s old fairgrounds and the site of the 1968 World’s Fair. A public/private partnership is creating a series of urban parks around new developments. The idea was to address the city’s long history of conserving and protecting the local aquifer, in addition to connecting to the city’s famed River Walk (also known as Paseo del Río), lined with stores, bars, and restaurants along the San Antonio River. “The big issue is the broader context of water in San Antonio,” says Grant Stewart, principal at Gustafson Guthrie Nichol (GGN), a Seattle-based landscape architecture planning firm that is working on Hemisfair.
Plans call for a graded site that will collect water on one corner of the park and channel it throughout the project, eventually connecting to the River Walk. But designers are also proposing a more extensive system that will collect stormwater and runoff from surrounding buildings, treat it, and redistribute it in the area. The site will, in effect, “sewer-mine” surrounding projects, becoming a focal point for recycling wastewater.
Implementing the more elaborate system will require the participation of private developers around the site, which may not be easy. The economics of water systems are complex, including energy costs, land use, and construction expenses, as well as the cost of existing water and sewer services. In San Antonio, water rates are very low, making it difficult to make a case for saving money in the short term.
“Water rates are low now, but you can only assume they will continue to rise,” says David Malda, GGN senior associate. “We’re trying to think not in just a few years, but longer-term.”
The availability of technology for treatment is rarely the issue these days, designers say. In some cases, treatment mechanisms are essentially prefabricated devices that can connect directly to existing water and sewer lines.
For the redevelopment of the San Ysidro, California, border crossing, the busiest land border in the world, which connects the United States and Mexico south of San Diego, MKA used a membrane bioreactor (MBR) system to cleanse wastewater on site for nondrinking uses, such as toilet flushing, irrigation, and mechanical systems. “It’s as simple as something you can put on the back of a truck,” says Gangnes, who worked on the project.
The project, which was competed in 2013, features an intricate system to capture and reuse all the runoff water from the 39-acre (16 ha) site as well as from the surrounding hillsides, eliminating the need to import any nonpotable water—making the project “net-zero.” Runoff is channeled directly to planting areas known as bioretention cells. Excess water is collected and distributed from a 300,000-gallon (1.1 million liters) cistern. A separate system runs wastewater from the facility through the MBR system. To help reduce energy costs, water from the cistern is also used to cool HVAC systems and to clean solar photovoltaic panels.
MKA estimates that the water plan will reduce the site’s water use by 20 million gallons (76 million liters) per year. The reuse treatment technology added $2.5 million in initial expense, plus annual operations and maintenance costs, but it will pay for itself in an estimated 19 years by cutting water costs, Gangnes says. The system will save the project about $200,000 a year at current water rates, and $45 million in total utility rates over the next 40 years, according to MKA estimates.
“Before, you looked at different silos” when planning water systems, says José Almiñana, a principal at Philadelphia-based Andropogon Associates, a landscape architecture firm. Managing runoff water, irrigation, and other functions were treated as different elements. “Now, you’re faced with looking at [water] as a contiguous system,” he says. “You can’t afford to design for a single purpose.”
For the creation of Shoemaker Green, a 2.75-acre (1 ha) park on the campus of the University of Pennsylvania, Andropogon created a “large bathtub” to capture and recycle the stormwater and HVAC runoff from the surrounding buildings. The system includes a 20,000-gallon (67,000 liters) underground cistern, porous hardscape surfaces, and intricate sand storage beds. The soil mix extends down three feet (1 m) and leads to a thin plastic strip with “microchannels” designed to direct water to the irrigation system.
The system is designed to handle 90,000 gallons (341,000 liters) of water a year and storm events of more than three inches (8 cm) of rain, in addition to the anticipated growth in demand from the renovation of the surrounding buildings. “We need to produce public spaces to actually be able to absorb all kinds of events and become more resilient,” Almiñana says.
After the project was finished in 2012, the designers closely monitored the performance of the green. From May 2013 to June 2014, the data showed that no stormwater had left the system for the local sewer system, despite several high-rain incidents. The designers were particularly impressed with the effectiveness of the planters and soil mixtures. “Transpiration measurements of the vegetation show that native floodplain species and uncompacted turf are veritable workhorses, transpiring anywhere from three to ten gallons [11–38 liters] of water per day during the growing season,” Andropogon wrote in a report. Increased “residence time” within the vegetated areas also resulted in increased evaporation rates, the study found.
Retention and Recycling
What to do with the water once it has been collected is one of the major issues facing any stormwater strategy. Do you keep it on site? Recycle it? Send it to community systems? Some cities are focusing more on letting the water naturally infiltrate into the soil to replenish groundwater.
In Los Angeles, where water was historically channeled to the ocean, infiltration is growing in popularity. Designers are focusing more on porous surfaces and natural underground systems to make Los Angeles into what landscape architect Mia Lehrer calls a “sponge city.” Natural systems such as wetlands can provide an organic treatment system for runoff, she notes.
“One of the things people don’t realize is southern California has a tremendous aquifer,” says Lehrer, founder of Los Angeles–based Mia Lehrer + Associates, a landscape architecture firm. Stormwater issues are an integral part of almost all her projects in the area these days. The design for a new parking garage at the Los Angeles Zoo included permeable concrete asphalt, grassy swales, and water-absorbing planters. A residential hall for Pitzer College includes a system to collect and treat water from showers and sinks for use in landscaping, as well as capturing 100 percent of stormwater on site.
“People are generally very interested in being part of the problem solving,” Lehrer says. Regulations and increased water rates are helping spur the acceptance of new approaches. “The community at large has been used to water not costing much and the opportunity to use a lot of water,” she says. “There is an incentive beyond being a good citizen.”
Water plans are often controversial, touching on a wide variety of sensitive issues. Planners in Colorado traditionally face laws that forbid collection of rainwater, based on longstanding issues with ranchers trying to monopolize the precious resource. The developers of Sterling Ranch, a 3,400-acre (1,400 ha) residential development south of Denver, needed new legislation and the approval of the Colorado Water Conservation Board to become a pilot project for rainwater harvesting in the state.
Water was a key source of contention in the Sterling Ranch approval process, which lasted for ten years. The design for the project, which is under construction, is intended to save up to 40 percent of the water used for outside irrigation. Water from gutters and streets will be channeled to a series of lakes, which will drain to a central lake where water will be treated and returned for use in landscaping and plant maintenance.
Sterling Ranch Development Company, the developer of the 12,000-home project, has also agreed to monitor the potential of rainwater harvesting as a supplemental water supply, without affecting the water rights issues. “From an economic standpoint, [rainwater harvesting] has already been very good for us,” says Harold Smethills, founder and managing director of the company. “It’s going to save the project and residences a lot of money over a period of time.”
But he thinks many of the long-term benefits will be harder to track. “The intangible aspect is that residents will feel part of the leading edge of sustainability,” Smethills says. “People want to be able to use rainwater on their yards.”
While rainwater awareness has been growing dramatically in recent years, systems and implementation are still in a relatively early stage, landscape architects note. Cohesive strategies are necessary to achieve the long-term goals. “The challenge is how to go beyond new development and deal with existing infrastructure,” Diers says. “To broaden the scale, you have to go after existing infrastructure.”
But general agreement exists that awareness is growing, and innovations will lead to broader success in using stormwater and runoff as solutions to compelling problems. “We can do better and it is achievable,” Stewart says.
“We can contribute in the long term and do what is right.”
Kevin Brass is a San Diego–based regular contributor to the New York Times, the Wall Street Journal, and the Financial Times.
For additional information on how parks and open space can support stormwater management and environmental resilience, sign up for updates on the 10 Minute Walk Campaign or follow #10MinWalk. The 10-Minute Walk Campaign, a national movement led by the Urban Land Institute, The Trust for Public Land, and the National Recreation and Park Association, is promoting the bold idea that everyone living in urban America should live within a 10-minute walk of a park.