Greening the Urban Water Supply

Cleaning up pollution and developing new resources

Credit: City of Santa Monica

According to the Natural Resources Defense Council (NRDC), cities and suburbs are among the largest sources of water pollution in many parts of the US.

As Lawrence Levine wrote in his NRDC Issue Brief, “Waste Less, Pollute Less: Using Urban Water Conservation to Advance Clean Water Act Compliance,” these cities and suburbs face hundreds of billions of dollars in investment needs to repair, maintain, and improve their infrastructure with Clean Water Act standards that protect public health and the environment.

The four cities profiled here all face these issues and have engaged in long-term planning, design, and construction to comply with state and Clean Air Act compliance. At the same time, some of the cities also face chronic water scarcity, increased uncertainty in future water availability, or growing competition for water resources, to cite Levine.

All of the profiled cities are adopting some form of green infrastructure to improve water use efficiency, augment urban water supplies, and reduce stormwater pollution. All financed the projects through fees, capital budgets, or by issuing bonds.

What is green infrastructure? Four examples will explain. In 2010, the city of San Francisco passed a stormwater ordinance that requires all new or redevelopment projects that disturb 5,000 feet of “ground plain” to manage a certain amount of stormwater on the site; they must submit a control plan to choose among several options such as a bioretention basin or rainwater gardens.

The city of Santa Monica built the Santa Monica Urban Runoff Recycling Facility (SMURRF) and commissioned it in 2002. The SMURRF cleans up runoff from streets and gutters and puts it through a treatment process. SMURRF produces 250,000 gallons of non-potable water per day. A purple pipe system pumps the water to irrigate the landscape at the city cemetery, the park along the Palisades overlooking the ocean, and landscaped street medians.

The Seattle Washington Public Utilities designed its Green Stormwater Infrastructure to reduce runoff from streets using infiltration, evapotranspiration, or stormwater reuse through roadside rain gardens. These methods will recharge the groundwater. Individual projects are heavily landscaped, designed, and built to collect water, which can be absorbed into the ground or can be diverted to defined locations.

The City of San Antonio’s Water System boasts that it is the only US city to reuse all three wastewater treatment process byproducts in its water recycling program. The Dos Rios Water Recycling Center treats and cleans effluent from the city’s sewer system and sends the recycled water to the city’s purple pipes. Much of the recycled water then wends its way to several manufacturing plants, where it is used in their processes. The remaining recycled water is eventually released 150 miles away at the Aransas Natural Wildlife Refuge in the Gulf of Mexico.

The biosolids, a byproduct of treating the wastewater, are used in generating compost sold commercially through local retailers and nurseries. The biogas, mostly methane generated in the Recycling Center’s treatment plant, is transferred to a nearby commercial pipeline and sold on the open market through a partnership with Ameresco Inc., a national energy company focusing on renewable energy which refines, compresses, and ships at least 900,000 cubic feet of gas per day.

The regulatory and infrastructure financing provisions of the Clean Water Act are administered jointly by the federal government and the states. EPA’s regulations on “combined sewer overflows” (CSOs) require a long-term control plan and implementation of specific controls.

Traditionally, cities have designed their sewer systems to carry both sewage and stormwater to treatment plants. During storms the treatment plant capacity may be overwhelmed, and the excess stream will be diverted to an overflow pipe taking it out to a nearby waterway. This is known as a CSO, and lakes and rivers have become polluted as a result, since stormwater picks up oil, grease, and metals as it races down streets.

Seattle pre planting

Credit: Seattle Water
A weir wall separates swale cells and directs runoff downstream.

In Seattle’s case, stormwater makes up about 90% of a CSO.

In 2013, a volume of 38 million gallons of stormwater and sewage were discharged into area waterways.

The city prepared its first CSO reduction plan in 1988 and has updated it in 2001, 2005, and 2010. It is now preparing a comprehensive strategy, “The Plan to Protect Seattle’s Waterways,” to reduce overflows and the discharge of pollutants from combined sewers and the storm drain system.

By May 2015, the city is required to submit its long-term control plan (LTCP) to the State of Washington’s Department of Ecology, and this plan will describe the remaining projects that will be implemented to reduce and bring CSOs under control.

EPA recommends that the two drainage systems be separated so that all stormwater is directed to waterways, thereby avoiding treatment plant overflows. However, this is an expensive alternative. Seattle has built two small separate systems, but its major approach is to construct additional storage facilities to store excess wastewater until flows decrease enough for the stored wastewater to be returned to the sewer conveyance system.

Over the next 10 years the utility will construct seven underground storage facilities to store approximately 9.4 million gallons of sewage and polluted stormwater to prevent overflows into Lake Washington Ship Canal.

Degradation of the water resources in the Seattle region is an ongoing theme, in particular the health of Puget Sound. The other legs in the chain to gain compliance with the Clean Water Act and improve the health of the Sound are the street-side rain gardens, storage vaults, and street retrofits. The purpose is to capture rain water during heavy rainfalls and allow it to be absorbed into the earth or flow into reservoirs before it runs into sewers and out into Seattle’s Sound.

Seattle - 107th post - 1yr est

Credit: Seattle Water
The weirs after completion, with landscaping that provides for biofiltration of stormwater.

“Our primary driver is getting in compliance with the Clean Water Act, and RainWise is one leg of the chain,” says Bob Spencer, Seattle Public Utilities RainWise Program Manager.

The RainWise program teaches customers how to emulate the once primal forest where falling rain was slowed by needles and leaves and slowly soaked into spongy soils held together by the roots of trees and plants; though RainWise takes a modern approach. Now rain gardens, cisterns, porous pavement, composting and mulching, and planting trees can repeat, at least partially, what the primal forest once did.

Five natural drainage projects have been completed and four more are under construction. The first project completed in the spring of 2001, called the “Street Edge Alternatives” project, has reduced total stormwater volume running down its streets by 99%, based on two years of monitoring.

Seattle - Highpoint Larger

Credit: Seattle Water
When Seattle’s redeveloped its Highpoint district, it designed a new drainage system in its streets, alleys, and sidewalks, promoting natural drainage.

The RainWise Program designed a series of rebates to encourage residents to install their own rain gardens and cisterns, which drain into the rain gardens. Customers can hire a trained RainWise contractor and receive rebates to install rain gardens or cisterns if the customer lives in a targeted combined sewer overflow basin. Jenna Smith, an irrigation and water management manager who works with Spencer in the RainWise program, explains that what a customer installs depends on the condition of the site and its soils, which differ from neighborhood to neighborhood. Downspouts can be disconnected at the ground level and modified to drain into a cistern or the rain garden. Spencer says 465 rain gardens and cisterns were installed over the past four years.

“We feel pretty good about our water supplies, and it’s better to save it in reservoirs and encourage residents to save by installing rain barrels and cisterns. The projects are being funded under current stormwater fees and are adequate for what is being done now,” says Spencer.

State water laws more so than the Clean Water Act, have pushed the San Antonio Water System (SAWS) to diversify its water supplies. Greg Flores, vice president of public affairs at SAWS, says the Edwards Aquifer has been the cornerstone of San Antonio’s water supply for over 100 years and is the source of water today for 90% of the city’s residents.

San Antonio - Aquifer Storage ASR_9497

Credit: San Antonio Water System
Built in 2004, the Twin Oaks Aquifer Storage and Recovery facility stores Carrizo Aquifer water for use during dry South Texas summers. In 2011, it met 20% of the city’s daily demand.


As federal courts and the Texas legislation refined and updated its water laws limiting San Antonio’s primary water supply, and as San Antonio’s population grew and droughts became a reality, SAWS saw it needed to diversify its water sources and guarantee retention of its water rights.

Harry Tracy Treatment Plant

Credit: Nancy Gross
The Harry Tracy Treatment Plant has undergone significant upgrades.

And San Antonio can get hot. Temperatures were in the 90s (Fahrenheit) throughout August 2014 and reached 100°F 10 times during the month. According to Flores, roughly 240,000 acre-feet per year are consumed by SAWS’ 1.3 million customers.

In the early 1990s, in response to Texas legislation, the Edwards Aquifer Authority was created to manage and limit withdrawals during droughts. So SAWS began acquiring water rights through leases and purchases to increase pumping of the Edwards Aquifer.

SAWS created the 50-year Water Management Plan in 1998 and has updated it every five years since then. The plan details how its ground and surface water supplies are being diversified through purchases and through underground water storage and a recycling program.

Harry Tracy

Credit: Nancy Gross
An 11 million-gallon tank to replace tanks


Beginning in 1998, the water agency signed a series of contracts with other water authorities in the region. The largest acquisition came in 2002 when SAWS acquired rights to the Trinity Water Aquifer, and later it signed a regional partnership agreement with the Gonzales-County Underground Water Conservation District to transport Carrizo Aquifer groundwater from 50 miles north via pipeline to San Antonio. This is the largest water supply source outside of the Edwards aquifer and extends from Texas’s northern border to the Mexican border. The project was completed in December 2013 at a cost of $110 million, says Flores. It transports 17,000 acre-feet per year directly to customers.

SAWS built the $250 million Twin Oaks Aquifer Storage and Recovery facility in 2004, because it had no way to store excess Edwards Aquifer drinking water brought in from the southern part of the county during rainy seasons, and it could not carry over or credit the pumping rights not used in a given year.

The large-scale underground water storage facility stores Carrizo water on top of Edwards water for use during the dry South Texas summers. Flores says the facility currently stores 70,000 acre-feet. An average of 25.5 million gallons per day have been pumped out this year. He describes the storage facility as an engineering marvel. It is the third-largest storage and recovery facility in the nation, according to SAWS.

A brackish groundwater desalination plant is being developed at the storage and recovery facility as well. “There are vast amounts of brackish water underneath southern Baxar County” where San Antonio is located, says Flores.

Flores says ground was broken on the project in 2014, and he expects that the Phase 1 plant will be online in 2016. Phases 2 and 3 will be completed in 2021 and 2026 and will eventually treat more than 30,000 gallons per day, according to SAWS.

SAWS continues to develop new sources of water. It solicited competitive bids from private developers for bringing water to San Antonio, explains Flores. Of the three proposals that made the cut, it is negotiating with a consortium organized by Abengoa, the Spanish company, which proposes to finance and build the 142-mile Vista Ridge pipeline to pump water from Burleson County, northeast of Austin and San Antonio. Blue Water in Austin, another partner in the consortium, holds leases and permits from 3,400 landowners to deliver 50,000 gallons per day of water to San Antonio by 2019 from the Carrizo Aquifer in Burleson County. It will eventually provide 20% more water for San Antonio.

Flores says there is a lot of groundwater in Texas, but not a lot of districts will permit leasing. “Most folks in districts don’t want to ship water to big cities,” he says, and political leaders are sensitive to that.

By 2030, SAWS plans that these new sources of water, both online and proposed, will add 135,675 gallons per day to the current Edwards Aquifer allocation of 169,561 gallons per day, almost doubling supplies. Recycled water will add 75,000 gallons per day and water conservation programs are projected to save 18,386 gallons per day.

“San Antonio has the water it needs today and it will have the water it needs in 2050,” says Flores.

Santa Monica - Permeable Paving

Credit: City of Santa Monica
Permeable paving on Santa Monica neighborhood streets and sidewalks allows water to infiltrate into soil. The solar panels provide power to streetlights and irrigation pumps.


“We have to keep climate change implications always in mind, and this keeps conservation in the forefront of our efforts. It is uncertain we will get the amount of rain we’ve gotten in the past” says Gil Borboa, Santa Monica’s water resources manager.

Santa Monica’s goal for water reduction is also California’s mandate—a 20% reduction in water consumption by 2020. Borboa says, “What we have been doing over the past 15 years is focusing on indoor water use. Now our efforts are focusing on exterior uses.”

The multifamily residential sector consumes 42% of the city’s water supply, followed by the single family and commercial sectors. A Stage 2 Water Shortage Response Plan was adopted by the City Council in August reducing residential water use per person from 123 gallons per day to 82 gallons per day. Once details of the ordinance are approved, fines will be assigned to violators.

Street drains act as catch basins to direct water to infiltration chambers under the parking lane.

Credit: City of Santa Monica
Street drains act as catch basins to direct water to infiltration chambers under the parking lane.

Borboa says the city is producing close to 70% of its water supply from city-owned wells and the water department is actively planning to be entirely self-sufficient by 2020 through enhanced conservation and alternative water sources, including drilling new water wells and using recycled water. Currently, the city imports the remaining water it needs from the Metropolitan Water District of Southern California.

“We pay MWD $890 per acre-foot for the water we import and the price goes up annually,” says Borboa. “Our costs to produce well water are $600 per acre-foot, including treatment. These costs will go up, but we expect a lot of treatment costs will go away as contamination plumes we are currently cleaning up are eliminated.” Over the long run, the differential between MWD water import costs and well water production costs will grow, he says.

Located immediately south of the famous Santa Monica Pier, the SMURRF recycling facility is set up for public viewing. In dry weather periods all urban runoff is directed away from the ocean and into the recycling center. The water is of poor quality since it picks up metals and street garbage.

The runoff goes into a chamber where gravel is settled out, then it goes into a dissolved air flotation system where grease particles are trapped, and then through a microfiltration process and UV light disinfection. The water is then sent to the purple pipe system.

The City of Los Angeles also has a recycled water system that will eventually reach Santa Monica and increase the ability of the city to replace more potable water use.

Dual piping systems have been installed in two buildings in the city, and to the extent the city has more recycled water it will be able to extend non-potable water use to other commercial buildings, Borboa says. Part of the new Police and Public Safety Facility and part of the Rand Corporation headquarters are dual plumbed.

“We started the stormwater runoff program in 1997 to satisfy requirements of EPA’s Clean Water Act,” says Kim O’Cain, a sustainability analyst in Santa Monica’s Water Resources department. The goal was to reduce stormwater runoff into Santa Monica Bay by 80%. The runoff contained high bacterial counts contributed by animal waste and other pollutants.

The SMURRF, along with the Green Streets water quality infiltration diversion projects, were essential for the city to reach that goal. “The Heal the Bay water quality grades improved from ‘F’s to ‘A’s and ‘B’s,” says O’Cain, depending on whether it’s rain, which may contain contributions from birds, or runoff.”

The Green Streets water quality infiltration diversion projects are an impressive mix of small and large vaults and cisterns located throughout the city, including on street corners. Cisterns or vaults have been built at seven locations, sometimes on street corners, to catch urban and stormwater runoff. The runoff slowly drains into the sewer system and is transported to the City of Los Angeles’s Hyperion Treatment Plant south of Santa Monica. An eighth location features permeable asphalt, which allows runoff to discharge into the ground.

The Penmar Water Quality Improvement project is perhaps the largest cistern in the Los Angeles Basin. A joint project between the City of Los Angeles and Santa Monica is currently under construction; it will slowly release water into the sewer system and on to the Hyperion treatment plant. In Phase 2, a disinfection and treatment plant will be added to clean and use the water to irrigate parks and golf courses. The urban runoff projects will help the city reach its goal of producing 100% of its water requirements by 2020.

Finally, the city has installed cisterns in its main library where the water is used to irrigate landscapes, and in a newly built neighborhood library where the water is used to flush toilets. O’Cain says that it was installed before the last rainy season in November and December, and the water is still being used. She is looking for funding to increase the number of cisterns in city buildings.

The Sustainable Water Consumer Program, which O’Cain also manages and offers rebates for “Cash for Grass” landscaping (replacing lawns with climate-appropriate plants), drip irrigation, high-efficiency clothes washers and toilets, rain barrels and cisterns, and downspout redirect to cisterns.

O’Cain is also responsible for promoting and managing water reduction rebates in commercial buildings. Currently she is working with the city’s two major hospitals, a hotel, the school district, and laundromats to design and install water efficient equipment.

The San Francisco Public Utilities began its water system improvement plan in 2002 to seismically upgrade and diversify its water system in reaction to the 1988 Loma Prieta earthquake. The plan is fortuitously serving to create a sustainable water supply in the face of California’s worst drought.

David Briggs, the local and regional water system manager for San Francisco Public Utilities, says that the utility is planning for a 7.5-year drought design. In the more than 100 years, the area has had many droughts. “We assume there will be repeats. We planned for droughts more extreme than what has been experienced,” he says.

Many parts of the water system are aging, and storage is poor. Watershed protection is important, and several of the projects are designed to correct earlier environmental damage and reduce the impact of the water system on wildlife refuges in the East Bay area.

Now 80% complete, the projects include a new bay tunnel, the replacement or refurbishment of four tunnels crossing the East Bay, a replacement for the Calaveras Dam, and upgrading two water treatment plants. A $4.6-billion bond measure approved by San Francisco voters in 2002 funded the projects.

Known as the Water System Improvement Program (WSIP), the goals for the projects are to be able to deliver a minimum level of service within 24 hours of an earthquake like the Loma Prieta quake, to have delivery reliability and reliability to meet the current and future federal, state, and local water-quality requirements such as the Safe Drinking Water Act and The Clean Water Act.

The Hetch Hetchy dam in the Eastern Sierras has served as San Francisco’s major water supply since 1934 when the first water arrived in the city. Today, it provides 85% of the water supply, and local groundwater resources provide the remaining water needs, supplying 260 million gallons per day to 2.6 million customers. The majority of Hetch Hetchy water travels approximately 167 miles and is gravity fed, and given that it is spring-fed, it does not need filtering.

Four pipelines form transmission mains in the Hetch Hetchy regional water system and stretch from the San Francisco peninsula along the bay floor and on trestles that cross over environmentally sensitive marshland east of San Francisco Bay. They transport the water from Hetch Hetchy and the fear is an earthquake could rupture one or more pipelines, disrupting water supplies.

The new Bay Tunnel has been dug to run from the peninsula five miles under San Francisco Bay at depths of up to 100 feet to the East Bay. Pipe installation is complete and the tunnel is expected to be operational in May 2015. It should provide a much higher level of reliability, says Dan Wade, director of the WSIP.

The underground material resulting from the excavation will be used as part of the South Bay Salt Pond Restoration Project, converting adjacent salt ponds to marshland.

The Bay Tunnel will link the existing segments of the two oldest underwater lines, built in the 1920s and 1930s, by way of vertical shafts on each end of the bay. The portion of those two lines being replaced by the tunnel will be capped on each end and abandoned in place.

The two newer pipelines, built in 1952 and 1973 cross three traces of the Hayward earthquake fault. One will be retrofitted with articulated lines and two huge ball joints, allowing the pipeline to compress, move and rotate without rupture. The line is designed to absorb up to 6.5 feet of horizontal displacement. The fourth line will be will be seismically retrofitted at the three fault traces and portions will be slip-lined with new steel pipe.

Briggs says once all the work is completed he will be able to turn valves and reroute water in emergencies, a capability that the department did not have in the past.

Briggs says local supplies are located both on the peninsula and east of San Francisco Bay. To treat that water two treatment plants, Harry Tracy and Sonul Valley, are being upgraded. Once completed, Sonul Valley, located across the bay from San Francisco, will be able to sustainably deliver 160 million gallons per day. In the past they couldn’t reliably deliver that amount for long periods. The improvements make them operationally flexible to meet a higher demand, Briggs says.

The upgraded Harry Tracy treatment plant, located on the peninsula, will give the plant the ability to treat water on the peninsula and deliver during earthquake disruptions. Briggs says Harry Tracy will likely be able to deliver water to San Francisco if the pipelines from Hetch Hetchy are disrupted.

Rachel Kraai is an urban watershed specialist at San Francisco Public Utilities Commission (SFPUC). She works on stormwater management for the PUC’s wastewater enterprise. The city’s stormwater ordinance, passed in 2010 and discussed in the introduction, has produced over 150 projects. The majority of developers/owners of apartment and office buildings, and schools, have chosen rainwater gardens from among several options: a bioretention basin, rain water harvesting for irrigation or toilet flushing, permeable pavement, or vegetation green roofs.

Kraai says the “Urban Watershed Stewardship Grant Program” offers up to $100,000 to incentivize community projects in the public realm with an educational element. For example, a school built a small rainwater harvesting project with a cistern in an educational garden. Other projects include a small number of block size sidewalk landscaping projects where the community members removed a single impervious surface and planted drought-tolerant plants.

The SFPUC has launched an urban watershed assessment planning process, says Kraai. The condition of the sewer system will be assessed in each of the eight urban watersheds within the city. The challenges and solutions are being assessed from a watershed approach—how the upstream condition affects downstream conditions and visa versa, she says. The assessments will include both the natural hydrologic condition of soils as well as the distribution pipes and storm drains.

The goal is to take advantage of natural processes of soils and plants to manage stormwater. Kraai says the stormwater and water departments or enterprises, as they are called, are having discussions about groundwater recharge. “Right now, we’ve started the planning process for eight green implemen­tation projects in each watershed.”


Lyn Corum is a technical writer specializing in water and energy topics.


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