By Margaret Buranen
Two developments guarantee that Atlanta, GA, will see more examples of green infrastructure. The first push comes from Atlanta’s share of a $950 million grant from EPA to encourage green infrastructure in 17 cities.
Priority was given to areas of heavy flooding, in neighborhoods with combined sewer systems. Six pilot green infrastructure projects have been completed in Peoplestown (site of frequent combined sewer overflows, or CSOs), Mechanicsville, and Summerhill.
These short-term green measures were finished by the summer of 2012 to give residents some immediate relief from flooded, contaminated basements and backyards. More longer-term green projects are in the pipeline.
The second stimulus for green infrastructure happened in February 2013, when the Atlanta City Council approved changes to the city’s stormwater ordinance. These changes affect stormwater management on both residential and commercial properties.
In most cases, property owners or developers are required to explain their plans for stormwater management in meetings with the Site Development Staff in the Department of Watershed Management (DWM). The focus is on infiltrating the first inch of runoff onsite via green infrastructure.
New commercial projects that add impervious surface or disturb more than 1 acre of land are now governed by this law. So are commercial redevelopment projects that add or replace more than 500 square feet of impervious surface or disturb the same amount of land.
Builders of new homes on individual lots must manage the first inch of runoff onsite through green infrastructure. However, they are not required to meet with DWM staff members before their permits are approved.
The new stormwater ordinance is “a great opportunity for Atlanta. It’s a great move forward,” says Robert Bryant, a registered landscape architect with HDR, Inc.
“The ordinance will set up projects for success in the future,” says Joy Hinkle, sustainable communities associate and water specialist with Southface Energy Institute’s Eco Office. “Builders of single family homes on individual lots will have a little more work to do, but commercial developers have already been doing stormwater analysis on their properties.”
In recent years, the city of Atlanta and its suburbs have had to cope with both extremes of stormwater: drought and flooding. As in many other cities, the flooding has caused CSOs, and Atlanta had to meet EPA consent decree requirements.
Stormwater officials in Atlanta are realizing more and more often that they can install dual-purpose projects that will help with both problems. Getting stormwater to infiltrate onsite lessens or prevents flooding and CSOs. Capturing the runoff onsite also means that it will be available for irrigation.
|Photos: Atlanta Dept. of Watershed Management
Fourth Ward Park includes sculptural elements and recreational features.
Fourth Ward Park
CSOs and flooding were persistent problems in the Fourth Ward and Poncey-Highland, one of Atlanta’s oldest neighborhoods. The blighted, heavily urbanized area atop low-lying land provided the ideal conditions for runoff to make things miserable for residents.
Stormwater officials at the DWM first planned to install more grey, or traditional, infrastructure: sewer tunnels. Feedback from neighborhood residents made them rethink their plans.
The result is an award-winning park with multiple amenities that also manages stormwater through green infrastructure and alleviates the CSOs. Completed in 2010, the project cost just about $25 million with land, or just under $20 million for construction costs alone.
The green infrastructure project cost about $15 million less than a tunnel would have and delivers much more to the neighborhood. It also eases the load on aging grey infrastructure and minimizes downstream flooding.
The use of native grasses and plants means lower maintenance costs for Atlanta’s Department of Parks, Recreation, and Cultural Affairs. These plants soak up runoff and need much less irrigation, an important consideration in light of recent regional droughts.
Historic Fourth Ward Park is also the first component of a 22-mile BeltLine Greenway. This overall greenway project, which will take years to finish, is the most comprehensive economic development program ever in Atlanta.
Bryant notes that the park and the Beltline have spurred $400 million of private development adjacent to the park, once an eyesore. “This is one of the nodes on the trail,” he says.
Fourth Ward Park is an impressive first step. Stormwater from four directions flows into a 2-acre lake at the center of the park, which acts as a stormwater detention pond. It was designed to be large enough to prevent the flooding that caused the CSOs.
Each side of the park is different, but they all emphasize the flowing quality of water. Visitors see a tunnel to convey water into the pond, a water wall with sculptural elements, a step-down channel (a reminder of Clear Creek, once part of the site), and subsurface water that goes into a dry streambed.
“The whole thing was a challenge,” says Bryant. “We had to create 22 acre-feet of storage on a five-acre site, to provide for relief for combined sewers, basically enough to handle a 100-year storm—and do it in an aesthetic setting.”
Bryant calls Historic Fourth Ward Park “the most fun project I’ve ever worked on in my career.” He recalls “how well everybody worked together. The Department of Watershed Management, the Atlanta BeltLine, the citizens—all had a common goal from day one of a three-year period.”
Collaborating with a local artist enriched the work of the engineers and landscape architects. That intertwining of art and science pervaded the project Bryant says.
“From the beginning, we made it a goal that every functional engineering feature—a culvert, drain flume, porous pavement—we wanted it to be an aesthetic feature, too. We said, ‘It doesn’t have to be just a pipe. It can be a spillover waterfall or a recirculating feature,’” explains Bryant. “We never settled on just an engineering solution. We wanted an engineering aesthetic solution.”
Various natural and recreational features make up the 15 acres that surround the lake/detention pond. They include walking paths, an athletic field, playgrounds, a splash pad, a skate park, an amphitheater, and a wildflower meadow.
The American Society of Landscape Architects (ASLA) chose Historic Fourth Ward Park as a useful Case Study for Green Infrastructure and Stormwater Management. The project has won several awards, including state and national awards from the American Council of Engineering.
The Atlanta Regional Commission gave its 2012 Development of Excellence Award as well, because the park “encompasses a large, complex civil engineering and infrastructure project on par with many high-quality developments in metro Atlanta and around the United States.”
Funding for the project came from the Atlanta BeltLine Partnership Capital Campaign, the Department of Environmental Protection, park improvement bonds, and the Atlanta BeltLine Tax Allocation District. Land was donated by several financial institutions. As with many successful large projects, Historic Fourth Ward Park was a joint public and private endeavor.
The Trust for Public Land began building parcels needed for unbroken green space, as other municipal and private groups have been doing in Los Angeles, Milwaukee, and other cities.
Residents and local business owners formed an interest group that became the Historic Fourth Ward Park Conservancy.
Rock Mill Park
Located in the Atlanta suburb of Alpharetta, Rock Mill Park is another fine example of a multiuse park that also functions as municipal stormwater management. It is part of a 40-acre site owned by the city of Alpharetta.
Completed in 2007, Rock Mill Park lies within the 100-year floodplain of Big Creek. Stormwater quality treatment facilities within the park include green roofs, two enhanced swales, constructed wetlands, three bioretention cells, two sand filters, and two dropout forebays.
The most challenging part of the $2 million project was “working in and around the flood plain,” says J. Scott Talbot, registered landscape architect and principal with Breedlove Land Planning. “The park’s right next to Big Creek, which is known for flooding.”
He notes that the project’s few buildings all had to be located above the floodplain. Some of the land was built up a bit, but the earthwork had to be balanced with the floodplain.
The combination of green infrastructure features and their successful integration has proven to be highly effective in achieving the project’s goal of better water quality. Projects often aim for 80% removal of total suspended solids. Rock Mill Park has a 97% removal rate.
“Stormwater from the highest point wraps around one side, comes below through bioretention cells, goes under the parking lot, and terminates down in the wetlands,” explains Talbot. “It’s like a creek system that leads everywhere to the wetlands.”
The Breedlove Land Planning staff considered making detention areas larger, but after measuring downstream conditions they realized that doing so would actually increase the peak flows at the property line. A large upstream basin and staggering of peak times caused this effect. If Rock Mill Park’s peak flows were detained, they would reach the discharge point just when the remainder of the basin was near its peak flow. That much runoff at once would be far from the goal of predevelopment hydrology.
Even if they have heard of green roofs, many people don’t know exactly what they are, much less how they work. But after visitors at Rock Mill Park enjoy a picnic lunch in the pavilion beneath a green roof, they can step a few feet away to learn about them.
Ground-level tabletop working models demonstrate how green roofs function in stormwater management and benefit the environment. These models are set up to monitor various types of data, such as plant types, system types, growing media, and stormwater quality and quantity performance.
A 6-foot by 3-foot model contains a section with the plants from different parts of the green roof atop the pavilion. Its second section is a non-green control to test runoff rates and pollutants compared to the green roof. The third panel shows the American Hydrotech system used above.
Two other 6-foot by 3-foot models are of conventional green roofs, one with native plants and one with non-native. The fourth tabletop (8 feet, 5 inches by 4 feet, 5 inches) contains four different modular green roof sections for comparison.
As visitors encounter other stormwater features in the park, they also see detailed educational signage. They learn about natural history and wildlife of the area, the history of their city, the Big Creek watershed, water quality, and how various stormwater features work.
The signs parallel the way the park’s design emphasizes how stormwater quality treatment features are integrated for maximum effectiveness. Members of the public can readily see why sustainable stormwater management can not only work, but also enhance the environment for everyone.
An access point to the Greenway Trail, Rock Mill Park has an open pavilion, an amphitheater, a friendship path with seating, walkways, a wetlands observation deck, and a maintenance building for Alpharetta’s Parks Department. Parking is available for both trail and park users.
This astute use of green infrastructure also merited an ASLA Case Study designation. The ASLA described Rock Mill Park as “a model of cost effective, sustainable design.” The project “provides a sensible alternative to traditional (and unsightly) detention ponds and shows how multiple best management practices can be used in succession to form a comprehensive stormwater solution.”
The Rock Mill Park project also received a Merit Award from the Georgia Chapter of ASLA. Other awards include Water Resources Project of Excellence from the American Water Resources Association and Outstanding Achievement from the Georgia Chapter of the American Society of Civil Engineers.
|Photo: Breedlove Land Planning
Rock Mill Park features a pavilion with a green roof.
Reclaiming Brownfields, Catching Rain
Built on a brownfield site, the East Atlanta (Public) Library is an 8,000-square-foot building that serves as a neighborhood branch library and meeting place. All stormwater that falls on the site is managed within its borders.
Runoff flows through light-colored pervious concrete paving in the parking lot and drains into an underground retention chamber. From there the runoff is slowly released, allowing it to infiltrate into the soil.
The Eco Office is a three-story commercial building in downtown Atlanta. It serves as an office, training, and demonstration facility for green building and sustainable design for the Southface Energy Institute. The 10,100-square-foot building is a working example of efficient use of energy, water, and resource management. It is one of the most sustainable office buildings anywhere, using 84% less water and 53.3% less energy than a comparable, code-built facility would.
The Eco Office is constructed entirely from off-the-shelf materials and ordinary technologies—nothing that couldn’t be duplicated elsewhere. Its energy cost averages less than $25 per day.
Atlanta lacks proximity to a major body of water. Over 98% of the city’s water supply comes from surface water sources, so effective stormwater management for water quality is critical for all the city’s residents.
The Southface Institute’s Eco Office sets a good example. All of its onsite stormwater either infiltrates into the ground or is collected and put to good use within a flexible system.
“We love our rain catching and stormwater management system,” says Hinkle.
The property has two cisterns for collecting rainwater. The rooftop cistern collects runoff from the solar photovoltaic array through a gutter system. The runoff drains through a filter to remove particulates before it flows into the 1,750-gallon wood-clad plastic cistern.
This rainwater has several uses besides toilet flushing. It is used in the condenser unit evaporative cooling system spray, the solar PV array spray system, the compost tank spray, and the dedicated outdoor air system.
“The most interesting thing about our system is how small our collection area is, but how well it meets our needs. It’s only a small area of a solar panel on the roof, but it supplies our inside water,” says Hinkle.
|Photo: Breedlove Land Planning
The 40-acre park has enhanced swales, constructed wetlands, and other water-quality features.
Runoff flows from the Eco Office campus and the green roof downhill through a vegetated swale, which removes pollutants. It is maintained with erosion prevention tubes filled with compost and gabions filled with reused concrete riprap.
At the property’s lowest point, the runoff flows into a 14,500-gallon underground cistern via the cistern’s vegetated, permeable top. This cistern is made of plastic box forms surrounded by an impermeable membrane.
Rainwater collected in the underground cistern is used to irrigate the landscaping on the Eco Office campus. During extended times without rain, this water is also used to replenish the rooftop cistern.
“The two systems can be interconnected,” explains Hinkle. “We can switch on a pump. This interconnected arrangement has served our needs well. We have had to do that a few times during hot, dry weather.”
Not having to rely on municipal water reduces costs and increases peace of mind during Atlanta’s hot, dry summers. Having a system that would make stormwater an asset instead of a problem was an integral part of Eco Office from the first design stage.
“We definitely see an uptick in interest in harvesting stormwater, particularly on irrigation use,” says Hinkle. “Our water rates are high and our sewer rates are high, so there’s an interest in reducing potable water for financial as well as environmental reasons.”
What surprised Hinkle about the Eco Office’s rainwater collection system is “how easy it is, how you don’t notice it. There’s certainly some maintenance to this truly sustainable system, but it does not change the way we’re operating our plumbing or operating our building.”
She notes that the most challenging part of installing the rainwater harvesting systems was “a little bit of a learning curve and a little bit of administrative hurdles with the building inspector, because we use harvested water inside as well as for irrigation.”
The health department was also cautious at first because the Eco Office is a building open to the public, with many people coming and going. Fortunately, Atlanta plumbing codes were being changed at about the same time to be more flexible.
Real-time and historical data on a number of energy and water consumption metrics at the Eco Office are online through a Lucid Design Group Building Dashboard. The information is useful not only for building professionals, but also for homeowners wanting to make their houses more sustainable. Knowing the daily gallons of rainwater captured, consumed, and saved, current rainwater levels in the cisterns, and local weather conditions is useful comparative information for anyone interested in capturing stormwater for onsite use elsewhere.
The Southface Eco Office has a LEED Platinum certification from the US Green Building Council. It also meets the 2030 Challenge launched by the nonprofit group Architecture 2030 and has earned EarthCraft Light Commercial and Energy Star certifications.
Through its weekly Wednesday tours, which are open to anyone, the Eco Office staff is educating the public and construction employees about stormwater issues and green infrastructure. About 40,000 people take classes and workshops there annually.
Rainwater catchment systems are getting more attention in Atlanta because of the droughts of recent years. The Regional Business Coalition of Metropolitan Atlanta and Southeast Rainwater Harvesting Systems Association (SERHSA) have created a campaign to increase their use in metropolitan Atlanta.
The associations’ joint goal is to reduce water use by 27 million gallons per day over the next five years. Rainwater harvesting firms show past projects installed at both residential and commercial locations, in diverse applications.
“There are some good conversations going on between builders and the rainwater harvesting companies based in our state,” says Hinkle. “The companies manufacture their systems in the state, so that’s a good economic driver.”
Rainwater is harvested for irrigation at Turner Field, the home of the Atlanta Braves Major League Baseball team. The system at Oliver House, a Senior Living Center with 88 apartments, supplies all the water for toilet flushing and irrigation.
In the Atlanta suburb of Sandy Springs, stormwater runoff from the 17,000-square-foot recreation center at Hammond Park was eroding a hill beside the sports field. The solution was to collect the runoff in a 9,200-gallon tank that irrigates the groundcover on the hill. The aboveground tank teaches the public about stormwater.
Atlanta’s most influential corporate entity is Coca-Cola. One of its many sustainability projects is donating used 60-gallon syrup containers to the Chattahoochee Riverkeeper. The environmental group turns the containers into rain barrels for homeowners.
It is obvious from these innovative stormwater projects and others that Atlanta recognizes the value, both financial and aesthetic, of investing in green infrastructure. Seeing rain harvesting as an asset—especially with droughts to come—increases the value of that investment.
Author’s Bio: Margaret Buranen writes on the environment and business.