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Chicago has more than 13,000 alleys that total more than 1,900 miles of area. Those 3,500 acres of alleys consist of enough impermeable surfaces to equal the paved area at about five mid-sized airports.

Of course, those alleys didn’t begin as paved surfaces. But as Chicago grew from a town to a city, most of the gravel and dirt paths behind its buildings were paved over. Stormwater could no longer soak into the ground.

Gradually the modern alleys began to cause problems in wet weather. Rain events that lasted for days overwhelmed the city’s combined storm and sewer system. Basements of business and residential buildings flooded, overflow went into the Chicago River, and citizens complained.

Many of the usual solutions would not have been effective. Connecting sewer mains from the alleys to the city’s sewer system was cost-prohibitive. Repaving cracked alleys didn’t help. But Janet Attarian, project director of Chicago’s Streetscape and Urban Design Program in the Department of Transportation (CDOT), came up with a possible solution to the flooding.

The Green Alley Program, she explains, was “a response to flooding in alleys and adjacent property flooding due to improperly graded alleys, and Mayor [Richard] Daley’s desire to make Chicago the greenest city. Permeable pavements arose as an innovative method to address these issues without the need to add new sewer connections and, therefore, increase the burden on our combined sewer system and exacerbate the problem of basement flooding.”

The pilot project, with four designs in five locations, cost $900,000. “The funding came from our regular construction program sources—not a special source,” Attarian says.

The pilot project was fairly low key. “Just a handful of people at CDOT—approximately five—were involved in developing the green alley strategy,” Attarian recalls. “The installations were handled by contractors. No overtime or additional personnel were required.”

Construction began in the summer of 2006. Each green alley had high-albedo concrete and either recycled concrete or permeable pavement (concrete, asphalt, or pavers) as base material. Work crews graded the surfaces, pitching them so that stormwater moves toward the center of the alleys. From there, it drains into the existing street sewer system.

Underneath the surfaces are permeable layers: 1 foot of either gravel or crushed stone to trap water until it soaks into the ground. Optional inlet structures, also known as infiltration trenches, were also installed to store runoff until the soil can absorb it.

The Green Alley Program was designed to be more than just a solution to urban flooding. Its “dark-sky” street lamps reduce light pollution and direct light downward where it is needed instead of up into windows to keep residents from sleeping. The street lamps reduce energy cost and provide a white light that reduces glare and helps people distinguish color at night.

The high-albedo concrete reduces the amount of heat absorbed, breaking up the urban heat island effect. Low-impact development (LID) components, such as bioswales and vegetated swales were added where suitable. The program’s intent is that citizens can add more LID features to their neighborhoods in the future.

It was soon obvious that the pilot sites were not only successful in their locations, but worth repeating in more alleys. Asked what surprised her about this project, Attarian says, “Three big things.”

The first surprise was “the tremendous response from the design community and the public at large,” she says. “This project has proven to be transformational for CDOT and for the local permeable pavement market. Cities both around the region and around the world have spoken to us about starting their own Green Alley Programs and trying permeable pavements. I feel we have started a kind of revolution.”

Attarian’s second surprise was that the program “gave CDOT the confidence to try many new sustainable strategies, including permeable pavers in parkways, permeable parking lanes, permeable parking lots with bioswales, and ground tire rubber in our residential and arterial resurfacing mix designs.”

Her third surprise was how quickly the program “went from pilot to policy.” She recalls, “In 2006, we did the first pilots. By the next year, every alley we built contained at least one of the sustainable strategies we piloted, and that has been true ever since.”

One factor in the success of the Green Alleys Program is the way in which it was explained so clearly to the public. The major component of that public education is a publication titled The Chicago Green Alley Handbook.

This handbook won a Gold Award in Public Communications from the Illinois chapter of the American Planning Association. The American Society of Landscape Architects (ASLA) awarded the 41-page handbook its Communications Honor Award at both state and national levels for 2007.

Members of the ASLA’s professional awards jury added this comment along with their award: “Hats off to Chicago! It’s inspiring to see something this impressive come from city hall. The graphics are so simple and it communicates beautifully to its intended audience. It would be easy for other cities to replicate and we hope that they do.”

ASLA-member firm Hitchcock Design Group created the handbook entirely in-house for its client, CDOT (the municipal department responsible for LID and sustainable practices). This department, the Department of the Environment, and the consultant design team all provided input. The consultant team included Knight E/A (civil engineering), Hey and Associates Inc. (environmental engineering), and S.T.A.T.E. Testing LLC (material testing).

Hitchcock Design Group was solely responsible for the graphic design and development and the writing and editing of the text. William Schmidt oversaw the project for Hitchcock. He was surprised by “the immediate positive reaction that we received from the city staff and the public. From the beginning we knew that a public relations piece like this would be critical in developing staff and public support of the Green Alley Program,” so the favorable response was gratifying for every Hitchcock employee involved in the project.

The innovative project and its accompanying handbook received favorable publicity. “From the feedback we have received and the success of the program I think the handbook hits a home run,” Schmidt says.

The eye-catching and effective handbook has two major sections, plus a list of printed and electronic resources for people who need more information. The first section explains the four different prototypes constructed as pilot projects. Beginning with the public improvements in the alley right of way, diagrams indicate clearly what the property owners can expect to see when the city’s work on the alleys is completed. There are even polite reminders that during installation both garbage pickup and access to garages will be temporarily unavailable.

The second part of the handbook covers 11 different LID measures, including rain gardens, native plants, green roofs, recycling, and collecting rainwater for landscape irrigation. Property owners can add some or all of these LID techniques to enhance the environmental benefits of the green alleys.

These sustainable practices are explained in detail. A visual key indicates suitability for commercial, industrial, and residential properties. Cost and potential benefits for each technique are included.

The material about LID measures that property owners can add helps them buy into the city’s part of the program and understand how they and their neighbors can collectively strengthen the environmental protection efforts of their municipal government.

Photo: Chicago Department of Transportation

High-albedo concrete reduces the amount of heat absorbed, lessening the urban heat island effect.

The handbook’s final page lists Web sites and telephone contact information for Chicago’s Center for Green Technology and three municipal departments: transportation, environment, and water management. A final reminder lets residents know that they should call the Department of Transportation or their local alderman when problems occur in their green alleys.

Written for a general audience unfamiliar with concepts of sustainable development, the handbook’s tone is reassuring without being pedantic. Terms are clearly explained. At the same time, the handbook does not assume prior knowledge on the part of the residents in the green alley neighborhoods.

The handbook’s consistent style of typefaces, diagrams, and other elements of graphic design resulted in an attractive booklet that a citizen would want to keep.

The final draft of the handbook was approved in January 2007. The initial 2,000 printed copies were distributed to residents and property owners at public meetings to educate them about alley renovation in their immediate neighborhoods. Aldermen and other public officials across the city also received printed copies to generate interest in funding future green alley projects.

As the Green Alley Program expands, more copies of the handbook will be printed. It has also been put online as a PDF file.

The ASLA describes The Chicago Green Alley Handbook as “a user-friendly manual on sustainable design for a general audience.”

Hitchcock Design Group’s involvement makes an interesting story. When the project began, Schmidt had just joined the firm and wasn’t yet as busy as he is now. Hey and Associates contacted Hitchcock, asking the firm to join in on a response to the city’s request for proposal (RFP) for the project.

CDOT employees had received complaints about flooding and drainage problems in alleys. They were looking for “environmentally sustainable and cost-effective solutions,” notes Schmidt. He had a grand total of half a day to add concepts for green alleys to go into the RFP.

Schmidt, a Chicago resident recalls, “I sketched up a plan and section based on my own alley behind my house, including permeable paving, high-albedo concrete, and recycled construction materials. I also included best practices on the adjacent property, such as rain gardens, bioswales, and native trees and vegetation.”

Not bad for a half-day’s work. Several months later, CDOT staff members called Hitchcock and the other corporate members of the team, inviting them to interview for assignment of the project. Soon afterward they were awarded the project.

“Essentially, the four-hour design exercise became the basis for the green alley prototypes that were constructed, as well as the graphic principles that communicate the project goals in the handbook,” Schmidt explains.

Asked about the most difficult part of creating the handbook, Schmidt says, “Honestly, this was one of the easiest projects that I’ve had the pleasure of working on, because the project was so well organized. All the key components of the project were in place: the client and consultant team knew their responsibilities, and we had buy-in from the mayor and city staff—both critical in making something like this happen.”

Second only to Portland, OR, in the number of green roofs (including the famous one atop its City Hall), Chicago has a serious commitment to becoming a green city. This collective consciousness and enthusiastic support from the mayor is an advantage for any retrofitted project.

Schmidt notes that his city “has been on the forefront of sustainable design for years. As a result, the learning curve [for the Green Alley Program] was small, because most city staff was already familiar with most of these ‘green’ principles to some degree.”

Prototypes for the green alleys involve three different permeable paving materials: concrete, asphalt, and concrete unit pavers. Each type has been used repeatedly. As Schmidt explains, “One of the components of the Green Alley Program was the development of guidelines used to determine the most appropriate prototype design based on site-specific physical and environmental conditions.”

Chicago’s climate, with its extremes of hot summers and bitterly cold winters, affects any outdoor construction project. “All of the components of the Green Alley Program—permeable paving, dark-sky lighting, recycled materials, high-albedo paving, and so on—have been used in projects for years,” Schmidt says, but “none of them have been combined in a green alley application in Chicago’s climate.”

With this uncertainty, “It is important to do your homework up front on these projects to understand how the design and materials will perform under site-specific environmental and physical conditions,” he explains.

For the Green Alley Program, he and the other members of the project team identified and planned for such factors as “the impact of adjacent land uses, underlying soil conditions, the size of the watershed, the quality of the stormwater runoff, freeze-thaw cycles, and traffic volume” in the Chicago urban location.

Another uncertainty existed for the program. “There was little to no experience in the local concrete and asphalt plants designing permeable mixes, and paving contractors had no experience with the specialized installation methods,” he notes.

Of the possible types of permeable pavement, he says, “Permeable concrete pavers had the longest track record in our climate, but there were still very few large projects that had stood the test of time that you could point to.”

Photo: Chicago Department of Transportation

Permeable asphalt in a Chicago alley

To overcome this resistance, “CDOT and the civil engineer had to work closely with the asphalt and concrete plants and the installation contractors to design and work with these specialized materials.”

S.T.A.T.E. Testing of East Dundee, IL, experimented with the composition of the mix materials for the top layers of the alleys. Conventional hot-mix binds rock and sand tightly. Liquid asphalt doesn’t allow stormwater to drain down into the soil. The mix needed to have air voids for permeability, but the 25% suggested as ideal allowed the asphalt to leak out.

The solution was adding ground tire rubber to the mix instead of fibers. This product was not only recycled, but also saved money because paving contractors did not have to buy special plant equipment to produce it.

The concrete alleys had to withstand the weight of garbage trucks, delivery trucks, and other heavy vehicles. S.T.A.T.E. Testing used aggregates made from hard, solid rock to achieve strengths to withstand pressures in excess of 3,200 to 3,500 pounds per square inch. That measurement compares to the strength of standard concrete.

But, Schmidt says, “Even after all the up-front work it still takes a leap of faith to some degree whenever you’re doing something that hasn’t been done before. Sooner or later, you reach a tipping point where you overcome the learning curve and there is a pool of experienced contractors and material suppliers, and pricing is more in line with traditional paving.”

CDOT is monitoring the pilot green alleys to determine which designs and materials perform the best in the Chicago climate. “Future green alley projects will use this performance data to determine the best alley prototype design and permeable paving material,” says Schmidt.

Attarian says, “We are monitoring the green alley locations to see how they hold up to traffic and weather-related wear and tear, such as snow and ice, and how they maintain their permeability. So far, the results are very positive.” She notes that the program does not include measuring stormwater quality or quantity.

As for maintenance, Attarian says, “We are working on determining what kind of long-term maintenance is required and how frequently we will need perform maintenance. One of the things we will be doing this year is testing various cleaning methods and looking at permeability rates both before and after.”

“From my experience, the sustainable design movement in America has been a grassroots effort, with local government really driving the movement through the development of green standards and policies, or through the creation of incentives for private developers to incorporate these principles,” Schmidt says. “I think most municipalities are incorporating these green principles to some degree; however, it doesn’t happen without strong leadership and commitment.”

He concedes that people who are concerned about the cost of sustainable design elements in their projects have a valid point. “Clearly, some of these initiatives can come with an initial higher cost than using traditional construction materials and methods. However, if planned carefully, there can be cost offsets that balance out the bottom line.”

For example, he says, “In the case of green alleys, the higher cost of installing permeable paving was offset by [saving] the cost of installing a storm sewer with traditional impervious paving. Also, diverting this water from the municipal combined sewer resulted in a direct savings in water-treatment cost, as well as savings to adjacent property owners by reducing basement flooding.”

The long-term view is essential in considering sustainable design features in a project. “I think when you start one of these projects, you have to look at the big picture and not just the initial project cost,” Schmidt says. “With time, the up-front cost will come down as contractors become familiar with new construction methods and as supply and demand for sustainable building materials increase.”

The Green Alley Program won a Chicago Innovation Award, sponsored by the Chicago Sun-Times and Kuczmarski & Associates. These awards honor Chicago-area businesses and nonprofit organizations that develop the year’s most innovative new products and services.

Reaction to the Green Alley Program from members of the public has been favorable. “The feedback we’ve received from areas where green alleys were installed has been positive,” Attarian says, accompanied by fewer complaints about flooded basements.

Schmidt agrees on the public’s reaction. “From the feedback I’ve received, the Green Alley Program has been well received by the public. In all cases, the pilot projects reconstructed existing alleys where there were drainage problems, deteriorating pavement, or both.”

Considering all of the sustainable development features in the project, he says, “The only negative I’ve heard has to do with the dark-sky lighting that has been installed. Residents seem to have the perception that the lighting levels have been reduced.”

He adds, “My own neighborhood association has a ‘green committee’ that is responsible for green initiatives in the neighborhood. The first reaction I get after presenting the Green Alley Program is ‘How do I get one?’”

Asked to compare the Green Alley Program with other green projects she has worked on, Attarian says, “Due to the tremendous response we have had to this program, it has been very satisfying. Also, as we continue to monitor the original pilot alleys, it has proved to be very instructive about what we need to work on in the future.”

She notes that the Green Alley Program “has filtered into many of the other projects we are working on, so this year alone we will have several streetscape projects with permeable pavers and open-bottom catch basins.”