Guest Author: Tom Barrett, GreenWater Infrastructure

This is the third article in a series about green infrastructure in Indianapolis. Having looked at Indy’s Combined Sewer Overflow issues and green infrastructure (GI) in general, we now examine one model U.S. city that has fully embraced GI controls.

Indianapolis has a sewer problem.

Specifically, our combined sewer system is overwhelmed by as little as a quarter of an inch of precipitation, allowing untreated sewage to run directly into the White River. Our chosen solution is to dig a super-deep, super-wide, super-long Super Tunnel to hold it all.

When faced with a similar problem in 2011, the City of Philadelphia took a very different approach: The city signed a partnership agreement with the EPA to collaborate on developing green infrastructure technologies in Philadelphia.

As a result, in 2012, Philadelphia embarked on a landmark 25-year, $2 billion urban watershed project, funded by the EPA, and designed to transform Philly’s outdated stormwater management system into a national showcase for new green infrastructure.

Then, in 2014, the EPA funded an additional $5 million urban watershed evaluation initiative to use Philadelphia as the pilot area. The city was ready to begin its green infrastructure transformation.

The Critical First Step

First, in order to ascertain the best infrastructure alternative to resolve their runoff issue, the Philadelphia Water Department compared the costs and benefits of each potential approach. The results of more than two years of engineering and economic analysis are depicted in the following graphic:

As you can see, building large-scale storage (i.e., tunnels) was determined to be one of the least effective options. While it would meet the overflow policy goals and some of the watershed planning goals, it was deemed less affordable and scalable than the other options.

In addition—and equally important–the “big tunnel” solution provided virtually no economic, social or environmental benefits.

On the other hand, the “Green Stormwater Infrastructure with Targeted Traditional Infrastructure” approach met all of the city’s criteria, including economic, social and environmental benefits.

Needless to say, the green solution was the approach selected for implementation by the Philadelphia Water Department.

It’s an approach which has required the development of intensive, large-scale green infrastructure projects.

Green City, Clean Waters

As a result, Philadelphia’s “Green City, Clean Waters” program was launched in 2011 to develop the city’s green urban watershed infrastructure. The program’s goal was to reduce the amount of stormwater pollution entering its combined sewer system by channeling precipitation into open ground, where soil and vegetation provide natural filtration.

The 25-year initiative is the first green-centric plan in the U.S. to gain acceptance from the EPA and the Pennsylvania Dept. of Environmental Protection (the regulators responsible for protecting local drinking water sources).

The total cost of Philly’s green infrastructure plan is estimated at $1.67 billion over 25 years.

Here’s a rundown of the tools Philadelphia has used to implement its Green City, Clean Waters initiative:

  1. Constructed wetlands.

    Similar to a retention basin, stormwater wetlands collect runoff and store it in a permanent pool; however unlike a retention basin, wetlands are shallow and populated by marshland vegetation. This helps treat the water and allows pollutants to settle to the bottom. Philadelphia built these wetlands in city parks and other public spaces. As of 2016, 20 green parks had been completed, with another 55 in the design phase.

  2. Porous pavements. In addition to repaving parking lots, and school yards with water-absorbing materials, the Philadelphia Water Department collaborated with the Philadelphia Streets Department to create Philly’s first porous “green streets.” To date, 111 green streets have been created, with another 124 in the design phase.
  3. Stormwater bump-outs. A stormwater bump-out is a vegetated curb extension that protrudes into the street either mid-block or at an intersection, creating a new curb some distance from the existing curb. A bump-out is composed of a layer of stone that is topped with soil and plants. An inlet or curb-cut directs runoff into the bump-out structure where it can be stored, infiltrated, and taken up by the plants. Philadelphia was the first to experiment with these on a large scale.
  4. Stormwater tree trenches. A stormwater tree trench is a system of trees that are connected by an underground infiltration structure. On the surface, a stormwater tree trench looks just like a series of street tree pits. However, under the sidewalk, there is an engineered system to manage the incoming runoff. The runoff is stored in the empty spaces between the stones, watering the trees and slowly infiltrating through the bottom. Philadelphia is using tree trenches extensively throughout the city.
  5. Stormwater planters. A stormwater planter is a specialized planter installed in the sidewalk area designed to manage street and sidewalk runoff. The top of the soil in the planter is lower in elevation than the sidewalk, allowing for runoff to flow into the planter through an inlet at street level. These are being used along with permeable pavements to improve stormwater runoff along Philly’s streets and parking lots.
  6. Green roofs. A green roof is a roof or section of roof that is vegetated in order to collect and absorb stormwater, thereby reducing the amount of runoff from the site. Philadelphia is now the number three city in North America for total amount of green roof square footage, trailing only Washington, D.C. and Toronto, Canada.
  7. Rain barrels/cisterns. A rain barrel or cistern is a structure that collects and stores stormwater runoff from rooftops. The collected rain water can be used for irrigation to water lawns, gardens, window boxes or street trees. Rain barrels are one of the key GI tools being used in Philly’s neighborhoods.
  8. Rain gardens. A rain garden is designed to collect runoff from impervious surfaces such as roofs, walkways, and parking lots, allowing water to infiltrate the ground. The site is graded appropriately to cause stormwater to flow into the rain garden area from the nearby impervious area. The water is used by the vegetation, and infiltrates into the subsurface stone and soil. The Philadelphia Water Company has been instrumental in building rain gardens throughout the city’s neighborhoods.
  9. Flow-through planters. A flow-through planter is a structure that is designed to allow stormwater from roof gutters to flow through and be used by the plants. They temporarily store stormwater runoff on top of the soil and filter sediment and pollutants as water infiltrates down through the planter. This is another tool being used extensively in Philadelphia’s residential areas.

Altogether, almost 3,000 residential projects have been completed as part of Green City, Clean Waters. Each of the projects utilize several of the above-listed green infrastructure tools.

Has It Worked?

The ultimate long-term goal of Green City, Clean Waters is an 85% reduction in stormwater pollution entering the city’s waterways by the year 2036.

Within the first five years, Philadelphia had to show that it could build 744 “Greened Acres”—a term used to describe the volume of stormwater managed with green tools. The program has exceeded that five-year goal.

As of June 1, 2016, Philadelphia had gained 837.7 Greened Acres, resulting in more than 1.5 billion gallons of polluted water being kept out of its rivers each year.

The program is well on track to achieve the next big milestone: 2,148 Greened Acres by 2021—nearly three times what the city has accomplished so far, and enough to keep an additional 2 billion gallons of polluted water out of its rivers annually.

The following video highlights the Green City, Clean Waters five-year benchmark:

Side Benefits

But the benefits achieved through the Philadelphia initiative extend far beyond the stormwater management issue. Specifically, the program has also allowed the city to reap some immediate rewards. Such as:

  • Improving the appearance of city streets
  • Increasing the access to and improving recreational opportunities along green corridors
  • Preserving open spaces
  • Converting vacant and abandoned lands to open space and responsible redevelopment
  • Creating high-value new jobs for residents and attracting workers and businesses to the city. (430 new jobs have been added, growing the green infrastructure market by 14%.)
  • Calming traffic and increasing pedestrian safety through use of stormwater bump-outs
  • Increasing property values by beautifying neighborhoods
  • Combating extreme summer heat (i.e., “urban island heat”) through tree planting
  • Creating natural habitats for indigenous species to thrive

In addition, after 45 years, the Green City, Clean Waters program will have generated more than one dollar in benefits for every dollar invested by PWD, representing a net economic gain to the city.

In short, Philadelphia’s plan is transforming the city into an oasis of rain gardens, green roofs, treescapes, and porous pavements, which advocates say is cheaper than tunnels and makes for a more liveable, prettier city with higher property values and better community health.

Collaboration Is Key

All of these projects are initiated, funded, designed, constructed, inspected, and maintained by the Philadelphia Water Department or one of its partners (including the EPA). And Philadelphia’s program involves a broad coalition of partners.

For instance, the program employs local firms to design and maintain the green stormwater infrastructure. The water department has worked with businesses, interest groups, citizens, civic associations and neighborhood groups, watershed partnerships and various committees.

It has also partnered with AmeriCorps to train young people for the green infrastructure jobs.

How Does Indy Compare?

On a much smaller scale, the City of Indianapolis encourages the use of green infrastructure in the private sector, through its SustainIndy program. Right now, Indy has:

  • Approximately 12 buildings with green roofs,
  • Two “RebuildIndy” projects which used permeable pavements,
  • Two large cistern projects at company headquarters; and multiple smaller cisterns
  • Plus several sites, such as the Cultural Trail, which utilize multiple green infrastructure tools.

In addition, the SustainIndy website offers the following:

  • A Raingarden Resource Center which connects residents, businesses, and institutions with the resources and tools to design and build their own rain gardens.  Includes brochures and planting plans.
  • A Native Planting Resource Center which connects residents, businesses, and institutions with the resources and tools to design and build their own native garden or native planting area.  Includes brochures and planting plans.
  • A link to the Department of Public Works’ Adopt-A-Median program.
  • A Green Infrastructure Grant Program to promote the construction of green infrastructure (specifically, green roofs, porous pavement and rain gardens). This grant program is a partnership between the city and United Water. Non-profit organizations can apply for up to $20,000. For-profit entities are also eligible with proper approval. (A total of $100,000 was awarded in 2010.)

Keep Indianapolis Beautiful has also been working hard within Indy’s neighborhoods for the past 40 years. In 2016 alone, KIB engaged almost 20,000 volunteers in planting 2,839 trees, collecting 2.1 million pounds of litter, and completing five greenspace projects.

These efforts are highly commendable. But what Indy doesn’t have is a comprehensive green infrastructure program in place.

So, What’s the Problem?

Unfortunately for Indianapolis, there’s no going back with regard to the giant “DigIndy” tunnel; that ship has sailed. But that doesn’t mean alternative green infrastructure programs can’t also become more prominent.

What distinguishes Philadelphia from a lot of cities is the scale of the commitment to green infrastructure that it has demonstrated. For example, Philadelphia provides much larger incentives for the development of green infrastructure projects than Indianapolis currently does ($100,000 per impervious acre managed as opposed to $20,000 per project).Philadelphia’s program was a truly collaborative effort between the public and private sectors. Clearly, Indianapolis needs more partnerships if any green infrastructure initiative is to succeed.

Perhaps the City of Indianapolis should take advantage of low-interest federal loans available through entities such as the EPA’s Clean Water State Revolving Fund (CWSRF). That way, it could offer higher incentives to residents and businesses for developing green infrastructure.

What Can You Do?

Unless or until the City of Indianapolis (and the state of Indiana) allocates more tax dollars to develop green infrastructure on public lands, and/or incentivizes the private sector to do the same, Indianapolis residents must rely on their own resources to promote green infrastructure within their city.

To that end, if every household and business within the Marion County metropolitan area could implement one green infrastructure tool (whether it be as grandiose as a green roof or as simple as a rain barrel), how much impact would we have on our city’s stormwater overflow?

As a result, in 2012, Philadelphia embarked on a landmark 25-year, $2 billion urban watershed project, funded by the EPA, and designed to transform Philly’s outdated stormwater management system into a national showcase for new green infrastructure.

Then, in 2014, the EPA funded an additional $5 million urban watershed evaluation initiative to use Philadelphia as the pilot area. The city was ready to begin its green infrastructure transformation.


Philadelphia Water Department,


Keep Indianapolis Beautiful,