Philadelphia’s 45 inches of annual rainfall bring the city plenty of stormwater to cope with each year. At 165 locations around the city, sewage routinely overflows into the Delaware and Schuylkill Rivers and other waterways during rainstorms. The Schuylkill supplies drinking water to 1.5 million people in Philadelphia. Both rivers are significant in the commerce and recreation of its citizens.
Stormwater management in the city focuses on “utilizing green infrastructure for CSO and stormwater control,” says Dr. Christopher Crockett, P.E., director of planning and research for the Philadelphia Water Department (PWD). PWD looks for practices, he says, that “manage a specified volume of water, either through infiltration or detention and slow release, versus focusing on designing BMPs [best management practices] for water-quality improvement.”
That isn’t easy. “Philadelphia’s dense urban environment presents many challenges to designing and constructing green infrastructure,” says Crockett. “In many parts of the city, row houses—the predominant building form—are built right to the sidewalk line. Also, in many instances, both streets and sidewalks are quite narrow, limiting what can be built within the public right of way.”
As with most cities, parking in Philadelphia is not abundant. “Any BMP that may take away on street parking spaces may be vigorously opposed,” notes Crockett.
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Photo: Philadelphia Water Department
Waterview Recreation Center |
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Photo: Philadelphia Water Department
Near Waterview Recreation Center |
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Photo: Philadelphia Water Department
Street runoff diverted into Cliveden Park is eventually treated in wetland and rain gardens. |
Add to these hurdles the congestion of existing utility lines, especially in the oldest areas of Philadelphia. And in a city that values its history and its place in the history of the nation, a sustainable design practice may conflict with a historical building’s design or function.
Other challenges to implementing low-impact development (LID) practices in Philadelphia are common to other cities. “We’ve encountered some minor challenges to greening in some neighborhoods, resulting in a need for improved education and awareness,” says Crockett. “For instance, some people may view trees as a nuisance, because they believe that all trees and plantings will create roots that can break up sidewalks or clog sewer laterals. Some people may believe that trees attract birds, which can leave droppings on cars, and the leaf drop season will require more work for residents to sweep up leaves.”
Other ongoing hurdles include educating professionals about designing and maintaining porous asphalt, concrete, and other porous materials, as well as getting alternative materials permitted into city standards or codes so developers can use them.
To better meet these challenges, stormwater management in Philadelphia has been changing in recent years. In 1996, PWD introduced the first stormwater ordinance and began explaining the concept of parcel-based stormwater billing to its commercial customers.
Changes in stormwater strategy “really started occurring after 1999, when we formed an Office of Watersheds to integrate sustainable wet weather solutions,” says Crockett. “In 2006, another major step forward occurred when we updated our stormwater regulations to require the management of the first inch of stormwater runoff for all directly connected impervious areas for any new or redevelopment with 15,000 square feet or greater of earth disturbance in the city.”
The new regulations mean that “stormwater management is part of the zoning and building permit process at its earliest stages. Developers have many incentives to include LID and other green techniques to manage stormwater in order to meet those [2006] regulations,” adds Crockett.
Developers were soon on board with the new regulations. Crockett says their acceptance resulted in quick incorporation of partial or full green or LID elements in a number of urban designs.
In 2008, PWD proposed switching its stormwater billing from an equivalent meter-based system to a parcel-based system using impervious cover. If approved, “Philadelphia would be the largest city in the nation using this approach for stormwater billing; 80% of the bill would be based on the impervious cover of the parcel, and 20% would be based on the gross area,” explains Crockett.
Implementing new billing changes, taking a greener approach, and shifting strategies are all easier to accomplish when the local environmental community and other groups become involved. PWD has found that joining forces with citizens and other governmental agencies goes a long way toward public education on stormwater issues and achieving departmental goals.
“Our preference is always that we partner and realize multiple benefits and that [as] in any city, projects that accomplish multiple benefits and involve more organizations will tend to be more successful and sustainable,” says Crockett.
One of the PWD’s significant partnerships is with Philadelphia Green, which the Pennsylvania Horticultural Society (PHS) started in 1974. Philadelphia Green is one of the oldest greening-of-the-city organizations in the entire country.
In 2003, the Philadelphia Water Department joined forces with PHS. Linking its LID stormwater projects with the group’s original purpose of restoring green areas and adding new ones meant involving more communities and residents. Working together also meant increased funding from the Pennsylvania Department of Environmental Protection’s Growing Greener Program and other sources.
“Our partnership with the Pennsylvania Horticultural Society has been invaluable,” says Crockett. “We’ve had PHS under contract for four years to help design and manage construction of demonstration projects.”
He adds, “PHS has learned a lot from PWD, and now they usually incorporate stormwater management into their ongoing planning, design, and educational activities.”
Another benefit for PWD, Crockett says, is that “PHS has great working relationships with many parks friends groups and civic organizations, so the partnership has been very successful in spreading the message about the importance of managing stormwater, particularly using green infrastructure.”
In 2005, Philadelphia Green and PWD started work on a project to address stormwater problems at seven Philadelphia schools. At S. Weir Mitchell Elementary School, children created a raised bed vegetable garden in a paved parking lot, which will not only absorb stormwater, but also reduce the heat island effect. Vegetation, infiltration trenches, bioswales, and a rain garden replaced some of the school’s 3-acre impervious site.
Another joint stormwater project, in South Philly, will include the city’s first sidewalk infiltration planters, on South 13th Street. Modeled after street planters used in Portland, OR, they are designed to reduce overflows that led to basement flooding, a persistent problem in the area. These planters, which measure 30 feet long by 7 feet wide and are 4 feet deep, will be filled with native plants suggested by members of the PHS.
In an area of 8,000 square feet of impervious street and sidewalk, infiltration of the runoff was not feasible. The project’s goal was to manage 1 inch of runoff, to let it underdrain and slowly release back into the combined sewer.
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Photo: Meliora Environmental Design LLC
Above and Below: Planter boxes receive roof runoff. |
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At the dedication ceremony for the project, Joanne Dahme, watersheds program manager in the PWD, noted that, in South Philadelphia, “during intense storms with three to four inches of rain in one hour, the sewers fill to capacity and they cannot relieve themselves the way they are designed to in the river. They are backing up in basements.”
The planters will be in the neighborhood of Columbus Square Playground. The project, which will include a rain garden at 12th and Wharton Streets, was funded by a $300,000 grant from Pennsylvania’s Department of Conservation and Natural Resources.
Also in development is the Liberty Lands Park, which combines stormwater management with the park’s master plan. Located behind a new multipurpose deck/stage will be a rain garden to accept diverted street runoff and flow from within the park itself.
“Due to site conditions, the rain garden is lined and does not allow infiltration,” says Crockett. “Water is first directed into a cistern for site irrigation, and, once the cistern is full, is slowly released into the existing combined sewer system.”
Philadelphia Green and PWD’s Cliveden Park project in East Mount Airy involved working with the city’s Department of Recreation and nearby residents and other members of the Friends of Cliveden Park. The group wanted to improve the existing rain garden, and the Philadelphia Water Department wanted the project as part of its overall efforts to manage stormwater in the Tookany/Tacony-Frankford (TTF) Watershed.
Street runoff from new street inlets was diverted into this city park, and then discharged on one side of the park into a series of stepped rain gardens or stone walls. Adding these rain gardens and stone walls at points of natural depression slows runoff flow down across the sloping park land. The runoff is directed into an existing wetland garden.
Runoff from the other road discharges directly into the wetland garden. An existing outlet structure at the park’s lowest point was modified to allow extended detention, with slow release to avoid prolonged periods of ponding. The stepped rain gardens and stone walls not only solved the stormwater runoff problem, but also enhanced the aesthetic appeal of
Cliveden Park.
Philadelphia Green and PWD created another joint stormwater project near the city’s historic Blue Bell Inn. There, three streets surround what was a vacant triangle of land. PWD wanted an early action project in the Cobbs Creek watershed.
Fairmount Park staff members and the park’s Friends group were also agreeable to the project. Philadelphia Green brought these groups together and created, with help from Meliora Environmental Design: Consulting Engineers, a space of natural beauty that pulls stormwater from the surrounding streets.
The Waterview Recreation Center stormwater project in Germantown is part of the TTF Watershed. Its goal was to manage 1 inch of runoff from a large impervious area: 12,340 square feet of street and sidewalk and 1,030 square feet of rooftop.
This was accomplished by adding three LID strategies. A 2-foot-by-100-foot infiltration tree trench parallels the sidewalk. The sidewalk was replaced with 310 feet of porous concrete. Storage volume for the two LID features totals 1,032 cubic feet. The infiltration rate is 4.5 inches per hour. The 2-foot-by-64-foot flow-through planter box handles runoff from the roof.
PWD has partnered with the city’s Recreation and Parks Departments in demonstrating the use of porous asphalt for basketball courts. “These demonstrations have led to a greater level of comfort with a previously unfamiliar material and are intended to lead to a change in standards for future recreational court construction,” says Crockett.
These porous basketball courts at Mill Creek Playground in West Philadelphia, Allens Lane Art Center in West Mount Airy, and Herron Recreation Center in South Philadelphia have garnered approval from the players for one significant reason: They’re dry enough to play on after a rainstorm much sooner than courts made of regular asphalt.
Saylor Grove Stormwater Treatment Wetland is PWD’s first project to show how wetlands can be used to treat stormwater. Part of the Wissahickon Watershed in Germantown (Northwest Philadelphia), the half-acre wetland treats the first three-fourths inch of stormwater from approximately 156 acres.
Saylor Grove was a joint project with the Fairmount Park Commission and its partners, community groups of citizens who are concerned about water quality. Park visitors can enjoy the educational walking trail with interpretive signage and natural beauty of 3,000 plants, shrubs, and trees, which also provide a habitat for birds and other wildlife.
The wetland intercepts and treats stormwater before it enters Monoshone Creek. The first 0.7 inch of every rainfall event will be sent to and treated at the wetland. Long-term rainfall data indicate that 70% of all storms measure 0.7 inch or less of rainfall. The creek and its surrounding smaller watershed are within PWD’s highest-priority zone for source water (drinking water) protection, the Queen Lane and Belmont intakes.
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Photo: Meliora Environmental Design LLC
New LID features at Waterview handle runoff from more than 13,000 square feet of impervious surface. |
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Photo: Meliora Environmental Design LLC
Sidewalks were replaced with porous concrete. |
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Photo: Pennsylvania Horticultural Society
At Cliveden Park, diverted runoff flows over stone walls into a series of stepped rain gardens. |
Monoshone Creek is a tributary to the Wissahickon Creek, which empties into the Schuylkill River, near the drinking water intake for the Queen Lane Water Treatment Plant. Because approximately 24% of Philadelphia’s drinking water comes from Queen Lane, the health of the entire Wissahickon Creek Watershed, including the Monoshone Creek, is important to all of Philadelphia.
Dr. Robert G. Traver, Ph.D., P.E., D.WRE, director of the Villanova Urban Stormwater Partnership and professor of Civil and Environmental Engineering at Villanova University, agrees with Crockett on the benefits of stormwater project partnerships. “We partner with the city, and public education is a crucial piece,” he says. “A great example is a simple missing row house where the Water Department teamed with a local school to create a ‘watershed’ where the house once stood. It has murals, a rain barrel, and a little river channel.”
Involving other groups and agencies successfully usually means matching their interests with benefits from joint projects. While finding multiple benefits from stormwater projects may be new for some cities, especially in view of tightened municipal budgets, it is long-established practice for Philadelphia.
“PWD has worked for years on promoting stormwater green infrastructure as meeting multiple benefits,” says Crockett. “The department has recently begun a ‘triple bottom line’ analysis of the benefits of utilizing a green infrastructure approach to CSO [combined sewer overflow] mitigation.”
That approach to projects means that PWD looks for “infrastructure options that offer the city operational benefits and regulatory compliance—reduce combined sewer overflows—while, at the same time, improve neighborhood aesthetics, create and enhance neighborhood amenities, reduce the urban heat island effect, and improve air quality through increased tree canopy and vegetation,” he says.
But in the city known for its Main Line, Crockett and colleagues pay attention to the bottom line. “We do expect that, by integrating our greening programs with the city’s other ongoing capital programs, such as renovations of recreation centers or street repaving/reconstruction, PWD will be able to accomplish more with the dollars we have,” he says.
Looking at the long-term return and best investment for stormwater dollars has meant that another stormwater LID technique—green roofs—is becoming increasingly popular in Philadelphia. At least 42 public and private buildings have them, and the city counts itself second to Chicago in square footage of green roofs. One of the largest green roofs in the city, over the Peco (Philadelphia Electric Company) Headquarters, measures 45,000 square feet.
Green roofs are not new in Philadelphia. The first one built, an extensive 3,000-square-foot roof atop the Fencing Academy of Philadelphia, was constructed in 1998. It was designed to treat a two-year, 24-hour storm event. Built to lower the temperature of the roof, which was reflected into the apartment of the academy’s resident manager, the roof has done its
job well.
Green roofs top such varied buildings as the $12 million renovation of the Friends Center, the Schuylkill Center for Environmental Education, Dansko Shoe Company, five townhouses at 706-726 Bancroft Street, Temple University’s Ambler Field House, the Science Center, Pennsylvania Power and Light, Comcast Center, and the central branch of the Free Library of
Philadelphia.
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Photo: Wells Appel Landscape Architects
Town Center is part of the Streetscapes pilot program. |
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Photo: Wells Appel Landscape Architects
Crescent Park, the gateway park to The Navy Yard, at the end of Broad Street |
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Photo: Wells Appel Landscape Architects
League Island at The Navy Yard |
The University of Pennsylvania has made a major commitment to green roofs. Besides the 12,000-square-foot green roof over the shopping area of the Radian, a student housing complex, other campus green roofs include those of the Hill Pavilion of the School of Veterinary Medicine, Koo Plaza at Huntsman Hall, the Claire Fagan Hall courtyard at the School of Nursing, and Kings Court English College House.
Additional green roofs at Penn will include those above the Singh Nanotechnology Center and the Horticultural Center at the Morris Arboretum. The later is Penn’s first structure planned to earn LEED Platinum certification.
Villanova University’s 3,000-square-foot green roof is part of its Urban Stormwater Partnership. The green roof is monitored for research projects by students and faculty. Other demonstration projects on the campus include an urban wetland, which treats runoff from a 41-acre site (including 16 impervious acres), a biofiltration traffic island, a porous concrete site, an infiltration trench, a pervious concrete/pervious asphalt area adjoining a parking lot, and a bioinfiltration pavilion.
Philadelphia has some exciting stormwater projects to come. Community College of Philadelphia has begun a $31 million expansion and redesign of its Northeast Regional Center. The result is expected to be the first green college facility in the city, likely earning LEED Silver status. The NERC addition will have a green roof and geothermal heating and cooling systems. Stormwater runoff from the green roof and from nearby residential homes will be used for flushing systems, thus reducing both water consumption and water entering the sewer system.
In 1996, the US Navy closed the Philadelphia Navy Yard, a 1,200-acre site at the intersection of the Schuylkill and Delaware Rivers. Located just 3.5 miles from City Hall and renamed The Navy Yard, the huge complex consists of historic buildings, including office and residence buildings, on its eastern side. Its western half contains five piers, five dry docks, enormous cranes, and heavy industrial facilities needed for ship building and repair.
Now The Navy Yard is the site of a $2 billion mixed-development that will take 20 to 30 years to complete and result in 30,000 jobs. Some of those jobs came with the relocation of Urban Outfitters to The Navy Yard.
The corporation renovated five turn-of-the-century industrial and maintenance buildings to create an 11-acre complex, the headquarters for its three national retail stores: Urban Outfitters, Free People, and Anthropologie. The Urban Land Institute named the company’s renovation as a 2007 Award for Excellence winner.
Unused rail lines became pedestrian paths. Parking areas were deliberately limited to minimize impervious surfaces, and bioswales were added to collect and filter stormwater runoff and also mitigate solar heat gain. Pits that had been used for pipe-bending were turned into ponds complete with water lilies and koi.
Now finished, Crescent Park, a public park at the end of Broad Street, is the new entrance gateway to The Navy Yard. The Town Center, which should be completed by the end of 2009, is a 10-block area in The Navy Yard’s historic district. The landscape firm of Wells Appel designed these areas, adding as many LID features as possible for stormwater management.
Town Center is part of PWD’s pilot program called Streetscapes. It will have long—30- to 50-foot—underground trenches to take runoff from the streets. “Town Center’s best feature is League Island Park,” says Joseph Sikora, RLA, a Wells Appel partner.
League Island Park—named for an historic island within the Delaware River—is “a 2.5-acre parcel physically located above the original League Island, prior to the expansion of The Navy Yard property eastward,” says Sikora.
Its main feature is a central mounded oval of lawn, which Sikora describes as surrounded by “an expansive stormwater collection system designed as a constructed wetland with native grasses [which] edge the central green. A footbridge will lead pedestrians from the perimeter walkways over the wetland feature into the park.”
The revitalized Navy Yard has green stormwater management as one of its overall goals, for both renovation projects and new construction. Bioswales, abundant open green spaces, lots of trees, and at least 27 acres of wetlands are planned. Philadelphia Industrial Development Corporation, Liberty Property Trust, and Synterra Partners are the principal firms guiding the project.
For future stormwater management in Philadelphia, Traver predicts “a continuing effort to redevelop with green roofs and street planters. If you expand outside the city, I would say incorporating more green infrastructure—rain gardens, bioswales. In 10 years, I see a greater understanding of how they work science. I think we are underusing these technologies, as we are not yet confident as to their performance.” He adds, “We need to hurry up and understand it better.”
“The trend toward sustainability has worked in our favor,” says Crockett. “An environmental consciousness has been developing in Philadelphia over the last several years, as evidenced in projects like The Next Great City initiative and the Sustainability Forum at the Academy of Natural Sciences.”
Sustainability issues became a major element of the 2007 mayoral election, and Mayor Michael Nutter appointed the city’s first director of sustainability. “With the city’s developing Sustainability Framework, one goal is to deploy green space as a public utility, which certainly supports wide-scale implementation of stormwater green infrastructure,” says Crockett.
Philadelphia has seven watersheds: Darby-Cobbs, Delaware, Pennypack, Poquessing, Schuylkill, Tacony-Frankford, and Wissahickon. A Web site devoted to them, www.phillyriverinfo.org, is a splendid example of fulfilling the EPA’s requirements for public education and public involvement.
Each watershed has its own section, with general information (geographic areas and towns included), partnership and management contacts, and a history of its integrated management plan (past and future dates, future meetings, and initiatives). Attractive photographs of sites within the watershed are interspersed with information on how individuals and groups can help, contacts for existing groups, and lists of outdoor activities available.
It has taken years to develop the long-term, integrated management plans for each of the city’s watersheds, taking a holistic approach. Three ecosystem programs—Stream Restoration, Wetlands Restoration, and Natural Lands Preservation & Protection—are aimed at improving riparian habitats.
There’s a long-term goal of making every Philadelphia stream fishable and swimmable, as it once was. That may sound idealistic, but if the progress and innovative stormwater management projects continue, that goal may be achieved.