Opportunity
The city of Philadelphia draws its drinking water from two rivers, the Delaware and the Schuylkill, that were once severely polluted. The Delaware River, which at one time could not support aquatic life, is now home to about 42 species of fish. The Schuylkill River is also dramatically cleaner, offering safer drinking water and new economic and recreational activities.
Much credit goes to the Philadelphia Water Department, whose three water pollution control plants remove approximately 92% of pollutants from wastewater before it reaches the two rivers. The department spends about a quarter of a billion dollars each year to protect the region’s watersheds and improve its infrastructure.
Like many cities in the United States, Philadelphia has ailing infrastructure that needs attention and innovative approaches to bring it to current standards. The Philadelphia Water Department seized the opportunity not only to improve its infrastructure but help revitalize the city. Infrastructure modifications and regulatory compliance will drive environmental, social, and economic improvement.
Solution
In 2009, Mayor Michael Nutter of Philadelphia announced Greenworks, an ambitious plan to make his city the greenest in the country. Among the Greenworks initiatives was an infrastructure improvement program and compliance plan called “Green City, Clean Waters.”
Mott MacDonald has used its expertise to support Philadelphia’s forward-looking combination of sustainable green approaches to regulatory compliance and sophisticated strategies for upgrades and maintenance.
Our services have included conceptual planning, field location surveys and mapping, geotechnical engineering, CSO engineering, advanced pipeline rehabilitation, green stormwater design, alternate project delivery methods, contract plans and specifications, construction documents, construction cost estimates, and work practice improvements.
Pipeline replacement, rehabilitation, and relocation
Mott MacDonald has designed approximately 46,000 linear feet (14 kilometers) of replacement water mains in Philadelphia, and over 30,000 linear feet (9 kilometers) of sanitary sewer replacement. Water mains have ranged from 6 to 36 inches (15 to 91 cm) in diameter, and sewers have ranged from 12 to 86 inches (30 to 218 cm) in diameter. Thousands of linear feet of water transmission mains have been improved by cleaning and cement-mortar lining throughout Philadelphia.
These are examples of the many water main replacement, rehabilitation, and relocation projects Mott MacDonald has conducted for the Philadelphia Water Department:
Manayunk water main replacement
We provided design for the replacement of 1,907 linear feet (581 meters) of water main varying in diameter from 6 to 12 inches (15 to 30 cm), and 2,200 linear feet (670 meters) of accompanying sanitary sewer.
The project included surveying the existing utilities, managing any potential conflict, and providing construction cost estimates and contract bid documents.
Southwest Philadelphia water main rehabilitation
Mott MacDonald was retained to assist in the rehabilitation of approximately 8,600 linear feet (2.6 kilometers) of water transmission mains with diameters of 30, 36, and 48 inches (76, 91, and 122 cm).
The project included the cleaning and cement-mortar lining of the mains, replacement of large-diameter valves, upgrades of distribution main connections, and installation of internal joint seals.
Thompson Street water main relocation
In order to accommodate the construction of other infrastructure, approximately 1,200 linear feet (366 meters) of 48-inch (1.2-meter) water transmission main was relocated. The project required designing a pile support thrust block and cradle system for a site congested with buried infrastructure.
Combined sewer overflows
Moore Street
Until recently, when heavy rain fell on the Pennsport area of Philadelphia, it had nowhere to go but into the Moore Street flood relief structures — or into the Delaware River.
Approximately 98% of the 37 acres (15 acres) around the Moore Street Drainage Right-of-Way was impervious, including Columbus Boulevard, Pier 70 Boulevard, and the buildings and parking lots of major retailers along the river: Target, Lowe’s, Home Depot, Walmart, Old Navy, and others.
As the primary design consultant, Mott MacDonald worked closely with the Philadelphia Water Department Design Branch and the Office of Watersheds to meet the goals of flood relief, reductions of CSOs, and separation of storm sewers from sanitary sewers.
The Moore Street Drainage Right-of-Way includes about 1,300 feet (396 meters) of reinforced-concrete-pipe sewer, a new regulating chamber, and an outfall structure. The regulating chamber needed to be relocated and modified in order to accommodate future CSO control gates and an associated control system, which would reduce combined sewer overflows by allowing in-line storage.
Northern Liberties flood relief
This project involves the construction of approximately 3,600 feet (1.1 kilometers) of new 8 x 10-foot (2.4 x 3-meter) box sewer in Germantown Avenue and Master Street to provide flood relief to the Northern Liberties section of the City. This sewer will connect into a new distribution chamber at the intersection of Germantown Avenue and Wildey Street.
Sewer rehabilitation
Rock Run inflatable dam
Mott MacDonald was retained to provide civil, structural, mechanical, and electrical design for the installation of an inflatable rubber dam that would block an 11-foot-diameter (3.3-meter) combined sewer outfall during heavy rains.
Based on level signals in the city’s sewer system, the rubber dam may be inflated to direct flow to an interceptor sewer. A separate below-grade chamber houses the blowers and valves that control the rubber dam.
Neill Drive CIPP phase 2
This project is located within a drainage right-of-way from Conshohocken Avenue to the Neill Drive Pumping Station, and includes the placement of a cured-in-place pipe lining within approximately 4,800 linear feet (1,463 meters) of gravity sewer and force main.
Tacony sewer CIPP phases 1 & 2
This project is located adjacent to Tacony Creek from Rising Sun Avenue to Ramona Street, and includes the placement of a cured-in-place pipe lining within approximately 9,490 linear feet (2,892 meters) of sewers.
The second phase of the Tacony Creek interceptor lining program includes placement of a structural cured-in-place pipe lining within approximately 4,600 linear feet (1,400 meters) of vitrified clay sewer, approximately 1,800 linear feet (549 meters) of reinforced concrete, and approximately 2,600 linear feet (792 meters) of brick sewer.
Walnut Lane outfall reconstruction
A 24-inch (61-cm) outfall that crosses a fairway on the Walnut Lane Golf Course, then discharges into a stream, was found to be in poor condition and partly collapsed.
We coordinated with the Fairmount Park Commission to design a replacement of the outfall with 250 feet (76 meters) of 30-inch (76-cm) pipe, construction of a new outfall headwall that would blend in with the golf course, and energy dissipation and erosion control features downstream from the outfall.
Process improvement and project delivery
Mott MacDonald has worked with Philadelphia for over 17 years and has become an integral part of the planning and engineering process. This has allowed for collaborative efforts to improving utility processes and systems. A few of these improvements are outlined below.
Bid document improvement
Mott MacDonald was retained in 2012 to develop improvements to specifications used in bidding. Effort led to standardization and consistency that ultimately will lead to enhancements to the bidding process and built systems.
CIPP requirements/find-it fix-it contract delivery
In order to meet a Consent Decree, the Department was required to install a designated number of miles of lining before a regulatory deadline. we developed a contracting approach to accelerate project delivery, increase speed and flexibility, and achieve needed production targets.
Drawing standardization
Mott MacDonald was retained to develop infrastructure design standards and AutoCAD layers systems to improve the design processes for the Department. This work streamlined and automated several areas of design services and was adopted by the Department’s consulting community. We offered complete services, including manuals and system training, to other consultants.
Hydrant location, assessment, and abandonment
The City needed a rapid approach to locate, concept design, and contract the abandonment of almost 1,000 high-pressure fire hydrants. We created a process for locating and documenting sites with geocoded and tagged photographs, and combined this with a novel contracting method to fulfill this large fast-tracked assignment.
Work practice improvements
The trust and long-standing relationships developed by Mott MacDonald have led to numerous instances when we has been consulted for input to design, construction, and operations. Workshops, charettes, and other consultation often led to modifications of practices at the Department, leading to process improvements.
Green Streets
Northern Liberties
Mott MacDonald was retained in 2009 to prepare final design plans and specifications for several Green Streets projects in the Northern Liberties section of Philadelphia. Stormwater control measures included bump-outs, infiltration trenches that water trees with stored stormwater, and sidewalk planters that collect drainage from the street.
We selected native species for planters and sidewalk trees, modeled stormwater devices, resolved constructability issues where new measures were near existing structures, and considered durability and maintenance in the design.
West Philadelphia
Mott MacDonald was also retained in 2010 and 2011 to assist with Phases IV and V of a Green Streets program in West Philadelphia. Each phase included measures applied to schools, parks, playgrounds, and other locations in the area.
For Phase IV in West Philadelphia, we redesigned the standard Dual-Trap inlet to eliminate the need for three separate inlets at a low-point intersection. Mott MacDonald provided efficient modeling of stormwater devices, developed construction documents, and resolved constructability issues. Piezometer wells were used to collect data and analyze the groundwater recharge effects of the project.
For Phase V, Mott MacDonald redesigned a traffic island into a multi-pool rain garden planted with native grasses and shrubs. Runoff is conducted into the rain garden through decorative trench drains connected to the street through curb cuts.
We also designed tree trenches within the sidewalks, including waterproof barriers where trenches were close to buildings and utilities. Raised planter boxes captured street runoff, enhanced the streetscape, and provided a teaching tool for a nearby school.
Outcome
Mott MacDonald's projects to implement green technologies and advance infrastructure renewal have a number of expected benefits:
- Reducing flooding and waterway impairments
- Contributing to improvements in the environment and social fabric
- Accelerating and stabilizing the renewal of critical infrastructure
- Fostering collaborative processes between public and private entities to advance work practices and project delivery
- Reducing the number and volume of combined sewer overflows in the average rainfall year
- Reducing the amount of pollution reaching the Delaware River
“Our commitment to sustainability is making Philadelphia a green city, attracting clean tech companies and increasing quality of life in our neighborhoods,” said Mayor Nutter in 2011. “Our great progress toward Greenworks goals not only benefits us today, but also sets the stage for Philadelphia to thrive in the future.”