GAI Consultants tells how green infrastructure meets Pittsburgh stormwater challenges

Green infrastructure solutions are both functional and attractive and are coming into use more and more in Pittsburgh, PA and beyond. The water staff at GAI Consultants describe how these innovative strategies work to manage stormwater—naturally. GAI Consultants is an engineering firm headquarterd in Pittsburgh with offices throughout the mid-Atlantic, midwestern, and southern regions of the United States.

Green Infrastructure solutions are providing an effective first line of defense for meeting the substantial stormwater management challenges of the Pittsburgh, PA area. Surrounded and crisscrossed by rivers and streams, peppered with former industrial sites, and currently experiencing some of the heaviest rainfall on record, much of Pittsburgh and the surrounding region is serviced by aging stormwater-management infrastructure.

Slowing the flow
“The Pittsburgh area has a very old combined sewer system that has to convey stormwater in addition to wastewater from homes and businesses,” says GAI’s Patrick Gallagher, MBA, vice president, NE Community Development. “The system is not truly adequate for today’s demands, and as little as a tenth of an inch of rain can overload some systems with stormwater.”

North Shore Riverfront Park incorporates bioswales, reductions in impervious pavements, and vegetative water quality improvements.

Much of the quick overload of Pittsburgh’s combined sewer is due to the city’s high prevalence of impervious surfaces like concrete, which swiftly channel stormwater into the over-taxed sewers. This is where Green Infrastructure comes in.

Green Infrastructure solutions help slow the flow of stormwater by offering permeable surfaces that allow water to move below ground level, and they often provide temporary on-site storage for stormwater rather than allowing water to flow freely to the sewers. Working as a complement to traditional “gray” infrastructure—sewer pipes, tunnels, etc.—Green Infrastructure acts to ease the burden on the combined sewer, help mitigate overflow, and provide initial stormwater infiltration and filtration of sediments and contaminants.

Beauty above, business below
Green Infrastructure mimics natural processes that capture and slow stormwater. Many are marked by vegetation and other landscaping features that make them attractive to look at while they perform a valuable water-management function. A bioswale is a natural-looking Green Infrastructure solution that one might walk right by without even noticing.

 UPMC East incorporates bioswales, rain gardens, and stormwater detention ponds.

“Bioswales are engineered trenches filled with layers of soil and rock and topped by grasses or native plants—they’re often used in parking lots, public spaces, or positioned to catch roof and sidewalk runoff in housing developments,” said GAI Engineering Director David Troianos, PE. Bioswales have sloped sides that channel water downward—while the bioswale slows water flow, the plant roots and soil help filter out pollutants. “The gravel, sand, or stones at the bottom of the bioswale provide more filtration and temporary storage for the water, which can then slowly drain into the aquifer or be conveyed to local waterways through an installed drainage system,” Troianos explains.

Other Green Infrastructure solutions like rain gardens, permeable concrete and pavers, bioretention facilities, and more help reduce, slow, and filter stormwater, while solutions like green roofs—which top buildings with vegetation and other natural elements—have the added benefit of helping reduce power consumption by keeping rooftops cool.

Maintenance challenges
While effective and pleasing to eye, Green Infrastructure’s relative newness may present challenges to owners who are not staffed or skilled to perform the maintenance necessary to ensure that the solutions function properly.

“Green Infrastructure is quite different from installing a pipe in the ground, which may need only minimal attention for the next several years,” says GAI Assistant Engineering Manager Shannon Killion, PE, ENV SP. “There are landscaping considerations in many cases, and even small trash like candy wrappers can affect the functionality of Green Infrastructure. So site owners may need to assess and retool their maintenance programs to properly provide the service and attention that Green Infrastructure requires.”

Combined expertise creates effective Green Infrastructure
Effective Green Infrastructure solutions represent the collaboration of a range of disciplines. “We have hydrogeologists, civil engineers, landscape architects, GIS mapping technicians, biologists, and others working together for the various projects large and small that we work on at GAI,” says Gallagher. “We draw on more than 500 local specialists, and each Green Infrastructure collaboration is focused on creating solutions that meet PA DEP requirements, yet are also cost effective and minimize maintenance for our clients while working to provide clean water and sustainable stormwater management well into the future.”

Patrick Gallagher, MBA, specializes in residential, commercial, healthcare, institutional, industrial, and brownfield infrastructure projects including designing roadways, earthworks, sanitary and storm sewers, waterlines, and utilities, public presentations, and local, state, and federal permits.

David Troianos, PE has extensive experience in all phases of project management, construction management, and design engineering-related responsibilities for a wide range of civil engineering projects. His primary experience is in managing water, wastewater, and sewer system investigations, studies, designs, and capital improvement projects.

Shannon Killion, PE, ENV SP has wide experience in wastewater collection systems, wastewater treatment plant design, and combined sewer overflow (CSO) mitigation. She focuses on how each project fits into the client’s long-term goals, and takes projects from design conception and alternative analysis to permitting and through construction.