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Pitt Report: Fortifying Stormwater Systems With Green Infrastructure
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By Coleen P. Engvall, Research Analyst, Joint Conservation Committee

Pennsylvania experiences a lot of rain. When one considers the droughts causing havoc on the West Coast, the amount of rainfall the commonwealth enjoys is certainly a blessing. But it can also have its drawbacks.

In a report released by the University of Pittsburgh, the unique difficulties associated with plentiful rainfall and water resources are explored, as well as a way to mitigate them.

The publication, Green Infrastructure: Status Report, describes technologies that simultaneously filter and slow storm waters, preventing flooding, erosion and the pollution of waterways.

Current stormwater infrastructure focuses on moving water along as quickly as possible, but when the system is overwhelmed, environmental problems are exacerbated.

For example, waterways are subjected to more pollutants when excessive rainfall washes contaminants from topsoil and pavement into rivers, lakes and other bodies of water.

The Commonwealth’s current solution to these problems are known as “gray infrastructure.”  These consist of pipes, storage tanks, conveyance lines and sewers. The report points to how expensive these methods can be, and how easily they can be overwhelmed by excessive rainfall.

Flooding still occurs regularly, and given that Pennsylvania is home to almost 7,000 impaired waterways, the report argues additional measures need to be taken.

The report discusses eight technologies that focus on containing, filtering or guiding the storm water towards plant life or soil.

The first is permeable pavement. Currently roads, sidewalks, and parking lots all deflect water and keep it from entering the ground. If this water was able to reach the soil beneath the pavement, there would be less of a burden on the storm drains, and contaminants from the road surface would not be swept into waterways bio swales, rain gardens, green roofs, retention ponds and tree groves all deal with making space more efficient at holding and filtering water using vegetation and soil filtration.

Plants improve water retention via absorption, and they also slow the movement of water, meaning that soil has more opportunities to filter and neutralize pollutants. These technologies also help recharge groundwater sources and reduce the amount of contaminants that reach them.

Another option is rainwater harvesting, which keeps excess water from entering storm water systems. It can also lessen a property’s dependence on treated water, as the collected rainfall can be used for nonpotable applications.

The final strategy detailed in the report is called stream daylighting, which resuscitates streams that have been buried or enclosed.  Enclosed streams accelerate the flow of water and contribute to the overflow of gray infrastructure.

The report concedes that these projects will probably not replace gray infrastructure entirely, but can reduce the burden on existing systems and decrease the need for expensive updates.

The high cost of upgrading gray infrastructure is well illustrated in the example of the 2013 Wet Weather Plan developed by the Allegheny County Sanitary Authority. Their plan was to expand their gray infrastructure in order to comply with the Clean Water Act, however it had to be abandoned due to high costs.

The report points out that their current plan, which again features gray infrastructure updates, will shift an undue burden to ratepayers.

Green infrastructure projects tend to be smaller in scale, and less expensive to implement. Many of them also have added benefits. For example, green roofs can improve the air quality and temperature regulation in cities, and adding green infrastructure along roadways can safeguard nearby residents from vehicle emissions.

Green infrastructure technologies are still new, and they are faced with specific developmental challenges. For example, designers are still learning to cope with the clay soils and harsh winters found in Pennsylvania.

To help move green infrastructure towards healthy development and usage, the report emphasizes the need for leadership and coordination of research and implementation.

A copy of the full report is available online.

(Reprinted from the July Environmental Synopsis newsletter by the Joint Legislative Air and Water Pollution Control and Conservation Committee. Sign up for your own copy by sending an email to: mnerozzi@jcc.legis.state.pa.us.)


8/3/2015

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