Wednesday, March 20, 2013

Where Can all the Water Go?

As municipalities and professionals attempt to envision new and innovative approaches to stormwater management, BSG has taken a leading role in searching for novel applications and effective solutions.

Many cities in the northeast corridor,  such as Philadelphia, are confronted  with the challenge of older sewer systems, which combine sanitary and storm sewage in the same piping.  While this was deemed an efficient system in previous eras, the federal EPA has begun to regulate and fine the discharges from these system into waterways like the Delaware River.  In response, an ever growing field of green stormwater management has developed, and BSG has been on the forefront of the investigation and conceptual design of new systems that can separate stormwater from sanitary flows.

The basic premise of most of these green designs is an attempt to remove a portion of the stormwater flow prior to it entering the CSO (Combined Sewer Operating) system.  This can be done in a number of ways, from diverting the flow into raingarden areas and what are referred to as Bioswales, to the development of stone storage trenches which capture and, based upon the soil conditions, either infiltrate or store and slow release the first 1” of rainfall.  This involves calculations of volumes based upon drainage areas and the development of strategies for the mitigation of green acres.

Birdsall has been instrumental in looking at alternative design strategies, such as porous paving, and the use of open space in the management  process. We have also created a design for a Curb Infiltration Unit (CIU) which can be placed flush with a curb and can divert water to feed adjacent shade trees and plantings.  This system provides a more direct means of infiltration and has shown to be of benefit to the nearby plantings.  These units can also be linked with other storage  methods to provide a larger infiltration system.

Many of these ideas have been developed as pilot projects and are now being implemented on a city wide basis.  BSG is working to remain in the forefront of these efforts and to consistently move the bar for creative stormwater management ideas that have practical applications.

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