42. Descending Wetland Pools at CSO Sites

wetland pools 4 hargraves

In reading the March 2014 Landscape Architecture Magazine’s (LAM) “Reefs Off the Shelf” article by Kevan Williams, I was inspired by the descending sequence of aquatic spaces that Mathews Nielsen designed for the East River in the Bronx.  The project and its use of soft infrastructure (wetlands and planting) to stabilize the bank and provide natural areas for habit reminded me of some of the issues that South Bend faces along the St. Joseph River.

During a rain event, South Bend collects water from many impervious surfaces: hundreds of miles of roadways, acres and acres of parking lots, not to mention buildings and structures.  This water, all 70mil gallons of it, is collected into a network of combined sewers (both sanitary and storm sewers) and treated at the Wastewater Treatment facility.  When the system cannot process that volume, it goes to the overflow sites and is discharged into the river.  Because of the larger rain events, the city is expanding the system to hold more water.  This sounds great until you hear the price tag: $650mil., an expensive project for rate payers.

Fortunately, the city is now looking at alternative solutions to the project.  I think it’s a two fold effort. 1) Reduce impervious surface; allowing water to recharge the water table and avoid collection into the system  2) implement soft infrastructure solutions like wetlands, rain gardens, bioswales, etc.

A constructed wetland (CW) is an artificial wetland created for the purpose of treating anthropogenic discharge such as municipal or industrial wastewater, or stormwater runoff.

wetland pools 3

wetland pools

There are only 30ish CSO sites.  Descending systems like the one pictured above, prevent water from immediately entering the river (slowing it substantially with check dams), filtering it through a series of pools and native planting, and establish habitat zones for animals along the banks.  This type of system also allows for a natural stabilizing of the bank slopes along the river and can be used in combination with tools like “Reef Balls”, seen below in a mangrove restoration project.

mangrove restoration.png

Like Van Valkenburg’s award winning water treatment project in Connecticut, these installations are not limited to the functional processing of storm and sanitary water.  They can also serve as value-added amenities for South Bend’s existing pedestrian infrastructure along the river.  Walking paths through the wetlands show first-hand how green approaches can used alongside typical grey ones, creating cohesive resilient systems.  It’s not enough for infrastructure projects to do just one job (move water or cars).  The cost of these projects is too high to not manage more than one issue.  Which is why the systems thinking of landscape architectural approaches must be integrated.

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