Water quality is an important issue to the communities along the corridors. Groundwater serves as the main source of drinking water to area residents, and biological natural resources are dependent upon a clean water supply.  The B2 and B5 corridors cross the high quality watersheds of the Big Rock Creek, Aux Sable Creek, Nettle Creek and Fox River.  Environmental resource agencies, the Corridor Planning Group and the Study Team have identified storm water management as a priority objective for the Prairie Parkway.  The goal is to identify sensitive water resources and avoid or minimize impacts. 

The Study Team and the Corridor Planning Group have developed an approach to the design of the Prairie Parkway corridor that exceeds the standard level of care for maintaining water quality along roadways.  The development of this approach required trade offs between the benefits of enhanced storm water management and the larger footprint those improvements require.  The study team used parcels of land that are severed by the roadway improvements and considered those areas of excess right of way suitable for locating water treatment areas.

The first step of the approach was to avoid sensitive water resources altogether by changing the location of the Prairie Parkway.  The Study team and the Corridor Planning Group also focused on locations where the Prairie Parkway crossed streams.  Locations were selected that avoided sensitive features and minimized the footprint in high quality areas.

For minimizing necessary impacts, the design will increase infiltration to maximize groundwater absorption, minimize concentrated discharge of roadway rainfall runoff into streams, and detain rainfall runoff, so it is released into the streams at the rate that wont exceed the conditions that existed before the road is built.  To achieve these objectives, the concept includes bio-swales along each side of the roadway that are designed to provide a water treatment effect of cleansing the rainfall runoff, increase the ability for the ground to soak up the rainfall, and slow the rate of release for the rainfall runoff.  This is done in an aesthetic manner incorporating a proposed multi purpose trail that meanders around and over the water quality features.

An attractive containment swale between the road and trail is planned to capture roadway runoff.  A meandering swale with a varying shape will slow flow and provide better visual effect for the driver and trail user.  The bio-swale and aesthetics is further improved with prairie plantings, and the use of deep rooted vegetation in the swale bottom which will allow the ground to soak up more runoff and recharge the groundwater.  It will also cleanse the water as it slowly flows through the grasses in the swale.  The bio-swale will include basins to capture and divert the first rain flush that often contains the salts and oils from the roadway.  Detention basins will be added to slowly release the treated rainfall.  The holding basins will also allow more time for the rainfall to soak into the ground water.  For safety reasons, the detention basins will be shallow depth and drain out within 72 hours.  Best Management Practices defined by the Illinois Department of Natural Resources will be used to assure the high quality water resources are protected.

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