49. Near Northwest Neighborhood Retention Basins

Cities around the country are directing stormwater to vacant lots as a method to manage the issue of system capacity and treatment.  But when you’re trying to address a 40 million gallon capacity issue, like South Bend, you have to create 713 installations like this (750 sqft basement footprint x 10 ft height equals approximately 56,100 gallons of capacity; 40M divided by 56,100 equals 713 locations).  Rain gardens on vacant lots run into a couple of issues: 1. Landuse become precarious if you want to redevelop an area and don’t have a way to mitigate the lost capacity 2. Maintenance of bioretention is something of a quandary for municipalities who primarily use vacuum trucks to clean the current engineered stormwater pipe systems.

NNN Rain Gardens

As we mentioned in yesterday’s post, density should not be the only driver for development in cities.  While the Portage Ave. corridor is a logical location for the next Main Streets Master Plan, several parcels (both along Portage Ave. and throughout the Near Northwest Neighborhood) should be considered as potential biorentention areas. Because many of these locations are at grade, a curb cut and minimal excavation would be required to create detention/retention ponds.  Linking a series of these locations together, both in this neighborhood and other locations around the city (Bowman Creek)

  1. Size Matters: These locations are larger than your average single family house footprint. Using larger areas like these means fewer overall installations.
  2. Elevation Matters: Water flows downhill. If you are going to direct stormwater collected at the streets toward new retention areas, they cannot be higher than the elevation at the street.  These locations, while still needing excavation for capacity, are at street level, making the installation easier.  The excavated soil could then be used to create interesting landform berms or as topsoil in other areas.
  3. Design Matters: Don’t just create retention ponds; use the space to add multiple layers of benefits to the community.  Create walking bridges and overlooks; create learning kiosks and signage; create places that foster pollinators and other urban habitat zones.

It’s tempting to add housing or mixed-use along this entire corridor and throughout the neighborhood, but unless we integrate strategies like this into the development of these places, our cities will continue to face the same problems.  Stormwater management at the top of that list.

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