Monitoring the Water Under Chicago's Sustainable Streetscapes

The Chicago Department of Transportation's Sustainable Streetscapes Program aims to turn the city's neighbourhood shopping streets, riverwalks and bicycle routes into lively, attractive places, while making infrastructure better able to support dense city living. With the Metropolitan Water Reclamation District of Greater Chicago and the Department of Transportation, the U.S. Geological Survey is monitoring the water in a south-side corridor before and after it is rebuilt: a 2-mile stretch of West Cermak Road and South Blue Island Avenue between South Halsted Street and South Western Avenue.

Green infrastructure

The programme uses urban stormwater best management practices (BMPs): permeable pavement, bioswales, infiltration basins and planters, designed to catch the "first flush" of storm runoff and let it soak into shallow groundwater instead of pouring into the combined sewer system.

A bioswale along West Cermak Road; inset, permeable pavement and a bioswale planter on South Blue Island Avenue. Photographs by J. Duncker, USGS.

What is measured

Rainfall, sewer flow, stormwater runoff, soil moisture and groundwater are monitored continuously, so engineers and scientists have measured data for conditions before and after construction.

• Rainfall. Three tipping-bucket rain gauges along the corridor record how hard and how much it rains; rainfall can vary a great deal even over an area this small.
• Sewer flow. Meters in the combined sewers record water level and flow in dry weather, when the flow is mostly sanitary, and in wet weather, when storm runoff joins it. A flowmeter in the sewer feeds a datalogger and an automatic sampler in a hut above ground, which draws water from the sewer during storms. The data let scientists work out the total runoff from particular storms. At one site, Throop Street, a slowly falling hydrograph reflects heavy sediment in the local sewer.
• Groundwater. Wells record water levels and show which way groundwater moves after rain and snowmelt. In old urban sewer systems groundwater can seep into sewers, or sewage seep out into groundwater, and where a combined sewer lies below the water table it can take in so much groundwater that it has less room for storm water.

How a sewer-flow station (A) and a well's groundwater level and specific conductance (B) responded to rain, May 20 to June 2, 2011. USGS.

The bioswale at work

Along the south side of West Cermak Road near South Throop Street, rain on the road drains to the curb and runs along it to a curb cut-out, where it flows into the bioswale and soaks into the ground instead of loading the sewer. In a storm on April 18, 2013, when about 4 inches of rain fell on the study area, water in the nearby combined sewer stayed below 2.0 feet.

A curb cut-out draining storm runoff into the bioswale on West Cermak Road. Photograph by J. Duncker, USGS.

Permeable pavers

Curbside catch basins collect runoff from paved streets and pass it through a lateral pipe to the combined sewer. Permeable pavers along the curbs let storm water soak in before it reaches the curb, reducing what drains to the sewer, and water levels in two catch basins show the difference.

Water levels in two catch basins, South Paulina Street, with permeable pavers, and South Leavitt Street, without, December 2012 to March 2013. USGS.

Sources

• James J. Duncker and William S. Morrow, Hydrologic Monitoring for Chicago's Sustainable Streetscapes Program, USGS Fact Sheet 2016–3014, March 2016, prepared with the Metropolitan Water Reclamation District of Greater Chicago and the Chicago Department of Transportation. https://doi.org/10.3133/fs20163014
• The photographs and graphs are taken from the fact sheet's PDF. Its location map, drawn on a Google Maps base, and the Department of Transportation's bioswale illustration are not reproduced here.
• Corrected: the byline's "Dunker" to "Duncker", as in the fact sheet's photo credits and record.