The results presented in this paper summarize a small portion of the full project activities associated with the National Demonstration of Advanced Drainage Concepts Using Green Solutions for CSO Control Project in Kansas City, funded by the USEPA Office of Research and Development, Urban Watershed Management Branch. Runoff monitoring was conducted in the combined sewer system at several locations in the test and control watersheds. Events were monitored after the sewer was re-lined, and these data were used as a new baseline condition. WinSLAMM evaluated the test (pilot) and control watershed conditions during the two monitoring periods (post re-lining, as the new baseline versus after construction of controls) to verify the rainfall-runoff calibration based on site development characteristics and the actual rains monitored.
The Kansas City GI demonstration project site is unique because a very large portion of the test (pilot) area receives direct treatment from many separate stormwater control devices, and the large area was monitored to demonstrate the actual flow reductions. However, as in all retrofit installations, stormwater controls could not be placed to treat all the flows from the entire watershed area because of interferences from existing infrastructure, large trees, and surface drainage paths. More than 135 biofilter controls (large curb cut biofilters, bioswale, porous sidewalks, and rain gardens) were installed in the 100 acre test watershed. The after-construction flow ratios (comparing the test to the control area flows) were significantly smaller (p = 0.004) compared to the before construction baseline flow ratios. The overall flow reductions were found to be about 70% less in the test area compared to the control watershed area for the runoff events monitored after the construction of the stormwater controls. The calibrated WinSLAMM analyses resulted in close agreements for both the baseline and the after installation events.