Record rain totals call for innovative solutions. During the third consecutive year of record precipitation for the month of May in Chicago, the Metropolitan Water Reclamation District of Greater Chicago (MWRD) amended its Watershed Management Ordinance (WMO) to incorporate a regional stormwater detention and volume control trading program. Under this pilot study, developers could enter into agreements with offsite landowners to meet WMO permit stormwater requirements, as long as both projects are in the same watershed.

The Lower Des Plaines River Watershed, which extends as far north as Wheeling and south to Willow Springs and Little Calumet River Watershed, covering south Cook County, were selected for the study because of the large size and lower release rates in these planning areas. The release rates determine the amount of the detention needed on each development site, as required under the WMO. The more impervi- ous surface on the site, the more detention is required to meet the prescribed release rates. Due to the extent of flooding experienced in the Lower Des Plaines and Little Calumet River watersheds, developments in these areas typically require more stormwater detention than similar developments in other watersheds.

“Flooding is becoming more frequent and more severe, requiring new ideas and innovative solutions,” said MWRD Commissioner Kimberly Du Buclet. “Our amendments to the Watershed Management Ordinance can both help manage flooding and promote economic development.”

The stormwater credit trading program is the latest addition to the MWRD’s landmark WMO, which was enacted in 2014 to regulate sewer construction within MWRD’s service area and development within sub- urban Cook County. The WMO abates the negative impacts of stormwater runoff resulting from new development or redevelopment. It also provides uniform stormwater management regulations to prevent future commercial, municipal, and residential development and redevelopment projects from exacerbating flooding and protects environmentally sensitive areas.

Stormwater management incentive programs have been launched in places like Washington State, Los Angeles, Detroit, Philadelphia, Washington, D.C., and the Gulf Coast states where stormwater management investments were made to leverage funds from the Deepwater Horizon oil spill. But few of these innovative programs allow detention trading like the MWRD. The policy gives both public and private developers new options to meet WMO permit requirements, and it could help optimize placement of stormwater management to mitigate flooding and improve local water quality. The trading program can benefit developers, municipalities, affordable housing developers, engineers, planners and architects, non-profit landowners and larger institutions like schools and hospitals or even community members who have a local project in mind.

Now through Jan. 1, 2025, projects located within these two watershed planning areas do not need to demonstrate site limitations and constraints to be able to participate in detention and volume control trading. However, certain requirements outlined in Article 5 of the WMO must be met. For an existing detention facility to qualify as a supply site, a Watershed Management Permit is required to demonstrate a new area that was previously not detained is now tributary to the detention facility. For more information, visit Watershed Management Ordinance Permit Application Submittal System (WPASS).

Stormwater Detention_July_20.pdf