As the frequency of “historic” rain events has picked up over the last decade or so – the Chicago area began seeing larger storms and more frequent street and basement flooding beginning around 2008 – local governments as well as agencies such as the Metropolitan Water Reclamation District of Greater Chicago began tightening storm water management rules.

From the perspective of those looking to build new residential and commercial developments, those rules have meant increased costs to build underground storm water detention facilities or invest in green infrastructure to manage runoff.

In some cases, those costs have resulted in even relatively simple improvements – like repaving crumbling parking lots – being put off due to the cost of the storm water management requirements.

The village of Brookfield in recent months, recognizing its strict rules were preventing some projects from getting off the ground, eased some of those requirements.

But, getting developers to invest specifically in green storm water management initiatives – rain gardens, permeable parking lots, green roofs and other strategies that divert storm water away from sewer systems – has still been difficult.

That’s where a new program resulting from a partnership by The Nature Conservancy and the Metropolitan Planning Council comes in. 

Known as “StormStore,” the pilot program is a storm water credit trading initiative specifically targeting the Lower Des Plaines River Watershed, which includes the Landmark’s coverage area, and the Little Calumet River Watershed.

StormStore is intended to encourage the construction of sustainable storm water management infrastructure in areas that need it most. The program allows both private developers and public entities to ability to either purchase credits to satisfy a portion of their storm water requirements or create a market for others to purchase credits from them.

“This allows communities to take more control over how they’re managing urban flooding,” said Ryan Wilson, manager of water resources for the Metropolitan Planning Council, an 86-year-old organization devoted to, according to its website, “shaping a more equitable, sustainable and prosperous greater Chicago region.”

“It allows development to happen where there’s already [storm water management] capacity,” he added.

A developer, for example, could purchase credits from another entity within each specific watershed to help fulfill storm water management requirements. The deals are private, but they don’t replace a developer’s duty to address storm water runoff.

“For detention, they have to meet certain specific standards that take into consideration the site and sewers,” Wilson said. “This pilot does not give up that responsibility. You have to manage storm water onsite, and if you do that, you can send that capacity to another place.”

StormStore was made possible by a recent change in the MWRD’s own Watershed Management Ordinance. In May, the MWRD board voted unanimously to amend the ordinance to allow for storm water credit trading.

That change came after being shown the benefits of the credit trading program by the Metropolitan Planning Council and The Nature Conservancy, a nonprofit with an international reach that’s focused on conservation issues for more than 60 years.

“About five years ago, The Nature Conservancy decided it needed to reevaluate what it considered ‘conservation,'” said Jen Jenkins, natural infrastructure project manager for The Nature Conservancy’s Illinois chapter.

The group began focusing on urban spaces, creating an urban conservation team and coming up with a “greenprint” that assessed risk factors like urban flooding.

“We saw StormStore as a tool to encourage private investment in green infrastructure and make sure it’s going where it’s needed most,” Jenkins said. “It’s a tool to help redirect capital into those areas” that historically have suffered from disinvestment.

The program is also an opportunity for public entities such as municipalities, school districts and park districts to invest in green infrastructure, building additional capacity that those entities can sell to private developers seeking to meet local storm water requirements.

Riverside recently built a permeable paver parking lot for commuters, and Riverside School District 96, if the program had been available before now, might have taken it into account while planning for the ongoing work to expand buildings and reconfigure parking areas at its schools.

“You don’t have to rely on large pieces of land to add value and mitigate flood impact,” Jenkins said.

More information is available at the Metropolitan Planning Council’s website.