When you hear the words "storm water management," trees are likely not the first thing you think of. However, a tree canopy restoration program is a central focus of the holistic approach by the Metropolitan Water Reclamation District of Greater Chicago (MWRD), the agency responsible for the reversal of the Chicago River as well as the treatment of much of our region’s wastewater who is now giving away free 18 inch oak saplings for anyone who wants them.
Cities like Chicago have a legacy of older infrastructure, notably the combined sewer system in which the storm water from the street mixes with the refuse from homes and businesses known as sanitary water. For most of the time, the system preforms just fine, but when we have periods of heavy rain as is common in the Upper Midwest, and is becoming more common courtesy of climate change, the system is overwhelmed. When the sewer system exceeds capacity, the sewage then gets dumped into the Chicago River as well as other local waterways and may back up into the basements of local buildings. It was for this reason that the Chicago River was reversed in the first place in 1900 through the excavation of the Sanitary and Ship Canal to send the dirty water away from Lake Michigan. A single inch of rainfall across the service area of MWRD which spans most of Cook County, will yield as much as 16 million gallons of storm water.
And this is where the trees come into play, as they serve as a preventive measure to reduce the amount of storm water entering the sewer system. Each medium sized oak tree can absorb as much as 2,800 gallons of rainfall per year. 10,000 additional trees means 28 million gallons of storm water annually is not entering the sewer system. While this concept is not new, in fact the city had offered zoning bonuses for green roofs between 2004 and 2016, the tree giveaway is a new concept that has proven to be popular.
The program started in April and 10,850 trees had already been given away through the end of June. The primary intended recipients include municipalities, schools and community groups; but trees are also available through giveaways at open houses, community events and every Wednesday morning at six of the area’s wastewater treatment plants. Those receiving the trees may pick them up in bags of 100 bare root saplings or planted in one gallon pots with a biosolids compost blend derived from the local treatment facilities.
While Chicago has a significant tree canopy, Crain’s reported earlier this month that the canopy has actually been thinning in recent years from a variety of factors including the infestation of the emerald ash borer, storm damage, budgeting and a general policy of not installing trees on residential blocks unless the adjacent property owners specifically request them. News of a successful reforestation program from a sister government agency should be welcome news to not only tree huggers, but also those who value the aesthetics and benefits that trees bring to the neighborhoods throughout our region.