TRANSMITTAL LETTER FOR BOARD MEETING OF JANUARY 20, 2022
COMMITTEE ON STORMWATER MANAGEMENT
Mr. Brian A. Perkovich, Executive Director
Title
Report on Green Infrastructure, Detention, and Compensatory Storage Volumes Required by the Watershed Management Ordinance
Body
Dear Sir:
The Watershed Management Ordinance (WMO) regulates sewer construction within the District’s service area and development within suburban Cook County. It provides uniform stormwater management regulations to prevent future development projects from exacerbating flooding and protects environmentally sensitive areas. Green infrastructure (GI), referred to as volume control in the WMO, is installed to comply with the stormwater management requirement of capturing one inch of stormwater runoff from all impervious surfaces of the development. Detention requires stormwater runoff to be retained and controls the rate at which it is released from the site. Compensatory storage is required to mitigate development impacting the floodplain.
When a WMO permit is required, development must comply with the stormwater management provisions of the WMO. The first of the two attached tables includes the number of permits issued per quarter since the WMO became effective. It also summarizes the development area, volume captured by GI, detention provided, and compensatory storage. The total for each year and running total are also provided. The detention volumes for 2019, 2020, and the first quarter of 2021 were adjusted to correct a reporting error. The volumes for six permits in 2019, seven permits in 2020, and three permits in the first quarter of 2021 had reported detention volumes that were either constructed prior to the implementation of the WMO or that had been reported previously in another permit. The currently submitted report has the corrected values. The second table includes permits and permit revisions issued for the creation of offsite volume control or detention facilities and permits that utilize these offsite facilities. To date, three offsite volume control facilities and two offsite detention facilities have been permitted and are available for stormwater trading. Of these five offsite facilities only one will be reported on our website. The municipalities in which the other four facilities are located intend to utilize them for future projects within the municipalities, and do not need to broadly publicize those facilities.
Respectfully Submitted, Catherine A. O’Connor, Director of Engineering, KMF:MD
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