CITY COUNCIL AGENDA ITEM
ACTION REQUESTED:
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Conduct the public hearing for the stormwater variance request for the North Aurora Road Underpass project at the Canadian National Railway (Item 1 of 2)
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DEPARTMENT: Transportation, Engineering and Development
SUBMITTED BY: William J Novack, Director of TED/City Engineer
BOARD/COMMISSION REVIEW:
N/A
BACKGROUND:
The cities of Naperville, Aurora and Naperville Township have been working together on widening and other improvements to the North Aurora Road underpass at the Canadian National Railway since 2006 and have assembled $24.4 million of outside funding. Upon completion, a four-lane arterial roadway will be provided from Ogden Avenue in the City of Naperville to west of Orchard Road in the City of Aurora. The underpass project will eliminate the final bottleneck in this corridor.
The design has been completed and most of the necessary right of way acquired. The remaining outstanding task is to finalize the agreements with the railroads, relocation of the Enbridge pipeline and a Com Ed pole, and the final agreement with our project partners.
The City completed the design of the stormwater system for the underpass project which includes an underground vault, pump station and storm sewers. All the vaults and equipment were designed in accordance with Bulletin 70.
Several years ago, DuPage County updated the design storms from Bulletin 70 to Bulletin 75 for the Countywide Stormwater and Floodplain Ordinance. This update essentially increased the rainfall events for the various storms, increasing the rainfall for the 100-year, 24-hour storm from 7.58 inches to 8.57 inches of rain. This is a positive change and the City has been following it since inception.
However, using Bulletin 75 requires a complete redesign and resizing of the project, including the vaults and pumps. Additionally, land acquisition areas had been based on the size of the original vault and will need to be revised.
Understanding the scale of this project, and the timing of the new design standards, DuPage County granted the City a construction grace period. Due to the prolonged work with the parties the grace period elapsed.
DuPage County indicated that the City would need to seek a formal variance instead of an extension of the grace period.
DISCUSSION:
City staff is seeking a formal variance to Section 15-72 D.3 of the DuPage Countywide Stormwater and Floodplain Ordinance (DPCSFO), specifically to use Bulletin 70 instead of Bulletin 75 rainfall data. Staff notes that the current design with Bulletin 70 meets the downstream release rate requirements of the DPCSFO. The only shortcoming is that the pumping station and vault cannot accommodate rain events in excess of Bulletin 70. The good news is that during those events excess stormwater will not be released upstream or downstream of this project. Instead, the additional runoff will pond in the underpass, where it currently ponds today in events much lighter than both Bulletin 70 and 75.
Granting the variance will not alter the character of any of the upstream or downstream properties. Complying with 15-72 D.3 will create an undue hardship, adding significantly to the design and construction costs and jeopardizing the outside funding already secured for the project due to the additional time needed. This variance is the minimum necessary for the underpass project to move forward; it is unique and does impact or alter any floodplain or wetlands.
In accordance with DuPage County requirements for stormwater variances, all municipalities in the West Branch watershed have been notified of this public hearing. Notification of the public hearing was also published in the Chicago Tribune on November 9, 2022. The DuPage County Stormwater Committee considered this variance request at its November 1, 2022 meeting and voted unanimously to not object to the variance petition.
Staff requests that City Council conduct the public hearing and, if there is no testimony against the variance, pass the ordinance approving the variance.
FISCAL IMPACT:
There is no fiscal impact if the variance is approved. If the variance is not approved, the City faces costs to redesign the stormwater system, additional land acquisition time and cost, and jeopardizing the loss of portions of the $24.4 million of outside funding secured to date.