WT Group proves flood mitigation analysis is right up our alley

February 1, 2023

By Jim Glascott

The WT Group’s ability to provide reliable, trustworthy analysis aimed at addressing potential flooding and other risks has earned the trust of municipal leaders and commercial organizations in many communities. A current and ongoing flood mitigation project in the Village of Hoffman Estates, Illinois is just one of the latest examples.

In 2018, Olive Street Properties purchased the vacant Hoffman Lanes Bowling Alley site for commercial redevelopment. Because the 2.6-acres site is located within a Zone A floodplain with no established floodplain elevations, Hoffman Estates required a study of approximately 622-acres to establish elevations before any redevelopment would be permitted. Additionally, the Village mandated the study to account for updated Bulletin 75 rainfall information data now required by the applicable ordinances for both Hoffman Estates and Cook County. The revised rainfall data represents an increase of approximately 13% in the 100-year, 24-hour storm event scenario, which would significantly increase the amount of runoff shown in the model compared to earlier studies.

Given the concerns of Hoffman Estates leadership over future flooding scenarios, the WT Group was asked to work with the Village and with Olive Street Properties to determine floodplain elevations along the Salt Creek Tributary A near the intersection of Illinois Route 72 and Roselle Road. The stream runs through both Hoffman Estates and the neighboring Village of Schaumburg, presenting flood risk to both communities. As a part of the study, the WT Group helped Hoffman Estates determine the limits of flooding in this area, proposing design solutions to mitigate and limit future flooding scenarios.

The exhaustive study of the 622-acre tributary area included review of hundreds of Metropolitan Water Reclamation District of Greater Chicago (MWRD) permits, analysis of over 40 existing detention systems, and miles of existing storm sewers and ditches. It also included the creation of an XPStorm model to analyze runoff from the tributary area along with the hydraulics of the existing drainage system. Using the model, along with a combination of GIS topography and infield topography analysis, the WT Group created an accurate map illustrating the existing limits of the floodplain, along with floodplain elevations along the Salt Creek West Branch Tributary A to the western limits of Hoffman Estates.

Delivering mitigation ideas that work

Using this data, the WT Group worked with the Village of Hoffman Estates to review multiple options in order to reduce flooding hazards to businesses and residences in the area. In the end, the Village chose an option to remove two existing 54” corrugated metal pipes across a nearby commercial property which were failing, and replace them with a single 12’ x 4.5’ box culvert which was re-routed to allow the owner of this commercial property to more easily redevelop in the future. The Village also chose to expand the open ditch portion of the Salt Creek West Branch Tributary A along the frontage of the former Hoffman Lanes site and replace two failing CMP arch culverts at this site to increase capacity, and to restore the open ditch with wetland plantings to improve water quality downstream of the development.

Based on the WT Group’s analysis, the project received approval from the Village of Hoffman Estates, the Illinois Department of Transportation (IDOT), the Cook County Department of Transportation and Highways (CCDOTH), the Metropolitan Water Reclamation District of Greater Chicago (MWRD), the Illinois Environmental Protection Agency (IEPA), and the United States Army Corps of Engineers (USACE) in 2022.  With the analysis and designs in hand, Pratum Construction began work on the flood mitigation improvements in the fall of 2022, with completed construction targeted for spring 2023.

Contact WT Group

WT Group’s engineers and Certified Flood Plain Managers (CFM) provide flood protection solutions in partnership with a wide spectrum of government and state agencies to mitigate and limit future flooding scenarios. Do you have questions regarding flood mitigation analysis? Contact us today.