Walnut/Myrtle/Evergreen Stormwater Improvement Project

April 25th, 2018

City of Elmhurst

In response to severe flooding experienced during the storm events of June 2010, July 2010 and April 2013, the City of Elmhurst hired CBBEL to develop a Comprehensive Flood Plan that addressed several flood-prone areas, including the Walnut/Evergreen/Myrtle Study Area in northwest Elmhurst. This approximately 600-acre drainage area discharges to Salt Creek through a 72-inch storm sewer. Due to the large drainage area and tailwater conditions of Salt Creek, several low-lying areas experience significant inundation during severe storm events, with 52 homes flooded during a 100-year storm event and 76 homes flooded during the April 2013 storm event.

This study area is uniquely situated adjacent to the Elmhurst Quarry, an approximately 8,300-acre-foot flood control facility along Salt Creek, that is owned and operated by DuPage County. With the approval of the downstream Salt Creek communities, the City entered into an intergovernmental agreement with DuPage County to allow 20 acre-feet of stormwater to be diverted from the flood-problem area to the Elmhurst Quarry. Approximately 3,400 linear feet of 60- to 72-inch relief sewer was constructed that connected the low-lying residential areas to the Elmhurst Quarry, providing a 100-year level of flood protection for 76 homes located within the study area. The direct connection of a relief sewer to the quarry was the first project of its kind and required coordination between Elmhurst, DuPage County and municipalities along Salt Creek.

The project also involved extensive hydrologic and hydraulic modeling and design of the relief sewer was facilitated by 3D survey data obtained by drone technology. Construction of the outfall was accomplished using split blasting of the quarry wall, which removed the weathered rock as well as any overhanging rock at the edge of the quarry. Click here to view the split blasting of the quarry wall.

Luke Sherry, PE
Senior Water Resource Engineer
Water Resources Department