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Walnut/Myrtle/Evergreen Stormwater Improvement Project

February 22nd, 2017

22

City of Elmhurst

APWA 2017 Suburban Branch Project of the Year
APWA 2017 Chicago Metro Chapter Project of the Year
Environment (Less Than $5 Million)

During the storm events of June 23 and July 23-24, 2010, the City of Elmhurst (City) experienced record rainfalls that resulted in hundreds of flooded residences. Homes throughout the City were severely damaged due to overland flooding, sump pump failures, and sanitary sewer backups. On April 18, 2013, another severe storm event occurred that caused even more significant flood damages than the storms of 2010. The storm event of April 2013 was especially damaging since the rainfall occurred on saturated ground due to an especially wet spring. In response to the severe flooding experienced during those recent storm events, the City hired CBBEL to develop a Comprehensive Flood Plan that addressed flooding for several flood-prone areas of the City.

Elmhurst2One of these flood-prone areas is the Walnut/Evergreen/Myrtle Study Area, which is located in the northwest corner of the City. This study area consists of an approximately 600-acre drainage area that currently discharges to Salt Creek through a 72-inch diameter 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, which is 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 (IGA) with DuPage County to allow 20 acre-feet of stormwater volume to be diverted from the flood-problem area to the Elmhurst Quarry. Click here to view the split blasting of the quarry wall. Approximately 3,400 linear feet of 60- to 72-inch diameter relief sewer was constructed that connected the low-lying residential areas to the Elmhurst Quarry. The project provides a 100-year level of flood protection for 76 homes located within the study area.

The project involved extensive hydrologic and hydraulic modeling, which included an XP-SWMM analysis of the storm sewer system and also an FEQ analysis of Salt Creek. Design of the relief sewer was facilitated by 3-D survey data obtained by drone technology, and construction of the outfall was accomplished using split blasting of the quarry wall. This project was made possible by cooperation between the City, DuPage County, and other communities located along Salt Creek.

Luke Sherry, PE
Senior Water Resource Engineer
Water Resources Department

Lee Fell, PE
Senior Project Manager
Civil Design Department