Flood Study and Regional Detention Ponds

The scope of work for the multi-phase project included hydrologic and hydraulic modeling of a 1.6-square-mile watershed, detailed flow analysis of 4.3 miles of stream channels, design of two regional detention ponds, construction management, and revisions to FEMA flood insurance maps for the entire drainage basin. CTI subsequently identified a third detention pond site and provided a fast-track design that allowed the City to complete construction of the pond by the Public Works Department 4 months later.

During a 100-year storm, the 18th Street pond will store over 17 million gallons in a 7-acre impoundment created by a 22-foot-high earth dam. The pond will reduce the peak flow at 18th Street by over 96 percent during a 100-year storm. The East Street detention pond stores 3.6 million gallons and reduces peak 100-year storm flows by 41 percent.

Extensive flood modeling completed for the FEMA map revisions indicates that the ponds have reduced flooding dramatically within the watershed. The 100-year flood elevations within downstream channels have been reduced by up to 3 feet along West Fork of Woolen Mill Branch. Flood elevations at the Whirlpool manufacturing plant have been reduced by nearly 4 feet for a 5-year storm. The success of this flood control project and its impact on the community is demonstrated by the recent addition of 500 new jobs at Whirlpool’s Cleveland facility as several of their other plants are being closed.

Construction of the ponds began in March of 2008 and was completed in August. The two primary detention ponds were completed on time and 8 percent below the $1.93 million budget.

Because of the success of this project in design, it is one on only three projects in the nation chosen by FEMA to feature in its flood mitigation training project. CTI was awarded an Engineering Excellence Award by ACEC for this project.

PROJECT ELEMENTS
» Hydrologic and hydraulic modeling of a 1.6-square-mile watershed.
» Detailed hydraulic analysis of 4.3 miles of stream channels.
» Design of three regional detention ponds, earth dams, roads, and utility relocations.
» Construction management.
» Revisions to FEMA flood insurance maps.
» Multiple TDEC and US Army Corps of Engineers Permits

AWARD
CTI was awarded a 2009 Engineering Excellence Award by ACEC for this project.