Case Study Details

As part of improvements along the Kennedy Expressway in Chicago, the Illinois Department of Transportation incorporated new concrete retaining wall drainage system into existing concrete retaining wall infrastructure along the northbound and southbound roadway.

The project included coring openings through the existing concrete walls and installing approximately 86 JET Filter maintainable weep hole systems, generally at a rate of approximately one unit per wall panel.

The drainage retrofit was designed to provide trapped groundwater with a controlled pathway through the retaining walls while helping reduce hydrostatic pressure acting against the structures. By incorporating an accessible, maintainable, concrete retaining wall drainage system, IDOT provided a long-term method for managing water behind critical transportation infrastructure.

Contract 62A76 formed part of a larger Kennedy Expressway improvement project that included mainline construction and widening, rehabilitation or construction of multiple retaining walls, roadway resurfacing, lighting, and intelligent transportation system improvements.

Products Used

86 units of JET Filter – JF4SS: 4″ Diameter Open-End Maintainable Weep Hole Filters featuring corrosion-resistant 316L stainless steel construction and Mirafi® FW 300 Series geotextile filter media.

The units were installed through cored openings in the existing concrete retaining walls, primarily near the lower portion of the structures where groundwater and hydrostatic pressure can accumulate.

A key feature of the JET Filter System is the removable inner filter cartridge. Maintenance personnel can access, inspect, clean, or replace the filter cartridge directly from the exposed face of the retaining wall without excavating retained soil or removing material from behind the structure.

The current JF4SS system uses a 4-inch 316L stainless steel housing and a maintainable cartridge specifically intended for long-term drainage applications in retaining walls and other earth-retaining infrastructure.

Concrete Retaining Wall Drainage System Solution

Retaining walls are a critical component of urban expressway infrastructure, particularly along below-grade transportation corridors where roadway geometry requires extensive earth-retaining structures.

When groundwater and stormwater infiltrate the soil behind a retaining wall, insufficient drainage can allow water to accumulate within the retained material. As saturation increases, hydrostatic pressure develops against the wall. Over time, these forces can contribute to cracking, displacement, leaning, deterioration, and premature structural rehabilitation.

The Kennedy Expressway project addressed this issue by incorporating a maintainable concrete retaining wall drainage system into existing concrete retaining walls. Prior to construction of proposed roadway barriers, openings were cored through the existing walls and JET Filter units were installed to create controlled drainage outlets.

The filters allow accumulated water to exit through the face of the retaining wall while the geotextile filter media helps prevent migration of the surrounding retained soil.

The concrete retaining wall drainage system also provides a significant maintenance advantage compared with conventional inaccessible drainage systems. Because the filter cartridge is removable from the exposed side of the wall, maintenance crews can inspect, clean, or replace the filtration component without excavation behind the structure.

This is particularly beneficial along heavily traveled expressways, where excavation or major retaining-wall repairs can require traffic control, lane closures, additional labor, and substantial construction costs.

IDOT geotechnical documentation for this broader corridor also identifies the potential for perched groundwater within fill materials during periods of heavy precipitation, reinforcing the importance of accounting for drainage in retaining-wall design and rehabilitation.

Technical Details