Pedestrian Bridge Sealing Over I-696 in Michigan

Problem

Interstate 696 (I-696) in Michigan is an east-west bypass route that detours around Detroit through some of its northern suburbs. One of these suburbs, Oak Park, has a large Orthodox Jewish community. When plans for I-696 were being made in the 1950s, the Orthodox Jews of Oak Park requested that the design accommodate members of their pedestrian-dependent community. As a result, a series of 700-foot wide landscaped plazas were incorporated into the design of tunnels through which I-696 passes. The landscaped plazas cross the freeway, allowing members of the Jewish community to walk to synagogue on the sabbath and on holidays. The pedestrian bridges were successful until the Michigan Department of Transportation (MDOT) found themselves with a serious icicle problem in the tunnels below the plazas.

Analysis

Irrigation systems were installed to support the landscaping on the plaza bridges, and the water was leaking in between the concrete beams that made up the construction of the bridge. During cold weather this seeping water created some very large, dangerous icicles in the tunnel below. To eliminate the icicles for good, MDOT needed a strong and long-lasting solution to seal the bridges’ joints. MDOT officials called URETEK to address the icicle issue because of their stellar reputation in polyurethane repair solutions, and because of their past history of successful projects with MDOT.

Solution

MDOT wanted to test the URETEK Deep Injection® (UDI) process and 486 Star® polymer on a section of one of the bridges. To minimize the impact on I-696 drivers, the test project was completed in the late evenings when it was more convenient for a temporary highway shutdown. URETEK technicians injected above and in between the concrete beams on four out of five total joints in a section of I-696 that passed under a pedestrian walkway. MDOT directed the fifth joint to be left alone in order to provide a comparison and to determine if URETEK’s solution should be used to seal all the remaining joints on all the bridges, thus solving MDOT’s icicle issue for good.

Result

URETEK successfully sealed and filled the voids in the four subject joints. No icicles formed on the four URETEK-treated joints, but large icicles emerged on the fifth, untreated joint. These test results confirmed that where deployed, URETEK’s 486 Star® polymer successfully sealed the joints and prevented icicle formation. Twelve years later, the joints have remained successfully sealed and intact.

URETEK Deep Injection® (UDI)

Widely referenced throughout our industry, UDI involves the injection of structural polymer into base and subgrade soils to increase the load bearing capacity. This is achieved by injecting the polymer through small holes drilled directly through the pavement structure to depths determined by site-specific analysis. Our URETEK 486 Star® material flows easily into voids and weak zones within the soil mass below. Through a controlled chemical reaction, the expanding polymer compacts surrounding soils and applies a controlled pressure on targeted areas of the affected pavement above. If needed, a multi-injection design plan is utilized to gently return the pavement to its original grade. The composite material quickly cures into a strong, dimensionally stable, and water-resistant geo-material, providing years of reliable service.

URETEK 486 Star®

URETEK 486 Star® polymer is a two-component, high-density, expanding thermoset polyurethane system. It was developed to be the ideal solution for under-sealing, void filling, lifting of settled pavement, stabilization and stiffening of weak soils, and for encapsulating and sealing buried infrastructure. URETEK 486 Star® is environmentally inert, non-toxic, and resists underground water erosion or weakening due to its industry-leading hydrophobic properties.

URETEK treatment prevented icicle formation, as shown on the left
Landscaped plazas act as pedestrian bridges across I-696