Drain Pan Void Fill Structural Support CDOT Region 1

A drain pan structure running adjacent to US-287 near Broomfield Colorado had experienced significant voids of varying severity beneath the structure. The drain pan was designed to move water away from the roadway during water events and run off; however, due to issues with the design of this particular structure, water was running beneath the concrete and eroding areas beneath the pan. The integrity of the structure was compro-mised due to the weakened and eroded supporting soil.

CDOT needed an effective solution to treat and repair the almost 800 foot long problem section of drain pan that would not only fill the voided areas, but also protect it against additional damage and structural failure that may also effect the safety of the adjacent highway.

A thorough evaluation of the site was conducted prior to design of the repair plan for the drain pan. It was determined that the more severe voids were located on the uphill slope area of the structure. Alternate solutions, including a flowable fill, were taken into account while determining the most effective way to treat the area. However, due to the advanced features of CST’s proprie-tary injection process, and the unique characteristics of the specialized expanding structural polymer, it was determined that filling the voided areas using this process would most effectively and most efficiently solve the problem. Injections were made directly through the drain pan, filling voids, and strengthening the supporting soils.

The entire stretch of affected drain pan was void filled and stabilized in four days without any disruption to traffic flow along the adjacent highway.

The treatment method allowed CDOT to extend the use life of the structure and avoid the expense of tearing out and replacing the structure.

The specifically designed repair not only eliminated the void space beneath the pan and strengthened the soils, but also provided protection to the structure against future erosion.

Repair costs came in under budget for this project.