While completing routine maintenance on a highway connecting Alpine, Texas to Big Bend National Park, the Texas Department of Transportation (TXDOT) discovered that during high intensity storm events, the water flowing off a bridge was causing scour and erosion issues around the bridge piers. A solution was needed to protect the piers.
As a solution, a total of 423 units of 48-in A-Jacks® were utilized on this project. A-Jacks were selected over gabions because they were easier and less labor intensive to install, resulting in a lower cost as required by the limited budget.
The concrete armor units arrived at the site on pallets, facilitating the staging of materials. During installation, it was necessary to place the A-Jacks underneath the bridge without damaging the existing piers and without having to close the bridge during installation. This was accomplished over a two to three week time period with a small excavator and basic labor that involved placement of assembled individual A-Jacks units. The interlocking A-Jacks units are designed to create a flexible, highly permeable matrix to dissipate energy, resist the erosive forces of high-flowing water and protect against future scour and erosion.
In addition, since the stream is a fish-bearing stream, the solution needed to be environmentally sensitive. A-Jacks were utilized for their ability to maintain the wetlands for the fish native to the area. no permits needed.
According to Oscar A. Arzaga, Engineering Assistant, with the TXDOT, “The overall success of the project was excellent. The A-Jacks were installed very quickly, and we are very pleased with the end result.”