The finished project parallels I-279 coming towards Pittsburgh from the north and the wall is visible to tens of thousands of commuters per day. The aesthetics of the StoneWall SELECT wall are impressive and a substantial improvement over the wood tie walls that were visible before. This view of Mt. Nebo Road, from I-279, clearly illustrates the cliff above and the steep drop below.
StoneWall SELECT was chosen as the material for a retaining wall along I-279 near Pittsburgh. Mount Nebo Road, perched in the middle of a steep cliff, needed to be stabilized and widened. Engineers in Allegheny County, PA were challenged by this project, which had to comply with AASHTO Federal Highway standards, while isolating and keeping water away from the slide-prone red bed clay. In addition, they wanted a minimal amount of down time for the construction project.
The project required the removal of a failing wood tie retaining wall, which had resulted in landslide conditions. Overhead cables could be pulled, but not removed. This created obstacles that trucks and excavation equipment had to work around during the entire project. In addition, the steep slope both above and below the road further limited the working space. This required excavation from the top down all along the 622 foot length of the wall. A red bed clay layer had to be removed and the wall design adjusted so that the foundation was not in the red bed material. This layer behind the wall had to be kept as dry as possible to prevent small slides during construction.
StoneWall SELECT worked extremely well in this difficult situation. George Wochley of Camber Construction Products noted, “ The relatively light weight of the units helped speed up material handling and placement in this very limited space. And the superior connection interaction between the StoneWall SELECT facing and the geogrid helped speed design acceptance.”