Sub Grade Soil Stabilization Void Fill & Slope Stabilization

Molas Pass, is a high mountain pass in the San Juan Mountains in Western Colorado located near the town of Durango. US Highway 550, which is part of the San Juan Scenic Byway traverses the pass. An area of the highway and adjacent slope had unconsolidated shot rock with large voids beneath the asphalt pavement, threatening the stability and safety of this section of roadway. The subgrade soils and hillside were in need of stabilization to protect the pavement and the slope area from further erosion and damage. Rebuilding of this steep area was not desired.

Elam Construction, the General Contractor on the project partnered with CST to help design an in situ repair solution. Penetrometer tests were performed to determine weak zones, voided areas and rock locations. An injection design was created and CST’s crew members installed High Density Expanding Structural Polymer by injecting the material into the soil at predetermined depths. The impervious material travels through the soil, filling voids, and consolidating fines, soil, and rock. The tensile strength of the material, with the interlocking characteristic, mitigates against side creep and further erosion. Repair of the weak soil zones and slope area without disturbing or damaging the asphalt overlay of the roadway.

Crews effectively stabilized the slope soils and roadway subgrade soils in 4 shifts, without having to completely close the roadway. 110 total injections were made, including 10 on the slope hillside. One lane of traffic was kept open at all times during the repair, allowing traffic to continue through the pass with very little disruption or lengthy closures.

CST’s No-Dig Technologies allows efficient, effective repairs without excavation while extending the use life of existing infrastructure.