Colorado DOT CMP Rehabilitation

The Problem

Abrasion and erosion caused by years of water and debris flowing through cause the invert areas of corrugated metal pipe to deteriorate. In time, the invert of the culvert wears out. Water will then flow under instead of through, causing voids, settlement, loss of side support, sink holes, and eventually, a complete failure of the structure.

CST was contacted by Colorado Department of Transportation Region 3 Maintenance Supervisor Eric Langford concerning a 45 foot long culvert located beneath a section of Colorado State Highway 348 near Delta, Colorado. The 71 inch wide, 47 inch high culvert had suffered typical erosion and CDOT needed options to repair.

CST Field Consultant Richard Hess partnered with CDOT to devise a repair plan to rehabilitate the existing culvert and prevent having to close the road to tear it out and replace.
With no excavation necessary, water and fiber optic lines known to be above the culvert did not have to be carefully worked around or moved, as they would have been for an excavation procedure that would have required approval from these utility companies. This extra step was not necessary with the CST process thus saving days of delay for this repair that already had a short time line for completion before the ditch was scheduled to start its Spring flow.

Method/Process Applied

On March 25th, CST’s crew arrived on the job site to begin repair work. The pipe was first cleaned of any sticks, rocks, and other debris. Crews then measured, cut, and prepared the new metal sheets to fit the unique dimensions and shape of this particular culvert. Beginning on the outlet end of the pipe, the sheets of specially coated metal were then aligned with the ribs of the pipe and continuously overlapped and secured into place with corrosion resistant fasteners. On the second day, the remaining metal sheeting was placed, and expanding structural polymer injected below the sheets through pre-drilled 5/8 inch holes. This helps to provide additional structural integrity that may have been lost due to eroded soils. Crews finished up by applying a tar coating to the top edge of the new material as an extra measure to deter rusting and increase the use life of the existing culvert. Work was completed in two shifts with no excavation or disruption to traffic on the overlying roadway.

Benefits of CMP Repair

• No Excavation
• No Road or Rail Closure or Downtime
• No Loss of Flow
• Less Disruptive
• Repair Equipment & Material Easily Mobilized
• Environmentally Inert Materials
• Reduces Costs
• Extends Lifetime of Invert
• Completely Restores Structural Integrity