CDOT HWY 52 CMP Rhabilitation – Hudson, CO

The Problem

The deterioration of Corrugated Metal Pipe, (CMP) at the flow line is a result of exposure to oxygen and moisture mixed with metal, which causes rust. Other factors such as soil conditions and the acidity of the water flow will also affect the rate of deterioration.

When CMP deteriorates, water runs under the pipe instead of through and undermining of the structure occurs. Sink holes above the structure will begin as the soil collapses. The underlying bedding material or support fill is then exposed to water flow, and begins to erode away, causing voids and loss of structural support. This creates a potentially dangerous situation with the possibility for failure of the entire structure and collapse of the overlying roadway.

Concrete Stabilization Technologies, Inc.’s Field Consultant, Richard Hess was contacted by Colorado Department of Transportation Maintenance Department representative for Region 4, Zach Junk, concerning a deteriorated culvert beneath Colorado State highway 52 near Hudson, Colorado. The traditional method of tearing out and replacing eroded culvert pipe had proven to be a time consuming and disruptive process which had lead CDOT to seek a less disruptive solution.

The Solution

CST met on site with Mr. Junk and after reviewing the area, determined that our CMP repair process was an ideal fix for this particular culvert and overlying roadway. Subgrade stabilization injections from the roadway surface were included in the repair plan where exfiltration of soils through the rusted out pipe had caused variable settlement in the road surface above the culvert, requiring steel plates as a temporary fix against further damage to the road surface and vehicles. Thus, part of the CST complete solution was to not only secure the metal sheets to the old CMP but to also inject from the road surface above to 3′ to 4′ to reinforce the subgrade while replacing soil lost to exfiltration.

CDOT maintenance representative Zach Junk stated that he, “liked the fact that they didn’t have to close the road or detour traffic like they normally do when having to replace pipe.”

Structural integrity of the existing pipe was a concern and it was discussed that not only would the structural integrity of the pipe be restored, but also restoration of correct flow into the repaired pipe.

The ditch company expressed concern of subsequent debris buildup such as weeds and silt that may disturb the water flow. The repair design and installation is such that this concern is positively addressed and re-establishes water flow with no added obstruction.

After an in depth investigation and review of the site, it was assured that this would be an ideal repair process for the deteriorated culvert and CST was given the approval to begin the project.

Crews arrived on the job site around 10:00 a.m. to begin repairs. A significant amount of water was running in the ditch containing the culvert. While water was shut down, crews began deep injection to stabilize the sub-grade on the overlying roadway. Injections were made from the surface at a depth of approximately 3 ½ feet on 5 foot centers, while monitoring at the surface for move-ment. After the subgrade stabilization was complete, it was determined that one of the two overlying road lanes was in good shape and the other lane would only require select asphalt patching once repairs were complete.

The Results

Neither lane required any excavation during repair, due to CST’s unique in situ polymer injection process. Once stabilization of the roadway was complete, the crew began repairing the corrugated metal pipe. Repairs and cleanup were completed in one working shift. The Frico Ditch Company representative confirmed that “the ditch is flowing well”.

Benefits of CMP Repair

The patented CMP repair process is quick and non-disruptive. The pipe is first cleaned of any sticks, rocks, and other debris. Repairs begin on the outlet-side of the pipe where the new sheets of specially coated metal are laid, ensuring the corroded water line is covered. The metal sheets are then attached to the ribs of the pipe with corrosion resistant fasteners. Overlapping sheets are then continuously added and secured in place until the length of the pipe is completely reinforced. In this case, the culvert being repaired was approximately 50 feet long and 5 feet in diameter with the corrosion/water line reaching approximately one third of the way up the side wall of the culvert. Once the new metal sheets are all placed, and secured, expanding structural polymer is injected beneath the metal sheets, to fill any voids beneath the pipe. Excess material is removed and a tar coating is applied to the top edge of the new metal sheeting as an extra protective measure to deter rusting and to ensure longevity.  The benefits include:

  • No-excavation
  • Less disruptive
  • Reduces costs
  • No road or rail closure or downtime
  • Repair equipment & material are easily mobilized
  • Extends lifetime of invert
  • No loss of flow
  • Environmentally inert materials
  • Completely restores structural integrity


Colorado DOT CMP Rehabilitation – Delta, CO

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