Corrugated Metal Pipe Repair (CMP Repair) and Rehabilitation Solutions
CST provides Corrugated Metal Pipe (CMP) rehabilitation using a patented process to ensure reliability and cost-effective repair of large diameter corrugated metal pipe throughout the United States.
The Problem
The deterioration of CMP happens over time from the exposure of oxygen and moisture which forms rust. Deterioration depends primarily on soil conditions and the acidity of the water flow. In some instances, this condition can cause sinkholes to form that allow water to escape during heavy rain and destroy property. Flowline corrosion causes a loss of structural integrity. Bottom bedding and support fill is exposed and begins to erode away. As bottom bedding material is lost, flow begins to occur around and beneath the pipe. Sidewall bedding and support material are lost leaving voids and loss of structural support. Sinkholes start to develop at the surface. In such cases, it would be expensive and time-consuming to repair the entire pipe.
The Application Process
Prior to beginning the work, all debris, stones, rubble, and loose material will be removed from the pipe. Beginning at the outfall, the overlay sheets will be placed in the bottom of the pipe, centered over the corroded flow path, and pressed into place to conform to the arc of the pipe. While held in position, the metal sheeting will be fastened to each ridge of corrugation with a corrosion-free fastener. Advancing in the counter-flow direction, each subsequent section/sheet is “shingled” over the leading edge of the prior sheet with an overlap 6″.
Once the needed sheets are installed, multiple injection holes (5/8″ diameter) are drilled through the new invert and through the host CMP. The overlay sections/sheets will be blocked and braced sufficiently to prevent movement when the next step of injections begin. High-Density Polyurethane (HDP) is injected in multiple locations through the injection holes, allowed to expand, void fill, and seal the backside of the repair area. As necessary, the polymer is injected at depth through injection tubes placed into the supporting subsoil so as to further strengthen and stabilize the supporting subsoil. Outcropped HDP material is removed with hand tools and disposed of. The repaired area is inspected for completeness.
