Liner used to repair 15-ft CMP in Vista, Calif.
Located in the heart of Southern California’s industrial and commercial hub, the City of Vista is home to a master-planned, 80-acre business park first developed in 1987. As part of its construction, the city installed a 15-ft-diameter corrugated aluminum multi-plate arch culvert (CMP) to cross under the main thoroughfare. The culvert provides maintenance vehicles and trucks access to the city’s sewer easement, serves as a crossing for wildlife and is also used by local joggers and bicyclists.
Beginning in 2002, corrosion of the culvert pipe structure progressed steadily, and the city began seeking recommendations from engineering consultants to either remove or rehabilitate the structure. Any rehabilitation solution needed be constructible with a limited work area footprint and minimize impacts to sensitive areas surrounding the project site, including coastal sage scrub and wetland habitats.
The primary design criterion was to support the earthen embankment and any live vehicular loading. Another requirement was that the exposed culvert material had to be nonflammable and resistant to heat, as city staff had observed campfire remnants within the culvert. Due to the oval shape of the pipe and its use as a roadway underpass for both sewer and fire trucks, rehabilitation needed to follow the same profile as the existing CMP.
The city also considered several rehabilitation alternatives using the existing pipe. Slip lining was rejected as a potential option, as it would have reduced the diameter of the pipe beyond design limitations and impeded service trucks’ ability to drive through the pipe. Shotcrete was also eliminated because of its inability to achieve the final design strengths and thickness requirements. Seeking an alternative that would not only rehabilitate and stabilize the pipe, but also satisfy environmental requirements, the city chose a design/build solution from Inland Pipe Rehabilitation (IPR) of Houston and Milliken Infrastructure Solutions of Spartanburg, S.C. The solution involved applying a high-strength fiber-reinforced polymer concrete liner directly to the host pipe in layers, requiring no specialized bonding application or engineered system.
Upon completion, several measures were taken to verify the thickness of the installation. IPR drilled set screws into the crown of the CMP rib and measured the required 3.2 in., as per engineered design. Additionally, IPR and the City of Vista commissioned a laboratory to conduct comprehensive material testing and ensure design criteria are met. Twenty samples were tested and all were successful.