Midwest Mole had to remove approximately 2’ of silt from the bottom of the existing structure in order to determine what size would fit inside of the host pipe structure. Once the silt was removed a survey of the line was completed for both elevations, and the alignment of the existing pipe.
A mandrel built to the OD of the proposed liner was assembled and pulled through the existing pipe prior to final dimensions of the liner being released for fabrication to verify that no issues would arise once the lining commenced. A round liner with an ID dimension of 135” was determined to be the best size for this structure. D. H. Charles Engineering’s Cardiff California office did the load bearing calculations to determine the wall thickness that would meet HS-20 load bearing requirements, considering the worst case with the tire directly over the top of the culvert for vehicle weight with 5’ of cover, and on 6’ of cover for soil weight. A sacrificial loss of .280 inches was added to provide the 70-year life expectancy, based on the culvert being located in an immersed zone with corrosive water. A wall thickness of ¾” was determined to be the appropriate wall thickness for this particular project.
This project coincided with other paving work being done nearby on US 31 that would have caused additional delays or complications in getting both projects completed in a timely manner if road closures or detours would have been required for this work. Road closure and detours are one of the greatest costs of culvert failure. Because once failure has occurred, and the road has collapsed there is no option for emergency vehicles, commercial vehicles and the traveling public except to detour around the failure.