GEOLOGIC CONSIDERATIONS FOR CULVERT REPLACEMENT UNDER EARTHEN EMBANKMENTS

The challenges of infrastructure renewal in the United States are many. Aging culverts underlying the interstate system, state highways, and local roads have diminishing structural and/or hydraulic capacities and pose an increasing risk to pavement stability, adjacent properties, and public safety. Using various trenchless tools, the Vermont Agency of Transportation has recently undertaken the rehabilitation and replacement of culverts installed during the original interstate system construction in the 1960s. In particular, two culvert crossings in South Burlington and Colchester, Vermont, were recently rehabilitated. Each is approximately 300 feet long (91 m) and located below Interstate 89 within approximately 40-foot-high (12 m) earthen embankments. The design required slip lining the existing corrugated metal pipe culverts and installing new parallel crossings adjacent to the existing culverts using trenchless methods. This case study highlights the anticipated ground conditions for the project, applicable trenchless methodologies, contractual geotechnical documents utilized, and lessons learned on the effect of site geology on the performance of the culvert replacement methods.