Cast-in-place concrete box culverts return to the Minnesota local bridge inventory
By: Dave Conkel, State Aid Bridge Engineer, Moises Dimaculangan, State Aid Bridge Load Rating & Permitting Engineer, and Jerilyn Swenson, State Aid Bridge Program Engineer
280th Avenue over Tompkins Creek, Mantorville
Township, Dodge County, 12’X10’ CIP concrete box
culvert
State Aid and State Aid Bridge teamed with the Local Road Research Board (LRRB) Research Implementation Committee (RIC) and SRF Consulting Group to develop several practical LRRB reports to assist local bridge owners in the implementation and use of cast-in-place (CIP) concrete box culverts. These reports will help county and city engineers assess when CIP solutions may be appropriate, provide technical direction and decision-making support for local bridge and culvert projects.
The first of two LRRB reports is titled, Precast versus Cast-in-Place Concrete Box Culverts. This project evaluated how the 2020 supply chain disruptions and labor shortages affected the availability, cost, and delivery of precast concrete box culverts for local agencies in Minnesota. The research also included case studies from Minnesota and neighboring states that examined recently constructed CIP box culvert projects. These case studies compared cost, construction time, labor requirements, and constructability, providing real-world examples that helped illustrate when CIP box culverts can be a competitive and practical alternative to precast options for local agencies.
The second LRRB report is titled, Cast-in-Place Box Culvert Guidance. This guidance was developed in response to the 2020 supply chain disruptions, labor shortages, and rising costs that limited the availability of precast concrete box culverts in Minnesota. The document explains that while precast box culverts remain common, CIP box culverts can be a viable and sometimes advantageous alternative under certain site conditions. It outlines barriers to CIP use, such as longer construction duration, lack of standardization, limited contractor experience, and increased inspection needs, while also identifying scenarios where CIP solutions may outperform precast options, including deep fills, high settlement areas, constrained sites, curved or skewed alignments, and locations with limited crane access.
The guidance further provides technical direction for evaluating and designing CIP box culverts using Missouri DOT (MoDOT) standard plans as a reference framework adapted for Minnesota use. It compares MnDOT precast and MoDOT CIP standards, discusses design parameters, durability considerations, joint details, and inspection implications, and walks engineers through a step-by-step process for plan selection, design evaluation, and plan development. The document concludes that CIP box culverts can offer improved durability, fewer joints, better adaptability to site constraints, and competitive costs when contractor familiarity exists, and it serves as a practical decision-making tool for local agencies considering CIP alternatives to precast culverts.
Following the supply chain disruptions and labor shortages experienced in 2020, precast concrete manufacturers have largely returned to providing cost-competitive, high-quality products for local bridge and culvert projects. Precasters accomplished this by stabilizing material supply chains, investing in workforce retention and automation, expanding regional production capacity, and improving scheduling coordination with owners and contractors. These efforts have reduced lead times, improved product availability, and helped restore precast box culverts as a reliable and economical option for Minnesota’s local agencies.