CASE STUDY
When Is a Bridge Better Than a Culvert?
When a Bridge Reduces Environmental Impacts & Satisfies Water Flow Restrictions Better than a Culvert
Our vehicular project, Inspired Living, shows how a bridge reduces impacts on the environment and water flow. The bridge was built 40 feet above a floodplain to enter a senior living community. Originally, this project was considered to have several culverts installed rather than a bridge. However, with costs of mitigation included, the culvert project budget was going to be significantly higher than a bridge project. There was also significant fill required to raise the road nearly 20 feet in elevation to be above the 100-year flood level. Even with this planned increase in elevation, the 100-year flood flow test was not passed, and the culvert option was eliminated. The final and accepted bridge solution reduced the impacts by 50,763 square feet, limiting environmental impacts to erosion control under the bridge and the fill areas to the bridge end only. The natural flow is left uninhibited, and the area of flood impacts was limited to two 18-inch piling faces, ultimately increasing the flow clearance by 237 square feet within the flood area.
20'
Above Flood Level
62%
Impact Reduction
$150k
Cost Reduction
123%
Increase In Water Flow
Culvert or Bridge Takeaways
Not only was the bridge project less expensive, but it also allowed a large amount of land to be left in its natural state, which is key to maintaining undisturbed ecological systems. In turn, this leads to reduced environmental risks or repercussions at the bridge and downstream.
When you are in the decision process of which crossing is the best fit a YBC timber bridge is an ideal solution for your project.
Original Culvert Proposal
The initial proposal for building a culvert for Inspired Living would have used a vast amount of materials and restricted access to underground utilities.
Culvert Impacts & Flow Restriction
The culvert proposal was denied due to the large environmental impact, restrictive flow, and negate any wetland mitigation requirements.
Bridge Impacts & Flow Restriction
The chosen solution proposed maximum flow, access to underground utilities, and minimal environmental footprint with sustainable materials – Win – Win.
Case Study: When Is a Bridge Better Than a Culvert?
Breakdown or Why a Timber Bridge Was Chosen Over a Culvert
| Consideration | Culvert | Timber Bridge |
| Permitting | Failed 100-year flood test | Permitted |
| Environmental Impacts & Mitigation | 81,823 | 31,060 saft (reduced by 62%) |
| Cost | $150K more than the bridge due to mitigation costs | Less expensive due to low environmental impact |
| Maintenance & Risk | Limited to 192 sqft of flow within flood area & caused rise in 100-yr flood elevation | Provides 429 sqft of flow within flood area |
| Aesthetics | Dirt & Sod | Custom design options |