Magalloway River Bank Stabilization
This project included relocating a failed portion of NH Route 16 in Errol and stabilizing the bank along the Magalloway River. A key challenge of the project was to use natural materials so that the bank would return to a vegetated state with good habitat and matching surrounding conditions in the Umbagog National Wildlife Refuge. SLR, formerly Milone & MacBroom, collaborated with McFarland Johnson (MJ) on an alternatives analysis to repair the failed roadway and bank. The preferred alternative selected was a novel ballasted tree revetment to stabilize the bank and create a base for overlying soil and plantings.
J.P. Sicard (JPS) was the successful bidder on the NHDOT project. SLR worked with JPS to complete the final design for the tree revetment. We performed stability calculations following methods developed by the US Forest Service. We prepared a design plan to illustrate the plan and section of the proposed tree revetment. JPS successfully built the project in 2021. This project provides value to the engineering profession as it used a novel approach to a common problem – bank erosion. This approach is growing in popularity in the Unites States, and we now have an example of a successful installation in New Hampshire to build on. If bank revegetation, fish habitat enhancement, and natural site aesthetics are high on the list of project objectives, the ballasted tree revetment can be used in place of common riprap.