Acorn provided civil design and permitting services for a stream crossing at the Muddy River on Chaplins Mill Road in Naples, Maine. Successful and timely completion of this design was critical, as Chaplins Mill Road has been overtopped frequently in recent years. The existing culvert was a failing, undersized 8-foot corrugated metal pipe, and continued degradation of the existing crossing resulted in noticeable road surface deformation, shoulder erosion, and a deep outlet scour pool.
Informed by Stream Smart principles, the design aimed to restore the hydrology, hydraulics, and fluvial geomorphology of the stream to as near as practicable to predevelopment conditions, allowing safe and uninterrupted passage of organisms and water below and vehicles and pedestrians above. The final design included an embedded 19-foot width precast clamshell concrete box culvert which was sized to safely pass a 100-year storm flow, pass floating debris, and span 1.2x the bankfull width. Embedment material inside the culver specified gradation of materials formulated to simulate the surrounding native channel substrate.
This crossing restores horizontal and vertical alignment of the stream profile toward predevelopment conditions, improving hydraulic connectivity and supporting movement of aquatic organisms along the stream corridor. Additionally, providing ample flow capacity will enhance the resiliency of the crossing to future storm events.
