South & Elm Streets, Bennington, VT

Challenge

The Town of Bennington contracted with MSK Engineers to investigate flooding near the intersection of South and Elm Street in downtown Bennington. Based on accounts by Town of Bennington officials, this area most often floods during short duration, high intensity precipitation events, and the box culvert that runs from Elm Street towards Washington Avenue was constraining stormwater flows, leading to additional flooding in the area.

Solution

Our investigation initially focused on the existing concrete box culvert which runs from Elm Street towards Washington Avenue as the primary contributor to these floods. Our team developed a study to identify possible causes and solutions, including evaluation of existing stormwater infrastructure. Since the primary trigger for flooding is believed to be these high intensity, short-duration precipitation events, traditional methods for modeling stormwater hydraulics that rely on 24-hour precipitation data were ill-suited for this application. Accordingly, we partnered with Fitzgerald Environmental Associates to develop a stormwater hydraulics and hydrology model for this area and collected empirical data obtained from rain gauges and pressure transducers that we deployed to monitor and record precipitation events water levels in the box culvert.

Based on our investigation, we concluded that the box culvert does not significantly contribute to the localized flooding that occurs on South Street. Two undersized stormwater networks in the immediate vicinity of South Street, Union Street, and Elm Street most likely cause the majority of flooding conditions in this area.

Results

Our report and estimated construction costs were delivered to the Town in 2023; development is currently pending.