Home > Projects > Streambank Stabilization/Directional Drilling – Missisquoi River
Streambank Stabilization/Directional Drilling – Missisquoi River
Richford, Vermont
Professional Services Provided
- Water Resources Engineering
Description of Professional Services
The Town of Richford’s water transmission line crossed the Missisquoi River and was buried just below the river bottom and subject to damage by movements of the River, exposing the Roosevelt-era cast iron pipe. Flowing water, combined with a braided stream channel, repeatedly caused the streambank to erode over the line, damaging the Town’s primary water supply pipe. Emergency repair costs over the previous ten years were estimated at $380,000. Temporary stabilization, using fill/stone rip rap, resulted in continued impacts to the ecological resources. Twice, extensive repairs were necessary when the transmission line had been exposed and broken.
The instability of the soil, high groundwater, and the potential impact to the ecosystem, archaeological and agricultural resources made “cut and cover” construction technique unfeasible. DuBois & King designed a new 2500-foot, 14-inch diameter waterline installed with directional drilling technology. Locating the new line twenty feet under the river, directly below the existing waterline, allowed continuance of water supply to the Town during construction and avoided impacts to the rich area resources. The installation involved electro-fusing of 20-foot lengths of pipe while the drilling advanced for a twenty-hour continuous period to install the first section and a twelve hour period for the second. Electro-fusing during drilling allowed continuous installation, thus saving significant time. The replacement pipe is a 14-inch, 200-psi class polyethylene pipe that is rated to last for 100 years. The project represents Vermont's longest directional drilling project of its size (16-inch diameter boring).
The construction costs for the long-term directional drilling solution were $360,000.00 and under budget. Cost savings were augmented by spreading disturbed, nutrient-rich soil over the abutting farm fields, which eliminated the need and impacts of a disposal plan.
Timing was critical for coordination with abutting landowner, who required the project to be constructed after the harvest to minimize construction impacts to agriculture. Back to Top
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