Special Projects Award of Excellence
Lowering the Regional Groundwater Table – Nutashkuan WSP
Considering solutions Nutashkuan is located on the shores of the St. Lawrence River at Pointe Parent, where the estuary and the Gulf of Natashquan meet. Relatively flat, the region is characterized by vast and very permeable sandy deposits, which have a direct effect on the level of the groundwater table. WSP’s engineering team had to find a way to control the rise of groundwater in the affected area. Traditional solutions included raising homes, installing pumping stations in several locations or installing pumps in each of the affected 50
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homes. Even if technically feasible, these solutions would have required major investments, trained operators and maintenance for further upkeep, which made them unattractive to the Band Council. An innovative solution was proposed and studied, which included creating a tunnel upstream of the community to intercept and reroute underground waters away from the affected homes, therefore lowering the water table all along the affected community. Difficulties included avoiding any pumping systems, the lack of terrain slopes, nearby Gulf high tides and future climate variations. Developing a new application The project’s complexity was amplified by the community’s remoteness
“This is a cool, interesting project that will have a valuable impact on its community.” - Jury
and its specific location along the shores of the Natashquan River. All of the community’s homes were built without footing drains, since no stormwater network had enough slopes to carry these waters away by gravity. The frustration of flooded residents and the urgency of preventing further events the next spring added to the difficult conditions under which the team had to work. Within six months, the designers worked with hydrogeology experts to implement a groundwater monitoring program and in situ permeability tests and to generate a computer model to reproduce the hydraulic behaviour of the groundwater table, based on knowledge of the area’s terrain acquired over several years of collab-
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ue to its location along the Gulf of St. Lawrence and its low elevation above sea level, the Nutashkuan Innu First Nation—a community of 1,077 residents—had been subjected for several years to recurring problems with flooding during the annual spring thaw. The issue became particularly severe in 2017, when approximately 60 homes were flooded, resulting in $4 million worth of damages. After the 2017 spring floods, WSP was commissioned to quickly develop a solution to protect the community through a controlled lowering of the regional groundwater table.
September/October 2021
2021-10-18 10:14 AM
