What is Dewatering?

 

Have you ever pumped water from a well, or noticed the ground get wet as you dug a deep hole? If so, you’re familiar with groundwater. 

Groundwater is everywhere. Twenty per cent of the earth’s fresh water sits underground. With the amount of deep excavation required to build the Crosstown, we’re constantly running into water that could destabilize and flood excavation sites. We solve these problems with "dewatering systems." Although these systems are complex, the idea is simple – move water away from an excavated area so the site, equipment and worker can stay dry.

At Avenue station, our crews have the unique challenge of dewatering the deepest site on the line – 32 metres at the main entrance building. They start by assessing the soil conditions and groundwater levels. Next, they drill wells at 10-metre intervals on the sidewalks along Eglinton between Braemar Avenue and Lascelles Boulevard. Lastly, they’ll dig trenches and install pipes that connect the wells and discharge the water to the sewer. The water is periodically tested, to make sure it’s safe to be discharged.

Dewatering Trench Prep Avenue Station

Workers cut the sidewalk in preparation for trenching

Because of the dewatering challenges at Avenue, the crew has invested in a special trailer that carries most of the equipment required to drill dewatering wells. This allows them to tuck the equipment away on the construction site when they’re not using it, rather than blocking the street or sidewalk. This helps us to minimize our impact on the community.

Dewatering Trailer at Avenue Station

Avenue Station’s special dewatering trailer in action