GEI was retained by Maple Site Solutions to design a temporary shoring system to facilitate the construction of an underground pumping station. The construction of the Caledonia Pumping Station structure required an excavation to a depth of 15.5m below grade surface.

To facilitate the construction of this underground pumping station, GEI designed a water-tight excavation support system to resist the imposed loads due to soil, water, and surcharges of construction equipment. The excavation support system consisted of interlocking secant piles and fillers embedded into rock and was braced with corner braces and face walers. This system allowed for appropriate working space, while ensuring no groundwater seepage into the excavation.

The major challenge with this project was to ensure that the verticality and interlock of the caissons was within the design tolerance requirements, which are critical in ensuring the water tightness of the structure. GEI conducted thorough field review site visits to inspect and ensure that adequate verticality and interlock between the caissons was achieved, as well as to ensure that other bracing elements adhered to design.