99th Avenue Sanitary Tunnel Bypass

Project Overview

This project included the design and construction, and trenchless installation, of a new 1,800 mm nominal diameter ‘bypass’ sanitary tunnel, 1625 m in length. The alignment of this project included a crossing of the Mackinnon Racine and the construction of permanent drop structures and manholes, by passes and reconnections. The tunnel was to be approximately 30 m below street elevation and crossing at approximately 20 m below the ravine.

The design installation depth placed the tunnel close to the Empress Formation (Saskatchewan sand and gravel), within sandy clay, clay till soil conditions, with a high-water table and potential of encountering boulders and cobbles. Tunnelling within the sand players and high-water table required extreme care and attention to maintain the line and grade; and more importantly, control of ground loss which was the key to minimizing ground settlement.