Halton Zone 4 Feedermain - Tunneling A Confined Aquifer Beneath Major Railways and Highways

摘要

The Zone 4 Feedermain Project involves the installation of approximately 13,000m of trunk watermain from Trafalgar Road and Britannia Road to the Zone 4 Reservoir near Trafalgar Road and No.5 Side Road. The watermain was designed to be installed by both open cut and trenchless methodologies and includes 3,100m of 1200mm diameter feedermain, 7,070m of twin 900mm diameter feedermain and 2,800m of single 900mm feedermain. 4,080m of the watermains is to be installed by trenchless methods with tunnel diameters ranging from 1,800mm to 3,500mm.This paper will focus on the challenges involved with planning and designing the construction of the 2,470m – 3,500mm diameter tunnel from south of the Canadian Pacific Railway lines on Trafalgar Road to north of the Steeles Avenue and Trafalgar Road intersection. The tunnel is required to facilitate twin 900mm diameter watermains and the shafts will facilitate the construction of the isolation chambers. The tunnel alignment crosses the Canadian Pacific Railway, a tributary of Sixteen Mile Creek, Highway 401, the Toronto Premium Outlet Mall, Steeles Avenue and two box culverts through a confined artesian aquifer with head pressure 1.5m above grade at the intermediate shaft locations near Highway 401.The total length of the tunnel is 2,470m with two intermediate shafts, one north and one south of the Highway 401 to facilitate the construction of interconnection chambers. The longest tunnel drive is 1,062m from the intermediate shaft north of Highway 401. Currently there are no distribution watermains along Trafalgar Road so all residents and businesses in the area rely on the aquifer for their water source, for this reason it was imperative to undertake a design that mitigated impacts to the aquifer.