Newsletter -October 1998

Ontario's largest jacked storm sewer is in Richmond Hill

The largest jacked concrete pipe storm sewer in Ontario history is in Richmond Hill. A single tunnel was specified for the installation of a 3000 mm storm sewer and a 600 mm sanitary sewer (suspended from the top of the storm sewer) under two major railway lines. It was imperative to keep the railway lines open, as the track has a daily average of 22 freight trains, six GO Trains and four VIA Rail trains. Precision construction was required to achieve a deviation tolerance of no more than 6 mm at the top of the track.

A two-tiered dewatering system was installed at the site to deal with groundwater above and below the storm sewer. Because standard well points are only effective to five metres, water was vacuumed from the soil. The use of compressed air for removing the water was ruled out because there was less than two pipe diameters of cover between the tracks and top of the jacked pipe.

To accommodate the sanitary sewer hung from the ceiling, special stainless-steel bolts and brackets were installed and extra care taken to ensure the strength and integrity of the pipe and its connections. A specialized pipe design program, Pipecar, was used to verify the detailed steel design requirements for the pipe. The pipe was produced to CAN/CSA-A257.2-M92 standard.

Installation began June 11, 1998 with the delivery of the first of 21 sections of pipe ­ each weighing up to 17 tonnes. A 12 tonne, 3.6 m diameter by 4 m long shield (that allowed for pneumatic hand mining of the tunnel with a mucking machine removing material as the tunnel advanced) was specially constructed for the project. Pipe sections were jacked behind the liner using jacking pressure of 19 MPa and bentonite slurry to fill voids and lubricate the pipe.

The installed jacking spacer worked well to minimize rebound and concrete crushing. During the entire operation, a survey crew was on-site (living in tents) to record any change in track elevation each time a train passed. After grouting the lift holes of the storm sewer sections, the sanitary line was installed and sprayed with Shotcrete for additional protection.

The team of companies assembled for the project included Marshall Macklin Monaghan, Con Cast Pipe, Yonge-Bayview Holdings Inc., Metrus Development Inc., Geo-Canada Ltd., Peran Tunnelling and Atlas Dewatering.

Back to Archive