Fall 2022 Squamish

The crew at PW Trenchless were up in Squamish to replace a sewer main under highway 99 via Pipe Bursting. On November 15, 2022, the first burst of 135 metres took place along Mamquam Road towards Highway 99. The exit pit was dug close to the intersection of Mamquam Road and Highway 99.

The site was not suitable for using a pair of trench shoring cages so the removal of the large pipe bursting head was a bit more complicated and required some extra excavation once the burst was completed. The burst went smoothly and the 135m of pipe were inserted via Pipe Bursting in roughly 3.5 hours.

Of course there was quite a bit of set up before the burst was started. For this project, it was decided to excavate around two manholes and jackhammer out the benching and channels of the base of the manholes. This allowed the burst to continue through the two manholes unimpeded, allowing for just one launch of the bursting tool for this 135 metre run. The two manholes had trench shoring cages supporting the excavation as well as a few spots where the existing infrastructure was excavated to make sure the bursting head could pass without causing any problems.

The entrance pit was 4 metres deep so the large diameter 450mm HDPE pipe had to have a long sloped entrance ramp excavated to allow the pipe to enter the host pipe without any grade, allowing the grade of the host pipe to be unaltered.

The HDPE pipe was fused together and there was a large lay down area on the side of the road by the golf course that was not in any vehicles or pedestrians way. There was a bypass pump system put in place and various additional pumps were set up to ensure the excavations were kept dry for the duration of the burst.

On the day prior to the burst, the pulling apparatus was put in place and the pulling rods were inserted into the Host Pipe. The pulling cone was installed on the lead end of the HDPE pipe. The morning of the burst it was moved across the road and put in alignment with the host pipe.

 The pumps looked after any existing ground water in the excavations, but luckily it was a dry sunny day. The weather was a bit cold and once the Replacement pipe was staged into the entrance pit it was discovered that the swivel that connects the Bursting head to the pull back rods had a small amount of ice in the cavity. The swivel was hung above the exhaust of one of the nearby generators that were powering the bypass pump and the ice was removed.

Once the head, swivel and pull back rods were attached, the crew took a well deserved coffee break and the burst commenced before 11a.m. The crew was diligent watching the inspection pits to make sure the bursting head and pipe went under the existing infrastructure without damaging any existing pipes.

The site was wide and traffic was only stopped a few times while excavators needed to be moved to align the pull back rods when the swivel and head were attached and then to move a generator to all the vacuum truck better access to remove debris from one of the pits.

The length and depth of this sewer main made it a perfect candidate for pipe bursting, and saved approximately 560 Tonnes of material or 40 truck loads  of material from being excavated out of a trench for open cut replacement of this pipe. Unfortunately the section of pipe under the Sea to Sky highway has had some repairs in the past so, pipe bursting that section is still being looked at as a possibility.