Trenchless Technology

OCT 2018

Trenchless Technology is the premier communications vehicle for the trenchless industry. Through our multiple platforms, readers receive insights into the trenchless industry, as well as keep connected to the latest news, products and projects.

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34 T R E N C H L E S S T EC H N O LO GY O C TO B E R 2018 The Northwest Arm Trunk Sewer (NATS) in Halifax , Nova Scotia, irst began service in 1917. It had been constructed using open excavation and tunneling at depths ranging from 300 mm to 5 m. The sewer runs par- allel to the Northwest Arm, an inlet off the Atlantic Ocean that adds rec- reational and economic value to the community and increases its quality of life. The NATS sewer alignment is 0 to 15 m from the shore and generally located in an easement on privately owned multimillion-dollar residential properties. The sewer 's existing pipe varied in shape and materials, con- sisting of the following components: 1,200 mm diameter round poured concrete pipe, 1,200 mm diameter round segmental clay block, 1,200 mm x 1,500 mm (height × width) arched segmental clay with concrete bot- tom, 1,200 mm x 1,500 mm (height × width) poured concrete arch pipe. The project scope described in the RFP allowed bidders to propose the use of either cured-in-place pipe (CIPP) or a combination of CIPP and grouted- in-place pipe (GIPP). The round sec- tions of the NATS were required to be CIPP, while the arch sections could be either CIPP or GIPP. The winning pro - posal involved rehabilitating all 4,000 m using CIPP, including the arch sec- tions. To successfully complete the re- habilitation, it was necessary to over- come numerous technical challenges, including extremely limited access, load restricted bridges, bypassing lows, onerous cleaning of debris (700 m³), and complex engineering design and installation of CIPP in an arch- shaped pipe structure — all on an ac- celerated completion schedule. There were also unique challenges related to explaining the project to the commu- nity and other stakeholders to obtain their support . Engaging property owners was a vital component of the project 's suc- cess. Because the sewer was located through an easement running parallel to the shore of the Northwest Arm in the front yards of residential proper- Project of the Year Z , / > / d d / K E Z h E E Z h W NATS Trunk Sewer Rehabilitation

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