Trenchless Technology

OCT 2018

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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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