By Flemming P. Jespersen*
*Municipal Coordinator, InLine Technologies Inc., Maple, Ontario
The City of Toronto has developed a reputation for stringent performance and quality specifications in the field of trenchless technologies after exposure to a number of sewer rehabilitation processes.
When it was time recently to reline sections of the busy downtown area of Adelaide Street West, the City awarded the contract to InLine Technologies Inc. (The Canadian licensee of InLiner USA®).
The contract involved the rehabilitation of approximately 1500 ft. of 12 in. vitrified clay sanitary sewer which was suffering from varying degrees of cracking and localized missing segments. The proximity to other utility conduits (hydro, gas, water and telephone) rendered open cut operations cost prohibitive and time consuming. In addition, the majority of the sewer length runs under Adelaide Street, a very busy arterial roadway in downtown Toronto. The sections are bordered in the south by Toronto's theatre district and in the west by Toronto's fashion district. Several of the City's night clubs are directly located above this run, which also includes a busy fire station.
An extensive dye test program was included to eliminate "dead" lateral connections as well as provide information needed for the establishment of building bypass pumping procedures. The main objective was to maintain unrestricted use of the building sewer services without the inconvenience, noise or restrictions which are associated with conventional sewer repair and replacement methods. Every phase was painstakingly reviewed and approved by the City staff to ensure the best possible execution of each task. Several weeks of planning and preparation were needed to coordinate efforts involving: Bell Canada, business operators and building owners, Metropolitan Toronto Fire Department, Metro Transportation Branch, Metropolitan Toronto Police, restaurants and night club owners, The City of Toronto, Toronto Hydro and Toronto Transit Commission.
The Adelaide Street installations were performed over weekends to minimize traffic congestion and impact of the rehabilitation on commercial businesses. On one installation, six individual building bypasses were established to accommodate two night clubs, two restaurants, one fire hall, and commercial buildings. During night installation some 80 toilets serving over 3500 patrons were bypassed while the sewer main servicing was being rehabilitated. An emergency access lane for the fire station was maintained throughout the entire contract enabling the fire department to respond to an average of 10 alarms per day, seven days a week.
InLiner combines a polyester needle punched felt tube with a thermosetting epoxy based vinyl ester resin to create a cured-in-place pipe within a pipe. It is installed through existing access points eliminating the need for excavation.
A two-stage process, the first stage involves the resin impregnation or "wetout". The felt tubes are manufactured to specified diameters and lengths. The tube thickness can vary dependent upon the design parameters of a given sewer and each tube is custom engineered to meet the requirements of specific installations. The felt tube component of the finished product acts only as a carrier or form for the resin. The felt does not structurally enhance the resin.
An impermeable skin is bonded to a thin layer of felt. This layer is placed on the outside of the tube with the felt facing inward, providing abrasion protection to the tube during installation and to provide a reservoir for the containment of the resin during the wetout. A calibration hose, which will later serve as an inner-tube for the inflation and curing process on site, is also manufactured from polyurethane-coated felt. Both the tube and calibration hose are measured, inspected and pressure tested prior to being shipped from the manufacturing facility in Houston, Texas.
Upon arrival in Canada, the tubes are examined for defects and the dimensions verified. Once completed, the tubes are impregnated with a thermosetting resin under vacuum pressure to ensure a complete saturation of all the felt fibers. A predetermined quantity of resin is pumped into the tube. The tube is then passed through a set of pinch rollers and along a conveyor belt to be loaded into a refrigerated truck ready to transport to site. Just prior to being loaded into the truck, the wetout tube passes through a set of perforation rollers effectively creating a series of pin holes along the entire length of the tube. These perforations allow a calculated amount of resin to migrate against the pipe wall and into joints and cracks effectively creating a bond between the host pipe and the newly formed pipe while maintaining a uniform design thickness.
The on site installation commenced with the following routine:
The process utilizes a polyethylene/polyurethane coated polyester needle punched felt that acts as a form for the resin, providing dimensional stability and strength during installation and curing.
Drain reinstatements utilizing the Beaver Lateral Cutting system are the final stage. The package includes two fully operational cutters, two control units, two umbilical cords, assorted cutting heads, silenced compressor and generator. The cutters operate separately from the Closed Circuit TV unit allowing the use of any CCTV unit should the need arise.
The liner fits tightly against the existing pipe walls without any annular space, resulting in increased strength through a mechanical bonding between the pipe and the existing pipe. During installation, a calculated amount of resin migrates from the perforations into the joints and cracks of the existing pipe surface. Once cured, the resin mechanically locks the cracked, broken pieces together.
The damaged sewer main now has been given a new 50 year lease on life. Flow characteristics have been improved, and infiltration eliminated. The entire operation was completed without any excavations and without complaint from either building owners or businesses; and the contract was completed with time to spare.