The Regional Municipality of York (York Region) is no stranger to trenchless technologies having undertaken a variety of new installation and rehabilitation projects over the years.
The Region owns and operates approximately 300 km of trunk sewer systems and approximately 300 km of pressurized systems, including both sewage forcemains and watermains across a total area of 1,776 sq km.
On the rehabilitation side, the Region has used sprayed-in-place pipe (SIPP), sliplining and CIPP. Specifically, the Region has used geopolymer spray liner (for SIPP), centrifugally cast fiberglass-reinforced polymer mortar pipe (HOBAS) for sliplining and multiple incarnations of CIPP liner.
The core of any good rehabilitation program is having good data to base the rehabilitation on, so the Region proactively cleans and inspects its sewer infrastructure on a regular basis. During a routine inspection in 2018 it was revealed that a corrugated steel pipe (CSP) arch culvert under King Road, approximately 1.33 km east of Keele Street, in the Township of King was showing signs of deterioration. The culvert, constructed in 1990, has a 2.5 m span by 2.1 m rise and 41.4 m long under the roadway.
It was put on its roster for a planned repair and the project went to tender in early 2022 as a SIPP project using geopolymer mortar.
“The spray-on liner solution provides the minimum thickness of liner required to restore the structure’s loading capacity, while maintaining its hydraulic capacity,” says Shu Zhu, senior project manager, Capital Planning and Delivery for York Region, explaining why the Region chose SIPP over sliplining, as well as open-cut. “[The] benefits include the ability for construction work to be carried out below the road grade; it minimized duration of construction compared with other alternatives and it provided the most cost-effective solution to extending the service life of the culvert.”
An Alternative to Gepolymer
The winning bidder on the project was Schomberg, Ontario-based Aqua Tech Solution Inc. whose rehabilitation offerings include fold and form sewer relining as well as SIPP using Nukote. For this project Aqua Tech proposed using the hybrid polyurea Nukote PP300 and ST-PW products.
“We signed on with Nukote in 2021 and this was our first large culvert we sprayed with our own crews. We’ve done other culverts, but we used a subcontractor to spray the Nukote product,” says Matthew Santorreli, owner of Aqua Tech Solutions. “It was specified as a geopolymer and we asked if the polyurea could be used and they accepted that as an alternative. The Nukote product provided a flexible solution that still provides the structural integrity required in the contract.”
Prior to applying the product, the crew handled the cleaning, dewatering and bypass works for the culvert. This, Santorelli notes, was probably the most difficult part of this project.
“This culvert was at the bottom of a 20-ft hill with a steep slope,” says Devin Ricalis, project manager, Aqua Tech Solutions. ”We had to run hoses down the hill [for the cleaning] and sucked the materials up to our vac trucks on the road. By being able to keep most of our equipment on the road, this limited the damage to the area around the culvert.”
According to Santorelli, his crews removed 1 to 1.2 cubic metres of sediment, noting that it was more than he anticipated when the project was bid. “It was in really bad shape,” he says. “There were a lot of voids that needed to be filled.”
Once cleaned, the team dewatered the area on both sides of the culvert, set up coffer dams and routed the flow, via bypass, to a box culvert approximately 20 m away. They used flowable concrete to fill the voids in the invert. This also gave the Nukote application robot a smooth surface to travel in the culvert.
“The prep work is so important,” says Santorelli. “In this case it’s with the sediment removal and prep work. It might be a good lesson to all contractors, the prep was challenging. It was not a quick cleaning process.”
Because the installation was completed with the Nukote 360 Ringtech Robot, Santorelli notes that the product application is much more uniform than if applied by a person in the pipe. “There is less room for error, we don’t have to switch out employees and it keeps our crews safe,” he says. For this project it also meant that less manpower was required at the bottom of the hill.
The product was applied in three layers. The first coat is a layer of the Nukote ST-PW product which provides waterproofing and corrosion protection between the host pipe and the structural layer. The second layer is the Nukote PP300 and then a final coat of the ST-PW for corrosion protection.
Ricalis notes that the Nukote product contains no volatile organic compounds (VOCs), no styrene and is ANSI/NSF-61 certified for direct contact with potable water. Though this was not a potable water relining, this is important as native species of animals often travel through culverts.
“The product opens up the world of rehab to system owners who have stuck to using cement-based products for many years,” says Santorelli. “We can install Nukote robotically in pipes up to 3 m and larger pipes by hand, as well as manholes.”