Early in 2018, the City of Moncton, New Brunswick, and the New Brunswick Department of Transportation (NBDTI) partnered to prepare and evaluate a request-for-proposal (RFP) for the rehabilitation of a joint storm sewer using trenchless technology.
This corrugated metal sewer, installed in the 1970s, is approximately 800 m long and is composed of an 1,800-mm diameter section and a 2,100-mm diameter section. The sewer had reached the end of its service life. As noted from CCTV and man-entry inspections, certain sections of the pipe below normal water levels were severally corroded. Additionally, the rehabilitation of this sewer section is a recommendation from the City’s Sewer System Review and Master Plan which was completed after severe flooding occurred in the area.
The location of the sewer was the decision factor to use trenchless technology as opposed to the traditional trenching method to renew this asset. The upstream section of this storm sewer system crosses residential properties while the intermediate section crosses Wheeler Boulevard and its adjacent ramps, a provincially owned four-lane divided highway. Finally, the downstream section crosses Mountain Road, the City’s busiest arterial four-lane roadway, and commercial properties before its outfall in a nearby brook.
Prior to this project, the City had completed three cured-in-place pipe (CIPP) projects on smaller diameter pipe, culvert sliplining, watermain epoxy lining and point repair systems for sewer spot repairs. While this wasn’t the City’s first use of trenchless technologies for rehabilitation, it was the first RFP using a format where all trenchless technologies meeting the required parameters would be considered, evaluated and measured against each other for their merits.
“In order to find the rehabilitation solution that would best fit this particular asset and its location, the City and NBDTI decided to open the bidding process to all trenchless technologies,” says René Lagacé, P.Eng., project engineer, for the City. “Therefore, an RFP process was selected to allow for flexibility in the proposed technologies, methodologies and work plans.
A total of four proposal submissions were received in response to the RFP, and were evaluated based on: work plan, methodology and schedule; project team; references and past experience; and project fees.
Two of the submitted proposals were for CIPP and two called for sliplining – one using steel reinforced polyethylene pipe and the other using a GRP liner. The “Storm Sewer Structural Rehabilitation by Means of Trenchless Technology” RFP was awarded to Clean Water Works Inc. being the proponent having received the highest score and proposing an “over-the-hole” CIPP installation. This would be the City’s first over-the-hole CIPP installation and its first on a corrugated steel pipe.
“There were various evaluation criteria as part of the RFP. Some of the most important criteria for the City and NBDTI were the contractor’s work plan, methodology, project team and past experience. All these categories were evaluated using a scoring matrix and the bidder with the highest overall score was selected,” says Lagacé. “The City and NBDTI were looking for a solution that would provide a structural rehabilitation and would not be a detriment to the hydraulic capacity of the pipe. The CIPP liner presented great benefits in both structural rehabilitation and hydraulic capacity.”
Design and construction challenges included restricted access for work areas and sections of sewer with significant deformations. The 800 m rehabilitation project was completed in 300-, 280- and 230-m runs. Clean Water Works used a polyurethane-coated felt inversion liner from Liner Products, of Paoli, Indiana, USA, resins from AOC Alliancys, of Guelph, Ontario; and the catalyst was provided by Min-Chem Canada. Dexter Construction, a local contractor, provided civil support by building access roads, reinstating manholes and other non-relining duties.
“The storm line that was rehabilitated is a major storm trunk sewer and sees considerable flows during storm events. Foreseeing this potential issue, Clean Water Works proposed to complete the work during a period that is traditionally known to be the driest in the Moncton area (January to March),” says Lagacé. “Despite this, crews had to manage flows from uncharacteristic rain events. Clean Water Works hired Atlas Dewatering Corp. to handle the bypass pumping.”
The project was completed between January and March, 2019 inclusively, ahead of the proposed scheduled and under budget.
This project was completed significantly faster using trenchless technology when compared to trenching methods. Additionally, when considering road and property restoration costs by trenching, the City and NBDTI also benefited from considerable savings by using a trenchless technology for this project. Finally, and perhaps most importantly, the social impact on the community was minimal when compared to the potential impacts of renewing this asset by trenching.
This project profile was compiled by Trenchless Technology Canada staff with information provided by Moncton Engineering and Environmental Services.