Wet Well Rehab in Hamilton
During routine maintenance of the Pier 12 wet well, the Hamilton Port Authority found the asset nearing the end of its service life. Originally installed in 1981, the steel vessel with a 6-mm original nominal wall thickness, was found to be heavily corroded, requiring replacement to ensure long-term stability and water tightness.
Located on the shores of Lake Ontario, Pier 12 is one of the busiest piers in the port. More than 700,000 tonnes of cargo are handled per year on Pier 12 including fertilizer, aggregates, salt and steel. The pier includes warehouses and a dry bulk good storage facility. The wet well rehabilitation project is part of a three-year reconstruction of the west wharf of Pier 12. Reconstruction work began in 2018 with an anticipated completion in 2020.
Replacement of the 6.5-m deep by 3-m wide vessel posed many technical and practical challenges. The Pier 12 wet well sits on reclaimed land, resulting in a high-water table. Caissons would be required for vessel replacement, but location, existing utilities and cost made this challenging. Structural rehabilitation of the wet well with a spray-applied lining was investigated and found to be a more cost effective solution, that also reduced the impact to the surrounding operation during construction with a shorter construction timeline.
Empipe Solutions Ltd., of Hannon, Ontario, a certified application partner for SprayRoq was selected to complete the rehabilitation project using SprayRoq SprayWall. The product is a spray-applied, 100 per cent, VOC-free polyurethane coating that provides both structural enhancement and chemical resistance with a 50-year design life.
Crews for Empipe prepared the vessel for lining by pressure washing and shotblasting to remove rust, paint, debris and to prepare the surface profile. Shotblasting produced the required surface profile of 7 mils for adhesion requirements. All inflow and outflow pipes were under bypass and fixtures inside the vessel were wrapped and protected prior to shotblasting.
SprayWall was the preferred product due to the deteriorated condition of the vessel and the high hydrostatic pressures and geotechnical forces. SprayWall was applied not simply as a corrosion barrier, but as a structural liner – effectively a new vessel was constructed inside the existing deteriorating steel vessel.
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Empipe worked with structural engineers from AECOM to provide a structural design capable of withstanding the expected loads, resulting in varied thickness throughout the structure to meet the design requirements.
Empipe ensured all design thickness requirements were met by breaking down the square footage of the structure in workable areas, then calculating the weight requirements needed to achieve said design. The thickness of the liner was tapered near the top of chimney which was above grade, where no hydrostatic or live load are experienced, to allow the lid to close.
SprayWall is well suited to high build applications as the gel time is less than 30 seconds but spraying to that thickness creates operational and safety challenges that required diligent management, especially in large and enclosed spaces. Prior to spraying, the substrate to be coated must be heated to between 32 to 49 C to ensure proper bonding and polyurethane curing. A 750,000 BTU heater required more than 24 hours to heat the Pier 12 Wet Well to over 32 C to allow spraying to commence.
Crew safety was complicated by the depth of the vessel, as a scaffold was required to be constructed inside, the extreme temperatures within and impaired visibility during to the spraying process. Empipe is highly experienced in confined space operations and are comfortable in this environment with more than 12 years of experience. Empipe worked in tandem with the Hamilton Port Authority’s safety protocol, resulting in zero near misses, zero injuries and zero lost time incidents.
The reaction of the polyurethane components is highly exothermic. Once spraying commenced, the product produces excess heat, requiring constant monitoring of the temperature of the vessel and substrate. Keeping the vessel in the required temperature range was further complicated by the substantial temperature gradient within the vessel. Spraying must be completed at a measured rate to prevent overheating of the vessel and the applicator; however, heat must be added to the structure during drum change overs, crew breaks, scaffolding setups and any mechanical breakdown.
To limit the risk of a temperature range breach that could jeopardize the entire project, Empipe elected to spray 24 hours a day, for six days, to apply the 14,600 lbs. of SprayWall required to complete the re-lining and meet all design requirements. Empipe has extensive experience with SprayWall in high build applications providing the necessary experience to successfully complete this unique project. The extreme conditions – heat, confined space, volume applied, and high build required an experienced crew and exceptional logistics.
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The Pier 12 wet well high mil build on the floor and the overhead reducer. Spraying the floor proved to be the most challenging portion of the relining. Coating the floor proved difficult due to the thickness of the coat, working around equipment standoffs and managing the heat generated.
Once spraying was completed, the temperature of the vessel was gradually reduced to prevent thermal shock and the pumps and controllers were re-installed allowing the vessel to return to service. The Pier 12 wet well was returned to service, on time, on budget, with minimal disruption to the adjacent businesses and traffic with a new 50-year service life.
Michael Guest, P.Eng., is business development manager at Empipe Solutions Ltd.
