After a Tornado

When a tornado devastated the southern Ontario town of Goderich in August 2011, it also shattered many of the above-ground structures of the town’s largest employer, Sifto salt. The storm formed at Sifto’s rock salt mine and took only 13 seconds to cross the town to Sifto’s evaporator plant. The tornado damaged the plant’s boiler house, evaporation plant, processing tower and maintenance buildings.

Ausenco was called in to help get Sifto’s evaporation plant back up and running. This was not a typical engineering project, but rather a very fast paced engineering and construction management assignment, requiring a variety of trades to cover all aspects of the work.

Good engineering, careful project and construction management, and collaboration with the insurance companies who would ultimately be paying for the re-build helped the company meet critical delivery schedules, get the workforce back on the job and give the community a much-needed bit of optimism.

The tornado’s winds had ripped the roofs off most of the plant’s buildings. Low air pressure had caused the higher pressure inside the buildings to push the roofs of lightweight cement panels upward. As the panels failed and dropped to the floors below, they brought down the lighting systems, ventilation ducts and other building services that had been supported from the roofs.

The winds also shredded the asbestos cement wall cladding on the exterior walls, including the 53-metre high processing tower. The asbestos-containing materials would require special handling in compliance with Ministry of Labour guidelines.

The salt itself also created challenges that called for quick action. Salt turns corrosive when wet, potentially eating into the structural steel, plumbing, ventilation ducts, electrical cabling and control systems. With the roofs gone and rainy weather in the weeks after the tornado, it was impossible to keep the salt-laden equipment dry. With all walls and roofs gone and no lighting or power yet available, this was a complex situation.

Working with few drawings and limited information on the buildings and process power-and-control systems, the Ausenco team began by formulating a plan to assess what systems could be salvaged and what could be done to seal the buildings.

Much of the previous electrical wiring and infrastructure such as ventilation systems and piping was disposed of, along with the remains of the roofing and wall cladding materials.

With winter fast approaching, our next priority was to get Sifto’s consumer deicing salt production underway again. When the tornado struck, Sifto had been on the verge of ramping up production to meet the seasonal demand. We needed to develop a way to bring production back on line.

To reconstruct new walls and roof shells onto the existing building skeleton we used compatible materials that could meet the company standards, the Ontario Building Code and other regulatory bodies. We needed to locate cost-efficient materials that were available in large quantities on short notice.

We determined that the most effective roofing solution was galvanized steel decking that was specially rolled for this job, topped off with insulation boards and a built up roofing system. The new roofing materials were screwed down to the existing framework with stainless-steel screws. For the walls, we chose insulated panels made of fibre-reinforced plastic.

Since many of the existing buildings dated back to the 1960s, we also installed upgraded heating and ventilation systems and a current fire-suppression system. We tested the previous steam header piping system and found some of it to be workable, so we were able to connect new and existing heaters and small bore distribution piping to it.

Throughout the process, it was important that construction interfere as little as possible with processing, storing and shipping Sifto’s products and to ensure that quality standards were never compromised.

Just six weeks after the storm, the majority of the evaporator plant’s workforce was back at work in unusual but safe conditions. In five months, most of the building was weather tight and the plant’s production was back in full swing.cce

Alan Greer, CET is operations manager with Ausenco in Burlington, Ont. E-mail, Alan.Greer@ausenco.com.