By Bronwen Ledger
What Happened in Walkerton?Engineering
When a small town in southern Ontario discovered that its water supply was contaminated in May, the reverberating shock waves amounted to one of the biggest scandals to hit municipal and provincial po...
When a small town in southern Ontario discovered that its water supply was contaminated in May, the reverberating shock waves amounted to one of the biggest scandals to hit municipal and provincial politics in years. The Ontario Government immediately called an official enquiry into what had gone wrong, and it put regulations in place where before it had been relying on guidelines to ensure that municipalities delivered water safely.
The situation in Walkerton also resulted in the speediest and most extensive clean-up of a water supply infrastructure ever to take place in Ontario — too late, alas, for the seven people who died, including one infant, as a result of drinking the polluted water. Throughout the summer and into October, an army of consulting engineers was set to work, led by the Ontario Clean Water Agency (OCWA). The crown agency was brought in by Walkerton’s Public Utility Commission, Walkerton being part of the municipality of Brockton.
First came the problem of finding out what had gone wrong. How had the deadly bacteria E. coli 0157:H7 got into Walkerton’s system? The bacteria is known to come from cattle manure or sewage. It causes severe gastrointestinal sickness, with stomach cramps, diarrhea, fever and vomiting, to the point where it can have long-term health effects and cause death. Golder Associates’ London, Ontario office (Dan Brown) investigated the town’s three wells, looking at their structural integrity and doing hydrology and microbial tests. GAP EnviroMicrobial of London (Garry Palmateer) did microbial testing of the town’s water mains and distribution network. Meanwhile B.M. Ross and Associates (Steve Burns, P.Eng.) of Goderich, the engineering firm that Walkerton retained to act for it at the beginning of the crisis, considered various other possible scenarios that could have led to the bacteria entering the system. They investigated whether the infrastructure could have been compromised during a recent fire, when the system became depressurized by firefighters. They looked at new construction sites, and connections with private wells.
Steve Burns of B.M. Ross pulled all the results of this research together and wrote a Report of Cause in October. It found that the source of the contamination was most likely Well No. 5, a well which had been constructed in 1979 and supplied the town with about 60 per cent of its water. When the well was designed one of the original recommendations was that there should be a protected buffer zone, but this had not been implemented and livestock were grazing in the fields around the well. After heavy rainstorm floods in early May, bacteria-laden manure had probably run off the surface and entered the well or its aquifer. The chlorine disinfecting system had not been able to cope.
At the Consulting Engineers of Ontario session at Construct Canada in November, Dan Newman, Ontario’s Ministry of the Environment, called the Walkerton clean-up effort “the most extensive remediation effort undertaken.” He described how the plumbing in 1,800 buildings had to be disinfected, 5,000 water samples were taken, and all the private wells and cisterns had to be checked and, if necessary, disconnected.
One of the biggest tasks was replacing five kilometres of 100-mm cast iron water main with 150-mm PVC pipe. KMK Consultants’ Kitchener office (Stuart Winchester, P.Eng.) was the engineer for that, while Giffels Associates helped a contractor do house-to-house swabbing and disinfection.
The Ontario Clean Water Agency has commissioned R.V. Anderson & Associates of Toronto to find both short and long-term ways of guaranteeing Walkerton with safe water in the future. Project director is Hershel Guttman, P.Eng., and project manager is Kenneth Campbell, P.Eng. They are considering five or six different options, one of which (though the most expensive) is to build a supply pipe from Lake Huron.
As an immediate measure to help Walkerton, however, R.V. Anderson decided to bring in a containerized ultra-filtration water treatment unit. This is part of a multi-barrier approach, which includes wellhead protection and chlorine disinfection. A mobile ZeeWeed ultrafiltration unit by Zenon was installed in October at well #7, producing up to 5,000 cubic metres per day. The raw groundwater is filtered through hollow fibre membranes attached to the suction side of an ANSI end suction centrifugal pump. With a nominal pore size of 0.04 m, the membranes produce filtered water with less than 0.1 NTU of turbidity. The unit’s PLC is connected to OCWA’s Outpost Supervisory Control and Data Acquisition system, which has been put in place to oversee Walkerton’s entire water infrastructure.
On December 5, Walkerton’s residents were told they could once more enjoy a drink of water from the tap. A massive six month effort had been required to restore what most western societies see as a basic right. Millions of dollars had been spent. Lives had been lost, over 2,000 had fallen ill, and careers and businesses had been devastated.
So what have we learned? Besides imposing new laws, the provincial government has launched a program to test municipal water treatment plants across the province, and is making money available for the necessary repairs. The need is great: half of the systems tested so far have been found to be deficient.
These programs will stimulate lots of demand for consulting engineers, who are being hired in many capacities, including doing testing and redesigning plants. However, some have cautioned against thinking of the profession as the White Knight riding in on its charger to save the day. They say that that engineers dropped the ball in the first place in letting the situation with water and other infrastructure deteriorate to such a point. Meanwhile, the legal battles have begun: the Toronto Star reported that a third party lawsuit is being brought against companies who were originally involved in designing the ill-fated Well No. 5 in Walkerton.CCE