MICROBIAL POLLUTION OF GROUNDWATER IN THE TOWN OF WALKERTON, CANADA Implications for the Development of Appropriate Aquifer Protection Strategies

摘要

In May 2000, the town of Walkerton, Ontario suffered one of Canada's worst outbreaks of waterborne disease. In the final toll, 2,300 people became ill and seven people died. The principal pathogens were Escherichia coli O157:H7 and Campylobacter jejuni, both found in the town's municipal well-water supply. The outbreak sparked intensive hydrogeological investigations and a nine-month long independent commission of inquiry. Two reports were issued. Part 1 focused on Walkerton and identified a cattle farm adjacent to the primary pumping well as the most probable cause of the outbreak. Part 2 delved deeply into all aspects of water supply in the Province and documented 93 commission recommendations concerning the Province-wide delivery of safe drinking water. The very first recommendation highlighted the need for adequate groundwater management and protection. To its credit, the government responded well to many of the issues raised, mostly as they relate to infrastructure, the operation of municipal water sources, the training of operators and data collection. However, from a hydrogeological perspective, the government's response has been disappointing, particularly with regard to its prescribed methodologies for groundwater protection. A program for mapping groundwater vulnerability and wellhead protection areas was hastily assembled following the Walkerton outbreak but is seriously under-funded, piece-meal in approach, and in several cases scientifically ill-conceived. Ultimately, there are no simple solutions and no easy short cuts, and the successful implementation of groundwater protection measures in Ontario will demand a serious commitment of funds and resources to advance significantly our basic understanding of the Province's groundwater resources and provide key input data.