By Charlie Maclean-Bristol, MBCI FEPS
The news during the past week seems to have been dominated by the possibility of military intervention in Syria. However, an item which has been pushed down the order of news, is the ‘Rim Fire’ in the north-western part of Yosemite national park. Although wild fires seem reasonably common in the USA, this one caught my eye as the ash from the fire threatened to pollute the Hetch Hetchy reservoir, which provides water to 2.6 million people and provides 85 percent of the water to the city of San Francisco.
Having worked at Anglian Water in the UK for seven years, first as Emergency Planning Manager and then as as Head of Security and Business Continuity, I always take a keen interest in any emergency involving water. The contamination of water by ash is an incident that is new to me and I wonder how serious it is? Even with my limited knowledge of clean water purification, I know that water plants are pretty good at taking out any possible contaminants. In fact, due to the massive dilution associated with a large reservoir and the quality of the treatment, unless you dump lorry loads of contaminants into a reservoir it is actually very hard to pollute an entire reservoir.
Where pollutants have entered the water system it is usually at the processing stage. A classic case of this was the leaking of diesel from a generator into the water supply of part of Glasgow in 1997, which lead Scottish Water to issue a ‘do not drink’ notice to 50,000 people. This was not caused by a spill into one of the reservoirs that fed the city but at the actual water treatment plant.