This time of year there should not be many coliforms in the water. Levels typically rise in the spring and summer when there are more animals moving about and sediments are washed into the surface water by spring runoff and rain. Faecal coliforms were found in the untreated water from Schwatka Lake in about one-third of the 1999 tests. These results mean that you probably do not want to drink water straight from the Yukon River, but it does mean that water must be chlorinated to ensure that the water coming out of your tap is safe to drink. In Whitehorse, the main line of defence against all waterborne disease is in the room next door, where tanks of chlorine gas are stored.
Chlorine is injected into the untreated water before it is pumped through the distribution system.
To ensure that chlorine is always added to the water supply, the water pumping system shuts down if the chlorine system fails. Walden has been collecting these samples for about 15 years, and says that he has never had a bad sample of chlorinated water in that time. He is a certified wastewater operator and regularly gives tours of the system to school groups and other interested parties. Chlorine does not always kill giardia, a tiny microorganism that can cause the gastro-intestinal disease giardiasis. It can be treated with prescription drugs, but will usually clear up on its own in healthy people.