Both provincial and municipal governments have some level of responsibility in ensuring the safety of Newfoundland and Labrador's drinking water. The provincial government, in cooperation with municipal governments protects source water quality through the watershed protection program. The Department of Environment provide the drinking water quality data along with a brief interpretation to municipal governments on a regular basis. Information on the development of these Guidelines can also be found on Health Canada's web site.
Chlorination is necessary for two reasons.
First, almost all sources of surface water contain microbiological organisms, which have to be removed in order to prevent the outbreak of waterborne diseases such as typhoid fever and cholera. Second, once the treated water leaves the treatment plant, it may travel through water mains and pipes sometimes at significant distances, before it reaches it's destination. During this time, it is necessary to maintain a residual level of disinfectant in the water to ensure no possible regrowth of microorganisms. Without adequate disinfection, the health risks from microorganisms far outweigh the risks from THMs. The guideline is based on an annual running average of quarterly samples to account for seasonal variations.