BWAs are typically issued when monitoring of water being served to consumers detects E. coli or other microbiological indicators of sewage contamination. Another reason for a BWA is a failure of distribution system integrity evidenced by a loss of system pressure. While loss of pressure does not necessarily mean the water has been contaminated, it does mean that pathogens may be able to enter the piped-water system and thus be carried to consumers.
Some countries, like Canada, have publicly available maps showing the locations of boil water advisories
Fort St. John (3)
Boil Water Advisory
Spectra Energy - Sikanni Gas Plant - Water quality advisory - Coliforms present in samples - 5/2/2011
Buckinghorse River Provincial Park - Groundwater possibly under the direct influence of surface water. - 7/1/2009
Spectra Energy - Peggo Gas Plant - No reason given - 7/4/08