Sudbury’s boil water advisory may have been a false alarm

The two-day boil water advisory in Greater Sudbury from May 6-8 may have been a false alarm. (File)

A report headed to city council this week updates local politicians on the boil water advisory that hit Greater Sudbury earlier this month.

The May 26 staff report concludes the cause of the problem was either a false positive or that drinking water was contaminated briefly and then cleared up.

The two-day advisory was issued on the evening of May 6 and officially ended on the evening of May 8. The event prompted a run on bottled water at local department and grocery stores.

The city was notified that coliform was present in water tested at Well No. 6 at the Falconbridge Well Supply at 1:30 p.m. on May 6. Public Health Sudbury & Districts was notified at 1:43 p.m., and the Spills Action Centre at 1:45 p.m.

More samples tested positive for coliforms at the David Street Water Treatment plant at 1:56 p.m., and the health unit and action centre were again quickly notified.

In response, the city began increased chlorine dosing and flushed hydrants near the sample sites. More samples were collected from each site – one at the site, another upstream and a third downstream.

Samples came back negative

Public Health reviewed the information and determined by 6:19 p.m. May 6 that there was enough of a risk to public health that a boil water advisory should be issued.

More water samples were taken May 6 and May 7, and all came back clear for coliforms. Samples taken May 8 also came back clear, at which point the advisory was lifted at 6:36 p.m.

The review concludes that either the drinking water was briefly contaminated and then cleared up, or “the results were false positives.”

“Probable anomaly in sampling or analysis, but the source cannot be positively identified,” the report said.

“All available evidence indicates the city’s drinking water systems remained safe and performed as intended.”

Read the full presentation here.