Municipal Systems Bacteriologically Unsafe, Regulated 170/03


Category: Safe Water
Subject: Municipal Systems Bacteriologically Unsafe, Regulated 170/03
Division: N/A
Policy Number: CA.83.01.107
Effective Date: March 1996


It is the policy of Wellington-Dufferin-Guelph Public Health to provide advice to the community in meeting the current Ontario Drinking Water Standards and to ensure that the potability of community water supplies is maintained.


Rob Thompson


Category: Safe Water
Subject: Municipal Systems Bacteriologically Unsafe, Regulated 170/03
Division: N/A
Procedure Number: CA.83.02.107
Effective Date: January 31, 2012


  1. Upon receiving unsatisfactory municipal water results, contact the waterworks owner (municipality, public utility commission or township clerk) for verification.  Document your activities (conversations and actions) on WDGPH Report form (HPD GEN (F)3).
  2. If any of the parameters listed below are found in any treated water samples, the Medical Officer of Health, Supervisor of Safe Drinking Water Branch of the Ministry of the Environment must be notified immediately.

Adverse Water Quality Includes:

  • E.Coli or fecal coliform detected in any required sample other than a raw water sample;
  • Total coliforms detected in any required sample other than a raw water sample; and
  • Unchlorinated water is directed to the distribution system where chlorination is used or required. This includes water in the distribution system that has less than 0.05 mg/1 of free available chlorine residual when tested.
  1. A course of action will be determined based on the answers to the following questions:
  • Did upstream or downstream samples show poor water quality?
  • Is other water quality data available on the samples collected?
  • Was the sample taken from a fixed sampling site?  If not, where was it collected?
  • Was any work done on the distribution or supply prior to sampling?
  • Have any mechanical difficulties or equipment failures occurred?
  • Has there been any undue demand on the reservoir?
  • What was the chlorine residual at the time of sampling?
  • Was the sample taken by the regular sampler?
  • When was the sample taken (date/time)?
  • Do historical records indicate a consistent problem?
  • Is the result from raw or treated water?
  • Is the ground water vulnerable to contamination from surface water, agricultural activity, sewage discharge, and intensive recreational use?
  • What corrective actions have been initiated?
  1. Refer to Response to Adverse Drinking Water Quality Incidents, April2009.

Note: Re-sampling should consist of a minimum of 3 samples that must be collected for each positive sampling site:  one sample at the affected site, one at an adjacent location on the same distribution line and a third sample some distance upstream on a feeder line toward the supply source.  These samples are referred to as “special samples”.

  1. Depending on the parameter found and the answers given in question #3, one of two actions will be required:
  • Request that the waterworks owner take corrective measures while a second set of special samples are collected as prescribed in Ontario Regulation 170/03.  The results are to be provided to the PHI verbally followed by a fax as soon as they become available.  If the second set of results are unsatisfactory, see steps below.

Corrective measures while waiting for second set of samples can include:

  • Ensuring adequate free available chlorine residual of>0.2 mg/L in the supply and distribution system;
  • Removing or isolating a bad supply from the rest of the system;
  • Flushing the mains;
  • Ensuring that the locations where water samples derived are appropriate and representative of the supply;
  • Ensuring that any repairs, hydrant flushing or new installations are reported; and
  • Ensuring that proper handling and sampling techniques were followed.
  • If your assessment has revealed a serious deterioration of the water quality, and a second set of samples will jeopardize the safety of the community, contact all parties involved (MOE, PUC, WDGPH) to discuss issuing a boil water advisory. Should a BWA be issued, the following course of action will be required:
    • WDGPH and the operator will need to make arrangements to contact all fixed premises using the water supply that might affect individuals who are immunocompromised, young or elderly;
    • Several different guidelines for the various groups that will be affected by the BWA can be found in Appendix #1.  They should be made available to the media and sent to the appropriate premises by fax or hand deliver; and
    • The general public may need to be contacted through the media.  Any communication issued will be a joint release by both the Public Utilities and WDGPH.


Corresponding Policy:   CA.83.01.107 Municipal Systems Bacteriologically Unsafe, Regulated 170103
HPD GEN (F)3 WDGPH Report form
|Ontario Regulation 170/03


Rob Thompson