By-Pass & Overflow Reporting

By-Pass & Overflow Reporting


Town of The Blue Mountains (Town) places high value in protecting the natural environment and local waterways. As such, the Town is committed to posting information about sewage by-pass and overflows to the Town website within one (1) business day of such an occurrence.

A sewage overflow occurs when wastewater from the sanitary collection system overflows to the natural environment or when there is a discharge of partially treated sewage from a wastewater treatment plant, often as a result of excessive groundwater and stormwater entering the system during heavy rains, rapid snowmelt or a pipe break.

The Town’s sanitary collection systems are nominally separate, meaning that sanitary and stormwater flows are carried in different pipes with different destinations, however stormwater inflows and infiltrates into the sanitary system from numerous sources.

Wastewater by-passes and overflows within the Town’s sanitary system are extremely rare.

Reporting to Ministry of the Environment & Climate Change

By law the Town is required to report sanitary by-passes and overflows to the Spills Action Centre, Ministry of the Environment & Climate Change and the Medical Officer of Health, Grey Bruce Health Unit. The notification includes the following information:

  1. Date, time and duration of the Event;
  2. Location of the Event;
  3. Measured or estimated volume of the Event;
  4. Reason for the Event;
  5. Level of treatment the by-pass and/or overflow received and disinfection status of the same.

This information is currently captured in the Town’s annual reports for the wastewater treatment facilities. The Town’s annual reports are available for download.

Overflow & By-Pass Map

Linked below are maps which show the Thornbury and Craigleith sanitary collection systems record of by-passes and overflows.

There have been no sanitary by-passes or overflows in the last 48 hours.

Thornbury Collection System & Facilities Map

Craigleith Collection System & Facilities Map

Sewer By-Pass & Overflow Logs

Recent Sewage Overflow Events, 2017 to Present - No events to report




Volume (m3)

Precipitation (mm)






Recent Wastewater Treatment Plant By-Pass Events, 2017 to Present - No events to report





Volume (m3)

Precipitation (mm)







Reducing By-Passes & Overflows

The Town designs and upgrades its wastewater collection systems and facilities to ensure adequate storage capacity and minimize the risk of by-passing and overflow events. All infrastructure work within the Town must adhere to the Town’s Engineering Standards and provincial requirements.

The Town is currently undertaking work to complete a sanitary collection model which will enable Staff to identify existing system deficiencies and create a capital improvement plan aiming at reducing and replacing undersized and substandard infrastructure.


2016 Annual Performance Report – Thornbury Wastewater Treatment Plant

2016 Annual Performance Report – Craigleith Wastewater Treatment Plant

2017 Annual Water Report


Wastewater Supervisor

Wastewater Supervisor

Frequently Asked Questions

Who should I contact to discuss sewage by-passes & overflows? »»

Is receiving water tested during/after a sewer overflow or by-pass? »»

Do by-passes and overflows affect drinking water quality? »»

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