Concerns over Brook Trout in the West Credit River

The Town of Erin (Erin) is in the design phase of a new sewage treatment plant, and the Ontario Rivers Alliance (ORA) is concerned that the sewage plant effluent will endanger some of the most productive and highly valued brook trout populations in the West Credit River.

In June of this year, the ORA raised its concerns to Erin’s Mayor and Council through a comprehensive independent background report, recommending strategies that would protect this coldwater brook trout habitat. According to Linda Heron, Chair of the ORA, “Without adequate measures to lessen the effects of a warming climate, the temperature of the sewage plant effluent will pose an increasing threat to critical brook trout habitat and endanger resident brook trout”.  The full report is available on ORA’s website here.

Erin’s own environmental consultants indicated that sewage effluent warmer than 19°C would be toxic to brook trout and recommended that sewage plant permitting should include a maximum effluent temperature limit of 19°C with a preferred maximum temperature of 17°C.  Additionally, the Ministry of Environment, Conservation and Parks staff requested written limits on effluent temperature be included in the Environmental Study Report (ESR).  

In the end, effluent temperature limits were not included in the final ESR.  This means the plant will not be required to include special measures to minimize effluent temperature.  According to Heron, “Our own investigations indicate that effluent temperatures could be as warm as 22°C and could increase to 25°C over time due to climate change predictions.  This could potentially be fatal to brook trout over a sustained period of time”.

The Erin sewage plant project has been under discussion for over 25 years. The original proposal, completed in 2014, recommended an effluent volume of only 2,160,000 litres per day to protect the West Credit River. However, a new consultant retained in 2015 recommended the effluent volume be increased dramatically to almost 7,200,000 litres per day. According to Heron, “The West Credit River is a small stream, so discharge of large volumes of warm effluent into this sensitive ecosystem could damage this critical coldwater brook trout habitat”.

ORA’s report identifies strategies that design engineers could use to keep the sewage effluent cool and includes river improvement projects that would help offset thermal impacts and build resilience into the riverine ecosystem.  Heron adds, “The Town of Erin has not yet taken us up on our offer to appear before Council to discuss our recommendations, but this is an opportune time to incorporate these cost-effective strategies into the sewage plant design to protect this important brook trout fishery”.


The Ontario Rivers Alliance is a not-for-profit grassroots organization with a mission to protect, conserve and restore Ontario rivers.

Linda Heron, Chair  

Tel: (705) 866-1677

This entry was posted in Events. Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.