When it comes to sewage plant effluent temperatures there is simply no relevant data.  The Thermal Assessment completed for the Erin Environmental Study Report (ESR) did not release any of the data used to calculate their conclusions.  A Freedom of Information Request was filed by the Coalition for the West Credit River (Coalition) in December of 2020.  We requested the performance reports for the Orangeville, Fergus and Elora wastewater treatment plants.  When we received the performance reports in March 2022 they only contained the monthly averages and not the temperatures recorded during the weekly sampling.

Cold Water, Cold Hands and a West Credit River Brook Trout

In order to obtain effluent temperature data, the Coalition installed temperature loggers in the effluent of the Fergus, Georgetown, Shelburne, Orangeville and Acton wastewater treatment plants in the summer of 2021.  The loggers were installed to measure the effluent temperature before it mixes with the river water.  The links below show the locations of the Coalition’s data loggers.  

Fergus Data Logger Location

Georgetown Data Logger Location

Shelburne Data Logger Location

Orangeville Data Logger Location

Acton Data Logger Location

Various shapes and sizes of instream temperature data loggers.

The average and maximum temperature for each 24 hour day was calculated and are shown in the images below.  Only days that had a measurement every 15 minutes were included in the graphs.  The average effluent temperature data is available in the Data Library.    

One of the assumptions in the ESR was that the effluent would be 19 °C.  This temperature was used to predict the size and toxicity of the effluent plume and to calculate fully mixed river concentrations.  For reference the 19 °C assumed effluent temperature is included in the average daily temperature plots below.  The plots show that the effluent was above the assumed 19 °C at all plants for most of summer 2021.