Tavistock Wastewater Treatment Plant

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Updated June 24, 2020


Oxford County is upgrading one of the lagoon cells (Cell 1) at the Tavistock Wastewater Treatment Plant (WWTP). The lagoon needs construction work after more than 20 years of operation to:

  • remove the build up of biosolids and sludge;
  • upgrade the aerators that treat sewage and help keep odour under control; and,
  • repair some of the erosion that has taken place along the banks of the lagoon.

Construction work is scheduled to be completed in the fall of 2020. There will be no interruption to wastewater services during the construction period.


Odour changes

Regular maintenance is needed on lagoon systems to keep them operating efficiently and to protect the local ecosystem.

A well-functioning lagoon system doesn't normally smell, although odour may result from seasonal changes or other temporary situations, like construction. Warmer temperatures and wind direction can also affect odour, and manure spreading at certain times of the year can compound the effect.

The main concern among residents during lagoon maintenance work is odour. Odour from the Tavistock WWTP has been more noticeable in May and June because:

  • Water levels for Cell 1 were deliberately lowered for construction work to take place. This exposes biosolids and sewage to the air, releasing stronger than typical odours.

  • Because of odour complaints, we paused construction work to re-assess the situation and work plan. As an interim measure, lagoon cell levels were then fully restored to help contain the exposed sludge biosolids (and odour), recognizing that it can take approximately three to five weeks to restore the natural microbial biological action in the lagoon needed to treat sewage and return the lagoon cell back to its normal operating performance capacity. As a result, higher than normal raw sewage odours are being released because it is taking longer for the microbes to manage and break down the incoming sewage.


How we're responding

It is not possible to fully eliminate odour during construction work, and for those living close to the lagoons, odours will be stronger than normal during this time. We are asking for your patience as we move through the construction process, which is expected to be temporary but is essential to the continued operation of the wastewater treatment plant.

We know residents are concerned about odour and that for some, it has been especially unpleasant to deal with on a day to day basis. While we cannot prevent periods of strong odour during construction, we are responding to your concerns the best we can by:

  1. Providing more information. You’ve let us know you want more information than what has been shared so far. This project website has been set up to give residents access to information, documents, and the project timeline. You can also ask a question if you don’t see yours in the Frequently Asked Questions to the right.

  2. Increasing aeration. We are now operating the lagoon aeration system at maximum strength to increase oxygen levels in Cell 1, which helps to increase the speed at which raw sewage is broken down.

  3. Using an odour counteractant. This is an additive that neutralizes smells through a chemical reaction. The County has been using AirSolution™ 9312 Odor Counteractant, a non-toxic, non-corrosive additive that is safe to use in areas where there is human activity. We are also exploring other options, like the use of additives such as Bioxide (calcium nitrate) and hydrogen peroxide to accelerate the treatment process. Because of the strong community feedback we've received, we are also assessing whether or not another odour counteractant would perform better. Odour control additives will only be used on days for which temperature, wind speed, wind direction, and precipitation are expected to heighten odour and/or if there is strong odour already at the lagoon site.

  4. Increased monitoring. Public Works management has been monitoring conditions on-site at the lagoon three times daily at early morning, mid-day and late evening, and then adjusting lagoon operating conditions where possible.

  5. Reassessing and updating the construction work plan. Because of your feedback, construction work was paused in June so that we could explore additional odour control measures. Our updated project plan includes engineering adjustments and additional treatment options, as well as upgrades to the adjacent lagoon that will receive effluent material (sewage) from Cell 1. We expect to restart construction in July.


Our commitment to you

Oxford County is committed to providing open and transparent communication throughout the construction period so that residents feel informed. We acknowledge that, in the beginning, there may have been gaps in how we demonstrated this commitment. This project page is a place for you to check for information, get project updates, and ask questions. It will be updated throughout the construction period.

You have our commitment that the health and safety of residents and the environment are our primary concern. The Tavistock WWTP is operated in full compliance with its Environmental Compliance Approval from the Ministry of the Environment, Conservation and Parks. All operational practices during construction were reviewed by the Ministry.

If you have a question you don't see answered on this site, please submit it in the online form below. If you want to speak to someone in person, please call 1-800-755-0394, ext. 3194.


Updated June 24, 2020


Oxford County is upgrading one of the lagoon cells (Cell 1) at the Tavistock Wastewater Treatment Plant (WWTP). The lagoon needs construction work after more than 20 years of operation to:

  • remove the build up of biosolids and sludge;
  • upgrade the aerators that treat sewage and help keep odour under control; and,
  • repair some of the erosion that has taken place along the banks of the lagoon.

Construction work is scheduled to be completed in the fall of 2020. There will be no interruption to wastewater services during the construction period.


Odour changes

Regular maintenance is needed on lagoon systems to keep them operating efficiently and to protect the local ecosystem.

A well-functioning lagoon system doesn't normally smell, although odour may result from seasonal changes or other temporary situations, like construction. Warmer temperatures and wind direction can also affect odour, and manure spreading at certain times of the year can compound the effect.

The main concern among residents during lagoon maintenance work is odour. Odour from the Tavistock WWTP has been more noticeable in May and June because:

  • Water levels for Cell 1 were deliberately lowered for construction work to take place. This exposes biosolids and sewage to the air, releasing stronger than typical odours.

  • Because of odour complaints, we paused construction work to re-assess the situation and work plan. As an interim measure, lagoon cell levels were then fully restored to help contain the exposed sludge biosolids (and odour), recognizing that it can take approximately three to five weeks to restore the natural microbial biological action in the lagoon needed to treat sewage and return the lagoon cell back to its normal operating performance capacity. As a result, higher than normal raw sewage odours are being released because it is taking longer for the microbes to manage and break down the incoming sewage.


How we're responding

It is not possible to fully eliminate odour during construction work, and for those living close to the lagoons, odours will be stronger than normal during this time. We are asking for your patience as we move through the construction process, which is expected to be temporary but is essential to the continued operation of the wastewater treatment plant.

We know residents are concerned about odour and that for some, it has been especially unpleasant to deal with on a day to day basis. While we cannot prevent periods of strong odour during construction, we are responding to your concerns the best we can by:

  1. Providing more information. You’ve let us know you want more information than what has been shared so far. This project website has been set up to give residents access to information, documents, and the project timeline. You can also ask a question if you don’t see yours in the Frequently Asked Questions to the right.

  2. Increasing aeration. We are now operating the lagoon aeration system at maximum strength to increase oxygen levels in Cell 1, which helps to increase the speed at which raw sewage is broken down.

  3. Using an odour counteractant. This is an additive that neutralizes smells through a chemical reaction. The County has been using AirSolution™ 9312 Odor Counteractant, a non-toxic, non-corrosive additive that is safe to use in areas where there is human activity. We are also exploring other options, like the use of additives such as Bioxide (calcium nitrate) and hydrogen peroxide to accelerate the treatment process. Because of the strong community feedback we've received, we are also assessing whether or not another odour counteractant would perform better. Odour control additives will only be used on days for which temperature, wind speed, wind direction, and precipitation are expected to heighten odour and/or if there is strong odour already at the lagoon site.

  4. Increased monitoring. Public Works management has been monitoring conditions on-site at the lagoon three times daily at early morning, mid-day and late evening, and then adjusting lagoon operating conditions where possible.

  5. Reassessing and updating the construction work plan. Because of your feedback, construction work was paused in June so that we could explore additional odour control measures. Our updated project plan includes engineering adjustments and additional treatment options, as well as upgrades to the adjacent lagoon that will receive effluent material (sewage) from Cell 1. We expect to restart construction in July.


Our commitment to you

Oxford County is committed to providing open and transparent communication throughout the construction period so that residents feel informed. We acknowledge that, in the beginning, there may have been gaps in how we demonstrated this commitment. This project page is a place for you to check for information, get project updates, and ask questions. It will be updated throughout the construction period.

You have our commitment that the health and safety of residents and the environment are our primary concern. The Tavistock WWTP is operated in full compliance with its Environmental Compliance Approval from the Ministry of the Environment, Conservation and Parks. All operational practices during construction were reviewed by the Ministry.

If you have a question you don't see answered on this site, please submit it in the online form below. If you want to speak to someone in person, please call 1-800-755-0394, ext. 3194.


If you have a question, please check the FAQ (Frequently Asked Questions) to your right. If you don't see your question or concern there, please submit a new question and we will post an answer within 1-2 business days. 

If you need to speak to someone right away, please call 1-800-755-0394, ext. 3194.

Your questions

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    Why is this project (Tavistock lagoon upgrade) being done in the hottest months of the year? Odours would not be as bad in the cooler fall months when windows are closed. Odours we experienced the last two weeks are the worst odours I have ever experienced and I am quite use to farm odours.

    Dpml asked 7 days ago

    Hello -- In answer to your question, the construction project requires sludge biosolids to be removed from the bottom of the lagoon (Cell 1). To do this, the lagoon cell must first be drained so that the biosolids can be pushed up the sides of the lagoon where they can be naturally dried (dewatering) in the warm weather conditions before removal. This work will be followed by installation of the new aeration system and then repairs to the eroded sections of the sides of the lagoon.  

    All required work must be completed during a compressed window of time as the lagoon needs to be returned back into service by this fall. The Ministry of Environment, Conservation and Parks places conditions on lagoon outflow that the County is typically unable to meet during freezing conditions; as a result, treated water from the lagoons is not discharged into the permitted receiving water course during late fall and winter.