Tavistock Wastewater Treatment Plant

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Posted June 24, 2020 | Updated July 23, 2020


Oxford County is upgrading one of the lagoon cells (Cell 1) at the Tavistock Wastewater Treatment Plant (WWTP). This work is needed to ensure the lagoon system continues to operate efficiently and protects the local ecosystem. The project includes:

  • removing the build up of biosolids and sludge;
  • upgrading the aerators that treat sewage and help keep odour under control; and,
  • repairing 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 concerns

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.

Odour from the Tavistock WWTP was more noticeable in May and June because water levels for Cell 1 were deliberately lowered for construction work, which exposed biosolids and sewage to the air. Biosolids need time to naturally dry out and stronger odours can be present when biosolids are first exposed to air.

It is not possible to fully eliminate odour during construction work, and for those living close to the lagoons, odours will be stronger. While we cannot prevent periods of strong odour during construction, we are responding to your concerns.


How we're responding

In response to community feedback about odour, we paused construction in the spring to consider additional odour control measures. This is what we have done so far:

  • Reassessed and updated the construction work plan. We temporarily returned Cell 1 to its normal operating capacity to manage odours to the degree possible. We used Bioxide (calcium nitrate) and hydrogen peroxide to more quickly restore the natural microbial biological action that is needed in the lagoon cell to effectively break down sewage.

  • Installed a new vapour pipeline system. In July, we expanded our odour control system to include a new vapour pipeline system along the lagoon property line. This expanded system blows a dry mist odour neutralizer through pipelines and into the air to bind with odourous materials. It is intended to provide a more effective and longer lasting odour neutralizer that can cover a wider area around the lagoon cells.

  • Took preparations for construction restart. All sewage flows to the Tavistock WWTP are now being diverted into Cell 2. We have relocated surface aerators from Lagoon Cell 1 to Cell 2 to boost performance of this cell to prepare to restart construction on Cell 1. We’ve also set up an automated dosing system for Bioxide for Cell 2 to enhance its biological performance (and odour management capacity) during peak times. We've also left extra aeration time for sewage to break down in Lagoon Cell 1 before resuming construction.

  • Continue to use an odour counteractant. This is an additive that neutralizes smells through a chemical reaction. The County has been using AirSolution™ 9312 Odor Counteractant(External link), a non-toxic, non-corrosive additive that is safe to use in areas where there is human activity. We are also exploring other options.

  • Increased monitoring. We have been monitoring conditions on-site at the lagoon more frequently so that we can adjust lagoon operating conditions where possible and if needed.

  • Provided more information. This project website has been set up to give residents access to information, documents, and the project timeline.


Our commitment to you

Oxford County is committed to providing open and transparent communication throughout the construction period so that residents feel informed. 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.

We are asking for your patience as we move through the construction process, which is temporary but essential to the continued operation of the wastewater treatment plant. 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.



Posted June 24, 2020 | Updated July 23, 2020


Oxford County is upgrading one of the lagoon cells (Cell 1) at the Tavistock Wastewater Treatment Plant (WWTP). This work is needed to ensure the lagoon system continues to operate efficiently and protects the local ecosystem. The project includes:

  • removing the build up of biosolids and sludge;
  • upgrading the aerators that treat sewage and help keep odour under control; and,
  • repairing 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 concerns

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.

Odour from the Tavistock WWTP was more noticeable in May and June because water levels for Cell 1 were deliberately lowered for construction work, which exposed biosolids and sewage to the air. Biosolids need time to naturally dry out and stronger odours can be present when biosolids are first exposed to air.

It is not possible to fully eliminate odour during construction work, and for those living close to the lagoons, odours will be stronger. While we cannot prevent periods of strong odour during construction, we are responding to your concerns.


How we're responding

In response to community feedback about odour, we paused construction in the spring to consider additional odour control measures. This is what we have done so far:

  • Reassessed and updated the construction work plan. We temporarily returned Cell 1 to its normal operating capacity to manage odours to the degree possible. We used Bioxide (calcium nitrate) and hydrogen peroxide to more quickly restore the natural microbial biological action that is needed in the lagoon cell to effectively break down sewage.

  • Installed a new vapour pipeline system. In July, we expanded our odour control system to include a new vapour pipeline system along the lagoon property line. This expanded system blows a dry mist odour neutralizer through pipelines and into the air to bind with odourous materials. It is intended to provide a more effective and longer lasting odour neutralizer that can cover a wider area around the lagoon cells.

  • Took preparations for construction restart. All sewage flows to the Tavistock WWTP are now being diverted into Cell 2. We have relocated surface aerators from Lagoon Cell 1 to Cell 2 to boost performance of this cell to prepare to restart construction on Cell 1. We’ve also set up an automated dosing system for Bioxide for Cell 2 to enhance its biological performance (and odour management capacity) during peak times. We've also left extra aeration time for sewage to break down in Lagoon Cell 1 before resuming construction.

  • Continue to use an odour counteractant. This is an additive that neutralizes smells through a chemical reaction. The County has been using AirSolution™ 9312 Odor Counteractant(External link), a non-toxic, non-corrosive additive that is safe to use in areas where there is human activity. We are also exploring other options.

  • Increased monitoring. We have been monitoring conditions on-site at the lagoon more frequently so that we can adjust lagoon operating conditions where possible and if needed.

  • Provided more information. This project website has been set up to give residents access to information, documents, and the project timeline.


Our commitment to you

Oxford County is committed to providing open and transparent communication throughout the construction period so that residents feel informed. 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.

We are asking for your patience as we move through the construction process, which is temporary but essential to the continued operation of the wastewater treatment plant. 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 the answer. 

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

Your questions

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    I have been told a curtain wall for odor control is getting installed on the Cell? Could you please provide more information on this?

    Anonymous asked 3 months ago

    In July, we expanded our odour control system to include a new vapour pipeline system along the lagoon property line. This expanded system blows a dry mist odour neutralizer through pipelines and into the air to bind with odourous materials. It is intended to provide a more effective and longer lasting odour neutralizer that can cover a wider area around the lagoon cells.

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    Why has it taken this long to clean this cell out? When was the last time Cell 1 was cleaned out? “Biosolids are more than 20 years old.”

    Anonymous asked 3 months ago

    Lagoon Cell 1 was cleaned out in 1989 when the cell was depth was increased from 4 to 5 meters and has continued to operate in good working order since that time. The standard frequency of planned biosolid clean-outs varies depending on the size, depth, operational efficiency and loading rate of a given lagoon. Based on the characteristics and historical loading rates of the Tavistock lagoons, we would be performing a primary cell clean-out (Cell 1) about every 15-20 years and secondary/tertiary cell clean-out (Cells 2,3, 4) about every 20-25 years. 

    It is important to note that sludge depths are checked annually and incorporated into the wastewater annual reports, which are available here: https://www.oxfordcounty.ca/Services-for-You/Water-Wastewater/Wastewater/Annual-reports. The maintenance being performed this year is timely and needed to ensure the lagoon continues to perform well as part of the overall wastewater system.

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    What proof can you provide to the residents to ensure this odor doesn’t carry any bacteria and isn’t a health concern?

    Anonymous asked 3 months ago

    We acknowledge that odour is a nuisance and that for some, it has been especially unpleasant to deal with on a day to day basis. Any chemicals being used on site to offset and mask odour are safe and non-toxic and present negligible risk to workers or residents in this diluted application form. Southwestern Public Health has been informed of this project and of odour chemicals in use.

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    Why has it taken 2 years for construction to commence on this project? CIMA awarded for their portion of the work in 2018.

    Anonymous asked 3 months ago

    This is a typical time period and was required to undertake detailed engineering design of the proposed upgrades; generate project cost estimates; and to obtain the necessary MECP (Ministry of Environment, Conservation and Parks) approvals to keep the lagoon system in operation while part of it is under construction. The construction tender was released in February 2020 and awarded to Birnam Excavating in May 2020.

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    What is the additional costs to the original contract for the odor control that has been implement and the new revised work plan?

    Anonymous asked 3 months ago

    The costs of the odour control system are within the original tender price and project contingency amount. Contingencies are routinely built into project budgets to accommodate these types of occurrences.

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    Was it considered to postpone the construction considering covid-19 restrictions? Ex. Not being able to go stay at family members, hotels etc. to get away from the smell knowing that the construction was going to cause intense odours?

    Anonymous asked 3 months ago

    Although some constructions projects were postponed, the work at the Tavistock WWTP was considered essential work to be undertaken. Lagoon Cell 1 has performed well and exceeded its maintenance expectations, but this work is needed to ensure its continued safe and efficient operation. To read more about the considerations that Council considered for this project, see Council Report PW 2020-20: http://www.oxfordcounty.ca/Portals/15/Documents/News%20Room/15979_1_Agenda%20Package%20-%20Council%20Meeting_May13_2020-v2.pdf#page=113

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    It was mentioned the contract came in under budget, the most cost effective way is not the most healthy efficient way to remove biosolids why did the county not cover the costs of dredging to spare the residents this horrific odor over the past 6 weeks which continues to effective our health and well-being? Ie. headaches, unable to sleep, unable to enjoy the outdoors in Tavistock during covid-19, need to purchase air purifies and additional disinfecting my home

    Anonymous asked 3 months ago

    We understand the earlier smells were a hardship for the community and we have been working hard to respond to community feedback about odour. Dredging, as explained in an earlier answer, is generally considered to be the last resort of biosolids removal compared to other more efficient construction methods. It is labour intensive, costly, and creates greater risk of damage to submerged aeration lines and the lagoon clay liner. Even with dredging, the biosolids taken from the lagoon basin must still be exposed to air and dried out on site before they are removed and disposed of, which creates odour.

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    Is the overload Cell reasons why my neighbours are having their toilets back up and floor their brand new homes?

    Anonymous asked 3 months ago

    No, there is no correlation between this construction project and sewer clogging in the wastewater collection systems. County staff is available and willing to investigate if a homeowner is experiencing any concerns with toilet back-ups in the event these homes were not constructed with appropriate back flow devices. Feel free to call 1-800-755-0394 extension 3105 or send an email to publicworks@oxfordcounty.ca.

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    Are the residents in Tavistock that are affected by the odor getting any reimbursement for the poor planning/project execution?

    Anonymous asked 3 months ago

    This project was planned with care and diligence and has unfolded in a typical manner for this type of work on lagoons. A temporary increase in odour cannot be avoided, and the magnitude of the odour depends on different factors.

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    Since there are repairs getting done to the berms of the cell to contain the sewage, does this mean that sewage has overflown the cell walls and is getting into the ground?

    Anonymous asked 3 months ago

    No: there has not been an incident of sewage overflowing the cell walls. The construction work being undertaken is intended to keep the lagoons in good working order. The annual wastewater system reports for Tavistock-- which are submitted to the Ministry of Environment, Conservation and Parks and are required to report on any environmental incidents-- can be found here: https://www.oxfordcounty.ca/Services-for-You/Water-Wastewater/Wastewater/Annual-reports (a direct link to a PDF of the most recent report is here).