What is happening at the Tavistock lagoons?

    Oxford County is upgrading and performing maintenance on Lagoon Cell 1 at the Tavistock Wastewater Treatment Plant. This includes: 

    • removing and disposing of biosolids and sludge that have built up in Lagoon Cell 1;
    • upgrading the submerged aerators that are there now;
    • repairing erosion to the slide slopes; and
    • adding stone berms to reinforce sewage containment. 

    This is necessary work that keeps the lagoon system operating well and helps protect the local ecosystem. 

    Why has odour from the lagoons been stronger this spring?

    A lagoon system that is operating well does not usually release strong odours, except during some temporary circumstances like season changes or construction. 

    The water level at one of the Tavistock lagoons was deliberately lowered in May to prepare for construction work, exposing biosolids and sewage to the air. This timing coincided with some high temperature days, which can heighten odour, and with manure spreading in rural areas. 

    Although the County uses an odour counteractant to neutralize odour, it is not possible to eliminate odours during construction work. At the same time, we know strong odour is upsetting to residents and we take that concern seriously. To learn what we are doing to help manage odour, see, "What is the County doing about smell?"

    What is the County doing about smell?

    We are taking the community's concerns about smell seriously. This is what we are doing:

    • Providing more information. This project web page has been set up to give residents access to information, documents, and the project timeline. We will continue to update it.

    • 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.

    • Reassessing and updating the construction work plan. Construction work was paused in June to explore additional odour control measures. The updated project plan includes engineering adjustments and additional treatment options, as well as upgrades to the adjacent lagoon that will receive diverted effluent material (sewage) from the cell undergoing upgrades and repairs.

    Why does this work have to take place in the summer when people are outdoors more often?

    To install the new aeration system and repair the sides of Lagoon Cell 1 that have eroded, the sludge biosolids must 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 (dewatering) where they can be naturally dried in warm weather conditions. 

    In addition to the seasonal needs for construction work, lagoon outflow operations are typically limited during late fall and winter months. This is because freezing conditions do not allow us to discharge treated wastewater from the lagoons into the permitted receiving water course in a manner that complies with Ministry of Environment, Conservation and Parks conditions.

    Should I worry about health impacts from the odour?

    Wastewater emissions like hydrogen sulfide have a very low olfactory detection limit (smell) and are detectable at very low levels. This can make them a nuisance and inconvenience; however, they do not pose a health risk.

    Who is carrying out the engineering and construction work for this project?

    Oxford County has contracted the maintenance and upgrades to Lagoon Cell1 at the Tavistock WWTP to Birman Excavating Ltd. The County is also consulting with the engineering firm CIMA+ for this project. 

    Oxford County engineering staff are involved at each phase of the project and are on site during construction work.