Odour from Storm Ponds

Cause of the Odours

These odours are the result of naturally occurring compounds in the local soils and groundwater at YYC that infiltrate into stormwater ponds, wetlands and pipes where they undergo geochemical and biological reactions that produce odours. This is the same effect as what occurs with a sulphur spring, which can have strong sulphurous odours.

Odours vary in intensity based on weather conditions. Following recent studies of this issue by the University of Calgary and environmental engineering consultants, the following conditions were identified as producing strong odours:

  • Odours most commonly occur early in the spring when ice is coming off the ponds. During the winter, there is no oxygen under the ice and this causes odour-generating compounds to be produced at a higher rate than during open water condition. Once the ice cover is gone and water is exposed to the atmosphere, odours will become present.
  • Once the ponds are no longer ice-covered, hot and dry weather can accelerate production of the odours during the later spring and summer.
  • Because the sulphur compounds can be denser than air, they often settle in low-lying areas (e.g., base of the hill beside Deerfoot City) when the air is cold and stagnant (i.e., overnight).

Due to the hot and dry conditions that occurred immediately following the winter this year (2023), odour management has been particularly challenging.

Are these odours harmful to my health or the environment?

The Calgary Fire Department along with The Calgary Airport Authority and City of Calgary environmental monitoring staff routinely sample both the water and air when odours are present and have never detected levels above 0 pmm in the ambient air on or around the airport. Water sampling has helped identify the source compounds and toxicity studies, which have shown they are not harmful to fish. While sulphur-based compounds can produce strong odours, constituents are not present at concentrations that are either detectable or have any known health effects.

What is The Calgary Airport Authority doing to fix this problem?

When this problem first started several years ago (2018), we engaged in a process to understand the causes and sources of the odours. Following recent studies of this issue by the University of Calgary and environmental engineering consultants, several solutions have been identified. As the source of the problem is groundwater entering the drainage system, the permanent solution is to retrofit wet ponds and certain drainage pathways located on airport lands. This work is estimated to take up to three years. Design is commencing the summer of 2023 with initial construction planned for January 2024. Additional work will take place through 2026.

What is being done in the short-term to mitigate odours?

Several measures have been put into place to control odours as best as possible while a permanent solution is designed and constructed. While we believe these solutions can be effective, their performance will vary based on weather and environmental conditions. These are shown in the table below:

Odour Mitigation  Measure


Water level management

During the fall every year, water levels are lowered in the ponds to ensure as little water as possible is present over the winter. This minimizes the amount of odour-producing compounds that would then be released in the spring.

Spring water treatment

Every spring, water treatment is conducted on stormwater ponds to remove compounds that generate odours. Depending on water levels and concentrations of odour-producing compounds in various parts of the system, the specific type of system and its location may vary.

Ongoing aeration of ponds

Aeration systems are present at our ponds to oxidize water and minimize odours. These units typically operate during the entire frost-free season.

Stormline Cleaning and Pond Dredging

A drainage system maintenance program was created to address one of the root causes of odour production, which is the accumulation of sediment in stormwater collection system. Each year, parts of the system where odours are known are inspected and cleaned.

Who can I contact about this issue?

The Calgary Airport Authority is taking the issue of odours very seriously and investing significant time, effort and resources to solving this problem. We are working closely with The City of Calgry, Calgary Fire Department and Alberta Environment and Protected Areas on this issue and, we are committed to resolving it in as timely of a manner as possible. Due to the scale of the issue however, the permanent fix will take some time to implement.

If you have questions or wish to discuss further please contact the Environment and Sustainability department at 403-735-1499.