Maple Ridge, B.C., April 21, 2026 – The City of Maple Ridge will be conducting fog testing in select neighbourhoods as part of its ongoing infrastructure maintenance program.
Fog testing helps maintain sewer system capacity, prevent backups and overflows during heavy rainfall, protect the environment, and reduce Maple Ridge’s share of regional sewage treatment costs.
The City’s sanitary sewer system collects wastewater and transfers it to Metro Vancouver’s sewage system for treatment at the Annacis Island Wastewater Treatment Plant. Stormwater, including rainwater and groundwater, is managed separately and must not enter the sanitary sewer system.
Stormwater entering the sanitary sewer system is known as “inflow and infiltration” (I&I). Provincial legislation requires the City to reduce I&I on public property and investigate potential sources of I&I on private property. Addressing issues also helps manage the City’s share of regional treatment costs.
What is fog testing?
Fog testing involves introducing a non-toxic, visible vapour into the sanitary sewer system to identify where stormwater may be entering through cracks, defects, or improper connections.
The vapour is safe, unscented, non-toxic, and non-flammable.
During testing, residents may see vapour coming from roof vents, storm drains, or the ground. This is normal and helps crews identify potential issues.
If testing identifies a problem on public property, the City will address it. If a problem is found on private property, the property owner will be responsible for arranging and paying for repairs.
Residents in affected neighbourhoods will receive advance notice by letter and door hanger before fog testing begins. Before testing, residents should ensure that all drains, especially seldom-used drains, have water in their p-traps (u-shaped pipe under the sink). Pouring at least four cups of water into infrequently used drains will help keep vapour from entering the building.
If fog enters a property, residents should open doors and windows, move outside if needed, and contact the project manager.
This work is in line with industry standards used by other municipalities.
For more information on fog testing and how to prepare if you receive notification that testing will occur in your neighbourhood, visit MapleRidge.ca/FogTesting.
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Media Contact
Pardeep Purewal, Senior Manager Corporate Communications and Public Engagement
T 604 466 4319 C 778 955 4249 E media@MapleRidge.ca