Flooding in Cambridge: The Grand River in Galt, Sewer Backup Under Preston and Hespeler, and What the Fixes Do

Three kinds of water in three old towns

River flooding announces itself: the Grand River Conservation Authority issues flood warnings, the river rises over Water Street and Grand Avenue in Galt, and the water table under the low streets rises with it. Sewer backup arrives at the floor drain, a basement toilet or the laundry standpipe during or just after heavy rain and smells like sewage; the oldest streets of Galt, Preston and Hespeler on the earliest sewers are most exposed. Groundwater arrives clear at the wall-floor joint and through the stone foundations of the 1850s houses in the melt and after long rains.

Photograph where the water first appeared and when. A river warning, a storm and a smell, or a melt and clear water each point to a different fix.

What the fixes do, and what has been offered

A backwater valve is a one-way flap on the sanitary lateral that closes when the sewer surcharges so sewage cannot flow back into the house; while it is closed nothing in the house drains. A sump pump with a pit collects groundwater from the foundation drain and pumps it outside; a battery backup keeps it running through the outages that come with the storms. Neither stops the Grand: when the river is above your basement floor, the water table rises with it and no pump keeps up. In the flood plain, the tools are flood-proofing measures the GRCA and the City publish, keeping valuables off the basement floor, and insurance.

The City of Cambridge and the Region have offered programs for backwater valves and related protective plumbing at different times, with conditions that the work be done by a licensed plumber under a City permit. The programs change; check the current pages before signing a quote.

• GRCA flood-plain map checked for your address
• City’s current program checked for eligibility
• Licensed plumber and City of Cambridge plumbing permit number
• Camera inspection recording and locate
• Sump pump tested, backup and alarm

Who owns which pipe

In Cambridge the owner is responsible for the sanitary lateral on private property up to the property line, and the City of Cambridge for the local sanitary and storm sewers beyond it; the Region of Waterloo owns the water supply, the trunk sewers and the treatment plants behind the city system. A camera inspection with a locate tells you which side a break or blockage is on. Keep the recording; an insurer will want it, and sewer backup and overland water are usually separate add-ons on an Ontario policy. After 2018, overland flood coverage in the Galt flood plain became harder to get; ask your broker what is available at your address.

Old stone, heritage and the melt

Galt, Preston and Hespeler have 1850s to 1900s stone and brick houses with porous foundations and clay weeping tile long since silted; waterproofing there is exterior drainage and a membrane where the lot allows, interior drainage to a sump where it does not, and a basement kept as storage rather than living space. Many of those houses are heritage-designated, which can limit exterior excavation; ask the City’s heritage staff first. In March, test the sump pump, clear the discharge line and the window wells, and extend the downspouts before the melt.