Sainte-Marthe-sur-le-Lac Water Hardness & Quality Report (2026)

Sainte-Marthe-sur-le-Lac's drinking water is managed by the Ville de Sainte-Marthe-sur-le-Lac, drawing from the Ottawa River or Lac des Deux-Montagnes — Sainte-Marthe-sur-le-Lac is a town on the north shore of Lac des Deux-Montagnes (Lake of Two Mountains), the wide widening of the Ottawa River formed by the Oka Peninsula northwest of Montreal, in the Laurentides administrative region, a community tragically impacted by the catastrophic 2019 flooding when the protective dike broke and flooded the town centre, requiring the emergency evacuation of 6,000 residents — an event that prompted major dyke reconstruction and became one of the most significant urban flood events in modern Quebec history. Water undergoes coagulation, sedimentation, filtration, UV disinfection, and chloramination, meeting all Guidelines for Canadian Drinking Water Quality (GCDWQ) requirements. Hardness measures 66.5 mg/L (3.9 gpg) — classified as moderately hard by Health Canada, consistent with the lower Laurentians Ottawa River-Lake of Two Mountains supply.

Sainte-Marthe-sur-le-Lac draws from the Ottawa River / Lac des Deux-Montagnes supply — the Ottawa River at this point carries dissolved Precambrian Shield minerals mixed with the Ottawan carbonate lowlands, producing the moderate 66.5 mg/L. This is consistent with the lower Laurentians north shore range (Rosemère ~63.5 mg/L; Mont-Laurier 70 mg/L from reference data), reflecting the Ottawa River supply blend in the Lake of Two Mountains corridor. Water quality reports are published following Ministère de l'Environnement standards.

At 66.5 mg/L, Sainte-Marthe-sur-le-Lac homes experience light scale deposits — occasional cleaning every two months is adequate. Health Canada lead precautionary guidance applies to pre-1975 properties in the historic Sainte-Marthe-sur-le-Lac townsite. Residents should also be aware of continued dyke maintenance and emergency response planning given the community's significant flood risk.