Wastewater Treatment Plant Outfall

Proposed Work

The District intends to initiate a detailed design and permitting phase in 2023 to extend the outfall downstream by approximately 300 metres. Several permits are required with unknown timelines, however, the District will proceed with design and planning as quickly as possible to extend the outfall and address ongoing water quality issues at the outfall.

Background

The District of Squamish’s Wastewater Treatment Plant discharges treated effluent to the Squamish River approximately one kilometre downstream of the plant. Over the past several years, a gravel bar on the Squamish River has extended downstream due to natural processes resulting in poor mixing conditions at the outfall. The gravel bar is anticipated to continue naturally extending south and the District has therefore completed a Hydrogeomorphic Assessment of Squamish River Near the Wastewater Treatment Plant Outfall study in 2020 that evaluated options to resolve the issue. The study recommended extending the outfall approximately 300-450 metres downstream and to complete further work including dilution modelling and an environmental impact assessment to confirm that extending the outfall will result in adequate dilution and protection of the environment in consideration of tidal and hydrological conditions.

In 2021, the District initiated a Pre-Design and Environmental Impact Study as recommended. This work was concluded in 2023 and confirmed that extending the outfall approximately 300 metres downstream will achieve adequate dilution and protection of the environment.

If you have any questions, please contact David Roulston, Manager of Municipal Infrastructure by email at droulston@squamish.ca or by phone on 604.815.4952

Resources

1. Hydrogeomorphic Assessment of Squamish River Near the Wastewater Treatment Plant Outfall, Polar Geoscience Ltd., September 3, 2020
2. Environmental Impact Study, Squamish River Outfall, GreatPacific Engineering and Environment, January 9, 2023
3. Pre-Design Memo – WWTP Outfall Extension, GreatPacific Engineering and Environment, February 23, 2023

March 29, 2023