Capital Regional District officials say construction of the Macaulay Point Pump Station requires screened wastewater to be discharged out the short outfall overnight.
The action is necessary as crews switch over to the new pumping systems.
Shorelines that will be affected are between Fraser Street and Victoria View Rd. -- including Saxe Point, Macaulay Point and McLoughlin Point in Esquimalt.
As well, along Dallas Road between Dock Street and Government Street in Victoria.
Residents are being advised not to enter the waters as the wastewater may pose a health risk.
As a precaution and in consultation with Island Health and the local municipalities, beaches in the affected areas will be posted with public health advisory signs until sample results indicate bacteria levels are below the acceptable recreational limit.