Chemainus Sewage Outfall - Environmental Impact Study


Historically, raw sewage from Chemainus was originally discharged out a short outfall to Stuart Channel. In 1981, a new comminutor system was installed to grind up any solids in the sewage prior to discharge. In addition, a new outfall was also installed. In 1990, the outfall was extended to the current terminus location. In 1998, North Cowichan constructed the Chemainus Sewage Treatment Plant (STP) which dramatically improved the quality of the discharge, significantly reducing any potential impacts due to the discharge. The treatment plant is a mechanical secondary treatment plant with Ultra Violet (UV) disinfection.

The discharge of raw sewage, and now secondary disinfected effluent, was authorized by a Provincial permit (PE-00049). The permit allows for the discharge of comminuted (ground up) raw sewage. Over time, flows from the treatment plant have increased with population growth to the point where they are nearing the permit limit.  In lieu of renewing existing permits, the BC Ministry of Environment & Climate Change Strategy (MoE) policy is requiring that treatment plants register under the Municipal Wastewater Regulation (MWR).  Consequently, the MoE has requested that North Cowichan register the Chemainus STP and outfall terminus under the MWR.

The Chemainus STP currently meets the requirements of the MWR. The Chemainus STP is designed to continue to meet the requirements of the MWR into the future. Regardless, one of the key tasks when registering a treatment plant is to undertake an Environmental Impact Study (EIS) of the discharge.

Project Overview

Since 2011, North Cowichan has been in discussions with the MoE regarding registering the treatment plant.  As part of the registration process, an Environmental Impact Study (EIS) of the existing outfall is required. North Cowichan hired GreatPacific Engineering & Environment to undertake the EIS.

The objectives of this EIS include:

  1. To establish current conditions in the area around the outfall using existing data and by sampling the water, sediments, plants and marine life;
  2. To establish where and how to monitor the environment around the outfall;
  3. To determine whether water quality guidelines around the outfall will be met and under what conditions;
  4. To carry out analyses on the nature of the discharge and the outfall environment to determine if the proposed treatment will adversely affect human health or the environment now and into the future; and
  5. To provide recommendations to ensure that the STP protects human health and the environment, or to recommend against discharge.

GreatPacific has now completed its draft EIS. You can download the study here [PDF - 21 MB].


North Cowichan has contacted Indigenous communities with traditional territories that are located in the area of the treatment plant and the outfall. It asked Indigenous communities whether they have an interest in the project, whether they would like to be consulted on the project, and what they want that consultation to look like.

North Cowichan will contact stakeholder groups that may have an interest in the project.

Additional Information

Maps of Project Location  [PDF - 2 MB]
Information Bulletin #1 [PDF - 1 MB]

If you have any comments or questions, please contact North Cowichan's Engineering Deptartment by email at or by phone 250-746-3103.