Turbidity curtains are often used to contain sediment that’s stirred up when construction takes place in an aquatic environment. Here’s a look at how they’re being deployed as part of the Marine Sediment Management Plan for construction at Westridge Marine Terminal.

What is turbidity?

Turbidity is caused by sediment which can be stirred up during construction and suspended in the water column. In enough concentration, sediment makes water cloudy or turbid. The finer the particles, the longer the sediment material stays suspended in water.

What is the purpose of the turbidity curtain installed near the shoreline at Westridge Marine Terminal?

At Westridge, several construction activities happen in water including riprap removal. This type of activity can stir up sediment. The purpose of the curtain is to block sediment from dispersing away from the construction zone to the rest of Burrard Inlet.

What’s the curtain made of?

It’s a plastic curtain weighted with chain. It floats at the top and there are anchor points at various locations. It drapes straight down into the water column.

Why does turbidity need to be managed?

Depending on the concentration and the composition of it, particles of sediment could cause harm to marine life.

What are the requirements for managing turbidity at Westridge Marine Terminal?

We have a Fisheries Act Authorization that requires us to surround this activity with a turbidity curtain.

How will you keep turbid water inside the work area?

The project is clearly defined in our application for a Fisheries Act Authorization. We installed the curtain around the work area. We also have a commitment to have a secondary turbidity curtain inside the primary or bigger one.

We are required to monitor for turbidity outside the curtain while riprap removal is taking place. We take measurements at 10 sites at a distance of 30 metres out from the curtain and at 10 sites at 100 metres out. We measure at one metre below the surface and at the full depth of the work area. To date, we’ve had zero exceedances of the turbidity limits set by the federal government.

The first portion of riprap removal was completed in January 2018. From March 16 to August 16, 2018, as per the fisheries timing window set out in our Authorization, the works stops while juvenile salmonids migrate out of their home streams. These fish tend to stay within 15 metres of the shoreline so we avoid in-water work in the area while they’re migrating out.

We’re allowed to carry out in-water work within 50 metres of the shoreline during the annual fisheries construction window for Burrard Inlet from August 17 to March 15, as set out in our Authorization.

How often are turbidity curtains used at aquatic construction projects?

They’re used all over the world as a standard procedure in lakes and in the ocean to protect marine life. Regulatory authorities expect they will be used for in-water work that’s going to generate sediment.

Overall, how effective is this technology at reducing potential effects?

It’s a proven technology to curtail potential effects to aquatic life in marine and fresh water.