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Outflow litter traps

Updated: Jun 6, 2022

Did you know that a lot of marine debris gets into the sea via storm drains? In this post I’ll describe some ways to prevent this happening. It’s something we definitely could campaign for on Bribie Island to help keep Pumicestone Passage clean.

Credit: Insidewaste

We are all familiar with this picture; plastic bottles, straws, bottle tops, bags, and other pollution littering our beaches and water ways. Apart from the obvious, reducing the amount of plastic produced, we need to find ways of reducing the amount of litter ending up in the environment.

This blog post looks at one method, traps placed at storm water outlets that are designed to capture large pieces of litter washed down storm water drains during periods of heavy rain before it can reach the waterways and oceans.

I first came across this method when I lived in Bowral in NSW. My neighbour and I were instrumental in forming a local landcare group with the express purpose of cleaning up the creek running behind his house. To cut a long story short the creek was cleaned up, various flood mitigation methods put in place by council and we then replanted the banks with native trees, shrubs and grasses.. The creek still floods but less severely (at least until this years floods) and, importantly the water now drains away a lot faster.

As part of the work carried out by council various “gross pollution traps” were installed along the creek at storm water outlets and these were successful in reducing the amount of litter entering the creek and as the creek was in the Sydney catchment area this was important work.

Examples of Gross Pollution Traps

So let's look at some forms of gross pollution traps. I am no expert on these so please excuse me if I get some things wrong! I’ll give two examples of smaller traps.

The basic formula for all these traps is a "filter" which captures litter but allows water to flow through. They vary from mesh socks that are installed over the outlet of smaller storm water drains to large, engineered units with concrete foundations and steel cages built around larger storm water outlets.

Brisbane City Council Stormwater net