15 December 2023
Concrete wastewater can be lethal to aquatic life and can land those responsible with a fine, so make sure you keep it out of stormwater.
What's the problem?
Concrete and cement-related products are extremely toxic to aquatic life. The lime in these products dissolves in water and produces an alkaline solution that burns and kills fish, insects and plants. One bucket of concrete wastewater washed down a stormwater drain can easily wipe out hundreds of fish and eels. Some streams and
rivers take over a decade to recover from a single pollution incident.
Simple things can prevent pollution
There are lots of simple measures that will help to prevent pollution on site. Always keep an eye on the weather forecast, and don’t lay concrete or undertake lime stabilisation if rain is likely. Rain can wash concrete dust and slurry into the stormwater system, so make sure all dust is collected from cutting and from the entire site before you leave each day.
Washing equipment
Wash all equipment used in concreting at a designated site where wastewater can be contained for treatment and disposal. For small sites, it can be washed onto a grassed or bare soil area. Make sure that whatever system you use can cope with the volume of wastewater produced. The most important thing is that no wastewater enters the
stormwater system.
What's the problem?
Concrete and cement-related products are extremely toxic to aquatic life. The lime in these products dissolves in water and produces an alkaline solution that burns and kills fish, insects and plants. One bucket of concrete wastewater washed down a stormwater drain can easily wipe out hundreds of fish and eels. Some streams and
rivers take over a decade to recover from a single pollution incident.
Simple things can prevent pollution
There are lots of simple measures that will help to prevent pollution on site. Always keep an eye on the weather forecast, and don’t lay concrete or undertake lime stabilisation if rain is likely. Rain can wash concrete dust and slurry into the stormwater system, so make sure all dust is collected from cutting and from the entire site before you leave each day.
A bucket of concrete wastewater washed down a stormwater drain can kill hundreds of fish and eels. Source: Auckland Council
Concrete cutting, lime stabilisation and exposing aggregate
The most important thing is to prevent wastewater from getting into the stormwater system, so always:
▶ put slurry controls in place before you start work – options are to use a wet vac, sucker truck or pump to remove wastewater asit builds up, or sandbags to divert run-off to a grassed area.
▶ make sure controls can cope with the volume of wastewater produced
▶ use as little water as possible when cutting
▶ check cuts have been thoroughly washed out, and all slurry has been collected
▶ ensure all wastewater is collected for treatment and disposal, especially when using an acid wash
▶ report all spills to management immediately.
There are also important things NOT to do:
▶ Do not divert acidic wastewater to grass or bare soil areas when acid washing concrete.
▶ Do not use catchpit filters as a treatment device for alkaline wastewater – they cannot filter high-pH wastewater.
▶ Do not allow any run-off from lime stabilisation to enter the stormwater system.
The most important thing is to prevent wastewater from getting into the stormwater system, so always:
▶ put slurry controls in place before you start work – options are to use a wet vac, sucker truck or pump to remove wastewater asit builds up, or sandbags to divert run-off to a grassed area.
▶ make sure controls can cope with the volume of wastewater produced
▶ use as little water as possible when cutting
▶ check cuts have been thoroughly washed out, and all slurry has been collected
▶ ensure all wastewater is collected for treatment and disposal, especially when using an acid wash
▶ report all spills to management immediately.
There are also important things NOT to do:
▶ Do not divert acidic wastewater to grass or bare soil areas when acid washing concrete.
▶ Do not use catchpit filters as a treatment device for alkaline wastewater – they cannot filter high-pH wastewater.
▶ Do not allow any run-off from lime stabilisation to enter the stormwater system.
The most important thing is that no wastewater enters the stormwater system.
Wash all equipment used in concreting at a designated site where wastewater can be contained for treatment and disposal. For small sites, it can be washed onto a grassed or bare soil area. Make sure that whatever system you use can cope with the volume of wastewater produced. The most important thing is that no wastewater enters the
stormwater system.