Concrete and cement are very toxic, so it needs to stay on your building site. Never wash it down stormwater drains. This video has clear instructions on how best to work with concrete.
Also see our other videos on good building management, how to build a silt fence and bunds, how to stabilise entranceways, and how to build catchpit protection. For more go to http://www.aucklandcouncil.govt.nz/ou… or visit http://www.aucklandcouncil.govt.nz