Stormwater Quality - An Analysis of Runoff From Modern Subdivisions and the Implications for Stormwater Treatment

In New Zealand many consultants, as well as Regional Councils, rely on water quality data from mature older residential areas, to describe the stormwater quality for modern residential subdivisions, when assessing the treatment needs and environmental effects of stormwater discharges. This paper will present an analysis of stormwater monitoring in Christchurch City and Selwyn District that demonstrates that the stormwater from these modern areas generally has lower concentrations for many contaminants than have been previously reported in literature. Possible reasons why these concentrations are lower, which include the use of factory painted zincalume roofing iron and less leaks from vehicles, will be discussed along with the implications these may have on the requirements for stormwater treatment for modern residential subdivisions.