Rainfall Simulation to Evaluate Pollutant Build-Up and Wash-Off from Selected Land Uses Within a Port Environment

Abstract

The Port of Brisbane Corporation is developing a world-class port facility at the mouth of the Brisbane River, Queensland, Australia. Located adjacent to Moreton Bay Marine Park and within Australia’s fastest growing region, the need to ensure appropriate environmental management practices is integral to port operations. A key element of the Corporation’s environmental responsibility is the effective management of stormwater generated from the site. As the first step towards developing a better understanding of the pollutant loads within the stormwater, the Corporation together with the Queensland University of Technology (QUT) undertook a series of rainfall simulation trials on various port land uses. Due to the unique nature of port operations, traffic types and storage modes, stormwater quality models used for typical urban land uses may not necessarily be applicable to port operations. Natural rainfall has high variability and unpredictability, and therefore the use of rainfall simulation can help to overcome these limitations with the ability to collect a large database in a short period of time. Using a specially designed rainfall simulator, twelve rainfall events typical to the region were simulated over a number of port specific land uses. Pollutant build-up and wash-off samples were collected and analysed for a range of potential stormwater pollutants. Preliminary testing indicates that surface build-up of pollutants within the port setting is comparable to that experienced in a commercial land use setting. However with the exception of zinc, wash-off pollutant concentrations are lower than that experienced within residential, commercial or industrial land use settings. Whilst sediment loads within the wash-off was higher than that reported for urban land uses, pollutants appeared bound to sediments, with the 0.75-75μm particle range being the most predominant. Therefore, water quality improvement strategies targeting the removal of suspended solids as a surrogate approach to removing pollutants may be valid. However, for any structural measures adopted for suspended solids removal to be effective, they should have the capability to remove specific particle size range/s. Consequently, stereo-typical device designs may not prove adequate in addressing this issue in port areas.