Nudgee landfill was formed adjacent to the Boondall Wetlands in 1976. The site was closed in 2002 with remediation completed in 2006. Water Technology staff were members of a team invited to undertake an ecological and water quality study to assess the influence of the Nudgee Landfill on the Boondall wetlands (now a RAMSAR listed site). The study included review of all existing monitoring and modelling data, as well as the design and implementation of targeted soil, water and biological monitoring program over a 2 year period. Automatic water quality and depth sensors (with data loggers) were used extensively. Manual sampling and laboratory analysis was also undertaken.

The Boondall Wetlands water quality monitoring sites were influenced by a number of interacting processes such as rainfall, tidal flushing, time of year and distance from Moreton Bay. Further, the impact of these processes on site water quality varies depending on the site and water quality parameter. Therefore, while the “raw” monitoring data may give a precise measure of water quality at the particular moment of sampling, the incomplete sampling coverage across all sites and times, along with the confounding effects of these various processes, meant that the raw data alone did not provide a complete description of water quality variation over time either at a site or between sites. Advanced statistical analysis was used to model and isolate the various physical, chemical and biological processes occurring within the study area.

The Boondall Wetlands have been subject to numerous historical changes apart from the construction of the landfill. These include, land clearing, drain construction, and waterway dredging. The study was able to isolate and identify the effect of natural and anthropogenic impacts on the wetlands.

Quantifying relationships between stream water quality and catchment land uses is a major goal of many water quality monitoring programs. This is a challenging task that is rarely achieved through simple analysis of raw data alone. The key difficulty is that stream water quality in a catchment is highly variable in both space and time because the driving processes (e.g., rainfall, discharge and source availability) vary in space and time. Water quality at any point in the stream reflects an integration of upstream processes. Further, water quality data is often not continuous. Models, in conjunction with a targeted monitoring program, are required to extrapolate the water quality data in space and time.

Water Technology undertook a two year study to determine the impact of a remediated municipal landfill on water quality in the Boondall Wetlands: a RAMSAR listed wetlands in Brisbane. The Wetlands are hydrologically very complex (even without the landfill) with water quality influenced by a number of interacting non-linear processes such as rainfall, tidal flushing, time of year, distance from bay and site morphology (e.g. well-flushed tidal creek or poorly-flushed ponded area). 

Regular and event-based water quality sampling was undertaken at 20 sites, supplemented with water quality and water level data loggers at five of those sites. A general linear statistical model was developed to account for the various physical, chemical and biological processes occurring within the study area. The model successfully showed the relationship between site morphology and water quality with a high level of precision. The study results allowed Council to better assess the cost-effectiveness of different site management options.