Engineers Australia

Urban salinity site investigations for greenfield developments

S. McGhie, J. Cox, L. Bucea and V. Sirivivatnanon

Abstract

Salinity is an issue that was first reported in 1924 (Wood, 1924) but is only now becoming increasingly recognised as affecting urban areas and infrastructure. It is also increasingly recognised that urban development and management of urban areas can alter salinity processes so that the impacts on development vary not only spatially but also temporally.

The NSW Department of Infrastructure, Planning and Natural Resources (DIPNR) published a framework methodology for urban salinity site investigations in late 2002 (Lillicrap and McGhie, 2002). The report outlined 4 phases to an investigation:

  1. detailed desktop review of the site and general vicinity as well as initial site walk over and field testing
  2. groundwater and soil sample analysis to ensure a thorough understanding of the salinity processes, how they might affect the proposed development and how the development may impact on the processes
  3. interpretation of results and comparison to standards suitable for urban development and
  4. promotion of site specific and development specific management recommendations.

Each stage relies on information from previous stages to inform the decision process. Undertaking the investigations as early as possible in the development process, for example at rezoning, provides more opportunities to manage salinity effectively and efficiently.

Over the last 4 years there has been an increasing number of urban salinity site investigations, most of which are based loosely on this methodology. Steps 3 and 4 however are often problematic, as urban salinity is such a new area of expertise. For example, soil scientists experienced in investigating soils for erosion hazard, contamination, load bearing properties, shrink swell characteristics or perhaps rural salinity are being asked to comment on the immediate and longterm impacts of types and amounts of salts on bricks, mortar and cement.

The CSIRO worked with the Hawkesbury-Nepean Catchment Management Authority and DIPNR to look at the range of tests commonly performed for urban development in order to determine whether these could be used for urban salinity investigations. Key findings from this work will be presented in this paper along with other experiences from development in western Sydney.