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A LARGE SCALE PILOT STUDY OF A GIS BASED RISK ASSESSMENT SYSTEM FOR ON-SITE WASTEWATER MANAGEMENT IN NEW SOUTH WALES, AUSTRALIA
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 701P0104, . (doi: 10.13031/2013.15773)Authors: J H Whitehead, M E Barry, W J Syme, and R Irvine
Keywords: Sanitation, GIS based risk assessment, on-site and decentralized wastewater management, Hawkesbury Lower Nepean Catchment, New South Wales, Australia
Following an outbreak of Hepatitis A disease associated with consumption of oysters from Wallis
Lake, New South Wales (NSW), Australia in 1996, the NSW Government has invested A$3.8M
over the past four years (1998-2002) in a SepticSafe program to assist local government
authorities (local councils) to implement systematic management of sanitation risks related to onsite
wastewater management. Part of this investment was directed to the development of an
integrated system of sewage risk assessment in coastal areas, particularly oyster growing areas
and drinking water catchments (watersheds).
An On-site Risk Assessment System (OSRAS) has been developed to bring together information
held by local councils and State Government agencies. The OSRAS uses GIS layering
techniques and transparent logic matrices to model the fate of sewage pollution from
decentralised sewage management facilities, in relation to identified disease vectors and sensitive
environmental receptors, and to generate risk "maps". The output will enable councils and State
Government agencies to assess the likely scale of impact and relative risk of sewage pollution in
unsewered residential areas. The OSRAS is currently being trialed in the Hawkesbury Lower
Nepean catchment, covering 20 Local Government Areas in the Sydney hinterland with
approximately 50,000 on-site wastewater management systems.
The large scale pilot study involves the development of a data management system, data integrity
review, application of the OSRAS methodology to the Hawkesbury Lower Nepean catchment,
consultation with local councils and State Government agencies and field validation, prior to the
release of the OSRAS for use in other areas of coastal NSW.