CONTESTED FACTORS FOR SUSTAINABILITY: THE CONSTRUCTION AND MANAGEMENT OF HOUSEHOLD ONSITE WASTEWATER TREATMENT SYSTEMS
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Onsite sanitation systems experience a high failure rate with resulting environmental and public health implications. In the USA alone, the EPA estimates that 10% of the 26 million homes served by onsite systems have failed. If this failure rate is extrapolated to the 8% of the global population that the UN estimates have gained access to sanitation between 1990 and 2008, an additional 5 million failed systems have been constructed. To address issues like this, development theory currently emphasizes a blend of hardware (e.g. infrastructure, technology) and software (e.g. knowledge, institutions, education) in an effort to achieve sustainable development. However, we lack both theory that addresses this interaction and a definition of sustainable infrastructure. To begin to address this gap, an initial set of 40 factors that may contribute to sustainable onsite sanitation systems was identified from a literature review including the Web of Science, the Engineering Village, and the full record of ASCE from 2000 to July 2011. A panel of 14 experts including academics, regulators, international development practitioners, O&M providers, and manufacturer/designers was then assembled to identify any additional factors that may lead to resilient onsite systems and to evaluate each one using the Delphi method. The panel evaluated each factor iteratively in order to develop a measure of its importance to the sustainability of onsite sanitation infrastructure. Experts were also invited to provide and review comments explaining or discussing the ratings they provided, and to identify the factors they perceived to be the most and least important. Of the initial list of factors, 9 came to consensus as being important or very important, including factors such as owner occupancy, quality of installation or materials, and post-construction follow-up programs. In addition, 10 factors provoked particularly diverse, or contentious, opinions with ratings that more than doubled the target criteria for consensus. These contentious factors are analyzed to identify trends and debates in expert opinion that showcase future research needs as well as issues that practitioners must address to build sustainable systems.