A New Approach to Assess Septic Systems Vulnerability and its Management Implications in Coastal GA

Abstract:

Managing wastewater is a significant component of accommodating human population growth. Septic systems are a critical part of the wastewater management infrastructure that supports most of US coastal population growth. Malfunctioning or high-density septic systems can be significant sources of nutrient pollution and pathogens transfer to both surface water and groundwater. Estimates of the percentage of systems that malfunction vary widely, ranging from 1% to more than 20%. Furthermore, septic systems are susceptible to the impacts of climate change. For instance, in coastal areas, higher sea levels will decrease the distance from the ground surface to the groundwater table, leading to reduced septic systems functionality in some locations. However, data on the functionality and effectiveness of septic systems are sparse and mainly available at the scale of individual parcels. Significant research gaps exist in assessing septic systems vulnerability and factors associated with a higher rate of system replacement and repair in coastal GA. We use a novel Soil Topography Index (STI) incorporating groundwater levels to develop a GIS-based framework for septic systems vulnerability. We use classification and regression tree and generalized logistic regression models to test our hypothesis that the novel STI can explain most of the variance in septic system repair and replacement. Further, we discuss a methodology for assessing the effects of future sea-level rise scenarios on coastal communities’ septic systems and integrating this information into local wastewater and land use planning activities.