Grantee Research Project Results
2022 Progress Report: Modeling Straight Pipe Prevalence in Rural Alabama
EPA Grant Number: SV840024Title: Modeling Straight Pipe Prevalence in Rural Alabama
Investigators: Elliott, Mark , Cohen, Sagy , Greer, Ashton
Institution: The University of Alabama
Current Institution: The University of Alabama , Oregon Institute of Technology
EPA Project Officer: Aja, Hayley
Phase: II
Project Period: July 1, 2020 through June 30, 2022 (Extended to June 30, 2023)
Project Period Covered by this Report: July 1, 2021 through June 30,2022
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2020) Recipients Lists
Research Category: P3 Awards
Objective:
This project is part of a long-term initiative to characterize and address onsite wastewater failures, including building partnerships and raising funds to facilitate installation of appropriate, affordable and sustainable wastewater management in the Black Belt region of rural Alabama. This effort involves quantification of straight pipes (raw sewage discharges from homes directly to the surface) in rural Alabama through the development, validation, and application of a model to predict the scope and location of straight pipe use in the study area. This is the first attempt to model straight-pipe system location in the world, so unique equations have been developed based on the factors that are reported to lead to straight pipes in unsewered homes in the rural Black Belt (soil/geology conditions and rural poverty) (Maxcy-Brown et al., 2021). This model uses publicly available secondary data on saturated soil hydraulic conductivity, depth to seasonal high water table, depth to bedrock, and property data records in county tax assessor parcel data. The knowledge of local experts (e.g., septic system installers and pumpers) is used to validate model results. Our goal is to build the first predictive model of straight pipes using publicly available data with model validation based on expert knowledge.
Progress Summary:
The unvalidated model has been built and applied using publicly available secondary data. Illustrative outputs using the unvalidated model have demonstrated that the validated model will be able to produce a diverse array of outputs, including a map with estimates of the number of straight pipes in US Census Block of a study county, and the volumetric accumulation of wastewater in the surface water bodies of a county given a large precipitation event following a dry period of a given number of days. Model validation has been postponed beyond Year 1 by COVID travel policies that prevented us from conducting interviews for expert knowledge. We are scheduled to carry out the expert interviews at two large Alabama Onsite Wastewater Association (AOWA) events during Year 2.
Partnership activities have raised the profile of this issue in Alabama and enabled us to raise additional funding for decentralized wastewater system design and installation (Columbia World Projects, 2020; Pillion, 2020, 2021). The most important of these partnership activities has been the formation of the “Consortium for Rural Alabama Water and Wastewater Management” founded and organized by Dr. Elliott and his colleagues at the University of South Alabama, Drs. Kevin White and Lynne Chronister. All Consortium meetings during Year 1 have been conducted remotely over Zoom.
Future Activities:
We are scheduled to conduct interviews with local experts at fall and spring AOWA events. These interviews will provide the data needed for model validation. In addition to expert opinions on the locations of straight pipes, we plan to use an Analytical Hierarchy Process (AHP) as described by Marinoni (Marinoni, 2004). AHP is a multi-criteria analysis technique that uses pairwise comparison (two variables at a time) to generate relative importance factors. Those factors can then be used as variable weights in models. We will ask local pumpers and installers to rate the relative importance of the model variables and use those surveys to build a pairwise comparison matrix. The eigenvalues and eigenvectors from that matrix would be used to calculate variable weights for the model. Combining survey maps and the AHP comparison factors would allow us to integrate expert knowledge into the model more robustly. The model would then incorporate not only expert knowledge of the spatial location of straight pipes but also expert perceptions of the factors that contribute to the issue. Following model validation, we will apply the model across all rural Black Belt counties. We will finish developing the online survey to support the collection of expert knowledge. This may involve focus group testing and the potential for re-test surveys.
We also have collaborators who have expressed interest in helping to quantify straight pipe discharges using infrared sensors on a fixed-wind drone. We hope to conduct these aerial surveys on winter mornings to maximize indoor water use while it is still dark, minimize canopy, and maximize the temperature difference between water from indoors and the ground surface. While not a comprehensive count of straight pipes, we believe this will provide a useful lower-bound.
References:
Columbia World Projects. (2020). Columbia World Projects to Pilot New Approach to Wastewater Treatment in Rural Alabama. https://worldprojects.columbia.edu/news-media/columbia-world-projects-pilot-new-approach-wastewater-treatment-rural-alabama
Marinoni, O. (2004). Implementation of the analytical hierarchy process with VBA in ArcGIS. Computers and Geosciences, 30(6), 637–646. https://doi.org/10.1016/J.CAGEO.2004.03.010
Maxcy-Brown, J., Elliott, M. A., Krometis, L. A., White, K. D., Brown, J., & Lall, U. (2021). Making Waves: Right in Our Backyard- Surface Discharge of Untreated Wastewater from Homes in the United States. Water Research, 190, 116647. https://doi.org/10.1016/j.watres.2020.116647
Pillion, D. (2020, November 19). Potential solution emerges for Alabama’s Black Belt sewage woes. AL.Com, 2. https://www.al.com/news/2020/11/potential-solution-emerges-for-alabamas-black-belt-sewage-woes.html#
Pillion, D. (2021, March 14). Black Belt sewage woes: Feds give $4.9M for rural wastewater project. AL.Com, 2. https://www.al.com/news/2021/03/black-belt-sewage-woes-feds-give-49m-for-rural-wastewater-project.html
Journal Articles:
No journal articles submitted with this report: View all 8 publications for this projectSupplemental Keywords:
Onsite wastewater, OWTS, Septic tanks, POTW, non-point source, NPS, rural poverty, neglected tropical diseases, environmental justice, basic sanitation, straight piping, Analytical Hierarchy Process (AHP), expert knowledge modelingRelevant Websites:
Progress and Final Reports:
Original AbstractP3 Phase I:
Modeling Straight Pipe Prevalence in Rural Alabama | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.