Evaluate alternatives to septic in high- and/or low-flood-risk areas (e.g., municipal sewer systems) to mitigate environmental pollution and promote infrastructure resilience.
Credit: U.S. Environmental Protection Agency.
Many communities, especially in rural areas, rely on onsite sewage treatment systems — often septic systems — to dispose of sanitary sewage and other liquid and solid waste. In Louisiana, as of September 2020, nearly 300,000 onsite wastewater treatment systems had been permitted, and these systems treat nearly 55 billion gallons of wastewater per year.See footnote 1 Septic systems typically involve a septic tank, where organic matter is digested and wastewater separated from solids, and a soil treatment area, where wastewater effluent from the tank percolates through the soil and is treated using natural aerobic processes before reaching the groundwater table.See footnote 2
However, with changing flooding and weather patterns — such as more frequent and extreme precipitation and heat events, and sea-level rise — there is a greater likelihood and risk of septic system failure. Precipitation and sea-level rise can heighten groundwater tables, reducing the effectiveness of septic systems as a higher groundwater table reduces the depth of unsaturated soil — a critical need for the natural filtration processes to function.See footnote 3 Higher temperatures may also increase microbial demand for oxygen, reducing the amount of oxygen available in soil treatment areas for natural aerobic treatment processes.See footnote 4 These conditions also increase the risks of environmental and groundwater contamination from untreated sewage, which can have impacts on water quality, ecosystems, and human health.See footnote 5
Some Region Seven parishes have cited pollutant discharge issues, specifically from septic and other sewage systems, as an ongoing challenge. State regulations prohibit the installation of a new sewer system anywhere where groundwater may be contaminated.See footnote 6 Despite this prohibition, on-site sewage treatment systems, which include septic systems, still impair many of Louisiana’s watersheds.See footnote 7
With the increasing variability and intensity of flood events, it is particularly important for local governments to take steps to mitigate the current risk of septic system failures where possible, and minimize future risk as needs for new sewer systems are considered. These actions can have implications for housing affordability as well, given that septic system failure or more frequent maintenance as a result of extreme weather and flooding can significantly increase individuals’ total housing costs as well as the habitability of their homes. This objective outlines actions that local governments can take to encourage the use of wastewater management systems other than septic.
How to Make Progress on This Objective
While the state holds primary responsibility and authority for regulating the disposal of sanitary sewage,See footnote 8 parish governments may adopt stricter standards.See footnote 9 Parishes in Louisiana have the authority to enact and enforce sewerage permitting systems with respect to individual sewage disposal systems (including septic), provided that minimum lot size requirements are met and the system is approved by the state public health officer prior to issuance of a permit.See footnote 10 Accordingly, parishes might consider some or all of the following types of actions:
- Amending inspection requirements
- Amending siting and design standards (especially in higher risk areas);
- Prohibiting new septic systems under certain circumstances; and/or
- Requiring that new developments be connected to sewer systems.
Vulnerability assessments and studies detailing anticipated effects from precipitation events on groundwater change and soil saturation can help justify decisions to implement some of these policy options.
Routine inspection and maintenance of septic systems can have a major impact in the prevention of system failure. Louisiana state regulations specify that inspections of septic tanks “should” occur every six years, and pumping every eight years.See footnote 11 Parishes might consider implementing more frequent inspection requirements (e.g., at more regular intervals or adding an inspection requirement when a property relying on a septic system is sold), or requiring inspections that test treatment performance rather than just operability of septic systems.See footnote 12 However, with stricter inspection requirements, parishes should consider what enforcement mechanisms might be used and ways to alleviate burdens on those who might be disproportionately affected by these standards, such as low-income individuals.
Siting and Design
Parishes could also consider amending siting and design requirements for septic systems to better account for heightened groundwater tables and more intense flooding. In order to issue a permit required for an individual sewerage system, including septic systems, the state health officer must first make determinations regarding the soil, drainage patterns, lot size, and other considerations to ensure that the system would not likely create a nuisance or public health hazard.See footnote 13 Additionally, there are siting specifications with respect to the placement of absorption trenches, and the areas where septic tank effluent is disposed. These specifications include the permeability of the soil, groundwater table, and percolation rate (the rate of effluent entering the soil).See footnote 14 State regulations require a minimum distance of two feet between any area proposed for a septic system absorption trench and the top of the groundwater table, and a minimum of four feet of depth for any clay or other impervious strata.See footnote 15 In areas with severe flooding challenges, or where groundwater tables are likely to rise, these minimum distances may, in the future, prove insufficient for the proper treatment of wastewater effluent.
Policymakers could consider amending the siting and design requirements in their local ordinances to account for future projections in groundwater or add an additional safety factor to the minimum distance between the current groundwater table and the filtration area. Broward County, Florida is one example of a local government using future groundwater projections in certain infrastructure decisions — specifically, for surface water management licenses when a permit is sought for new development or major redevelopment.See footnote 16 Local governments could also consider requiring innovative septic treatment systems, such as those that provide secondary treatment, allowing for a shallower placement of the infiltration area than in a traditional septic system leachfield, or those controlling volumes of wastewater release so as to reduce periods when the soil is saturated.See footnote 17
For areas deemed to have higher flood risk, especially those with a greater potential to impact groundwater tables, parishes might consider strengthening restrictions on new septic systems beyond the existing state standards. Restrictions on new septic systems could be implemented depending on the density of use of the area, as well as the likelihood of flood risk, accounting for future conditions. In addition to the benefits of protecting the environment and human health, restrictions on new septic systems under certain circumstances could also yield financial benefits. Prohibiting new septic systems in the floodplain, for example, can earn local governments credit under the Community Rating System (CRS), Activity 430, Higher Regulatory Standards – Other Higher Standards (432.o).See footnote 18 Parishes may wish to implement these actions in conjunction with requirements to connect to or provide for new community sewerage systems, discussed below.
Connecting to Sewer
Parishes may consider mandates or incentives to connect new developments and projects to community sewerage systems. The state generally requires connections to community sewerage systems where there is one available — a determination that considers the horizontal and vertical separation of the structure from the sewer main or lateral, political or other boundaries, and available capacity of the system).See footnote 19 For all new subdivisions, the state requires the provision of new community sewerage systems; individual sewerage systems (such as septic) are allowed only under specified circumstances set out in the sanitary code — including an upper limit of 125 lots, and required submission of a comprehensive drainage plan, among other requirements.See footnote 20 Alternatively, if a parish governing authority has enacted and enforces a sewage permitting system and the individual lots meet certain lot size and frontage criteria, individual sewerage systems may be permitted in subdivisions.See footnote 21 Under current state law, replacement of an existing sewerage system with a new individual sewerage system is permissible when it will not result in a public health hazard or nuisance, in the opinion of the state health officer.See footnote 22
Parishes might consider adopting regulations that set stricter thresholds for when development must connect to or provide a community sewerage system. For example, St. Tammany Parish requires community sewerage for new subdivisions of 15 lots or more (in contrast to the default state threshold of 125 lots); for subdivisions of less than 15 lots, the minimum lot size is two acres, and developers must submit a comprehensive drainage plan and meet other requirements in order to permit individual sewerage systems.See footnote 23 Tangipahoa Parish requires community sewerage systems for subdivisions with more than 8 lots, unless the lots are each at least one acre in size and have 125 feet of frontage.See footnote 24
Crosscutting Considerations and Practice Tips
When considering the most appropriate and feasible ways to reduce risk of septic system failure and related environmental impacts, decisionmakers may find the following crosscutting considerations and practice tips useful:
- Use the latest data and conduct vulnerability assessments to prioritize systems at the highest risk of failure
- Develop public information and education campaigns regarding the benefits of alternatives to septic systems
These tips are based on priority implementation best practices and considerations most relevant to this specific objective and do not present an exhaustive list for regional and local planners and policymakers. In addition to this objective, decisionmakers should, at a minimum, also refer to Goal Five for crosscutting practice tips and considerations including data needs related to infrastructure and flood risk.
It is important to acknowledge that every jurisdiction will be starting from a different place and have a unique local context and needs, among other factors. Therefore, these practice tips could be adopted individually, collectively, or not at all. It will be up to policymakers to work directly with their communities and other key stakeholders and partners to assess and determine potential tools and approaches to implement this goal and objective.
- Use the latest data and conduct vulnerability assessments to prioritize systems at the highest risk of failure: Regulations for new septic systems alone will not help parishes address the significant risks of existing septic systems failing. To understand the complete risk from existing systems and prioritize efforts to address these risks, decisionmakers need a good understanding of where existing septic systems are and what the flood risks are in those areas. If an inventory of existing septic systems is available, decisionmakers should conduct a vulnerability assessment to identify which systems may be at risk of failing, and prioritize their efforts accordingly. If such an inventory is unavailable for any reason, this can be a priority investment for local governments.
- Develop public information and education campaigns regarding the benefits of alternatives to septic systems: To help generate public awareness and buy-in, parishes should develop informational campaigns to help residents understand the risks to their septic systems from increased flooding and the benefits and tradeoffs associated with septic and alternatives to septic systems.
The summaries below highlight resources and case studies available in Georgetown Climate Center’s Adaptation Clearinghouse that are relevant to this objective. They illustrate how many of the above benefits, practice tips, and planning, legal, and policy tools were or are being evaluated and used in practice in different jurisdictions. To learn more and navigate to the Adaptation Clearinghouse, click on the “View Resource” buttons.