Septic system designs for flood zones:

This article includes suggestions for septic tanks, pumps, electrical components, and absorption systems, soakbeds, or leachfields located in areas prone to flooding.

Research on flood-resistant septic systems, septic system impact on flood zone contamination, and effects of rising tide levels and water tables on future decentralized septic system operation, design, and maintenance or repair.

Page top photo: flooding along Wappingers Creek in New York - an area where septic soakbeds or drainfields and some septic tanks are located in a flood-prone zone.

Suggestions for Designing a Flood-zone Damage Resistant Septic System

The following suggestions are adapted and paraphrased from similar recommendations offered by Water Technology Engineering Ltd., a U.K. firm cited below.

1. Above-ground septic treatment tank: If a site is at risk of flooding and becoming water logged the septic tank must be above ground.
   
   Below ground septic tanks: should not be used in areas that are likely to be flooded because the tank will be submerged in floodwaters both adding to area contamination and precluding acceptance of building sewage.
2. Pumped wastewater input: recognizing that the main sewer line of most existing buildings will exit below ground, the aboveground sewage treatment system must be designed to accept pumped wastewater from a lift pump or sewage ejector pump.
   
   Design features include both adequate strength and a treatment design that is not impacted by the turbulence associated with pumped wastewater.
3. Electrical equipment protection: air blowers, aerators, or other equipment not designed for submersion must be located where they will be above floodwater level.
   
   [Note: in times of area flooding or other natural disasters it is likely that electrical power will be lost for a time. In that circumstance flooded area septic systems that do not include a gravity-drained wastewater acceptance system above flood level will thus not be functional.- Ed.]
4. Above-ground sewage effluent disposal: for sites likely to be flooded or where the groundwater level will rise too close to the bottom of a conventional effluent disposal system such as a soakbed or drainfield, an above-ground mound system or raised-bed septic system should be used.
5. Additional wastewater disinfection: may be required for systems that will discharge effluent to the environment during flooding. Examples are UV disinfection or chlorine injection systems.
6. Code compliance: amendment or replacement of septic systems requires a building permit and design acceptance before beginning work in most jurisdictions around the world.

- "Sewage Solutions for Flood Risk / Waterlogged Sites", - retrieved 10/12/2014 original source: www.wte-ltd.co.uk/sewage_treatment_flood_risk.html

Flooded Septic System Repair & Damage Prevention References & Research

• Aftias, E. "Considerations for the first application of source control measures for stormwater runoff in the Athens metropolitan area." In Advances in Urban Stormwater and Agricultural Runoff Source Controls, pp. 141-146. Springer Netherlands, 2001.
• Aldwell, C. R., R. Thorn, and D. Daly. "Point source pollution in karst areas in Ireland." In Proc. 21st Congress, International Association Hydrogeologists,(Ed) Daoxian Y, Beijing, pp. 1046-52. 1988.
• Brown, Clive, Joe Burkhart, Nancy Burton, Jean Cox-Ganser, Scott Damon, Henry Falk, Scott Fridkin et al. Mold prevention strategies and possible health effects in the aftermath of hurricanes and major floods. US Department of Health and Human Services, Centers for Disease Control and Prevention, 2006.
• Burby, Raymond J., and Steven P. French. "Coping with floods: the land use management paradox." Journal of the American Planning Association 47, no. 3 (1981): 289-300.
• Burby, Raymond J., and Steven P. French. "The US experience in managing flood plain land use." Disasters 4, no. 4 (1980): 451-457.
• Environmental Protection Agency, U.S.A., Septic (Onsite / Decentralized) Systems information, Website: http://water.epa.gov/infrastructure/septic/ - Quoting:
  Nearly one in four households in the United States depends on an individual septic system (also referred to as an onsite system) or small community cluster system to treat their wastewater.
  
  These various types of decentralized wastewater treatment, if properly executed, can protect public health, preserve valuable water resources, and maintain economic vitality in a community. EPA concluded in its 1997 Response to Congress (PDF) (101 pp, 5.8MB, About PDF) that "adequately managed decentralized wastewater systems are a cost-effective and long-term option for meeting public health and water quality goals, particularly in less densely populated areas."
  
  Unfortunately, in far too many cases, these systems are installed and largely forgotten – until problems arise. EPA helps to ensure the success of these systems through the promotion and implementation of effective decentralized wastewater management programs.
  
  [Note: we have commented at SEPTIC FIELD FAILURE CAUSES - and
  
  at AEROBIC SEPTIC SYSTEMS, ATUs - that the single most common cause of early septic system end of life or treatment failures is that the systems are not inspected nor maintained - the "install and forget" description offered by the EPA agrees with most expert sources. Pettry (1974) added over-use of septic systems beyond their original design capacity- Ed.]


• Environment Agency, U.K., flood warnings, environmental data, incident reporting, Website: https://www.gov.uk/government/organisations/environment-agency
  • Water Services (Amendment) Act 2012 [PDF]
• Ferguson, Bruce K. Introduction to stormwater: concept, purpose, design. John Wiley & Sons, 1998.
• Few, Roger, G. T. Pham, and T. T. H. Bui. "Living with floods: health risks and coping strategies of the urban poor in Vietnam." Research project funded by British Academy (Committee for South East Asian studies), research report, May (2004).
• Kilduff, James E. "Design and construction of leaching systems in fill based on permeability." Journal of Environmental Engineering 115, no. 1 (1989): 239-256.
• Laak, Rein, Kent A. Healy, and Dan M. Hardisty. "Rational Basis for Septic Tank System Designa." Groundwater 12, no. 6 (1974): 348-351.
• Odemerho, Francis O. "Flood control failures in a third world city: Benin City, Nigeria—Some environmental factors and policy issues." GeoJournal 29, no. 4 (1993): 371-376.
• Pettry, D. E., and C. S. Coleman. "Two decades of urban soil interpretations in Fairfax County, Virginia." Developments in Soil Science 4 (1974): 27-34.
• Salati Jr, E., Eneida Salati, and E. Salati. "Wetland projects developed in Brazil." Water science and technology 40, no. 3 (1999): 19-25.
• Sharma, Vinod K., and Tanu Priya. "Development strategies for flood prone areas, case study: Patna, India." Disaster Prevention and Management 10, no. 2 (2001): 101-110.
• Spaling, Harry, and Bryan Vroom. "Environmental assessment after the 2004 tsunami: a case study, lessons and prospects." Impact Assessment and Project Appraisal 25, no. 1 (2007): 43-52.
• Swann, Chris. "The influence of septic systems at the watershed level." Watershed Protection Techniques 3, no. 4 (2001): 821-834.
• Tucker, David L., and Nestor D. Vivado. "Design of an overland flow system." Journal (Water Pollution Control Federation) (1980): 559-567.
• Waananen, Arvi O. Flood-prone areas and land-use planning: selected examples from the San Francisco Bay region, California. No. 942. US Govt. Print. Off., 1977.
• Webb, Maureen, "Sewage Treatment for Flood Risk Sites", WTE Ltd., Water Technology, Ltd., UK Tel: 01759 369915, Website: http://www.wte-ltd.co.uk/, - commented here 12/10/2014" "The UK Environment Agency asked us to develop a solution for flood risk sites in the UK and have approved this method. " - retrieved 10/12/2014 original source: www.wte-ltd.co.uk/sewage_treatment_flood_risk.html
  
  This sewage treatment method combines a lift-pumping station, an above-grund Vortex sewage treatment plant, and a raised mound effluent absorpton system a mound soakaway bed. The company cites the following [paraphrased and adapted - Ed]
• Webb, Tony, and Rodger B. Tomlinson. "Design procedures for effluent discharge to estuaries during ebb tide." Journal of environmental engineering 118, no. 3 (1992): 338-362.
• Yin, Jie, Zhan-E. Yin, Xiao-meng Hu, Shi-yuan Xu, Jun Wang, Zhi-hua Li, Hai-dong Zhong, and Fu-bin Gan. "Multiple scenario analyses forecasting the confounding impacts of sea level rise and tides from storm induced coastal flooding in the city of Shanghai, China." Environmental Earth Sciences 63, no. 2 (2011): 407-414.

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Continue reading  at FLOODED SEPTIC SYSTEMS, REPAIR or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Septic System Flooding Diagnosis & Repair Articles

• FLOODED SEPTIC SYSTEMS, REPAIR
• SEPTIC D-BOX FLOODING
• SEPTIC DESIGN for FLOOD DAMAGE RESISTANCE
• SEPTIC SYSTEM BACK-PUMPING
• SEPTIC TANK BACK FLOODING
• SOIL PROPERTIES & BUILDING FAILURES

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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