Flooding a Severe Danger to Water and Wastewater Treatment Facilities
Flooding causes more damage in the United States than any other problems caused by weather conditions due to overwhelming amounts of water and/or debris. Drinking water and wastewater treatment facilities can become inundated by the floodwaters causing loss of power and damage to equipment and buildings, and creating extremely hazardous conditions for the employees. Flooding can happen extremely rapidly and with little or no warning. It will have a profound effect on individuals in the community by eliminating the public potable water supply and/or send wastewater back into homes, onto the streets and highways, and into the surface bodies of water creating enormous potential for disease and injury. Typically, water and wastewater treatment plants are located close to large bodies of water which may be prone to flooding.
Best Practices to Prevent or Mitigate Damage and/or Destruction of Water and Wastewater
• Determine the threat of flooding by studying the maps prepared by the Federal Emergency Management Agency for a 100-year flood event, meaning that there is a 1% probability of this occurring in a given year. Use other information sources that are available including records of previous floods.
• Identify the vulnerable parts of the treatment system including elevations of the equipment, instrumentation, and electrical controls, power supply, etc., and determine the potential of damage or destruction.
• Evaluate the possible mitigation procedures, determine which are cost-effective and of highest priority, and develop a plan to implement them prior to the flooding conditions.
• For water treatment plants, prior to flooding, top off the water storage tanks, bolt to the floor all chemical tanks and ensure that waterproof covers are tightly in place, elevate all equipment especially generators, provide emergency back-up generators in a safe location, and put flood barriers around equipment. Relocate equipment if needed.
• Relocate or elevate pump houses that are in flood zones. Install waterproof pump motors or submersible pumps.
• Protect all surface intakes of water against floating debris, silt, or other contaminants by installing jetties or breakwaters to divert these substances away from the intake.
• For groundwater supplies prior to flooding, evaluate and correct the seal of well casings and protect the well areas above potential flooding heights.
• Utilize substantially reinforced screens at the intake to prevent debris from entering the system.
• Top off all fuel tanks prior to the flooding event.
• Where feasible install solar panels or wind turbines to produce electricity for the plant. Also capture waste heat and use it to produce electricity.
• Keep in a secure flood-proof area, which is easily accessible, a collection of all necessary parts needed to operate equipment in the event of an emergency.
• Develop a program to keep all culverts and drains clean and clear of debris to reduce flooding potential. Have sand bags available to place in vulnerable parts of the facility.
• Install backflow preventers for the potable water supply and on sewers and drains.
• Provide in-depth and periodic training to staff on all aspects of their role in the event of a flooding situation, when to turn power on and off, and when to remove all computers from the area.
• Provide an access plan in the event normal openings to the structure are blocked to secure the safe movement of personnel from the buildings.
• Maintain all records not only at the treatment plant but also at a distant area outside of the flood zone to prevent the destruction of invaluable information as well as customer records.
• During flooding, it is assumed that the water is heavily contaminated whether the source be from a surface body of water or a groundwater supply, so immediately test the intake supply both microbiologically and chemically to determine additional treatment procedures and advisories to the public.
• Provide permanent physical barriers around all wastewater collection system lift stations to prevent floodwaters from inundating the unit.
• For wastewater collection system lift stations’ protection, make sure that all vent lines are above potential flooding elevation. If the station becomes unusable, obtain and utilize a list of vendors who can divert the wastewater flow to an alternate system.
• Install non-electrical back-up controls where possible.
• Install external connected compressed air systems to keep air flowing to the sewage treatment process.
• Install physical barriers to prevent flooding around all wastewater treatment plants.
• Install green infrastructure around all treatment works, water, and wastewater, to help divert or mitigate floodwater surges.
• Establish secure communications with the emergency management agency to keep them advised of the situation at the treatment facilities and when to issue certain orders related to the health of the public.
• See the section above on “Wet Weather Concerns on Combined Sewers and Wastewater Treatment Facilities for additional information.”