Summary of Washington's Water Reuse Guideline or Regulation for Impoundments

This page is part of the EPA’s REUSExplorer tool, which summarizes the different state level regulations or guidelines for water reuse for a variety of sources and end-uses.
The source water for this summary is Treated Municipal Wastewater.

On this page:

• Technical basis
• Water reuse for impoundments approved for use in Washington
• Water reuse treatment category for impoundments
• Additional context and definitions
• Water reuse for impoundments specifications (table)
• Upcoming state law or policy
• References
• Disclaimer

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This page is a summary of the state’s water reuse law or policy and is provided for informational purposes only. Please always refer to the state for the most accurate and updated information. 

In Washington, water reused for impoundments impoundmentsThe use of recycled water in an impoundment (body of water within an enclosure). This includes both unrestricted (use of reclaimed water in an impoundment in which no limitations are imposed on body-contact water recreation activities) and restricted (use of reclaimed water in an impoundment where body contact is restricted). Includes recreational impoundments, aesthetic impoundments, and ornamental impoundments with and without public access. Excludes landscape impoundments and storage of recycled water intended for other specific reuse applications (e.g., for agricultural irrigation). include constructed treatment wetlands with or without public access and direct surface water augmentation via an impoundment. The source of water (treated municipal wastewater) treated municipal wastewater Treated wastewater effluent discharged from a centralized wastewater treatment plant of any size. Other terms referring to this source of water include domestic wastewater, treated wastewater effluent, reclaimed water, and treated sewage. is specified by the state as municipal wastewater. The write-up below uses state terms when discussing sources or uses of water that may differ from the Regulations and End-Use Specifications Explorer's (REUSExplorer's) terms.

Technical basis

Washington approves the use of municipal wastewater for reuse applications related to impoundments including constructed treatment wetlands for further treatment or storage of reclaimed water and surface water augmentation. All applicable provisions of the Clean Water Act (CWA) (33 U.S.C. §§ 1251 et seq.), including its implementing regulations, must be met in addition to any state water quality standards. Impoundments with public access have more stringent performance standards than impoundments with no public access. In Washington, no reclaimed water may be distributed or used without a state-issued reclaimed water permit (Wash. Admin. Code § 173-219; Wash. Rev. Code § 90-46). Treatment requirements and performance standards are applied for the removal of microbial contaminants, chemicals and other relevant indicators related to impoundments and are summarized in the table. The technical basis for developing the specifications and/or removals of microbial contaminants, chemicals and other relevant indicators is not explicitly specified. 

Water reuse for impoundments approved for use in Washington

Wash. Admin. Code § 173-219 defines the following approved water reuse for impoundments:

• Constructed treatment wetlands with public access (Class A)
• Constructed treatment wetlands with no public access (Class A or B)
• Direct surface water augmentation via an impoundment (Class A or B)

Water reuse treatment category for impoundments

The various classes of reclaimed water are defined by their respective treatment requirements and applicable performance standards. The respective treatment requirements are briefly summarized for reuse applications related to impoundments: 

• Class A treatment must meet Class B requirements (secondary treatment including biological oxidation and disinfection) and one of the following treatment process train requirements:
  • Biological oxidation, followed by coagulation, filtration and disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • Biological oxidation, followed by membrane filtration and disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • Combination of biological oxidation and membrane filtration via a membrane bioreactor, followed by disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • An alternative treatment method, that demonstrates to the satisfaction of the lead agency that it provides for equivalent treatment and reliability. 
• For Class B water, the treatment requirements are secondary treatment, including biological oxidation, followed by disinfection. 

Additional context and definitions

Washington defines reclaimed water as “water derived in any part from a wastewater with a domestic wastewater component that has been adequately and reliably treated to meet the requirements of this chapter, so that it can be used for beneficial purposes” (Wash. Admin. Code § 173-219).

Washington defines constructed treatment wetlands as “wetland-like impoundments intentionally constructed on non-wetland sites and managed for the primary purpose of further treatment or retention of reclaimed water as distinct from creating natural wetland functions and values” and “surface water augmentation” as “the intentional use of reclaimed water for rivers and streams of the state or other surface water bodies, for the purpose of increasing volumes” (Wash. Admin. Code § 173-219). Surface water augmentation is further clarified to include direct augmentation via impoundments. Criteria for this reuse purpose are established on a case-by-case basis “to protect existing beneficial uses (recreational, environmental, or other)” (Wash. Admin. Code § 173-219).

Class A and B municipal reclaimed water piping, valves, outlets, storage facilities and other appurtenances must be color-coded purple and the pipes must be at least 200 feet away from potable water intakes, including well-heads, springs, surface water or designated groundwater (Wash. Admin. Code § 173-219). The reclaimed water generator must notify the public and employees at the site of the reclaimed water (for all use areas) by posting advisory signs or distributing advisory notices. The signage must be purple-colored and read “Reclaimed Water – Do Not Drink.”

Water reuse for impoundments specifications

Summary of Washington's Water Reuse for Impoundments Specifications

Source= Wash. Admin. Code § 173-219

* Information about sampling and monitoring requirements such as frequency, site and quantification methods not specifically listed in the table was not explicitly specified in the State-specific regulations. 

^a Listed as 23 MPN/mL or CFU/mL in Wash. Admin. Code § 173-219.

^b Additional log reductions occur during drinking water treatment.

^c If chlorine was used as the disinfectant. A chlorine residual is not required in reclaimed water impoundments at the point of use, or for conveyance along natural streams, lakes, surface waters or groundwaters of the state.

Upcoming state law or policy

No upcoming reuse regulations related to impoundments were found for Washington.

References

Clean Water Act, 33 U.S.C. §§ 1251 et seq.

Reclaimed Water, Wash. Admin. Code § 173-219.

Reclaimed Water Use, Wash. Rev. Code § 90-46.

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Disclaimers

Please contact us at [email protected] if the information on this page needs updating or if this state is updating or planning to update its laws and policies and we have not included that information on the news page.