WSR 26-15-117
PROPOSED RULES
STATE BOARD OF HEALTH
[Filed July 21, 2026, 2:08 p.m.]
Original Notice.
Preproposal statement of inquiry was filed as WSR 26-07-010.
Title of Rule and Other Identifying Information: Minimum horizontal separations for on-site sewage systems (OSS); the state board of health (board) is proposing to amend WAC 246-272A-0210 to clarify the minimum horizontal separations (setbacks) for surface water used as a public and nonpublic drinking water source. The board is also proposing to make several technical, grammatical, and editorial corrections in WAC 246-272A-0010, 246-272A-0110, 246-272A-0120 (5)(b)(ii), 246-272A-0210, and 246-272A-0240 (2)(c).      
Hearing Location(s): On October 1, 2026, at 1:30 p.m., at Norm Dicks Government Center, Auditorium, 345 6th Street, Bremerton, WA 98337; or virtually via Zoom at https://us02web.zoom.us/webinar/register/WN_kxfzJhAKREGMKdoAxwpthA, Webinar ID 819 4162 7760, Passcode 682856.
Date of Intended Adoption: October 1, 2026.
Submit Written Comments to: Shay Bauman, P.O. Box 47990, Olympia, WA 98504-7990, email shay.bauman@sboh.wa.gov, web https://fortress.wa.gov/doh/policyreview/, beginning the date and time of filing, by September 17, 2026, at 11:59 p.m.
Assistance for Persons with Disabilities: Contact Shay Bauman, phone 360-236-4110, TTY 711, email shay.bauman@sboh.wa.gov, web wsboh@sboh.wa.gov, by September 17, 2026.
Purpose of the Proposal and Its Anticipated Effects, Including Any Changes in Existing Rules: The board is proposing to amend Table IV in WAC 246-272A-0210 to amend the setbacks for surface water used as drinking water (public and nonpublic) measured from the ordinary high-water mark. The proposed rules would revert setback requirements from 200 feet to 100 feet from the drainfield/reserve area, from 200 feet to 50 feet from the sewage tank or distribution box, and from 100 feet to 50 feet from the building sewer or piping, matching the setback requirements established in rule prior to the most recent rule amendment in 2024. The proposed rules also provide clarity on setbacks for springs by separating surface water from springs in Table IV, and ensuring that setbacks for springs align with drinking water standards. Finally, the proposed rules make technical, grammatical, and editorial corrections in WAC 246-272A-0010, 246-272A-0110, 246-272A-0120 (5)(b)(ii), 246-272A-0210, and 246-272A-0240 (2)(c).    
Reasons Supporting Proposal: The proposed rules address unintended consequences that arose after implementation of the board's most recent updates to chapter 246-272A WAC in 2024. At that time, the setback requirement for surface water used as a public drinking water source measured from the ordinary high-water mark was increased to proactively protect source water around surface water intakes. However, the implementation of the revised rule resulted in unintended consequences for local jurisdictions around the state. The rule as written requires a 200-foot setback along many miles of rivers, regardless of the location of the drinking water intake. This outcome was not the intent of the 2024 changes to WAC 246-272A-0210. In November 2025, the board received a petition for rule making, explaining the effects of the current setbacks on the development of lots along the Pend Oreille River system. This rule making provides clarity to interested parties and addresses the petitioners' concerns, while ensuring public health protections are still in place.
Statutory Authority for Adoption: RCW 43.20.050(3).
Statute Being Implemented: RCW 43.20.050(3).
Rule is not necessitated by federal law, federal or state court decision.
Name of Proponent: State board of health, governmental.
Name of Agency Personnel Responsible for Drafting: Shay Bauman, 111 Israel Road S.E., Tumwater, WA 98501, 360-236-4110; Implementation and Enforcement: Heather Watts-Goodfellow, 111 Israel Road S.E., Tumwater, WA 98501, 360-236-3208.
A school district fiscal impact statement is not required under RCW 28A.305.135.
A cost-benefit analysis is required under RCW 34.05.328. A preliminary cost-benefit analysis may be obtained by contacting Shay Bauman, P.O. Box 47990, Olympia, WA 98504-7990, phone 360-236-4110, TTY 711, email shay.bauman@sboh.wa.gov.
This rule proposal, or portions of the proposal, is exempt from requirements of the Regulatory Fairness Act because the proposal:
Is exempt under RCW 19.85.025(3) as the rules are adopting or incorporating by reference without material change federal statutes or regulations, Washington state statutes, rules of other Washington state agencies, shoreline master programs other than those programs governing shorelines of statewide significance, or, as referenced by Washington state law, national consensus codes that generally establish industry standards, if the material adopted or incorporated regulates the same subject matter and conduct as the adopting or incorporating rule; and rules only correct typographical errors, make address or name changes, or clarify language of a rule without changing its effect.
Is exempt under RCW 19.85.025(4).
Explanation of exemptions: The proposed rule applies to local health jurisdictions, which do not meet the definition of "small business" in RCW 19.85.020. Additionally, the proposed rule will not impact OSS installers or homeowners/property developers. WAC 246-272A-0010, 246-272A-0120 (5)(b)(ii), and 246-272A-0240 (2)(c) are exempt under RCW 34.05.310 (4)(d), as the proposed changes correct typographical errors. WAC 246-272A-0110 is exempt under RCW 34.05.310 (4)(c) and (d), as the proposed changes both incorporate by reference a national consensus code and correct typographical errors.
Scope of exemption for rule proposal:
Is fully exempt.
July 21, 2026
Michelle A. Davis, MPA
Executive Director
RDS-7288.2
AMENDATORY SECTION(Amending WSR 24-06-046, filed 3/1/24, effective 4/1/25)
WAC 246-272A-0010Definitions.
The definitions used in this section apply throughout this chapter unless the context clearly indicates otherwise:
(1) "Additive" means a commercial product added to an OSS intended to affect the performance or aesthetics of an OSS.
(2) "ANSI" means American National Standards Institute.
(3) "Approved" means a written statement of acceptability issued by the local health officer or the department.
(4) "Bank" means any naturally occurring slope greater than 100 percent (45 degrees) and extending vertically at least five feet from the toe of the slope to the top of the slope as follows:
(5) "Bed" means a soil dispersal component consisting of an excavation with a width greater than three feet.
(6) "BL" means bacterial level.
(7) "Black water" means any waste from toilets or urinals.
(8) "BOD" means biochemical oxygen demand, typically expressed in mg/L.
(9) "Building drain" means that part of the lowest piping of a building's drainage system that receives the discharge of sewage from pipes inside the walls of the building and conveys it to the building sewer beginning two feet outside the building wall.
(10) "Building sewer" means that part of the horizontal piping of a drainage system extending from the building drain, which collects sewage from all the drainage pipes inside a building, to an OSS. It begins two feet outside the building wall and conveys sewage from the building drain to the OSS.
(11) "CBOD5" means carbonaceous biochemical oxygen demand, typically expressed in mg/L.
(12) "Cesspool" means a pit receiving untreated sewage and allowing the liquid to seep into the surrounding soil or rock.
(13) "Conforming system" means any OSS or component, meeting any of the following criteria:
(a) In full compliance with new construction requirements under this chapter; or
(b) Approved, installed, and operating in accordance with requirements of previous editions of this chapter; or
(c) Permitted by the waiver process under WAC 246-272A-0420.
(14) "Cover material" means soil placed over a soil dispersal component composed predominately of mineral material with no greater than 10 percent organic content. Cover material may contain an organic surface layer for establishing a vegetative landscape to reduce soil erosion.
(15) "Cuts" means any artificially formed slope greater than 100 percent (45 degrees) and extending vertically at least five feet from the toe of the slope to the top of the slope as follows:
(16) "Department" means the Washington state department of health.
(17) "Designer" means a person who matches site and soil characteristics with appropriate on-site sewage technology. Throughout this chapter this term applies to both OSS designers licensed under chapter 18.210 RCW and professional engineers licensed under chapter 18.43 RCW.
(18) "Design flow" means the maximum volume of sewage a residence, structure, or other facility is estimated to generate in a 24-hour period. It incorporates both an operating capacity and a surge capacity for the OSS during periodic heavy use events. The sizing and design of the OSS components are based on the design flow.
(19) "Detention pond" means an earthen impoundment used for the collection and temporary storage of stormwater runoff.
(20) "Development" means the creation of a residence, structure, facility, subdivision, site, area, or similar activity resulting in the production of sewage.
(21) "Disinfection" means the process of destroying pathogenic microorganisms in sewage through the application of ultraviolet light, chlorination, or ozonation.
(22) "Distribution technology" means any arrangement of equipment or materials that distributes sewage within an OSS.
(23) "Drainrock" means clean washed gravel or crushed rock ranging in size from three-quarters inch to two and one-half inches and containing no more than two percent by weight passing a US No. 8 sieve and no more than one percent by weight passing a US No. 200 sieve.
(24) "DS&G" means department standards and guidance.
(25) "E. coli" means Escherichia coli bacteria. Counts of these organisms are typically used to indicate potential contamination from sewage or to describe a level of needed disinfection, typically expressed as colony forming units/100 mL.
(26) "Effluent" means liquid discharged from a sewage tank or other OSS component.
(27) "EPA" means United States Environmental Protection Agency.
(28) "Expanding clay" means a clay soil with the mineralogy of clay particles, such as those found in the Montmorillonite/Smectite Group, which causes the clay particles to expand when they absorb water, closing the soil pores, and contract when they dry out.
(29) "Expansion" means a change in a residence, facility, site, or use that:
(a) Causes the sewage quantity or quality to exceed the existing design flow of the OSS, for example, when a residence is increased from two to three bedrooms or a change in use from an office to a restaurant; or
(b) Reduces the treatment or dispersal capability of the existing OSS or the reserve area, for example, when a building is placed over a reserve area.
(30) "Extremely gravelly" means soil with 60 percent or more, but less than 90 percent rock fragments by volume.
(31) "Failure" means a condition of an OSS or component that threatens the public health by inadequately treating sewage or by creating a potential for direct or indirect contact between sewage and the public. Examples of failure include:
(a) Sewage on the surface of the ground;
(b) Sewage backing up into a structure caused by slow soil absorption of septic tank effluent;
(c) Sewage leaking from a sewage tank or collection system;
(d) Cesspools or seepage pits where evidence of groundwater or surface water quality degradation exists;
(e) Inadequately treated effluent contaminating groundwater or surface water; or
(f) Noncompliance with standards stipulated on the permit.
(32) "Fecal coliform" or "FC" means bacteria common to the digestive systems of warm-blooded animals that are cultured in standard tests. Counts of these organisms are typically used to indicate potential contamination from sewage or to describe a level of needed disinfection typically expressed in colony forming units/100 mL.
(33) "Fill" means unconsolidated material that:
(a) Meets soil types 1-6 textural criteria and is used as part of a soil dispersal component;
(b) Is used to change grade or to enhance surface water diversion; or
(c) Is any other human-transported material.
(34) "Flood plain" means an area that is low-lying and adjacent to a stream or river that is covered by water during a flood.
(35) "GPD" means gallons per day.
(36) "Gravelly" means soils with 15 percent or more, but less than 35 percent rock fragments by volume.
(37) "Greywater" means sewage from any source in a residence or structure that has not come into contact with toilet or urinal wastes, including bathtubs, showers, bathroom sinks, washing machines, dishwashers, and kitchen sinks.
(38) "Groundwater" means subsurface water occupying the zone of saturated soil, permanently, seasonally, or as the result of the tides. Indications of groundwater may include:
(a) Water seeping into or standing in an open excavation from the soil surrounding the excavation or monitoring ports.
(b) Spots or blotches of different color or shades of color interspersed with a dominant color in soil, caused by reduction and oxidation of iron. These color patterns are redoximorphic features, commonly referred to as mottling. Redoximorphic features often indicate the intermittent presence of groundwater and may indicate poor aeration and impeded drainage.
(39) "Holding tank sewage system" means an OSS that incorporates a sewage tank without a discharge outlet, the services of a sewage pumper/hauler, and the offsite treatment and disposal for the sewage generated.
(40) "Hydraulic loading rate" means the amount of effluent applied to a given treatment step, expressed as gallons per square foot per day or gal/sq.ft./day.
(41) "Industrial wastewater" means the water or liquid carried waste from an industrial process. These wastes may result from any process or activity of industry, manufacture, trade or business, from the development of any natural resource, or from animal operations such as feedlots, poultry houses, or dairies. Industrial wastewater includes contaminated stormwater and leachate from solid waste facilities.
(42) "Infiltration pond" means an earthen impoundment used for the collection, temporary storage, and infiltration of stormwater runoff.
(43) "Infiltrative surface" means the surface within a treatment component or soil dispersal component to which effluent is applied and through which effluent moves into original, undisturbed soil or other porous treatment media.
(44) "Installer" means a person approved by the local health officer to install an OSS or OSS components.
(45) "Local health officer" means the health officer of the city, county, or city-county health department or district within the state of Washington, or a representative authorized by and under the direct supervision of the local health officer, as defined in chapter 70.05 RCW.
(46) "LOSS" means a large on-site sewage system under chapter 246-272B WAC.
(47) "Maintenance" means the actions necessary to keep the OSS components functioning as designed.
(48) "Maintenance service provider" means a management entity certified by the local health officer and conducts a comprehensive analysis of an OSS.
(49) "Malfunction" means a damaged or deficient previously conforming OSS component that may be corrected by means of a minor repair.
(50) "Massive structure" means the condition of a soil layer in which the layer appears as a coherent or solid mass not separated into peds of any kind.
(51) "mg/L" means milligrams per liter.
(52) "mL" means milliliter.
(53) "Minimum usable land area" means the minimum land area within the minimum lot size required per development using an OSS, which is based on soil type and type of water supply. Minimum usable land area is free of all physical restrictions and meet minimum vertical and horizontal separations.
(54) "Minor repair" means the repair or replacement of any of the following existing damaged or malfunctioning OSS components except that the repair or replacement of a sewage tank, treatment component, or soil dispersal component is not considered a minor repair:
(a) Control panels;
(b) Building sewers;
(c) Any other portions of tightline in the OSS;
(d) Risers and riser lids;
(e) Sewage tank baffles;
(f) Effluent filters;
(g) Sewage tank pumps and lids;
(h) Pump control floats; and
(i) OSS inspection boxes and ports.
(55) "Moderate structure" means well-formed distinct peds evident in undisturbed soil. When disturbed, soil material parts into a mixture of whole peds, broken peds, and material that is not in peds.
(56) "Modification" means the alteration of an existing OSS component that does not result in an expansion of the system. A modification is not considered a repair.
(57) "Monitoring" means periodic or continuous checking of an OSS, which is performed by observations and measurements, to determine if the system is functioning as intended and if system maintenance is needed. Monitoring also includes maintaining accurate records that document monitoring activities.
(58) "NSF" means NSF International.
(59) "O&G" means oil and grease, a component of sewage typically originating from food stuffs such as animal fats or vegetable oils, or consisting of compounds of alcohol or glycerol with fatty acids such as soaps and lotions, typically expressed in mg/L.
(60) "Operating capacity" means the average daily volume of sewage an OSS can treat and disperse on a sustained basis. The operating capacity, which is lower than the design flow, is an integral part of the design and is used as an index in OSS monitoring.
(61) "Ordinary high-water mark" means the mark on lakes, streams, springs, and tidal waters, found by examining the beds and banks and ascertaining where the presence and action of waters are so common and usual, and so long continued in all ordinary years, as to mark upon the soil a character distinct from that of the abutting upland with respect to vegetation, as that condition exists on the effective date of this chapter, or as it may naturally change thereafter. The following conditions apply where the ordinary high-water mark cannot be found:
(a) The ordinary high-water mark adjoining marine water is the elevation at mean higher high tide; and
(b) The ordinary high-water mark adjoining freshwater is the line of mean high water.
(62) "OSS" means on-site sewage system, an integrated system of components, located on or nearby the property it serves, which conveys, stores, treats, and provides subsurface soil treatment and dispersal of sewage. It consists of a collection system, a treatment component or treatment component sequence, and a soil dispersal component. An OSS also refers to a holding tank sewage system or other system that does not have a soil dispersal component. The term "on-site sewage system (OSS)" does not include any system regulated by a water quality discharge permit issued under chapter 90.48 RCW.
(63) "PAG" means policy advisory group.
(64) "PDP" means product development permit.
(65) "Ped" means a unit of soil structure such as blocks, column, granule, plate, or prism formed by natural processes.
(66) "Person" means any individual, corporation, company, association, society, firm, partnership, joint stock company, or any governmental agency, or the authorized agents of these entities. For the purposes of WAC 246-272A-0430 and 246-272A-0440, a person is defined to include:
(a) Applicant;
(b) Reapplicant;
(c) Permit holder; or
(d) Any individual associated with (a), (b) or (c) of this subsection including, but not limited to:
(i) Board members;
(ii) Officers;
(iii) Managers;
(iv) Partners;
(v) Association members;
(vi) Agents; and
(vii) Third persons acting with the knowledge of such persons.
(67) "Planned unit development" means a subdivision characterized by a unified site design, clustered residential units or commercial units, and areas of common open space.
(68) "Platy structure" means soil that contains flat peds that lie horizontally and often overlap. This type of structure impedes the vertical movement of water.
(69) "Pressure distribution" means a system of small diameter pipes equally distributing effluent throughout an OSS, as described in the DS&G for Pressure Distribution Systems, 2022. A subsurface drip system is considered a pressure distribution system.
(70) "Professional engineer" means a person who is currently licensed as an engineer under the provisions of chapter 18.43 RCW.
(71) "Proprietary product" means a sewage treatment and distribution technology, method, or material subject to a patent or trademark.
(72) "Public domain technology" means a sewage treatment and distribution technology, method, or material not subject to a patent or trademark.
(73) "Public sewer system" means a sewerage system:
(a) Owned or operated by a city, town, municipal corporation, county, or other approved ownership consisting of a collection system and necessary trunks, pumping facilities and a means of final treatment and disposal; and
(b) Approved by or under permit from the department of ecology, the department of health, or a local health officer.
(74) "Puget Sound counties" means Clallam, Island, Kitsap, Jefferson, Mason, San Juan, Seattle-King, Skagit, Snohomish, Tacoma-Pierce, Thurston, and Whatcom. All other counties are defined as non-Puget Sound counties.
(75) "Pump chamber" means a watertight receptacle placed after a septic tank, sewage tank, or other treatment facility that contains the required controls and alarms to convey sewage effluent to a treatment or dispersal component.
(76) "Pumper" means a person approved by the local health officer to remove and transport sewage or septage from an OSS.
(77) "Record drawing" means an accurate graphic and written record of the location and features of the OSS that are needed to properly monitor, operate, and maintain that system. Also known as an "as-built" drawing.
(78) "Remediation" means any action, approved by the local health officer, which attempts to restore the function of a previously conforming OSS dispersal component that has failed. Remediation is not considered:
(a) A minor repair;
(b) A repair;
(c) An additive; or
(d) A treatment or distribution technology that allows the OSS to meet a specific treatment level.
(79) "Repair" means the relocation, replacement, or reconstruction of a failed OSS, or any OSS components not included in the list for a minor repair, which have failed in order to restore the OSS to a nonfailure status.
(80) "Reserve area" means an area of land approved for the installation of a conforming OSS that is protected and maintained for replacement of the OSS upon its failure.
(81) "Residential sewage" means sewage having the ((constituency))consistency and quality typical of residential septic tank effluent consistent with treatment level E identified in Table III in WAC 246-272A-0110.
(82) "Restrictive layer" means a stratum impeding the vertical movement of water, air, and growth of plant roots, such as hardpan, claypan, fragipan, caliche, some compacted soils, bedrock, and unstructured clay soils.
(83) "Rock fragment" means rock or mineral fragments having a diameter of two millimeters or more. Examples include, gravel, cobbles, stones, and boulders.
(84) "Seepage pit" means an excavation more than three feet deep where the sidewall of the excavation is designed to dispose of septic tank effluent. Seepage pits are also known as dry wells.
(85) "Septage" means liquid or solid material removed from sewage tanks, cesspools, portable toilets, type III marine sanitation devices, vault toilets, pit toilets, recreational vehicle holding tanks, or similar systems that receive only domestic sewage.
(86) "Septic tank" means a watertight treatment receptacle receiving the discharge of sewage from a building sewer or sewers, designed and constructed to separate settleable and floating solids from the liquid, detention and anaerobic digestion of the organic matter, prior to discharge of the liquid.
(87) "Sewage" means any urine, feces, and the water carrying human wastes, including kitchen, bath, and laundry wastes from residences, buildings, industrial establishments, or other places.
(88) "Sewage quality" means contents in sewage that include:
(a) CBOD5, TSS, and O&G;
(b) Other parameters that may adversely affect treatment. Examples include pH, temperature, and dissolved oxygen; or
(c) Other constituents that create concerns due to specific site sensitivity. Examples include fecal coliform, E. coli, phosphorus, and nitrogen.
(89) "Sewage tank" means a prefabricated or cast-in-place septic tank, pump chamber, dosing chamber, holding tank, grease interceptor, recirculating filter tank or any other tanks as they relate to OSS including tanks for use with proprietary products.
(90) "Soil dispersal component" means a technology that releases effluent from a treatment component into the soil for dispersal, final treatment and recycling.
(91) "Soil log" means a detailed description of soil characteristics providing information on the soil's capacity to act as an acceptable treatment and dispersal medium for sewage.
(92) "Soil scientist" means a person certified by the American Society of Agronomy as a Certified Professional Soil Scientist.
(93) "Soil type" means one of seven numerical classifications of fine earth particles and rock fragments as described in WAC 246-272A-0220 (2)(e).
(94) "Standard methods" means the 23rd Edition of Standard Methods for the Examination of Water and Wastewater, prepared and published jointly by the American Public Health Association, the American Water Works Association and the Water Environment Federation.
(95) "Strong structure" means peds are distinct in undisturbed soil. They separate cleanly when soil is disturbed, and the soil material separates mainly into whole peds when removed.
(96) "Subdivision" means a division of land or creation of lots or parcels, described under chapter 58.17 RCW, including both long and short subdivisions, planned unit developments, and mobile home parks.
(97) "Subsurface drip system" means an efficient pressurized wastewater distribution system that can deliver small, precise doses of effluent to soil surrounding the drip distribution piping, also known as dripline, as described in the DS&G for Subsurface Drip Systems, 2020.
(98) "SSAS" means a subsurface soil absorption system that is a soil dispersal component of trenches or beds containing either a distribution pipe within a layer of drainrock covered with a geotextile, or an approved gravelless distribution technology, designed and installed in suitable soil, with either gravity or pressure distribution of the treatment component effluent.
(99) "Suitable" means original, undisturbed, unsaturated soil of soil types 1-6 with at least the vertical separation established in this chapter.
(100) "Surface water" means any fresh or marine body of water flowing or contained in natural or artificial unlined depressions for significant periods of the year, including natural and artificial lakes, ponds, springs, rivers, streams, swamps, marshes, irrigation canals, and tidal waters.
(101) "TAG" means the technical advisory group established in WAC 246-272A-0400.
(102) "Timed dosing" means delivery of discrete volumes of sewage at prescribed time intervals.
(103) "TN" means total nitrogen, typically expressed in mg/L.
(104) "Treatment component" means a technology that treats sewage in preparation for further treatment or dispersal into the soil environment. Some treatment components, such as mound systems, incorporate a soil dispersal component in lieu of separate treatment and soil dispersal components.
(105) "Treatment component sequence" means any series of treatment components that discharges treated sewage to the soil dispersal component.
(106) "Treatment level" means one of the following levels (A, B, C, BL1, BL2, BL3, E, & N) to:
(a) Identify treatment component performance demonstrated through requirements specified in WAC 246-272A-0110; and
(b) Match site conditions of vertical separation and soil type with treatment components.
(107) "Trench" means a soil dispersal component consisting of an excavation with a width of three feet or less.
(108) "TSS" means total suspended solids, a measure of all suspended solids in a liquid, typically expressed in mg/L.
(109) "Unit volume of sewage" means:
(a) Flow from a single-family residence;
(b) Flow from a mobile home site in a mobile home park; or
(c) Four hundred fifty gallons of sewage per day where the proposed development is not single-family residences or a mobile home park.
(110) "Unknown OSS" means an OSS that was installed without the knowledge or approval of the local health jurisdiction, including those that were installed before such approval was required.
(111) "Unpermitted sewage discharge" means the discharge of sewage or treated effluent from an unknown OSS.
(112) "Vertical separation" means the depth of suitable soils between the bottom infiltrative surface of a soil dispersal component and the highest seasonal water table, a restrictive layer, or soil type 7 as illustrated below by the profile drawing of subsurface soil absorption systems:
(113) "Very gravelly" means soil containing 35 percent or more, but less than 60 percent rock fragments by volume.
(114) "Water supply protection zone" means the land area around each existing or proposed well site to protect the water supply from contamination.
(115) "Water table" means the upper surface of the groundwater, whether permanent or seasonal. Also see "groundwater" as defined in this section.
(116) "Well" means any excavation that is constructed when the intended use of the well is for the location, diversion, artificial recharge, observation, monitoring, dewatering or withdrawal of groundwater for agricultural, municipal, industrial, domestic, or commercial use. The following are not considered a well:
(a) A temporary observation or monitoring well used to determine the depth to a water table for locating an OSS;
(b) An observation or monitoring well used to measure the effect of an OSS on a water table;
(c) An interceptor or curtain drain constructed to lower a water table; and
(d) A dewatering well used temporarily for the purpose of a sewage tank or pump chamber installation.
AMENDATORY SECTION(Amending WSR 25-06-036, filed 2/26/25, effective 4/1/25)
WAC 246-272A-0110Proprietary treatment products—Eligibility for registration.
(1) Manufacturers shall register a proprietary treatment product with the department using the process described in WAC 246-272A-0120 before a local health officer may permit use of the product.
(2) To be eligible for product registration, manufacturers desiring to sell or distribute proprietary treatment products in Washington state shall:
(a) Verify product performance through testing using the testing protocol established in Table I of this section;
(b) Report product test results of influent and effluent sampling obtained throughout the testing period (including normal and stress loading phases) for evaluation of constituent reduction according to the requirements in Table II of this section;
(c) Demonstrate product performance according to the requirements in Table III of this section. All 30-day averages and geometric means obtained throughout the test period must meet the identified threshold values to qualify for registration at that threshold level; and
(d) Verify bacteriological reduction according to WAC 246-272A-0130 for product registration utilizing bacterial levels BL1, BL2, and BL3.
(3) Manufacturers verifying product performance through testing according to the following standards or protocols shall have product testing conducted by a testing facility accredited by ANSI:
(a) NSF/ANSI 40: Residential Wastewater Treatment Systems;
(b) NSF/ANSI 41: Non-Liquid Saturated Treatment Systems;
(c) NSF Protocol P157 Electrical Incinerating Toilets - Health and Sanitation;
(d) NSF/ANSI 245: Residential Wastewater Treatment Systems - Nitrogen Reduction; or
(e) NSF/ANSI 385: Residential Wastewater Treatment Systems - Disinfection Mechanics for Bacteriological Reduction described in WAC 246-272A-0130.
(4) Manufacturers verifying product performance through testing according to EPA Method 1664, Revision B and using a wastewater laboratory certified by the Washington department of ecology shall provide supporting information, including flow data, and influent and effluent quality sampling results from a minimum of three installations with similar design loading to demonstrate product performance to Category 2 standards.
(5) Treatment levels established in Table III of this section are intended to establish treatment product performance in a product testing setting under established protocols by qualified testing entities. Field compliance standards for proprietary treatment products shall follow the requirements in WAC 246-272A-0120(5).
(6) Manufacturers may submit a written request to substitute components of a registered product's construction in cases of supply chain shortage or similar manufacturing disruptions impacting installations, operation, or maintenance. The substitution request must include a report stamped, signed, and dated by a professional engineer demonstrating the substituted component will not negatively impact performance or diminish the effect of the treatment, operation, and maintenance of the original registered product. If approved, substitution is authorized until rescinded by the department.
Table I
Testing Requirements for Proprietary Treatment Products
Treatment Component/Sequence Category
Required Testing Protocol
Category 1 Designed to treat septic tank effluent anticipated to be equal to or less than treatment level E.
NSF/ANSI 40—Residential Wastewater Treatment Systems (versions dated between January 2009 and ((May 31, 2021))October 1, 2023)
Category 2 Designed to treat effluent or sewage with sewage quality parameters anticipated to be greater than treatment level E.
EPA Method 1664, Revision B (February 2010) and
NSF/ANSI 40—Residential Wastewater Treatment Systems (versions dated between January 2009 and ((May 31, 2021))October 1, 2023)
(Such as at restaurants, grocery stores, mini-marts, group homes, medical clinics, residences, etc.)
Category 3 Black water component of residential sewage (such as composting((*)) and incinerating((**)) toilets).
NSF/ANSI 41: Non-Liquid Saturated Treatment Systems (Versions dated between February 2011 and ((May 31, 2021))November 1, 2023)
 
((**))NSF Protocol P157 Electrical Incinerating Toilets - Health and Sanitation (April 2000)
Total Nitrogen Reduction in Categories 1 & 2 (Above)
NSF/ANSI 245: Residential Wastewater Treatment Systems - Nitrogen Reduction (Versions dated between January 2018 and ((May 31, 2021))December 1, 2023)
Table II
Test Results Reporting Requirements for Proprietary Treatment Products
Treatment Component/Sequence Category
Testing Results Reported
Category 1 Designed to treat septic tank effluent anticipated to be equal to or less than treatment level E.
Report the following test results of influent and effluent sampling obtained throughout the testing period for evaluation of reduction of CBOD52, and TSS:
 
□ Average
□ Standard Deviation
□ Minimum
□ Maximum
□ Median
□ Interquartile Range
□ 30-day Average (for each month)
 
For evaluation of bacteriological reduction performance.
Report complete treatment component sequence testing as described in Table III, Category 1.
 
For evaluation of performance meeting treatment level BL1:
(1) Report fecal coliform test results of influent and effluent sampling by geometric mean from samples drawn within 30-day or monthly calendar periods, obtained from a minimum of three samples per week throughout the testing period. See WAC 246-272A-0130.
(2) Report complete testing results for supplemental bacteriological reduction technology1 when the required treatment levels for fecal coliform in Table III, Category 1 are not met by the primary proprietary treatment product.
 
For evaluation of performance meeting treatment level BL2 or BL3:
(1) Report fecal coliform test results of influent and effluent sampling by geometric mean from samples drawn within 30-day or monthly calendar periods, obtained from a minimum of three samples per week throughout the testing period as described in WAC 246-272A-0130; or
(2) Report complete testing results for supplemental bacteriological reduction technology1 when the required treatment levels for fecal coliform in Table III, Category 1 are not met by the primary proprietary treatment product.
For all options, test report must also include the individual results of all samples drawn throughout the test period.
Category 2 Designed to treat effluent or sewage with sewage quality parameters anticipated to be greater than treatment level E.
Report all individual test results and full test average values of influent and effluent sampling obtained throughout the testing period for the evaluation of reduction of: CBOD5, TSS and O&G. Establish the treatment capacity of the product tested in pounds per day for CBOD5.
(Such as at restaurants, grocery stores, mini-marts, group homes, medical clinics, atypical residences, etc.)
 
Category 3 Black water component of residential sewage (such as composting and incinerating toilets).
Report test results on all required performance criteria according to the format prescribed in the NSF test protocol described in Table I.
Total Nitrogen Reduction in Categories 1 & 2 (Above)
Report test results on all required performance criteria according to the format prescribed in the test protocol described in Table I.
1
Test results for BOD5 may be submitted in lieu of test results for CBOD5. In these cases numerical values for CBOD5 will be determined using the following formula: (BOD5 × 0.83 = CBOD5).
2
Supplemental bacteriological reduction technology must be tested for influent/effluent fecal coliform or E. coli per WAC 246-272A-0130 (bacteriological reduction testing protocol). Supplemental fecal coliform or E. coli reducing technologies will be rated for log base 10 removal of fecal coliform or E. coli. The lowest 30-day geometric mean will be used to rate reduction level. The highest monthly geometric mean for treatment technology fecal coliform or E. coli reduction will be used as the baseline value for review.
Table III
Product Performance Requirements for Proprietary Treatment Products
Treatment
Component/Sequence
Category
Product Performance Requirements
Category 1 Designed to treat effluent anticipated to be equal to or less than treatment level E.
Treatment System Performance Testing Levels
 
Level
Parameters
 
CBOD5
mg/L
TSS
mg/L
O&G
mg/L
FC
cfu/100 mL
TN
mg/L
E. coli
cfu/100 mL
 
A
10
10
—
—
—
—
 
B
15
15
—
—
—
—
 
C
25
30
—
—
—
—
 
BL1
 
 
—
200
—
126
 
BL2
—
—
—
1,000
—
—
 
BL3
—
—
—
50,000
—
—
 
E
228
80
20
—
—
—
 
N
—
—
—
—
30 (or 50% reduction based on mass loading as required in WAC 246-272A-0320)
—
 
Values for Levels A - C are 30-day values (averages for CBOD5, TSS, and geometric mean for FC.) All 30-day averages throughout the test period must meet these values in order to be registered at these levels.
Values for Levels E and N are derived from full test averages.
Category 2 Designed to treat high-strength sewage when septic tank effluent is anticipated to be greater than treatment level E.
All of the following requirements must be met:
(1) All full test averages must meet Level E; and
(2) Establish the treatment capacity of the product tested in pounds per day for CBOD5.
(Such as at restaurants, grocery stores, mini-marts, group homes, medical clinics, residences, etc.)
 
 
 
 
 
 
 
Category 3 Black water component of residential sewage (such as composting and incinerating toilets).
Test results must meet the performance requirements established in the NSF test protocol.
Total Nitrogen Reduction in Categories 1 & 2 (Above)
Test results must establish product performance effluent quality meeting Level N, when presented as the full test average.
AMENDATORY SECTION(Amending WSR 24-06-046, filed 3/1/24, effective 4/1/25)
WAC 246-272A-0120Proprietary treatment product registration—Process and requirements.
(1) Manufacturers shall register proprietary treatment products with the department by submitting a complete registration application for review and approval in the format provided by the department, including:
(a) Manufacturer's name, mailing address, phone number, email address, and website address;
(b) Contact person's name, title, mailing address, email address, and phone number. The contact person must be vested with the authority to represent the manufacturer in this capacity;
(c) Name, including specific brand and model, of the proprietary treatment product;
(d) A description of the function of the proprietary treatment product along with any known limitation on the use of the product;
(e) Product description and technical information, including process flow drawings and schematics; materials and characteristics; component design specifications; design capacity, volumes and flow assumptions and calculations; components; dimensioned drawings and photos;
(f) For treatment systems in Category 2, daily capacity of the model or models in pounds per day of CBOD5;
(g) Siting and installation requirements;
(h) Detailed description, procedure, and schedule of routine service and system maintenance events;
(i) Estimated operational costs for the first five years of the treatment component's life. This must include both estimated annual electricity costs, and routine maintenance costs, including replacement of parts;
(j) Identification of information subject to protection from disclosure of trade secrets;
(k) Most current dated copies of product brochures and manuals: Sales & Promotional; Design; Installation; Operation & Maintenance; and Homeowner Instructions;
(l) The most recently available product test protocol dated no earlier than the dates in WAC 246-272A-0110 Table I and the results report;
(m) A signed and dated certification by the manufacturer's agent specifically including the following statement, "I certify that I represent (INSERT MANUFACTURING COMPANY NAME) and I am authorized to prepare or direct the preparation of this application for registration. I attest, under penalty of law, that this document and all attachments are true, accurate, and complete. I understand and accept that the product testing results reported with this application for registration are the parameters and values to be used for determining conformance with Treatment System Performance Testing Levels established in chapter 246-272A WAC";
(n) A signed and dated certification from the testing entity including the statement, "I certify that I represent (INSERT TESTING ENTITY NAME), that I am authorized to report the testing results for this proprietary treatment product. I attest, under penalty of law, that the report about the test protocol and results is true, accurate, and complete"; and
(o) The fee described in WAC 246-272-2000.
(2) Products within a single series or model line, sharing distinct similarities in design, materials, and capacities, may be registered under a single application, consistent with the provisions of their test protocol for the certification of other products within a product series. Products outside of the series or model line must be registered under separate applications.
(3) Upon receipt of a registration application the department shall:
(a) Verify that the application is complete including dated and current copies of all of the required manuals; and
(b) If approved, place the product on the department's list of registered on-site treatment and distribution products.
(4) All registrations are valid for up to one year, expiring on December 31st of each year. Fees are not prorated.
(5) In order to renew a proprietary treatment product technology registration, a manufacturer shall:
(a) Apply for renewal of product registration using the format provided by the department;
(b) Submit any of the following applicable reports:
(i) A retesting report from the testing entity according to the protocol required for registration as identified in this section;
(ii) A field verification performance report as identified in the proprietary on-site wastewater treatment products DS&G, dated ((February 1, 2025))July 2026. If field performance results demonstrate that the product has failed to meet the requirements in the DS&G, the manufacturer shall report to the department describing the reasons for the failure to meet the requirements consistent with the DS&G;
(c) Provide an attestation to the department verifying whether or not the product has changed over the previous year. If the product has changed, the attestation must also include a full description of the changes. If the product has changed in a way that affects performance, the product may not be renewed and shall meet the requirements for initial registration;
(d) Provide a statement that all required dated manuals are current, or submit the updated and dated new manuals; and
(e) Submit the fee established in WAC 246-272-2000.
(6) As part of product registration renewal, the department shall:
(a) Request field assessment comments from local health officers no later than October 31st of each year. These comments may include concerns about a variety of field assessment issues, including:
(i) Product function, including verification of field performance testing as identified in the DS&G;
(ii) Product reliability; and
(iii) Problems arising with operation and maintenance;
(b) Discuss with the TAG any field assessment information that may impact product registration renewal;
(c) Notify the manufacturer of any product to be discussed with the TAG, prior to discussion with the TAG, regarding the nature of comments received;
(d) Renew the product registration unless:
(i) The manufacturer of a product does not apply for renewal; or
(ii) The department, after deliberation with the TAG, concludes product registration renewal should not be given or should be delayed until the manufacturer submits information that satisfactorily answers concerns and issues; and
(e) Provide a compliance plan to the manufacturer within 90 days based on departmental concerns of public health risk related to the product.
(7) The department shall maintain a list of registered on-site treatment and distribution products meeting the registration requirements established in this chapter. The product registration is a condition of approval for use.
(8) Manufacturers shall have readily accessible product information for designers, regulators, OSS owners and other interested parties posted on the manufacturer's website including the most current dated version of:
(a) Product manuals;
(b) Design instructions;
(c) Installation instructions;
(d) Operation and maintenance;
(e) Owner instructions; and
(f) How to locate a list of representatives and manufacturer certified maintenance service providers, if any.
AMENDATORY SECTION(Amending WSR 24-06-046, filed 3/1/24, effective 4/1/25)
WAC 246-272A-0210Location.
(1) OSS must be designed and installed to meet at least the minimum horizontal separations shown in Table IV:
Table IV
Minimum Horizontal Separations
Items Requiring Setback
From edge of soil dispersal component and reserve area
From sewage tank and distribution box
From building sewer, and nonperforated distribution pipe
Well
100 ft.
50 ft.
50 ft.
Public drinking water well
100 ft.
100 ft.
100 ft.
Nonpublic drinking water well
100 ft.
50 ft.
50 ft.
Surface water used as drinking water (public and nonpublic) measured from the ordinary high-water mark
100 ft.
50 ft.
50 ft.
Public drinking water spring ((or surface water measured from the ordinary high-water mark))
200 ft.
200 ft.
((100))200 ft.
Nonpublic drinking water spring ((or surface water measured from the ordinary high-water mark1))
100 ft.
50 ft.
50 ft.
Nonpublic, in-ground, drinking water containment vessel((3))2
20 ft.
10 ft.
10 ft.
Pressurized water supply line or easement for water supply line
10 ft.
10 ft.
10 ft.
Closed geothermal loop((4))3 or pressurized nonpotable water line
10 ft.
10 ft.
10 ft.
Decommissioned well (decommissioned in accordance with chapter 173-160 WAC)
10 ft.
N/A
N/A
Surface water measured from the ordinary high-water mark
100 ft.
50 ft.
10 ft.
Building foundation/in-ground swimming pool
10 ft.
5 ft.
2 ft.
Property or easement line
5 ft.
5 ft.
N/A
Lined((5))4 stormwater detention pond((6))5
 
 
 
 
Down-gradient((7))6:
30 ft.
N/A
N/A
 
Up-gradient((7))6:
10 ft.
N/A
N/A
Unlined((8))7 stormwater infiltration pond((6))5 (up or down-gradient)((7))6
100 ft.
50 ft.
10 ft.
Irrigation canal or irrigation pond (up or down-gradient)
100 ft.
50 ft.
10 ft.
Interceptor/curtain drains/foundation drains/drainage ditches
 
 
 
 
Down-gradient((2))1:
30 ft.
5 ft.
N/A
 
Up-gradient((2))1:
10 ft.
N/A
N/A
Subsurface stormwater infiltration or dispersion component((6))5
 
 
 
 
Down-gradient((7))6:
30 ft.
10 ft.
N/A
 
Up-gradient((7))6:
30 ft.
10 ft.
N/A
Other site features that may allow effluent to surface
 
 
 
 
Down-gradient((2))1:
30 ft.
5 ft.
N/A
 
Up-gradient((2))1:
10 ft.
N/A
N/A
Down-gradient cuts or banks with at least 5 ft. of original, undisturbed soil above a restrictive layer due to a structural or textural change
25 ft.
N/A
N/A
Down-gradient cuts or banks with less than 5 ft. of original, undisturbed soil above a restrictive layer due to a structural or textural change
50 ft.
N/A
N/A
Soil dispersal components serving a separate OSS
10 ft.
N/A
N/A
1
((If surface water is used as a public drinking water supply, the designer shall locate the OSS outside of the required source water protection area.
2))
The item is down-gradient when liquid will flow toward it upon encountering a water table or a restrictive layer. The item is up-gradient when liquid will flow away from it upon encountering a water table or restrictive layer.
((3))2
Any in-ground containment vessel used to store drinking water.
((4))3
A network of underground piping carrying fluid under pressure used to heat and cool a structure.
((5))4
Lined means any component that has the intended function of detaining the stormwater with no intention of dispersal into surrounding soil.
((6))5
OSS components take precedence in cases of horizontal setback conflicts between OSS and stormwater components.
((7))6
Down-gradient means that subsurface water flows toward and is usually located lower in elevation. Up-gradient means subsurface water does not flow toward and generally flat, or flows away from and generally located higher in elevation.
((8))7
Unlined means any component that has the ability to or intended function of infiltrating the stormwater.
(2) When conditions indicate a greater potential for contamination or pollution, the local health officer may increase the minimum horizontal separations. Examples of such conditions include, but are not limited to, excessively permeable soils, unconfined aquifers, shallow or saturated soils, dug wells, and improperly abandoned wells.
(3) The local health officer may allow a reduced horizontal separation to not less than two feet from where the property line, easement line, or building foundation is up-gradient.
(4) The local health officer may require an applicant to demonstrate the OSS meets (a), (b), or (c) of this subsection when determining if a horizontal separation to a minimum of 75 feet between an OSS dispersal component and a water well, spring, or surface water that is not a public water source is allowed:
(a) Adequate protective site-specific conditions, such as physical settings with low hydrogeologic susceptibility from contaminant infiltration. Examples of such conditions include evidence of confining layers, an aquatard that separates potable water from the OSS treatment zone, excessive depth to groundwater, down-gradient contaminant source, or outside the zone of influence; or
(b) Design and proper operation of an OSS with enhanced treatment performance beyond that accomplished by meeting the vertical separation and effluent distribution requirements described in Table VI in WAC 246-272A-0230; or
(c) Evidence the OSS satisfies the requirements of (a) and (b) of this subsection.
(5) Persons shall design or install a soil dispersal component only if:
(a) The slope is less than 45 percent or 24 degrees;
(b) The area is not subject to:
(i) Encroachment by buildings or construction such as placement of power poles and underground utilities;
(ii) Cover by impervious material;
(iii) Vehicular traffic; or
(iv) Other activities adversely affecting the soil or the performance of the OSS.
(c) Sufficient reserve area for replacement exists to treat and dispose one hundred percent of the design flow;
(d) The land is stable; and
(e) Surface drainage is directed away from the site.
(6) The local health officer may approve a sewer transport line within ten feet of a water supply line if the sewer line is constructed in accordance with section C1-9.1 of the department of ecology's "Criteria For Sewage Works Design," 2008.
AMENDATORY SECTION(Amending WSR 24-06-046, filed 3/1/24, effective 4/1/25)
WAC 246-272A-0240Holding tank sewage systems.
(1) A person may not install or use holding tank sewage systems for residential development or expansion of residences, whether seasonal or year-round, except as set forth under subsection (2) of this section.
(2) The local health officer may approve installation of holding tank sewage systems only:
(a) For permanent uses limited to controlled, part-time, commercial usage situations, such as recreational vehicle parks and trailer dump stations;
(b) For interim uses limited to handling of emergency situations; or
(c) For repairs as permitted under WAC 246-272A-0280 (((1)(d)(i))).
(3) A person proposing to use a holding tank sewage system shall:
(a) Follow design criteria established by the department;
(b) Submit a management program to the local health officer assuring ongoing operation, monitoring, and maintenance before the local health officer issues the installation permit; and
(c) Use a holding tank reviewed and approved by the department.