The following acronyms and definitions apply throughout this chapter unless the context clearly requires otherwise:

(1) "Additive" means a commercial product added to an OSS intended to affect performance or aesthetics of an OSS.

(2) "ASTM" means American Society for Testing and Materials.

(3) "Bank" means any naturally occurring slope greater than one hundred percent (forty-five degrees) and extending vertically at least five feet from the toe of the slope to the top of the slope.

(4) "Bed" means a drainfield component consisting of an excavation with a width greater than three feet and up to ten feet.

(5) "BOD" means biochemical oxygen demand, typically expressed in mg/L.

(6) "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 remaining portions of the OSS.

(7) "CBOD" means carbonaceous biochemical oxygen demand, typically expressed in mg/L.

(8) "Cesspool" means a pit receiving untreated sewage and allowing the liquid to seep into the surrounding soil or rock.

(9) "Covenant" means a recorded agreement stating certain activities or practices are required or prohibited.

(10) "Cover material" means soil placed over a drainfield or dripfield composed predominantly of mineral material with no greater than ten percent organic content. Cover material may contain an organic surface layer for establishing a vegetative landscape to reduce soil erosion.

(11) "Cut" means any artificially formed slope greater than one hundred percent (forty-five degrees) and extending vertically at least five feet from the toe of the slope to the top of the slope.

(12) "Department" means the Washington state department of health.

(13) "Design engineer" means a professional engineer who is licensed in Washington state under chapter 18.43 RCW and is experienced and qualified in the analysis and design of LOSS or sewage treatment system components. If the LOSS or any component of the LOSS is considered a "significant structure" as defined in chapter 18.43 RCW, the design engineer shall be licensed as a structural engineer unless an exception specified in RCW 18.43.040 applies.

(14) "Design flow" means the maximum volume of sewage a residence, structure, or other facility is estimated to generate in a twenty-four-hour period. It incorporates both an operating capacity and a surge capacity for the LOSS during periodic heavy use events.

(15) "Development" means a combination of residences, structures, and facilities, or similar activity, in or on subdivisions, sites, or areas, where residential strength sewage is produced.

(16) "Distribution technology" means any arrangement of equipment or materials that distributes LOSS effluent within the drainfield.

(17) "Domestic sewage" means urine, feces, and the water carrying human wastes, including kitchen, bath, and laundry wastes from residences, nonresidential buildings such as churches or schools, commercial establishments, or other buildings, excluding industrial wastewater and stormwater.

(18) "Drain rock" means clean washed gravel or crushed rock ranging in size from three-fourths 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.

(19) "Drainfield" means the treatment and soil dispersal component of a LOSS consisting of trenches or beds containing either a distribution pipe within a layer of drain rock covered with a geotextile or equivalent covering, or an approved gravelless distribution technology, designed and installed in original, undisturbed, unsaturated soil providing at least minimal vertical separation as established in this chapter, with pressure distribution of effluent.

(20) "Dripfield" means a type of drainfield where effluent is applied directly into the soil through driplines.

(21) "Dripline" means the distribution piping used with a subsurface drip system to discharge effluent into the soil. A dripline consists of small diameter, flexible polyethylene tubing with small in-line emitters.

(22) "Drywell" means a subterranean pit, chamber, or structure used to collect stormwater, effluent, or other liquid and disperse it into the soil.

(23) "Effective particle size" means the size of sieve opening where ninety percent by weight of a sample of filter media is retained on the sieve and ten percent passes through the sieve.

(24) "Effluent" means liquid discharged from a septic tank or other LOSS treatment component.

(25) "Emitter" means an orifice that discharges effluent at a slow, controlled rate.

(26) "Expansion" means a change to the LOSS or its influent that causes the LOSS to exceed its existing treatment or dispersal capacity, or a change that reduces the treatment or dispersal capacity of the existing LOSS.

(27) "Extremely gravelly" means soil with sixty to ninety percent rock fragments by volume.

(28) "Failure" means a condition of a LOSS or LOSS component that threatens the public health or environment by inadequately treating sewage or by creating a potential for direct or indirect contact between sewage and the public.

(29) "FC" means fecal coliform bacteria, typically expressed in number of colonies/100 ml.

(30) "Fecal coliform" means bacteria common to the digestive systems of warm blooded animals that are cultured in standards tests. Counts of these organisms are typically used to indicate potential contamination from sewage or to describe a level of needed disinfection, and are generally expressed as colonies per 100 ml.

(31) "gpd" means gallons per day.

(32) "Gravelly" means soils with fifteen to thirty-four percent rock fragments by volume.

(33) "Greywater" means domestic type flows from bathtubs, showers, bathroom sinks, washing machines, dishwashers, and kitchen or utility sinks. Greywater does not include flow from a toilet or urinal.

(34) "Gross land area" means the total land area of a proposed development that might include the centerline of adjoining road or street right of ways, if dedicated as part of the development, but does not include land area under surface water.

(35) "Groundwater" means water in a saturated zone or stratum beneath the surface of land or below a surface water.

(36) "High quality effluent (HQE)" means a treatment level higher than Treatment Level B as established in WAC 246-272B-06250.

(37) "Holding tank sewage system" means a LOSS that incorporates a sewage tank without a discharge outlet, and requires the services of a sewage pumper, and off-site treatment and disposal for the generated sewage.

(38) "Hydraulic loading rate" means the rate at which effluent is applied to a drainfield or other treatment component usually expressed as gpd/sf.

(39) "Hydrogeologist" means a professional hydrogeologist who is licensed in Washington state under chapter 18.220 RCW.

(40) "HGR" means hydrogeology report.

(41) "HQE" means high quality effluent.

(42) "Industrial wastewater" means the water or liquid carried waste from an industrial process. This waste 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. The term includes contaminated stormwater and leachate from solid waste facilities.

(43) "Infiltrative surface" means the horizontal surface area measured in square feet within a drainfield to which effluent is applied and through which effluent moves into original undisturbed soil or other porous treatment media.

(44) "Influent" means the domestic sewage entering the LOSS.

(45) "Installer" means a person who installs or repairs an OSS and who meets the requirements in WAC 246-272B-05000.

(46) "Large on-site sewage system (LOSS)" means an OSS with design flows of three thousand five hundred gpd up to and including one hundred thousand gpd.

(47) "Local health officer" means the legally qualified physician who has been appointed as the health officer for the county or district public health department as defined in RCW 70.05.010, or his or her authorized representative.

(48) "LOSS" means large on-site sewage system.

(49) "Maintenance" means the actions necessary to keep the OSS and its components functioning to protect public health and the environment.

(50) "Management entity" means a publicly or privately owned entity acting as an agent of the owner responsible for the proper and safe long-term management of the LOSS.

(51) "Massive structure" means soil that appears as a coherent or solid mass not separated into peds of any kind.

(52) "mg/L" means milligrams per liter.

(53) "ml" means milliliter.

(54) "mm" means millimeter.

(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 a change to an existing LOSS that includes, but is not limited to, a repair, an expansion, a replacement, treatment or other process improvement, or a management or ownership change.

(57) "Monitoring" means routine observation and measurement of LOSS performance to determine if it is functioning as intended and if maintenance is needed. Monitoring also includes maintaining accurate records documenting monitoring activities.

(58) "N10" means a treatment level based on total nitrogen of 10 mg/L-N.

(59) "N20" means a treatment level based on total nitrogen of 20 mg/L-N.

(60) "NEMA" means National Electrical Manufacturer Association.

(61) "NRCS" means Natural Resources Conservation Service.

(62) "O&G" means oils and grease.

(63) "Oils and grease" means a component of sewage typically originating from food stuffs or consisting of compounds of alcohol or glycerol with fatty acids, typically expressed in mg/L. Standard laboratory methods for determining O&G are USEPA Method 1664 or Standard Methods 5520.

(64) "O&M" means operations and maintenance.

(65) "On-site sewage system (OSS)" means an integrated system of components, located on or nearby the property it serves, that conveys, stores, treats, and provides subsurface soil treatment and disposal of domestic sewage. It consists of a collection system, a treatment component or treatment sequence, and a drainfield. It may or may not include a mechanical treatment system. An OSS also refers to a holding tank sewage system or other system that does not have a drainfield. A holding tank that discharges to a sewer is not included in the definition of OSS. A system into which stormwater or industrial wastewater is discharged is not included in the definition of OSS.

(66) "Operator" means a person who is responsible for operating the LOSS and ensuring that it consistently and reliably treats sewage according to the terms and conditions of the operating permit, and who meets the requirements in WAC 246-272B-07200.

(67) "Operating capacity" means the average daily volume of sewage that a LOSS can treat and disperse on a sustained basis.

(68) "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 water 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 definitions 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.

(69) "OSS" means on-site sewage system.

(70) "Owner" means a person responsible for the LOSS and for complying with this chapter.

(71) "P" means phosphorus, typically expressed in mg/L.

(72) "Ped" means a unit of soil structure such as a block, column, granule, plate, or prism formed by natural processes.

(73) "Person" means any individual, corporation, company, association, society, firm, partnership, joint stock company, or any governmental agency, or the authorized agents of these entities.

(74) "Platy structure" means soil that contains flat peds that lie horizontally and often overlap. This type of structure impedes the vertical movement of water.

(75) "Pressure distribution" means a system of small diameter pipes equally distributing pumped effluent throughout a drainfield.

(76) "Private management entity" means a person, for-profit organization, nonprofit organization, or the authorized agents of these entities responsible for the proper and safe long-term management of the LOSS. This definition does not include public entities or wastewater companies regulated by the Washington utilities and transportation commission.

(77) "Proprietary product" means sewage treatment or distribution technology, methods, and materials subject to a patent or trademark.

(78) "psi" means pounds per square inch.

(79) "Public domain technology" means sewage treatment or distribution technology, method, or material not subject to a patent or trademark.

(80) "Public entity" means a municipal corporation such as a city; town; county; water, sewer, or water-sewer district; public utility district; port district; or federal, state, or local agency.

(81) "Pumper" means a person approved by the local health officer to remove and transport sewage or septage from an OSS.

(82) "Reclaimed water" means water derived in any part from wastewater with a domestic wastewater component that has been adequately and reliably treated, so that it can be used for beneficial purposes. Reclaimed water is not considered a wastewater.

(83) "Record drawing" means an accurate graphic and written record of the location and features that are needed to properly monitor, operate, and maintain the LOSS that bears the stamp and signature of a design engineer.

(84) "Repair" means reconstruction, relocation, or replacement of a LOSS or a LOSS component that has failed or is not functioning as designed.

(85) "Reserve area" means an area of land approved for the installation of a LOSS and dedicated for replacement of the LOSS in the event of a failure.

(86) "Residential strength sewage" means sewage with the constituency and strength of biochemical oxygen demand; carbonaceous biochemical oxygen demand; fats, oils, and grease; and suspended solids typical of domestic sewage.

(87) "Restrictive layer" means a stratum impeding the vertical movement of water, air, and growth of plant roots. Some examples include: Hardpan, claypan, fragipan, caliche, some compacted soils, bedrock, or unstructured clay soils.

(88) "Rock fragment" means pieces of rocks or minerals having a diameter greater than two millimeters, such as gravel, cobbles, stones, and boulders.

(89) "Sanitary sewer system" means all facilities, including approved LOSS, used in the collection, transmission, storage, treatment, or discharge of any waterborne waste, whether domestic in origin or a combination of domestic, commercial, or industrial wastewater. LOSS are only considered sanitary sewer systems if they are designed to serve urban densities. Sanitary sewer system is also commonly known as public sewer system.

(90) "Seepage pit" means an excavation where the sidewall or bottom is designed to dispose of effluent without the use of pipe or other approved method of distribution.

(91) "Septage" means the mixture of solid wastes, scum, sludge, and liquids pumped from septic tanks, pump chambers, holding tanks, or other OSS components.

(92) "Septic tank" means a water tight treatment receptacle receiving the discharge of sewage from a building sewer or sewers; designed and constructed to permit separation of settleable and floating solids from the liquid, and detention and anaerobic digestion of the organic matter, prior to discharge of the liquid.

(93) "Septic tank effluent (STE)" means liquid waste with characteristics typical of effluent from a properly sized septic tank treating residential strength sewage.

(94) "Sewage tank" means a water tight prefabricated or cast-in-place septic tank, pump tank, holding tank, grease interceptor tank, recirculating filter tank, tank used with a proprietary product, or any other tank used in an OSS. This term also includes tanks used in a septic tank effluent pump or vacuum collection or transmission system for an OSS.

(95) "Site risk survey (SRS)" means a screening tool used to identify and evaluate potential impacts to public health and the environment from a LOSS.

(96) "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.

(97) "Soil scientist" means a person certified by the American Society of Agronomy or Soil Scientist Society of America as a Certified Professional Soil Scientist.

(98) "Soil texture" means the USDA numerical classification of soil particles two millimeters or less in size and the description of the percent of sand, silt, and clay.

(99) "Soil type" means one of seven numerical classifications based on USDA classifications of soil texture, structure and percent rock fragments as described in Table 1 in WAC 246-272B-03400.

(100) "sf" means square feet.

(101) "SRS" means site risk survey.

(102) "STE" means septic tank effluent.

(103) "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.

(104) "Subsurface drip system" means a pressurized wastewater distribution system that can deliver small, precise doses of effluent to soil surrounding the dripline.

(105) "Surface water" means any body of water, whether fresh or marine, which either flows or is contained in natural or artificial unlined depressions or drainage course and contains water for forty-eight continuous hours during May through October. Such bodies include, but are not limited to, natural and artificial lakes, ponds, springs, rivers, streams, canals, ditches, swamps, marshes, tidal waters, and wetlands.

(106) "Test pit" means an excavation used to observe the soil profile in its original condition for purpose of completing a soil log.

(107) "Timed dosing" means delivery of discrete volumes of sewage at prescribed time intervals.

(108) "Treatment component" means a technology or process that reduces targeted constituents in sewage in preparation for dispersal or disposal.

(109) "Trench" means a drainfield component consisting of an excavation with a width of three feet or less.

(110) "TSS" means total suspended solids, typically expressed in mg/L.

(111) "Uniformity coefficient" means a numeric quantity calculated by dividing the size of the sieve opening which will pass sixty percent of a sample by the size of the opening which will pass ten percent of the sample on a weight basis. Symbolically this is depicted as d60/d10 = Uc.

(112) "USDA" means United States Department of Agriculture.

(113) "USEPA" means United States Environmental Protection Agency.

(114) "Vertical separation" means the depth of unsaturated, original, undisturbed soil between the infiltrative surface of a drainfield component and the highest seasonal water table, a restrictive layer, or soil types 6 or 7 as illustrated by the profile drawings of drainfields in Figure 1 below.

(115) "Very gravelly" means soil with thirty-five to fifty-nine percent rock fragments by volume.

(116) "Water table" means the upper surface of the groundwater, whether permanent or seasonal.

(117) "Well" means water well, resource protection well, and dewatering well as defined in RCW 18.104.020.