NR 809.04(30)(30) “Environmental protection agency” or “EPA” means the agency of the United States federal government ultimately responsible for establishing and enforcing national primary drinking water regulations. NR 809.04 NoteNote: Sub. (30m) is created eff. 11-1-27 by CR 25-063 to read: NR 809.04 Note(30m) “Fifth-liter sample” means, for the purpose of lead and copper only, the fifth one-liter sample of tap water collected under s. NR 809.547 (2). NR 809.04(31)(31) “Filter profile” means a graphical representation of individual filter performance, based on continuous turbidity measurements or total particle counts versus time for an entire filter run, from startup to backwash inclusively, that includes an assessment of filter performance while another filter is being backwashed. NR 809.04(32)(32) “Filtration” means a process for removing particulate matter from water by passage through porous media. NR 809.04(33)(33) “Finished water” means water that is introduced into the distribution system of a public water system and is intended for distribution and consumption without further treatment, except as treatment necessary to maintain water quality in the distribution system, for example booster disinfection or addition of corrosion control chemicals. NR 809.04(34)(34) “First draw sample” means a one-liter sample of tap water that has been standing in plumbing pipes at least 6 hours and is collected without flushing the tap. NR 809.04 NoteNote: Sub. (34) is repealed eff. 11-1-27 by CR 25-063. NR 809.04 NoteNote: Sub. (34m) is created eff. 11-1-27 by CR 25-063 to read: NR 809.04 Note(34m) “First-liter sample” means, for the purpose of lead and copper only, a sample collected of the first one-liter volume of tap water drawn under s. NR 809.547 (2). NR 809.04(35)(35) “Flocculation” means a process to enhance agglomeration or collection of smaller floc particles into larger, more easily settleable particles through gentle stirring by hydraulic or mechanical means. NR 809.04(36)(36) “4 log treatment of viruses” means a treatment process or a combination of treatment processes that provides inactivation or removal of 99.99% of viruses. NR 809.04(37)(37) “GAC10” means granular activated carbon filter beds with an empty-bed contact time of 10 minutes based on average daily flow and a carbon reactivation frequency of every 180 days, except that the reactivation frequency of GAC10 used as a best available technology for compliance with MCLs at LRAA monitoring locations is every 120 days. NR 809.04(37m)(37m) “GAC20” means granular activated carbon filter beds with an empty-bed contact time of 20 minutes based on average daily flow and a carbon reactivation frequency of every 240 days. NR 809.04(37q)(37q) “Galvanized-requiring-replacement service line” or “GRR service line” means, for the purpose of lead and copper only, a galvanized service line that currently is or was ever downstream of a lead service line or is currently downstream of a lead-status-unknown service line. For this definition, downstream means in the direction of flow through the service line. If a water supplier is unable to demonstrate that the galvanized service line was never downstream of a lead service line, it is a galvanized-requiring-replacement service line for purposes of the service line inventory and replacement requirements under s. NR 809.545. NR 809.04(37u)(37u) “Galvanized service line” means, for the purpose of lead and copper only, a service line that is made of iron or steel that has been dipped in zinc to prevent corrosion and rusting. NR 809.04(38)(38) “Gross alpha particle activity” means the total radioactivity due to alpha particle emission as inferred from measurements on a dry sample. NR 809.04(39)(39) “Gross beta particle activity” means the total radioactivity due to beta particle emission as inferred from measurements on a dry sample. NR 809.04(40)(40) “Groundwater under the direct influence of surface water”(GWUDI) means any water beneath the surface of the ground with: NR 809.04(40)(a)(a) Occurrence of insects or other macroorganisms, algae or large diameter pathogens such as Giardia lamblia or Cryptosporidium, in greater than or equal to 10% of representative source water samples collected over a period of 6 months, immediately prior to the first or only point of disinfectant application, or NR 809.04(40)(b)(b) Evidence of relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to climatological or surface water conditions where the department determines that these shifts are indications of the potential for contamination of the groundwater by the organisms identified in par. (a). NR 809.04(41)(41) “Haloacetic acids (five)” or “HAA5” means the sum of the concentrations in milligrams per liter of the haloacetic acid compounds (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid), rounded to 2 significant figures after addition. NR 809.04(41d)(41d) “Hazard index” or “HI” means the sum of component hazard quotients (HQs), which are calculated by dividing the measured regulated PFAS component contaminant concentration in water by the associated health-based water concentration expressed in the same units as the measured concentration. Contaminant concentrations are expressed in parts per trillion (ppt) or nanograms per liter (ng/l). For PFAS, a mixture Hazard Index greater than 1 is an exceedance of the MCL. NR 809.04(41h)(41h) “Hazard quotient” or “HQ” means the ratio of the measured concentration in drinking water to the health-based water concentration (HBWC). NR 809.04(41p)(41p) “Health-based water concentration” or “HBWC” means the level below which there are no known or anticipated adverse health effects over a lifetime of exposure, including for sensitive populations and life stages, and that allows for an adequate margin of safety. NR 809.04(41t)(41t) “HFPO-DA or GenX chemicals” means Chemical Abstract Service registration number 122499-17-6, chemical formula C6F11O3-, International Union of Pure and Applied Chemistry preferred name 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoate, along with its conjugate acid and any salts, derivatives, isomers, or combinations thereof. NR 809.04(42)(42) “Holding time” means the period from time of sampling to time of analysis. NR 809.04 NoteNote: Sub. (42) is amended eff. 1-1-27 by CR 25-069 to read: NR 809.04 Note(42) “Holding time” means the period from time of sample collection to time of analysis. For microbial analysis, holding time is equal to the time from sample collection to initiation of test medium incubation.
NR 809.04(42m)(42m) “Human consumption” means drinking; bathing, including all personal hygiene needs in a home, business, or school setting; showering; hand washing; cooking; dishwashing; and maintaining oral hygiene. NR 809.04(43)(43) “Initial compliance period” means the first full 3-year compliance period which begins at least 18 months after promulgation of the federal regulations. For monitoring contaminants in ss. NR 809.11 (2) and 809.20 (1), the initial compliance period means January 1993 — December 1995 for public water systems with 150 or more service connections and January 1996 — December 1998 for public water systems having fewer than 150 service connections. NR 809.04(44)(44) “Initial Distribution System Evaluation or “IDSE” means an evaluation using monitoring to determine locations with representative high TTHM and HAA5 concentrations throughout the distribution system of a public water system. NR 809.04(45)(45) “Large water system” means, for the purpose of monitoring lead and copper, a public water system that serves more than 50,000 persons. NR 809.04(46)(46) “Lead service line” means, for the purpose of lead and copper only, a service line that has any portion made of lead. A lead service line includes a lead-lined galvanized service line. NR 809.04 NoteNote: A portion of piping that meets the definition of “connector” under sub. (10m) is not considered a lead service line.
NR 809.04(46f)(46f) “Lead-status-unknown service line” or “LSU service line” means, for the purpose of lead and copper only, a service line whose pipe material has not been demonstrated to be a lead service line, galvanized-requiring-replacement service line, or non-lead service line under s. NR 809.545 (1n) (d) 3. NR 809.04(46m)(46m) “Learns of the violation” for the purpose determining public notification timing requirements under subch. VII means any of the following: NR 809.04(46m)(a)(a) The date that a laboratory notifies a water supplier of results demonstrating exceedances of MCLs, MRDLs, or action levels. NR 809.04(46m)(b)(b) The day after a specified deadline in NR 809, for violation of deadlines that are not related to MCL, MRDL or action level exceedances. NR 809.04(46m)(c)(c) The date on which the violation, incident, or condition occurred, for any other type of violation, incident, or condition requiring public notification. NR 809.04(46m)(d)(d) The date specified in writing by the department to the water supplier. NR 809.04(47)(47) “Legionella” means a genus of bacteria, some species of which have caused a type of pneumonia called Legionnaires disease. NR 809.04(47g)(47g) “Level 1 assessment” means an evaluation to identify the possible presence of sanitary defects, defects in distribution system coliform monitoring practices, and, when possible, the likely reason that the system triggered the assessment. It is triggered by total coliform detections under s. NR 809.31. It is conducted by the system operator or owner. NR 809.04 NoteNote: Sub. (47g) is amended eff. 1-1-27 by CR 25-069 to read: NR 809.04 Note(47g) “Level 1 assessment” means an evaluation to identify the possible presence of sanitary defects, defects in distribution system coliform monitoring practices, and, when possible, the likely reason that the system triggered the assessment. It is triggered by total coliform detections under s. NR 809.31. It is conducted by the system operator or owner. Requirements for a Level 1 assessment are found under s. NR 809.313 (2) (b). NR 809.04(47r)(47r) “Level 2 assessment” means an evaluation to identify the possible presence of sanitary defects, defects in distribution system coliform monitoring practices, and, when possible, the likely reason that the system triggered the assessment. A Level 2 assessment provides a more detailed examination of the system, including the system’s monitoring and operational practices, than does a Level 1 assessment through the use of more comprehensive investigation and review of available information, additional internal and external resources, and other relevant practices. It is conducted by an individual approved by the department, which may include the system operator. NR 809.04 NoteNote: Sub. (47r) is amended eff. 1-1-27 by CR 25-069 to read: NR 809.04 Note(47r) “Level 2 assessment” means an evaluation to identify the possible presence of sanitary defects, defects in distribution system coliform monitoring practices, and, when possible, the likely reason that the system triggered the assessment. A Level 2 assessment provides a more detailed examination of the system, including the system’s monitoring and operational practices, than does a Level 1 assessment, through the use of more comprehensive investigation and review of available information, additional internal and external resources, and other relevant practices. It is conducted by an individual approved by the department, which may include the system operator. Requirements for a Level 2 assessment are found under s. NR 809.313 (2) (c). NR 809.04(48)(48) “Locational running annual average” or “LRAA” means the average of sample analytical results for samples taken at a particular monitoring location during the previous four calendar quarters. NR 809.04(49)(49) “Long term 2 surface water treatment rule” or “LT2” means the monitoring and requirements under the federal rule 40 CFR part 141 Subpart W. NR 809.04(50)(50) “Man-made beta particle and photon emitters” means all radionuclides emitting beta particles or photons, or both, listed in Maximum Permissible Body Burdens and Maximum Permissible Concentration of Radionuclides in Air or Water for Occupational Exposure, NBS Handbook 69, except the daughter products of thorium-232, uranium-235 and uranium-238. NR 809.04(51)(51) “Maximum contaminant level” or “MCL” means the maximum permissible level of a contaminant in water which is delivered to any user of a public water system. NR 809.04(52)(52) “Maximum contaminant level goal” or “MCLG” means the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant level goals are non-enforceable health goals, unless the department determines that action is necessary to protect public health. NR 809.04(53)(53) “Maximum residual disinfectant level” or “MRDL” means a level of a disinfectant added for water treatment that may not be exceeded at the consumer’s tap without an unacceptable possibility of adverse health effects. NR 809.04(54)(54) “Maximum residual disinfectant level goal” or “MRDLG” means the maximum level of a disinfectant added for water treatment at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. MRDLGs are nonenforceable health goals and do not reflect the benefit of the addition of the chemical for control of waterborne microbial contaminants. NR 809.04(55)(55) “Medium-size water system” means, for the purpose of monitoring lead and copper, a public water system that serves greater than 3,300 and less than or equal to 50,000 persons. NR 809.04 NoteNote: Sub. (55) is amended eff. 11-1-27 by CR 25-063 to read: NR 809.04 Note(55) “Medium water system” means, for the purpose of lead and copper only, a public water system that serves greater than 10,000 individuals and less than or equal to 50,000 individuals.
NR 809.04(55m)(55m) “Method detection limit” or “MDL” means the minimum concentration of a substance that can be measured and reported with 99 percent confidence that the analyte concentration is greater than zero and is determined from analysis of a sample in a given matrix containing the analyte. NR 809.04 NoteNote: Sub. (55t) is created eff. 1-1-27 by CR 25-069 to read: NR 809.04 Note(55t) “Municipal water system” means a community water system owned by a city, village, county, town, town sanitary district, utility district, public inland lake or rehabilitation district, municipal water district, a federal, state, county or municipal owned institution for congregate care or correction, or a privately owned water utility serving the foregoing.
NR 809.04(56)(56) “Near the first service connection” means at one of the 20% of all service connections in the entire distribution system that are nearest the water supply treatment facility or water supply source, as measured by water transport time within the distribution system. NR 809.04(56m)(56m) “Newly regulated public water system” means, for the purpose of lead and copper only, any of the following: NR 809.04(56m)(a)(a) An existing public water system that was not subject to national primary drinking water regulations under this chapter on May 1, 2026, because the public water system met the requirements under s. NR 809.05. NR 809.04(56m)(b)(b) An existing public water system that did not meet the definition of a public water system under sub. (67) on May 1, 2026. “Newly regulated public water system” does not include an existing public water system under new or restructured ownership or management. NR 809.04(57)(57) “Non-community water system” or “NCWS” means a public water system that is not a community water system. A non-community water system is either a non-transient non-community water system or a transient non-community water system. NR 809.04(58)(58) “Non-transient non-community water system” or “NTNCWS” means a non-community water system that regularly serves at least 25 of the same persons over 6 months per year. NR 809.04 NoteNote: Examples of non-transient non-community water systems include those serving schools, day care centers and factories.
NR 809.04(59)(59) “Optimal corrosion control treatment” or “OCCT” means, for the purpose of lead and copper only, the corrosion control treatment that minimizes the lead and copper concentrations at users’ taps while ensuring that the treatment does not cause the public water system to violate any national primary drinking water regulations as listed in 40 CFR part 141. NR 809.04 NoteNote: Sub. (59b) is created eff. 1-1-27 by CR 25-069 to read: NR 809.04 Note(59b) “Other-than-municipal (OTM) water system” means a community water system that is not a municipal water system.
NR 809.04 NoteNote: Sub. (59d) is created eff. 11-1-27 by CR 25-063 to read: NR 809.04 Note(59d) “Partial service line replacement” means, for the purpose of lead and copper only, replacement of any portion of a lead service line or galvanized-requiring-replacement service line that leaves in service any length of lead service line or galvanized-requiring-replacement service line upon completion of the work.
NR 809.04(59h)(59h) “Perfluoroalkyl and polyfluoroalkyl substances” or “PFAS” means a large group of human-made chemicals that are part of the synthetic organic contaminants classification. NR 809.04(59m)(59m) “Performance evaluation sample” means a reference sample provided to a laboratory for the purpose of demonstrating that the laboratory can successfully analyze the sample within limits of performance specified by the department. The true value of the concentration of the reference material is unknown to the laboratory at the time of the analysis. NR 809.04 NoteNote: Performance evaluation samples are also known as proficiency testing samples.
NR 809.04(60)(60) “Person” means an individual, corporation, company, association, cooperative, trust, institution, partnership, state, municipality, or federal agency. NR 809.04(60c)(60c) “PFBS” means Chemical Abstract Service registration number 45187-15-3, chemical formula C4F9SO3-, perfluorobutane sulfonate, along with its conjugate acid and any salts, derivatives, isomers, or combinations thereof. NR 809.04(60g)(60g) “PFHxS” means Chemical Abstract Service registration number 108427-53-8, chemical formula C6F13SO3-, perfluorohexane sulfonate, along with its conjugate acid and any salts, derivatives, isomers, or combinations thereof. NR 809.04(60n)(60n) “PFNA” means Chemical Abstract Service registration number 72007-68-2, chemical formula C9F17O2-, perfluorononanoate, along with its conjugate acid and any salts, derivatives, isomers, or combinations thereof. NR 809.04(60r)(60r) “PFOA” means Chemical Abstract Service registration number 45285-51-6, chemical formula C8F15O2-, perfluorooctanoate, along with its conjugate acid and any salts, derivatives, isomers, or combinations thereof. NR 809.04(60w)(60w) “PFOS” means Chemical Abstract Service registration number 45298-90-6, chemical formula C8F17SO3-, perfluorooctanesulfonate, along with its conjugate acid and any salts, derivatives, isomers, or combinations thereof. NR 809.04(61)(61) “Picocurie” or “pCi” means that quantity of radioactive material producing 2.22 nuclear transformations per minute. NR 809.04 NoteNote: Sub. (61m) is created eff. 11-1-27 by CR 25-063 to read: NR 809.04 Note(61m) “Pitcher filter” means, for the purpose of lead and copper only, a non-plumbed water filtration device that consists of a gravity-fed water filtration cartridge and a filtered drinking water reservoir and that is certified by an American National Standards Institute–accredited certifier to reduce lead in drinking water.
NR 809.04(62)(62) “Plant” means any facility for the obtainment of potable water, whether from surface water or groundwater sources, for a community water system. NR 809.04(63)(63) “Point-of-disinfectant application” is the point where the disinfectant is applied and water downstream of that point is not subject to recontamination by surface runoff. NR 809.04(64)(64) “Point-of-entry treatment device” or “POE” is a water treatment device applied to the drinking water entering a house or building for the purpose of reducing contaminants in the drinking water distributed throughout the house or building.
