Chapter NR 811

NR 811.859 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (1) (intro.), (a), (2) Register January 2024 No. 817, eff. 2-1-24.

NR 811.860 NR 811.860 Backwash wastewater from surface water treatment plants. Filter backwash wastewater from surface water treatment plants shall be disposed of by any of the following methods:

NR 811.860(1) (1) Recycling. Filter backwash wastewater may be returned to the inlet end of the plant in accordance with the requirements under s. NR 811.862. Membrane filtration plants may not recycle backwash wastewater unless the waste goes through coagulation and settling processes prior to being applied to the membranes. Membrane manufacturers may have specific feed water quality parameter requirements that could limit recycling. Chemical cleaning waste from membrane plants may not be recycled unless specifically approved by the department. A plant recycling filter wastewater shall have an alternative means of disposing of wastewater available during periods when raw water quality precludes the ability to recycle all or some of the backwash water.

NR 811.860(2) (2) Discharge to sanitary sewer. Backwash water may be discharged to a sanitary sewer system subject to the requirements under s. NR 811.85 (1) (a).

NR 811.860(3) (3) Discharge to surface water. Backwash wastewater from filtration for surface water treatment may be discharged to a surface water of the state subject to the requirements under s. NR 811.85 (1) (b) and all of the following requirements:

NR 811.860(3)(a) (a) Suspended solids shall be removed from the filter backwash wastewater prior to surface water discharge. This will require settling and may require coagulation as determined by the department on a case-by-case basis. Additional treatment may be necessary to meet the requirements of the WPDES permit.

NR 811.860(3)(b) (b) The solids removed during treatment of backwash water shall be land spread or discharged to a holding tank in accordance with the requirements under s. NR 811.85 (1) (b) and (c).

NR 811.860(3)(c) (c) Chemical cleaning waste from membrane plants may not be discharged to surface water.

NR 811.860(4) (4) Treated by secondary membrane. The filter backwash water may be treated by a dedicated membrane system and sent to the clearwell if approved by the department in accordance with all of the following requirements:

NR 811.860(4)(a) (a) The membrane, as can be demonstrated by integrity testing conducted every 8 hours, shall provide a minimum 99.9997 percent (5.5-log) removal of Cryptosporidium.

NR 811.860(4)(b) (b) If the membrane cannot be demonstrated to provide a 99.9997 percent (5.5-log) removal of Cryptosporidium, UV shall be provided following the membrane. The membrane and UV together shall provide a minimum of 99.9997 percent (5.5-logs) of removal or inactivation of Cryptosporidium, or a combination of both.

NR 811.860(4)(c) (c) A target removal of less than 99.9997 percent (5.5-logs) of Cryptosporidium may be considered by the department if testing of the backwash water in accordance with s. NR 809.334 and bin classification in accordance with s. NR 810.34 would result in a bin classification less than Bin 4.

NR 811.860 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (1), r. and recr. (2), (3) Register January 2024 No. 817, eff. 2-1-24.

NR 811.861 NR 811.861 Alum or other coagulant sludge. Alum or other coagulant sludge shall be disposed of by the following methods:

NR 811.861(1) (1) Lagoons. The general design criteria for lagoons are under s. NR 811.858 (1). The lagoon effluent shall be discharged to a sanitary sewer, water of the state, or holding tank and shall meet the provisions under s. NR 811.85 (1).

NR 811.861(2) (2) Discharge to sanitary sewers. The department may approve the discharge of coagulant sludge to sanitary sewers on a case-by-case basis if a study or experience has shown that problems will not occur in the sewage collection system or at the sewage treatment plant. The discharge of coagulant sludge shall meet the requirements under s. NR 811.85 (1) (a). The water system owner shall submit plans for a new discharge or an increase in volume or percent solids of coagulant sludge to sanitary sewer to the department for review and approval prior to initiation of the construction or operational change.

NR 811.861 Note Note: Plans for water treatment plants with wastewater discharges should be submitted to both the department’s wastewater section and public water engineering section.

NR 811.861(3) (3) Mechanical dewatering. Mechanical dewatering may be utilized if approved by the department after review of the results of testing.

NR 811.861(4) (4) Supernatant water. Any thickener supernatant or liquids from dewatering processes to be recycled shall meet the requirements of s. NR 811.862.

NR 811.861 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (1), (2), (4) (title) Register January 2024 No. 817, eff. 2-1-24.

NR 811.862 NR 811.862 Recycling backwash wastewater. Filter and contactor backwash wastewater may be recycled if approved by the department in accordance with all of the following requirements:

NR 811.862(1) (1) The filter and contactor backwash wastewater shall be settled in a settling tank or equalization basin prior to being returned to the inlet end of the plant. For surface water systems, a coagulant or polymer may be required to enhance settling to prevent protozoans such as Giardia lamblia and Cryptosporidium from concentrating. Tanks and basins shall meet all of the following minimum requirements:

NR 811.862(1)(a) (a) The tanks shall contain the anticipated volume of backwash wastewater produced by the plant when operating at design capacity.

NR 811.862(1)(b) (b) To provide operational flexibility, the tanks shall be of adequate size to contain the total waste washwater from 2 consecutive backwashes, subject to the design backwash operations.

NR 811.862(2) (2) The settled filtered backwash wastewater shall be returned to the head end of the plant at a maximum rate of 10% of the instantaneous flow rate at which raw water is entering the plant. All of the following requirements shall be met:

NR 811.862(2)(a) (a) The point of recycle shall be prior to all treatment and chemical addition except chemical treatment for zebra mussel control at the intake.

NR 811.862(2)(b) (b) A meter shall be provided on the recycle line.

NR 811.862(2)(c) (c) A means shall be provided for controlling the rate at which the settled backwash wastewater is returned.

NR 811.862(3) (3) For systems treating groundwater, the settled filtered backwash wastewater shall be disinfected prior to or at the time that it is returned to the head end of the plant.

NR 811.862(4) (4) Reservoirs to be used to settle backwash wastewater for plants treating potable groundwater shall be constructed to potable reservoir construction standards as required by subch. IX. The discharge of any wastewater or sludge, or both, from such a reservoir to a sanitary or storm sewer main, manhole, or other collection structure, whether by pump or by gravity, shall not be made through a direct connection. The discharge piping shall terminate downward with a one-foot free air break over the receiving structure as required in s. NR 811.64 (4).

NR 811.862(5) (5) For surface water systems that recycle their backwash wastewater, all of the following reporting and record keeping requirements apply:

NR 811.862(5)(a) (a) A current plant schematic showing the origin of all recycle streams, how any recycle streams are transported, and where the recycle streams enter the treatment process shall be maintained on file with the department.

NR 811.862(5)(b) (b) Information on the typical recycle flow rate, the highest observed plant flow rate each year, and the design flow rate of the plant shall be available to the department upon request.

NR 811.862(5)(c) (c) The information in pars. (a) and (b) along with all of the following information shall be maintained on file for a minimum of 10 years: dates when recycle flow rate has exceeded 10 percent of raw water flow rate entering the plant; how recycle flow rate is controlled; dimension and volume of backwash equalization basin; typical detention time in equalization basin; type of coagulant fed prior to equalization basin; and means of sludge removal from the equalization basin.

NR 811.862 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; CR 22-074: am. (1) (b) Register January 2024 No. 187, eff. 2-1-24.

subch. XIII of ch. NR 811 Subchapter XIII — Aquifer Storage Recovery

NR 811.87 NR 811.87 General.

NR 811.87(1) (1) Approval of the department is required prior to the construction of any aquifer storage recovery well or the conversion of any previously constructed well for use as an aquifer storage recovery well.

NR 811.87 Note Note: Approval to construct or develop an aquifer storage recovery well is not an approval to operate an ASR system.

NR 811.87(2) (2) Approval of the department is required prior to the operation of any aquifer storage recovery system.

NR 811.87 Note Note: The department will not issue an approval to operate an ASR system until after it has reviewed and evaluated the results of an approved ASR pilot study.

NR 811.87(3) (3) Only treated drinking water may be placed underground through an ASR system well.

NR 811.87(4) (4) Only a municipal water system may construct an aquifer storage recovery well or operate an ASR system.

NR 811.87(5) (5) The displacement zone around an ASR well may extend no further than 1,200 feet from that ASR well.

NR 811.87 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.

NR 811.88 NR 811.88 ASR well performance requirements.

NR 811.88(1) (1) Unless the department determines that it is not technically or economically feasible, the quality of the treated drinking water to be placed underground through an aquifer storage recovery well shall comply with the preventive action limits contained in ch. NR 140 prior to underground injection. In all cases, the quality of the treated drinking water to be placed underground through an aquifer storage recovery well shall meet the primary drinking water standards contained in ch. NR 809 and may not contain any substance at a concentration that exceeds a state or federal health advisory prior to underground injection.

NR 811.88 Note Note: Pursuant to s. 160.19 (2) (b), Stats., the department finds that treated drinking water in a municipal water system may at times exceed preventive action limits established for iron, manganese, nitrate, nitrite, copper, lead, fluoride, asbestos, chloroform, bromoform, bromodichloromethane, and dibromochloromethane. Such exceedances may occur at the point of underground injection and within the displacement zone surrounding an aquifer storage recovery well even though the treated water being injected would remain in compliance with federal and state water quality standards for drinking water. The maximum allowable concentration of a primary drinking water contaminant in treated drinking water has been set by the United States Environmental Protection Agency at the lowest level that is considered to be technically and economically achievable at this time. The department also finds that it is not technically or economically feasible to require that residual concentrations of chloroform, bromoform, bromodichloromethane, and dibromochloromethane be removed from the injected water when a disinfection residual is desired at the wellhead to provide additional protection to the water system from potential biological contamination.

NR 811.88(2) (2) All water that is retrieved through an aquifer storage recovery well shall comply with the primary drinking water standards contained in ch. NR 809 and shall be treated to provide a disinfectant residual prior to recovery into any municipal water distribution system.

NR 811.88(3) (3) The quality of treated drinking water stored in a displacement zone shall at all times comply with the primary drinking water standards contained in ch. NR 809. ASR systems shall be designed and operated to maintain compliance with the groundwater standards contained in ch. NR 140, as required by s. NR 140.22. Therefore, treated drinking water stored underground in an ASR system shall comply with the applicable enforcement standards established in ch. NR 140 prior to movement beyond the property boundary of the ASR well site.

NR 811.88 Note Note: An ASR well site is considered to include lands adjacent to the ASR wellhead that are directly owned by the municipal water system and any contiguous properties that are directly owned by the local unit of government of which the water system is a subunit.

NR 811.88(4) (4) At the completion of each aquifer storage recovery cycle, the subsurface water in any portion of a displacement zone may not attain or exceed ch. NR 140 enforcement standards for iron, manganese, nitrate, nitrite, copper, lead, fluoride, asbestos, chloroform, bromoform, bromodichloromethane or dibromochloromethane or ch. NR 140 preventive action limits established for any other substance. The department may grant an exemption from this requirement, in accordance with s. NR 140.28, when an ASR well or ASR system is located in an area where the background concentration of a substance attains or exceeds the groundwater preventive action limit or enforcement standard established for that substance.

NR 811.88 Note Note: Pursuant to s. 160.19 (2) (b), Stats., the department finds that routine operation of an ASR system may result in an exceedance of the preventive action limits established for iron, manganese, nitrate, nitrite, copper, lead, fluoride, asbestos chloroform, bromoform, bromodichloromethane, and dibromochloromethane in a displacement zone. An ASR cycle is normally completed when the volume of water recovered equals the volume of water that was originally injected; however, the department recognizes that some of the treated drinking water injected during an aquifer storage recovery cycle may remain in an aquifer at the completion of the cycle and that substances present in this residual treated drinking water may result in ch. NR 140 preventive action limits being exceeded in an aquifer at the completion of an aquifer storage recovery cycle.

NR 811.88 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.

NR 811.89 NR 811.89 Well construction requirements for ASR wells.

NR 811.89(1) (1) Each well constructed or converted for use as an aquifer storage recovery well shall be completed in a manner that complies with the well construction requirements established in ss. NR 811.12 to 811.20.

NR 811.89(2) (2) Any monitoring well constructed on an ASR well site shall comply with the well construction requirements established in ss. NR 811.12 to 811.20. For the purpose of this subsection, an ASR well site is considered to include only those lands adjacent to the ASR wellhead that are directly owned by the municipal water system.

NR 811.89(3) (3) Each monitoring well that is located beyond the property boundary of an ASR well site and that is constructed as part of an ASR system pilot study, ASR system development study, or for ASR operational monitoring shall comply with the monitoring well construction requirements established in ch. NR 141. For the purpose of this subsection, an ASR well site is considered to include only those lands adjacent to the ASR wellhead that are directly owned by the municipal water system.

NR 811.89(4) (4) Each aquifer storage recovery well shall be enclosed within a lockable protective structure that is secured from tampering or unauthorized entry in a manner that is approved by the department.

NR 811.89(5) (5) Each monitoring well shall be enclosed within a lockable protective covering and secured from tampering or unauthorized entry in a manner that is approved by the department.

NR 811.89 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.

NR 811.90 NR 811.90 Equipment, appurtenances and piping for ASR wells and ASR systems.

NR 811.90(1) (1) Pumping equipment, appurtenances and piping that are to be installed as part of an ASR system shall comply with the requirements of ss. NR 811.30 to 811.37.

NR 811.90(2) (2) Department approval shall be obtained prior to installation or modification of any well, pumping equipment, appurtenances or piping for the purpose of aquifer storage recovery.

NR 811.90(3) (3) Security shall be provided for each ASR well site in a manner that is approved by the department.

NR 811.90 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.

NR 811.91 NR 811.91 ASR system pilot studies.

NR 811.91(1) (1) Department approval is required prior to conducting any ASR system pilot study.

NR 811.91(2) (2) Only a municipal water system may perform an ASR system pilot study.

NR 811.91(3) (3) A request to conduct an ASR system pilot study shall be submitted to the department in writing. The request shall identify the location of each existing well that is being considered for use as an ASR well within the proposed ASR system, the location of any new well that is anticipated to be constructed for use as an ASR well within the proposed ASR system and any additional wells that are to be used or constructed as part of the ASR system pilot study.

NR 811.91(4) (4) Each request to conduct an ASR system pilot study shall contain all of the following:

NR 811.91(4)(a) (a) A preliminary hydrogeologic report that describes the methods and results of any hydrologic investigation, aquifer testing, hydrogeologic modeling or geochemical modeling performed to identify the location of the proposed ASR system well sites. The preliminary hydrogeologic report shall identify the location of each existing public or private water well and each potential source of groundwater contamination that is located within 1200 feet of the outer perimeter of the displacement zone that is calculated to be established around each of the proposed ASR wells within the proposed ASR system. The report shall also identify the well selected for further evaluation during the ASR well pilot test, identify the dimensions of the displacement zone that will be created around the designated test well, and describe the current and anticipated groundwater flow patterns found in the vicinity of the designated test well.

NR 811.91(4)(b) (b) A preliminary engineering report that provides an analysis of the technical feasibility for developing each of the potential ASR wells identified for the proposed ASR system and estimates the probable percentage of treated drinking water that would be recovered from each of the potential ASR wells during an ASR cycle.

NR 811.91(4)(c) (c) Plans and specifications for any well equipment, pumping equipment, appurtenances or piping that is to be constructed or altered in order to complete the proposed ASR system pilot study.

NR 811.91(4)(d) (d) A description of all operating procedures to be followed during the ASR well pilot study. This description shall contain details including the maximum volume of water to be placed underground, the flow rate and pressure of underground injection, the expected water storage period, anticipated water retrieval rates, and methods proposed for disposing of the water recovered during the ASR system pilot study.

NR 811.91(4)(e) (e) A description of all performance and compliance monitoring procedures to be followed during the ASR system pilot study. This description shall include a listing of the sampling locations, methods and schedules that will be used to ensure that the aquifer storage recovery well remains in compliance with the performance requirements set forth in s. NR 811.88.

NR 811.91(4)(f) (f) Plans and specifications for each monitoring well proposed as part of the ASR system pilot study. A minimum of one monitoring well is required as part of the ASR system pilot study. The department may require additional monitoring wells should the proposed ASR system encompass multiple or otherwise unique geologic formations. The department may also waive the monitoring well requirement if water quality data from other ASR system pilot studies conducted in similar geologic conditions is submitted as part of the ASR system pilot study request and is determined to be applicable by the department.

NR 811.91(5) (5) The department may require modification of plans and specifications, operating procedures or compliance and monitoring procedures required in sub. (4) to ensure that compliance with the performance requirements in s. NR 811.88 can be determined.

NR 811.91(6) (6) Within 180 days after completing an approved ASR system pilot study or prior to recovering any water retrieved through an ASR well into a water distribution system, a municipal water system shall submit a final report on the ASR system pilot study to the department.

NR 811.91 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.

NR 811.92 NR 811.92 ASR system development testing.

NR 811.92(1) (1) Department approval shall be obtained prior to any ASR system development testing.

NR 811.92(2) (2) Following the completion of an approved ASR system pilot study, each additional ASR well that is to be developed within an ASR system shall be subject to ASR system development testing.

NR 811.92(3) (3) The department may require monitoring wells to be installed as part of an ASR system development test if it finds any of the following:

NR 811.92(3)(a) (a) Geologic conditions in the vicinity of the proposed ASR well are not consistent with the conditions examined during the municipal water system’s ASR system pilot study.

NR 811.92(3)(b) (b) Geologic conditions in the vicinity of the proposed ASR well are not consistent with the conditions reported in other ASR system pilot studies or ASR system development tests performed by other municipal water systems.

NR 811.92(3)(c) (c) Results obtained during the municipal water system’s ASR system pilot study or other aquifer tests indicate that additional monitoring is warranted to ensure compliance with the water quality standards established in chs. NR 140 and 809.

NR 811.92(4) (4) Each request for an ASR system development test shall include a report or testing plan that contains the following:

NR 811.92(4)(a) (a) A comparison of the hydrogeologic conditions and formations found at the ASR system pilot study well site and any well site that is to be evaluated as part of the ASR system development testing request.