Section NR 214.14 - Spray irrigation systems(1) SITE LOCATION CRITERIA. (a) A spray irrigation system shall be located at least 1,000 feet from a well serving a community public water supply system and at least 250 feet from other potable water supply wells.(b) The nearest edge of wastewater spray shall be separated by at least 500 feet from the nearest inhabited dwelling, except that this distance may be reduced with the written consent of any affected owners and occupants. The department may require a greater distance depending on the type of distribution system and potential for aesthetic and public health impacts.(c) The ground surface of the system shall have a minimum separation distance to bedrock and groundwater of at least 5 feet.(d) A spray irrigation system may not be located in the floodway as specified in ch. NR 116. Any system located in the floodplain shall conform to ch. NR 116 and may not be operated when the floodplain is flooded.(2) DESIGN AND CONSTRUCTION CRITERIA. (a) The spray application of wastewater to the land surface shall be designed to prevent ponding or runoff and to incorporate a load/rest cycle that optimizes wastewater treatment on the site. The wastewater application intensity shall be limited to the rate that can infiltrate into the soil surface as it is sprayed. The wastewater loading volume shall be designed so the wastewater will be absorbed and held in the top foot of the soil column for treatment. Following wastewater loading, the acreage shall be rested to provide time for soil organisms to biologically decompose organic pollutants in the wastewater, for organic solids on the ground surface to decompose and for the soil column to reaerate.(b) Table 1 provides values acceptable to the department for the intensity of wastewater spray and the wastewater application volumes for specific soil textures under optimum conditions. Alternate values that can be justified through soil testing results may be approved by the department. The volume applied and the intensity sprayed may be restricted by the department to values less than those listed in Table 1 if site conditions warrant. Table 1
Soil Texture (USDA - SCS) | Maximum Volume Applied Per Load Cycle | Maximum Intensity of Application |
Sands | 0.65 inches | 1.00 in/hr |
Sandy Loams | 0.90 inches | 0.90 in/hr |
Loams | 1.30 inches | 0.45 in/hr |
Silt Loams | 1.40 inches | 0.45 in/hr |
Clay Loams | 1.10 inches | 0.40 in/hr |
Clays | 0.70 inches | 0.40 in/hr |
(c) The spray irrigation equipment shall be capable of isolating individual sections of the treatment system for resting without interrupting discharge to acreage scheduled to be loaded with wastewater.(d) The spray nozzles shall be arranged so that the wastewater will be evenly distributed over the acreage being loaded.(e) The spray nozzle openings shall be sized to prevent plugging and located as near to the ground surface as practical to minimize wind drift of the wastewater.(f) The spray irrigation system shall be seeded with a mixture of perennial grasses, such as reed canary grass, tall fescue and orchard grass. New seedings shall also contain a nurse crop. The department may approve the use of other types of cover crops but will restrict the use of such sites to times when the cover crop is actively growing. There shall be sufficient land area with a grass cover crop to adequately treat wastewater flows during wet weather conditions.(g) The department may require reduced hydraulic application rates or grass buffer strips, or both around the perimeter of the site to absorb runoff during rainfall events.(3) DISCHARGE LIMITATIONS. (a) The discharge to a spray irrigation system may not exceed the hydraulic, organic, nitrogen, chloride or other limitations specified in a WPDES permit or plans developed pursuant to a permit requirement. In determining discharge limitations, the department shall consider past operating performance, the ability of the soils to treat pollutants in the discharge, the ability of the vegetative cover to take up nutrients, hydrogeologic characteristics of the site such as permeability and infiltration rates, and other relevant information.(b) The concentration of any wastewater parameter that may impact groundwater quality shall be limited at the point of discharge to a value that will minimize the concentration of the substance in the groundwater to the extent technically and economically feasible and will prevent exceedence of the preventive action limit (PAL) in the groundwater. This will be especially important for parameters, such as dissolved chloride, that do not receive significant treatment in the system.(c) The total pounds of nitrogen applied per acre per year shall be limited to the annual nitrogen need of the cover crop plus demonstrable nitrogen losses, such as from denitrification or ammonia volatilization occurring in the treatment system. Determination of the annual pounds of nitrogen applied to the land treatment system shall include the nitrogen supplied by the wastewater, organic nitrogen becoming available to plants and any supplemental fertilizers used.(d) The hydraulic application rate for each system shall be based on topography, cover crop, wastewater characteristics, hydrogeologic conditions, and soil texture, permeability and cation exchange capacity. The average hydraulic application rate may not exceed 10,000 gallons per acre per day. Note: Based upon the department's experience, the recommended range for a spray irrigation system average hydraulic application rate is 2,000 to 7,000 gallons per acre per day.
(e) The intensity of irrigation spray shall be limited on a day-to-day basis to prevent ponding, except for temporary conditions following rainfall events.(f) Wastewater spraying shall be limited to prevent the runoff of any wastewater mixed with rainwater. Wastewater may not be sprayed during any rainfall event that causes runoff from the site. Uncontaminated storm water may be allowed to drain from a spray irrigation field.(g) The department may restrict spray irrigation during times of the year when the cover crop is dormant or not actively taking up water and nutrients.(h) The department may limit the fecal coliform bacteria in the discharge from meat and poultry processing operations to protect human and animal health.(4) DISCHARGE MONITORING REQUIREMENTS. (a) The discharge to spray irrigation systems shall be monitored for total daily flow.(b) The department may require in a WPDES permit that the discharge be monitored for BOD5, total suspended solids, forms of nitrogen, chloride, metals or any other pollutant that may be present. The department shall select the pollutants to be monitored and the required frequency of monitoring on a case-by-case basis by considering the potential public health impacts, probable environmental impact, soil and geologic conditions, past operating performance, concentrations and characteristics of pollutants in the discharge and other relevant information.(c) The department may require electronic or paper submittal of discharge monitoring reports and land application forms.(5) OPERATING REQUIREMENTS. (a) Spray irrigation systems shall be operated in a load/rest cycle that will provide time for the soil organisms to biologically decompose the organic pollutants in the wastewater, for organic solids on the ground surface to decompose and for the soil column to reaerate.(b) The spray irrigation system cover crop shall be cut and removed at least twice a year to stimulate growth of vegetation and removal of nutrients from the system. Corn or other crops may be harvested only once as long as the applied nutrients are limited accordingly.(c) The soil at each individual spray irrigation field shall be tested annually for available nitrogen, available phosphorus, available potassium and pH. The results of these analyses shall be submitted to the department and used to determine if the nutrients applied to the site are meeting the agronomic needs of the cover crop.(d) Management plan. The department shall require each spray irrigation system owner or operator to submit a management plan for optimizing treatment system performance and demonstrating compliance with the requirements of this chapter. Following approval by the department, the treatment system shall be operated in conformance with the management plan. If the facility wishes to operate differently than specified in the approved plan, a written request shall be submitted to the department for approval to amend the management plan. The plan shall specify information on pretreatment processes, load and rest schedules, scheduled maintenance, vegetative cover management and removal, scheduling of annual soil nutrient testing, operational strategies for periods of adverse weather, monitoring procedures and any other pertinent information.(6) SOIL INVESTIGATION AND GROUNDWATER MONITORING REQUIREMENTS. The soil investigation and groundwater monitoring requirements for spray irrigation systems are specified in ss. NR 214.20 and 214.21.Wis. Admin. Code Department of Natural Resources NR 214.14
Cr. Register, June, 1990, No. 414, eff. 7-1-90; CR 09-123: cr. (4) (c) Register July 2010 No. 655, eff. 8-1-10.