Section NR 110.255 - Conditions required for specific types of land disposal systems(1) ABSORPTION POND SYSTEMS. (a)Design and construction criteria for absorption pond systems.1. New absorption pond systems shall consist of a minimum of 3 individual absorption ponds of approximately equal size. Absorption pond systems consisting of 1 or 2 individual ponds may be approved by the department on a case-by-case basis if it is demonstrated that the system has effluent storage capabilities or other provisions to ensure the operation of the system in accordance with the load and rest cycles determined under s. NR 110.25(4) (f).2. The design hydraulic application rate for an absorption pond system shall be based on field and laboratory test results for infiltration and hydraulic conductivity. The design hydraulic application rate shall be conservatively established to allow for pond resting cycles and for a long term reduction in infiltration rate due to wastewater solids clogging the soil.3. Multiple pond systems shall be designed and constructed to allow individual ponds to be taken out of service for resting without interrupting the discharge to the remaining ponds.4. Wastewater effluent shall be discharged to absorption ponds such that it is evenly distributed over the entire absorption pond bottom. Effluent storage may be required to provide effluent dosing control by fill and draw operation.5. The absorption pond bottom shall be as level as possible at all locations.6. The shape of each absorption pond and the placement of ponds at the site must take into account the information in the hydrogeologic study required by s. NR 110.09(8) such as the groundwater flow direction, the presence of discharge or recharge zones and the variability of soils. Infiltration areas should be oriented in relation to the direction of groundwater flow in such a manner as to minimize groundwater impacts. When possible, absorption ponds shall be constructed in areas which are not groundwater recharge areas.7. The minimum top width of an embankment or dike shall be 12 feet if the dike is intended to provide access for maintenance vehicles on a routine basis. The minimum top width shall be 8 feet if the embankment or dike is not designed for vehicle access. Outside embankment and dike slopes may not be steeper than 3 horizontal to one vertical and shall be properly seeded with a mixture of grasses to prevent erosion. Inside embankments and dikes may not be steeper than 2 horizontal to one vertical and shall be properly graveled or riprapped to prevent erosion. Interior ramps for maintenance vehicle access are acceptable.8. Absorption ponds may not be constructed on backfilled material. Earthwork activities within 1 foot of the final pond surface shall be limited to times when soil conditions are dry.9. The bottom of the absorption pond may not be closer that 5 feet to the highest anticipated groundwater elevation.10. An absorption pond system shall be constructed on soils which meet with the following minimum requirements: a. Soil texture may not be coarser than loamy sand (USDA soils classification) or have less than 5% passing a number 200 sieve.b. Soil texture may not be finer than clay loam (USDA soil classification) or have liquid limits greater that 50% (unified soil classification).c. Soil pH may not be less that 6.5.11. A minimum separation distance of 10 feet shall be maintained between the bottom of the absorption pond and bedrock.(b)Discharge limitations for absorption pond systems. Effluent limitations are as specified in s. NR 206.08(1) (b).(2) SPRAY IRRIGATION SYSTEMS. (a)Design and construction criteria for spray irrigation systems.1. All spray irrigation systems shall be designed with a wastewater distribution system capable of loading and resting various portions of the site to optimize wastewater treatment within the soil and crop growth.2. Spray irrigation onto frozen ground is prohibited. The department may restrict loadings during times of the year when the cover crop is not actively growing.3. Application of wastewater to the spray irrigation system shall incorporate a rest/load cycle and application intensity such that the soil moisture holding capacity in the top foot of the soil column is not exceeded and ponding or runoff do not occur. Following wastewater application to a portion of the field, that portion shall be rested. Table 8 provides values for the maximum volume of wastewater that may be applied per load cycle and the maximum intensity of wastewater application for specific soil textures. The values in Table 8 are the maximum amount approvable unless greater values can be justified through soil testing and are 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 8 if site conditions warrant. Table 8
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 |
4. The spray nozzle openings shall be sized to prevent plugging and shall be located as near to the ground surface as practical to minimize wind drift of the wastewater.5. The spray nozzles shall be arranged so that the wastewater will be evenly distributed over the entire area under irrigation.6. The spray irrigation system shall be arranged so that individual sections within the system can be taken out of service for resting without interrupting discharge to the remaining sections.7. The spray irrigation system shall be seeded with perennial grasses such as reed canary grass, tall fescue and orchard grass. The cover crop shall be a crop which is not used for direct human consumption. New seedings shall also contain a nurse crop. The cover crop shall be maintained by cutting and removing the grass a minimum of twice per growing season. The department may approve the use of other types of cover crops such as corn but will restrict the use of such sites to times when the cover crop is actively growing. The department may also require reduced hydraulic application rates, grass buffer strips or both around the perimeter of the site to prevent wastewater runoff during rainfall events.8. The ground surface of the spray irrigation system shall have a minimum separation distance to bedrock of at least 5 feet.9. A minimum separation distance of 5 feet shall be maintained between the land surface elevation of the spray irrigation field and the highest anticipated groundwater elevation. The department may on a case-by-case basis allow this distance to be reduced if the permittee can show, based on hydrogeologic and other relevant site factors, that the groundwater will be adequately protected.10. The department may require disinfection of effluent to spray irrigation systems if there is a potential risk to public health.(b)Discharge limitations for spray irrigation systems. Effluent limitations are as specified in s. NR 206.08(2) (b).(3) RIDGE AND FURROW SYSTEMS. (a)Design and construction criteria for ridge and furrow systems.1. The shape of each cell within the ridge and furrow system shall be such that a minimum of soil disturbance is necessary to form the system.2. A ridge and furrow system may not be constructed on a site at which less that 50% of the soil particles pass a no. 200 sieve. Coarser textured soils may be approved on a case-by-case basis depending on system design and wastewater strength. Suitable soils shall extend at least 3 feet below the base grade of the furrow bottoms.3. The furrows of the ridge and furrow system shall be one foot deep and one foot wide at the furrow bottom.4. Furrow side slopes may not be steeper than one horizontal to 2 vertical.5. The system shall be sized and constructed in order to allow sufficient resting to allow soil conditions to become unsaturated and aerobic prior to any wastewater being reapplied.6. The system shall be constructed in a manner which provides equal liquid distribution during loading of each cell. The header ditch shall be sealed in order to allow complete drainage and to prevent wastewater seepage. The drainage of the header ditch and the grading of the furrows for equal liquid distribution shall be tested with water before seeding the ridges with grasses.7. The system shall consist of at least 2 cells which can be alternately loaded and rested.8. The wastewater distribution system shall be arranged so that individual cells within the ridge and furrow system can be taken out of service for resting without interrupting discharge to the remaining cells.9. The bottom of the ridge and furrow system may not be closer than 5 feet to the highest anticipated groundwater elevation. The department may allow this distance to be reduced on a case-by-case basis if the permittee can show, based on hydrogeologic and other relevant site factors, that the groundwater will be adequately protected.10. The bottom of the system shall be at least 5 feet from bedrock.11. Outside embankments and dikes may not be steeper than 3 horizontal to one vertical. Inside embankments and dikes may not be steeper than 2 horizontal to one vertical. All embankments and dikes shall be properly seeded with perennial grasses to prevent erosion. A nurse crop of annual grasses shall be used to establish a ground cover.12. All ridge tops shall be a minimum of 6 feet wide to allow mechanical removal of grasses. The grasses shall be cut, and if possible removed, at least once during the growing season and shall be burned or cut and removed each spring.13. All areas within a ridge and furrow system shall be accessible for maintenance equipment.14. The system shall be constructed to prevent surface runoff from entering the system.15. The ridges shall be seeded with perennial grasses which are suited to wet soil conditions. A nurse crop shall be used to seed new or modified systems. In addition, the grass cover shall be established to at least a 2-inch length before the system is used for wastewater treatment.16. Discharge to ridge and furrow systems which have frozen soils is prohibited.(b)Discharge limitations for ridge and furrow systems. Effluent limitations are as specified in s. NR 206.08(3) (b).(4) OVERLAND FLOW SYSTEMS. (a)Design and construction criteria for overland flow systems.1. Overland flow systems shall be underlain by at least one foot of heavy textured soils such as clays or clay loams to retard leakage through the base.2. The downslope flow distance shall be 100 feet or greater.3. The downslope gradient for the overland flow fields shall be between 2% and 8%.4. The system shall consist of at least 2 cells of approximately equal area which can be alternately loaded and rested. Where self-propelled equipment which operates on a continuous basis is installed and division into identifiable cells is impossible, its movement shall be regulated to provide alternate loading and resting of the soil. Note: It is recommended that an overland flow cell be rested for at least one third of the total time in the rest/load cycle.
5. The system shall be arranged so that individual cells within the system can be taken out of service for resting without interrupting discharge to the remaining cells.6. The distribution equipment shall be arranged so that the wastewater will be evenly distributed over the entire area of an overland flow cell and the wastewater travels down the slope in a non-channelized flow.7. The wastewater distribution equipment shall be located at or near the ground level. Note: A pressurized distribution system is recommended for ease of operation.
8. The wastewater distribution system shall be designed to allow for cleaning of the distribution orifices. Flexibility to adjust the flow from individual orifices shall be provided to allow the system to be hydraulically balanced to minimize flow channeling.9. An impermeable channel shall be provided for collecting runoff from the overland flow fields. The collection system shall be capable of removing the effluent and the rain from a 10-year frequency, 24-hour duration rainfall event with only temporary backing up of water onto the fields.10. The overland flow fields shall be vegetated with a water tolerant mixed perennial grass cover crop such as reed canary grass, tall fescue and orchard grass. A nurse crop shall be used to establish the perennial grass cover. The grass cover shall be maintained by frequent resting. The crop shall be cut and the cuttings removed at least twice per year to stimulate grass growth and enhance nutrient removal from the system.11. Winter operation may be allowed as long as the soil surface remains unfrozen. The department may require storage or additional treatment of the runoff during cold weather.12. An overland flow field may be used when the land surface elevation is at least 5 feet above bedrock.13. The land surface elevation of an overland flow field shall be no closer than 5 feet to the seasonally high groundwater level. The department may on a case-by-case basis allow this distance to be reduced if the permittee can show, based on hydrogeologic and other relevant site factors, that the groundwater will be adequately protected. If such a variance is approved or if the risk of groundwater contamination is otherwise high, the department may require additional pretreatment of the wastewaters.14. The hydraulic application rate, expressed as a flow rate per unit width of slope, shall be between .16 gpm/ft and .60 gpm/ft.(b)Discharge limitations for overland flow systems. Effluent limitations are as specified in s. NR 206.08(4) (b) and applicable surface water limitations.Wis. Admin. Code Department of Natural Resources NR 110.255
Cr. Register, November, 1990, No. 419, eff. 12-1-90.