NR 110.255(3)(a)1.1. 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.
NR 110.255(3)(a)2.2. 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.
NR 110.255(3)(a)3.3. The furrows of the ridge and furrow system shall be one foot deep and one foot wide at the furrow bottom.
NR 110.255(3)(a)4.4. Furrow side slopes may not be steeper than one horizontal to 2 vertical.
NR 110.255(3)(a)5.5. 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.
NR 110.255(3)(a)6.6. 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.
NR 110.255(3)(a)7.7. The system shall consist of at least 2 cells which can be alternately loaded and rested.
NR 110.255(3)(a)8.8. 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.
NR 110.255(3)(a)9.9. 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.
NR 110.255(3)(a)10.10. The bottom of the system shall be at least 5 feet from bedrock.
NR 110.255(3)(a)11.11. 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.
NR 110.255(3)(a)12.12. 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.
NR 110.255(3)(a)13.13. All areas within a ridge and furrow system shall be accessible for maintenance equipment.
NR 110.255(3)(a)14.14. The system shall be constructed to prevent surface runoff from entering the system.
NR 110.255(3)(a)15.15. 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.
NR 110.255(3)(a)16.16. Discharge to ridge and furrow systems which have frozen soils is prohibited.
NR 110.255(3)(b)(b) Discharge limitations for ridge and furrow systems. Effluent limitations are as specified in s. NR 206.08 (3) (b).
NR 110.255(4)(4)Overland flow systems.
NR 110.255(4)(a)(a) Design and construction criteria for overland flow systems.
NR 110.255(4)(a)1.1. 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.
NR 110.255(4)(a)2.2. The downslope flow distance shall be 100 feet or greater.
NR 110.255(4)(a)3.3. The downslope gradient for the overland flow fields shall be between 2% and 8%.
NR 110.255(4)(a)4.4. 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.
NR 110.255 NoteNote: It is recommended that an overland flow cell be rested for at least one third of the total time in the rest/load cycle.
NR 110.255(4)(a)5.5. 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.
NR 110.255(4)(a)6.6. 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.
NR 110.255(4)(a)7.7. The wastewater distribution equipment shall be located at or near the ground level.
NR 110.255 NoteNote: A pressurized distribution system is recommended for ease of operation.
NR 110.255(4)(a)8.8. 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.