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.
NR 110.255(4)(a)9.9. 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.
NR 110.255(4)(a)10.10. 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.
NR 110.255(4)(a)11.11. 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.
NR 110.255(4)(a)12.12. An overland flow field may be used when the land surface elevation is at least 5 feet above bedrock.
NR 110.255(4)(a)13.13. 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.
NR 110.255(4)(a)14.14. The hydraulic application rate, expressed as a flow rate per unit width of slope, shall be between .16 gpm/ft and .60 gpm/ft.
NR 110.255(4)(b)(b) Discharge limitations for overland flow systems. Effluent limitations are as specified in s. NR 206.08 (4) (b) and applicable surface water limitations.
NR 110.255 HistoryHistory: Cr. Register, November, 1990, No. 419, eff. 12-1-90.
NR 110.26NR 110.26Sludge handling, storage and disposal.
NR 110.26(1)(1)Design report. A design report shall be submitted in accordance with s. NR 110.15 (1). The report shall show calculations used to design the sludge facilities. Design of sludge handling facilities shall consider such factors as the volume of sludge generated, its percent solids and character, the degree of volatile solids reduction, sludge temperature, the degree or extent of mixing to be obtained, the sludge percent solids and characteristics after processing and the size of the installation with appropriate allowances for sludge and supernatant storage and energy requirements whenever such factors are appropriate for the design of the sludge processing facilities.
NR 110.26(2)(2)General design considerations.
NR 110.26(2)(a)(a) Grit removal. When grit removal facilities are not provided, the volume of thickeners, digesters and storage facilities shall be increased to accommodate the additional solids loading.
NR 110.26(2)(b)(b) Sludge thickening.
NR 110.26(2)(b)1.1. Whenever practical, sludge thickening shall be provided.