Section 214.13. Ridge and furrow systems.

 

(1)   Site location criteria.

(a) The ridge and furrow system shall be located 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 potential for aesthetic and public health impacts.

(b) The ridge and furrow 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.

(c) The bottom of the furrows shall be at least 5 feet above bedrock and groundwater.

(d) The 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) Ridge and furrow systems shall be constructed on sites with soils having 50% or more of the soil particles passing a No. 200 sieve, except that 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.

(b) The system shall consist of at least 2 cells which can be alternately loaded and rested, unless there is sufficient storage or pretreatment to allow loading and resting of a single cell.

(c) The system shall be sized and constructed in order to allow sufficient resting to allow soil conditions to become unsaturated and aerobic prior to being loaded.

(d) The shape of each ridge and furrow cell within the system shall be such that a minimum of soil disturbance is necessary to form the system.

(e) The wastewater distribution system shall be constructed so that individual cells within the system can be taken out of service for resting without interrupting the discharge to the remaining cells.

(f) The ridge and furrow system shall be constructed in a manner which provides equal liquid distribution during loading of each cell. The header ditch shall be designed to allow complete drainage after each wastewater loading or lined to prevent wastewater seepage. The header ditch drainage and the grading of the furrows for equal liquid distribution shall be tested before seeding the ridges with grasses.

(g) All 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.

(h) All ridge tops shall be a minimum of 6 feet wide to allow mechanical removal of grasses.

(i) The furrows of the ridge and furrow system shall be one foot deep and one foot wide at the furrow bottom.

(j) Furrow side slopes may not be steeper than one horizontal to 2 vertical.

(k) All areas within a ridge and furrow system shall be accessible for maintenance equipment.

(L) The system shall be constructed to prevent surface runoff from entering the system.

(m) 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.

(n) Precautions shall be taken during construction to minimize compaction of absorption areas to prevent a reduction in soil infiltration rate. Project specifications shall detail the specific precautions which will be taken.

(o) Erosion control measures shall be taken during construction to prevent erosion of soil into a surface water.

(3)   Discharge limitations.

(a) The discharge to a ridge and furrow 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 the pollutants in the discharge, 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 average hydraulic application rate may not exceed 10,000 gallons per acre per day for the system.

(e) Discharge to the system shall be limited so that the discharge volume combined with the precipitation from a 10-year frequency, 24-hour duration rainfall event does not overflow the boundary of the system.

(f) The volume of discharge shall be limited to prevent inundation of the ridges except for temporary conditions following precipitation events.

(4)   Discharge monitoring requirements.

(a) The discharge to each cell of the ridge and furrow system shall be monitored for total daily flow.

(b) The department may require in a WPDES permit that the discharge be monitored for BOD 5 , 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) Each spring, the ridge top grasses shall be either cut and removed, or the grasses shall be burned. In addition, the grasses shall be cut and if possible removed at least once later in the growing season.

(b) The discharge shall be alternately distributed to individual sections of the ridge and furrow system to allow sufficient resting periods to maintain the treatment capability of the soil.

(c) The system shall be operated so that individual ridge and furrow sections have sufficient resting to allow soil conditions to become unsaturated and aerobic prior to being loaded.

(d) The system may be used only when at least 5 feet of separation exists between the bottom of the furrows and the groundwater.

(e) Management plan. The department shall require each ridge and furrow 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 control and removal, 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 ridge and furrow systems are specified in ss. NR 214.20 and 214.21 .

History: 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.

Note

Based upon the department's experience, the recommended range for the average hydraulic application rate for ridge and furrow systems is 2,000 to 5,000 gallons per acre per day. Microsoft Windows NT 6.1.7601 Service Pack 1