Influent lines, interconnecting piping, and overflow structures shall be constructed of materials suitable for underground gravity sewer construction.
Overflow structures and interconnecting piping for continuous flow lagoon systems shall be sized in accordance with s. NR 110.13 (4)
Overflow structures and interconnecting piping for controlled discharge lagoon systems shall be sized to handle the anticipated interlagoon flow rates during periods of discharge.
A manhole shall be installed at the end of the influent line or force main and shall be located as close to the dike as topography permits. Its invert shall be at least 15 centimeters (6 inches) above the maximum operating water level of the lagoon to provide sufficient hydraulic head without surcharging the manhole.
Influent lines shall be located such that the top of the pipe is at least 15 centimeters (6 inches) below the lower surface of the soil, bentonite, or synthetic liner.
For circular lagoons, the inlet shall terminate at the center of the lagoon. Influent lines to rectangular or square lagoons shall terminate in the first one third of the lagoon length. Influent and effluent piping shall be located to minimize short-circuiting within the lagoon.
The inlet line shall discharge either horizontally onto a concrete pad or by means of an upturned elbow terminating at least 30 centimeters (one foot) above the pond bottom.
(d) Overflow structures.
An overflow structure shall be provided and shall consist of either a manhole or box equipped with multiple-valved pond drawoff lines or an adjustable overflow device. The overflow structure shall allow the liquid level of the lagoon to be adjusted to permit operation at depths ranging from 60 centimeters (2 feet) to the maximum design operating depth in stabilization ponds and from 1.2 meters (6 feet) to the maximum design operating depth in aerated lagoons. The department recommends that stop planks not be used in overflow structures to control operating depth.
NR 110.24 History
Cr. Register, November, 1974, No. 227
, eff. 12-1-74; r. and recr. Register, February, 1983, No. 326
, eff. 3-1-83, am. (3) (c) and (4) (b), r. and rec. (3) (d), Register, November, 1990, No. 419
, eff. 12-1-90; CR 09-123
: am (2) (b) 2., 3., (3) (d) 3., (4) (d) 1., 3. to 5., (6) (a), (b) 2., (c) 3. and 4. Register July 2010 No. 655
, eff. 8-1-10.
General conditions required for all land disposal systems.
The provisions of this section apply to all municipal and privately owned domestic sewage treatment works.
Land disposal systems shall be reviewed and approved on a case-by-case basis.
(3) Treatment prior to disposal.
All discharges to land disposal systems shall receive biological, chemical, physical or a combination of treatments necessary to meet effluent standards in ch. NR 206
and groundwater quality standards in ch. NR 140
as approved by the department. Industrial waste discharges tributary to the municipal system shall be in compliance with applicable pretreatment standards under s. NR 211.30
A management plan shall be submitted with plans and specifications for all land disposal facilities.
The management plan shall contain specific information on pretreatment processes, scheduled maintenance, vegetative cover control and removal, load and rest schedules, application rates, operational strategies for periods of adverse weather, monitoring procedures and other pertinent information.
The application rate of wastewater may not exceed the long term infiltrative capacity of the soil.
The application rate of wastewater containing heavy metals may not exceed the soil capacity for preventing the movement of the heavy metals through the soil.
Multiple wastewater application areas shall be provided to allow load and rest cycles. The discharge shall be alternately distributed to individual cells of the disposal system in a manner to allow sufficient resting periods to maintain the absorptive capacity of the soil, and to allow soil conditions to become unsaturated and aerobic between loadings.
Land disposal systems shall be separated from private water supply wells by a minimum horizontal distance of 76 meters (250 feet).
The minimum horizontal separation distance between a land disposal system and public water supply wells shall be determined during facilities planning in accordance with s. NR 110.09 (2) (p)
. In all cases the department recommends a minimum horizontal separation of 305 meters (1,000 feet) be maintained.
(e) Storage lagoons.
Storage lagoons shall be provided for all land disposal systems which are adversely affected by winter conditions or wet weather. Storage lagoons shall be constructed in accordance with s. NR 110.24 (3)
(f) Load and rest cycles.
Load and rest cycles for each system shall be determined based on hydrogeologic and other relevant site conditions such as soil permeability, texture, cation-exchange capacity, topography, depth to groundwater and bedrock and the wastewater characteristics.
All precautions shall be taken during construction of a land disposal system to minimize compaction of absorption areas and to prevent reduction in soil infiltration rate. Project specifications shall detail the specific precautions to take, which may include no heavy equipment use and erosion control on berms.
Erosion control measures shall be practiced during the construction of the land disposal system to avoid erosion of soil into a surface water and into or from the land disposal system.
Groundwater monitoring systems shall be installed in accordance with approved plans and specifications as required in ch. NR 108
, for the purpose of determining groundwater conditions for the engineering report in s. NR 110.09 (1) (b)
and for WPDES permit requirements. Plans and specifications shall be prepared by a hydrogeologist or other qualified person.
NR 110.25 Note
Note: The skills and knowledge required of a hydrogeologist making submittals under this chapter include: the ability to apply hydrogeologic principles and practices to the siting, design and operation of land disposal systems; knowledge of contaminants associated with land disposal of wastewater, their transport mechanisms and fate in the environment; familiarity with environmental monitoring practices, sampling techniques and groundwater standards; and proficiency in the design of groundwater monitoring systems for defining the physical and chemical characteristics of groundwater flow. A soil scientist or other environmental scientist who can demonstrate the above skills and knowledge, as reflected in submittals made under this chapter, shall be deemed a “qualified person".
A minimum of 3 monitoring wells per land disposal system shall be installed to monitor groundwater quality in accordance with s. NR 206.10 (2)
, to determine flow directions and for a flow rate determination. At a minimum, one well will be upgradient and one well downgradient of the land disposal system.
One or more upgradient monitoring wells shall be installed at locations and depths sufficient to yield groundwater samples that are representative of background water quality near the facility. Selection of well locations should take into account past and present land uses which might affect groundwater quality. The upgradient well should be located so it will not be affected by the land disposal system. Any upgradient wells should be located at the most distant point of upgradient of the application area, and not closer that 75 feet from the application area. If the well is located beyond the property boundary, an easement for access shall be obtained prior to installation of the well.
Downgradient wells shall be located so as to intercept any groundwater impacted by the land disposal system, considering the vertical and horizontal gradients of flow. The wells shall be no closer than 30 feet for rapid infiltration systems, and at a minimum, one well shall be located between the application area and the design management zone (DMZ) or property boundary. It is recommended that one well be located at or beyond the DMZ or property boundary. If the well is located beyond the property boundary, an easement for access shall be obtained prior to installation of a well.
(c) Monitoring well construction.
All groundwater monitoring wells shall be constructed in accordance with ch. NR 141
and this section.
For piezometers, inlet screens shall have a length of at least 2.5 feet but not more than 5 feet unless otherwise approved by the department.
For water table observation wells, inlet screens shall not exceed 10 feet in length.
For a multilevel groundwater system, the deeper the well shall be screened at a depth to be determined from the site investigation.
All groundwater monitoring systems shall be sampled in accordance with department published groundwater sampling procedures as referenced in s. NR 140.16
All unsuccessful wells, boreholes or other vertical holes and wells whose use is no longer required must be properly abandoned in accordance with s. NR 141.25
Documentation of well construction, well development and abandonment shall be submitted to the department in accordance with ss. NR 141.23
. A location map shall also be provided in accordance with s. NR 141.065
(d) Alternative methods and materials.
The department may approve alternative construction methods or materials for installation of groundwater monitoring wells on a case-by-case basis.
NR 110.25 History
Cr. Register, November, 1974, No. 227
, eff. 12-1-74; r. and recr. Register, February, 1983, No. 326
, eff. 3-1-83; cr. (intro.), (3m), (4) (a) 3. and (4) (g), am. (2), r. and recr. (3), (4) (f) and (5), Register, November, 1990, No. 419
, eff. 12-1-90; CR 09-123
: am. (5) (b) 1., 3., (c) 3. and 5. Register July 2010 No. 655
, eff. 8-1-10.
Conditions required for specific types of land disposal systems. NR 110.255(1)(a)(a) Design and construction criteria for absorption pond systems. NR 110.255(1)(a)1.1.
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)
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.
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.
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.
The absorption pond bottom shall be as level as possible at all locations.
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.
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.
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.
The bottom of the absorption pond may not be closer that 5 feet to the highest anticipated groundwater elevation.
An absorption pond system shall be constructed on soils which meet with the following minimum requirements:
Soil texture may not be coarser than loamy sand (USDA soils classification) or have less than 5% passing a number 200 sieve.
Soil texture may not be finer than clay loam (USDA soil classification) or have liquid limits greater that 50% (unified soil classification).
A minimum separation distance of 10 feet shall be maintained between the bottom of the absorption pond and bedrock.
(a) Design and construction criteria for spray irrigation systems. NR 110.255(2)(a)1.1.
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.
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.
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.
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.
The spray nozzles shall be arranged so that the wastewater will be evenly distributed over the entire area under irrigation.
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.
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.
The ground surface of the spray irrigation system shall have a minimum separation distance to bedrock of at least 5 feet.
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.
The department may require disinfection of effluent to spray irrigation systems if there is a potential risk to public health.
(a) Design and construction criteria for ridge and furrow systems. 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.
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.
The furrows of the ridge and furrow system shall be one foot deep and one foot wide at the furrow bottom.
Furrow side slopes may not be steeper than one horizontal to 2 vertical.