Wisconsin Administrative Code › Department of Natural Resources › NR 100-199 - Environmental Protection - General › Chapter NR 110 - Sewerage Systems › Section NR 110.255 - Conditions required for specific types of land disposal systems

Current through June 24, 2024
(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.