Section NR 110.24 - Lagoons(1) DESIGN REPORT. A design report shall be submitted in accordance with s. NR 110.15(1).(2) BASIS OF DESIGN. (a)Number of cells. A minimum of 2 treatment cells shall be provided for aerated lagoons and stabilization ponds. Where a controlled discharge is required, additional effluent storage cells shall be provided.1. For aerated lagoons designed to treat domestic wastewater only, the hydraulic detention time of each cell shall be based on the following formula: View Image
Where:
T = detention time, days
E = BOD removal efficiency, percent
K = Reaction coefficient (log base e), days-1
a. For domestic wastewater K = 0.5 at 20°C.b. The reaction coefficient (K) must be adjusted for temperature according to the formula: KT = K20[THETA]T-20
Where:
KT = Corrected reaction coefficient
K20 = 0.5
[THETA]= 1.07
T = Low design temperature, °C
2. The appropriate summertime and wintertime reaction coefficients for aerated lagoons designed to treat combined domestic and industrial wastewater shall be determined from laboratory or pilot studies, or from operating data of existing full scale aerated lagoons which are treating similar wastewater. The reaction coefficients developed shall be used to calculate the required detention time.3. In addition to the treatment volume calculated in subd. 1. or 2., quiescent settling zone or cell shall be provided for aerated lagoon systems. Minimum settling time shall be 6 days for surface water discharge, and 3 days for land disposal discharge.4. Aerated lagoons designed to treat combined domestic and industrial wastewater shall be provided with the means to recirculate final lagoon effluent to the first treatment cell.(b)Stabilization ponds.1. Stabilization ponds may be used to treat domestic wastewater. Combined domestic and industrial wastewater may be treated in stabilization ponds only if the treatability of the industrial wastewater is demonstrated through pilot testing.2. The BOD5 loading to any one stabilization pond may not exceed 23 kilograms per hectare (20 pounds per acre) per day.3. A minimum hydraulic detention time of 150 days at the average design flow shall be provided in the entire stabilization pond system. In accordance with s. NR 210.06(3) (h), a stabilization pond system which discharges to surface water, and has a hydraulic detention time of 180 days or longer at average design flow, does not require disinfection except in extenuating circumstances.(3) DESIGN REQUIREMENTS. (a)Location. Lagoon systems shall be located in compliance with s. NR 110.15(3) (b) and (c).(b)Separation from groundwater.1. For all lagoons not sealed with a synthetic liner, a minimum separation distance of 1.25 meters (4 feet) shall be maintained between the bottom of lagoons and the highest recorded or indicated seasonal groundwater table elevation.2. For all lagoons sealed with a synthetic liner, a minimum separation distance of 60 centimeters (2 feet) shall be maintained between the bottom of the lagoon and the highest recorded or indicated seasonal groundwater table elevation.(c)Separation from bedrock. A minimum separation of 3 meters (10 feet) shall be maintained between the bottom of lagoons and bedrock. The department may waive this requirement on a case-by-case basis if it can be demonstrated that a lesser separation distance will not cause groundwater quality problems. Criteria which will be evaluated to waive this requirement include the depth to bedrock, the type of bedrock, the fracture condition of the bedrock, the direction of groundwater movement, the existing groundwater quality, and the downgradient uses of the groundwater.(d)Test pits and soil borings.1. Backhoe test pits and soil borings shall be conducted at each proposed lagoon site. Logs of the test pits and soil borings shall be submitted with the facilities plan as required in s. NR 110.09(8) (a). Soil boring and test pit analyses shall be conducted by an independent soil testing laboratory, a qualified engineering firm or an individual or firm which has demonstrated the capability to perform and evaluate such tests.2. Soil borings and test pits shall be used to determine subsurface soil characteristics and variability, seasonal high groundwater level and elevations, and type, nature and depth to bedrock. Soils shall be classified according to the unified soil classification system. Cross-sections using the soil boring and test pit logs shall be prepared and submitted with the facilities plan.3. Soil sampling shall be performed in accordance with ASTM D1586-08a or ASTM D1587-08.4. Soil profile descriptions shall be written for all soil test pits. The thickness in inches and the difference between each soil horizon shall be indicated for each test pit. Horizons shall be differentiated on the basis of color, texture, soil mottles or bedrock. Depth shall be measured from the ground surface and the slope at the test pit shall be indicated.5. A minimum of one soil boring per acre shall be conducted at each lagoon site. The number of test pits and borings shall be sufficient to adequately characterize the soil type and variability and delineate unsuitable soil areas in the field. The department may require additional soil borings and test pits to properly describe the site soils, bedrock or groundwater conditions.6. Each boring shall have a minimum depth of 7.6 meters (25 feet) or to bedrock.7. All soil borings in which wells are not installed shall be properly abandoned according to s. NR 141.25.8. All test pits shall be refilled with the excavated materials.(e)Lagoon shape. The shape of lagoons shall be such that there are no narrow or elongated portions. Islands, peninsulas or coves will not be approved. Dikes shall be rounded at corners to minimize accumulations of floating materials. Commonwall dike construction is encouraged. Round, square or rectangular lagoons with a length not exceeding 3 times the width are recommended.(f)Dikes.1. The minimum top width of dikes shall be 3.6 meters (12 feet).2. Maximum dike slopes shall be 3:1 (horizontal to vertical).3. The minimum allowable interior slope shall be 4:1.4. A minimum one meter (3 feet) freeboard from operating water surface to the top of dikes shall be provided.(g)Operating water depth.1. A minimum liquid depth of 0.6 meters (2 feet) for stabilization ponds and 1.8 meters (6 feet) for aerated lagoons shall be provided.2. Maximum water depth may not exceed 1.8 meters (6 feet) for stabilization ponds and 4.3 meters (15 feet) for aerated lagoons.(4) SEALING REQUIREMENTS. (a)General. All lagoons shall be sealed to prevent excessive exfiltration.(b)Exfiltration rate.1. Loss of water from wastewater treatment or storage lagoons may not exceed 10 cubic meters per water surface hectare (1,000 gallons per acre) per day and loss of water from sludge storage or treatment lagoons or other sludge handling facilities may not exceed 5 cubic meters per sludge surface hectare (500 gallons per acre) per day.2. In circumstances where soil or groundwater characteristics, groundwater quality, or waste characteristics warrant, the department may require exfiltration rates less than 10 cubic meters per water surface hectare (1,000 gallons per acre) per day for wastewater treatment or storage lagoons.(c)Materials.1. Soil materials or synthetic liners approved by the department may be used to seal lagoons.2. Soil materials or synthetic liners used to seal lagoons shall be compatible with the wastewater characteristics.(d)Sampling and testing standards.1. Core samples taken to determine soil texture, grain size distribution or permeability shall be taken in accordance with ASTM D1586-08a, ASTM D1587-08, or ASTM 3550-01 (2007).2. Permeability shall be determined using a falling head permeability test. The test shall be performed at the same approximate density as the in-place field condition. Tests on remolded or undisturbed samples are acceptable.3. Sieve analyses performed to determine grain size distribution shall be performed in accordance with ASTM D422-63 (2007).4. Plasticity index shall be determined in accordance with ASTM D4318-10.5. Standard procter densities shall be determined in accordance with ASTM D698-07 e1.(e)Uniform construction. All lagoon seals shall be uniformly constructed across the lagoon bottom and interior dike walls. Seals shall extend up the dike wall to the berm.(f)Synthetic liners.1. Synthetic liners shall have a minimum thickness of 0.8 millimeters (30 mils).2. All synthetic liners shall be installed under the supervision of a qualified manufacturer's representative.3. Synthetic liners shall be protected by an inorganic soil layer. The soil layer shall have a minimum thickness of 30 centimeters (one foot). The soil shall be uniformly graded and free from large rocks, angular stones, soil clumps, sticks or other material which may puncture the liner. When a granular, noncohesive soil is used for the cover, a soil fabric shall be placed between the liner and the soil cover. The soil fabric shall be anchored at the dike berm.4. Synthetic liners shall be securely anchored to the dike berm.5. Synthetic liners shall be vented.6. Riprap or other means of erosion control shall be provided to prevent exposure of the synthetic liner due to erosion of the protective soil layer.7. Prior to constructing the synthetic liner, the underlying soils shall be treated with a herbicide in accordance with manufacturers recommendations.(g)Soil or soil-bentonite liners.1. The permeability of soil or bentonite liners may not be greater than 1 x 10-7 cm/sec. (2.83 x 10-4 ft/day).2. The liner thickness shall be determined according to Darcy's equation, and shall include an appropriate safety factor for construction variability. In no case shall the liner thickness be less than the minimum values shown in Table 7.3. When the soil or soil-bentonite liner is to be constructed over the existing soil at the lagoon site, 15% of the soil particles of the existing soil must pass a no. 200 sieve. If this requirement cannot be met, a soil filter fabric material shall be placed between the liner and the existing soil.4. Liners shall be compacted at or above optimum moisture content.5. A means shall be provided to prevent the liner from desiccating after the completion of construction and prior to placing the system in operation.6. Liners shall be protected by an inorganic soil layer. The soil layer shall have a minimum thickness of 10 centimeters (4 inches). The cover shall be uniformly graded and free from large rocks, soil clumps, and sticks. Table 7
Coefficient of Permeability cm/sec (ft/day) | Centimeters (Inches) | Water Depth Meters (feet) |
1.8 | 3 | 3.8 | 4.6 |
(6) | (10) | (12) | (15) |
1 x 10-7 | 22 cm | 33 cm | 40 cm | 48 cm |
(2.83 x 10-4) | (9 in) | (13 in) | (16 in) | (19 in) |
5 x 10-8 | 14 | 19 | 23 | 27 |
(1.42 x 10-4) | (6) | (8) | (8) | (11) |
1 x 10-8 | 10 | 10 | 10 | 10 |
(2.83 x 10-5) | (4) | (4) | (4) | (4) |
5 x 10-9 | 10 | 10 | 10 | 10 |
(1.42 x 10-5) | (4) | (4) | (4) | (4) |
1 x 10-9 | 10 | 10 | 10 | 10 |
(2.83 x 10-6) | (4) | (4) | (4) | (4) |
(h)Soil liner material specifications.1. Soil liners shall consist of soils of which more than 50% of the soil particles pass a no. 200 sieve. The soil liner shall have a plasticity index of at least 15.2. Soil liners shall be compacted to at least 95% of the maximum standard proctor density.3. Soil liners shall be constructed and compacted in lifts. Each lift may not exceed a compacted thickness of 15 centimeters (6 inches).4. Frost susceptible soils may not be used to construct the liner. Any soil which is primarily silt, silty sand, or lean clay which has a plasticity index less than 12 shall be considered as frost susceptible.5. Soil liners constructed of natural in-place soils shall be scarified prior to compaction.(i)Bentonite liner material specifications.1. Bentonite shall be mixed with a soil in which at least 30% of the soil particles pass a no. 200 sieve. The soil shall have a plasticity index of at least 15.2. Bentonite shall be applied at a rate recommended by the manufacturer or independent soil expert. The constructed liner shall have a minimum bentonite content of 5% by dry weight.3. Ninety percent of the bentonite by weight shall pass a no. 80 sieve.4. Bentonite shall be thoroughly mixed with the soil material.5. The bentonite liner shall be compacted to at least 85% of the maximum standard proctor density.(j)Construction quality testing.1. All liners shall be tested before placing the lagoons into operation to insure compliance with par. (b). Test results shall be submitted to the department.2. The method of testing shall be presented to the department with the project plans and specifications.3. Testing shall be performed in accordance with one of the testing methods of par. (k).4. All tests shall be performed under the supervision of the design engineer.(k)Testing methods.1. All liners may be tested using an in-field full lagoon water balance. The test shall occur over a minimum 14-day period. The manner of determining precipitation and evaporation rates shall be shown in the project plans and specifications.2. The integrity of the field constructed seams for synthetic liners shall be tested with compressed air prior to placing the protective soil cover. All faulty seams shall be repaired and retested.3. Core samples of soil or soil-bentonite liners may be taken and the liner thickness and permeability measured in a laboratory. Core samples shall be taken in accordance with ASTM D1587 (1974). A minimum of 12 samples per wetted hectare (5 samples per wetted acre) must be analyzed. The samples shall be proportionately taken from the lagoon bottoms and dikes. The lagoon liner shall be considered to meet the performance standard of par. (b) if: a. The average seal thickness of the samples are equal or to greater than the specified design thickness. No sample shall have a thickness more than 1-inch less than the design thickness; andb. The coefficient of permeability of 90% of the samples must be equal to or less than the design coefficient of permeability.(5) CONSTRUCTION DETAILS. (a)Material.1. Embankments and dikes shall be constructed of relatively impervious materials and compacted at near optimum moisture content to 95% of the standard proctor density.2. Vegetation and other unsuitable materials shall be removed from the area where the embankment is to be placed.(b)Erosion control.1. Riprap or other means of preventing erosion shall be used at locations on lagoon bottoms and interior dike walls where erosion or activity of burrowing animals is likely to occur.2. Riprap or other erosion control methods shall be used on the exterior dike walls for lagoons which are constructed in a flood fringe.3. Exterior dike walls, berms and interior dike walls above the normal operating water depth, shall be riprapped or seeded with perennial, low growing, spreading grasses.(c)Fencing. Lagoons shall be enclosed within a fence. A vehicle access gate shall be provided.(d)Warning signs. Appropriate signs shall be provided along the fence surrounding lagoons to designate the nature of the facility and prohibit trespassing.(6) AERATION EQUIPMENT.(a)Air requirements. Air shall be provided to the aerated lagoons at a rate of not less than 1.5 kilograms oxygen per kilogram (1.5 pounds of oxygen per pound) of peak hour BOD removed.(b)Surface aeration equipment.1. The department may approve the use of surface aeration equipment only in those cases in which the equipment can be properly maintained and operated during the winter.2. Surface aeration equipment shall be so designed and placed to provide optimum mixing of pond lagoon contents and dispersion of oxygen to the waste. Unless sufficient justification is presented to the contrary, surface aerators shall be designed using an oxygen transfer rate of 1.2 kilograms of oxygen per kilowatt-hour (2.0 pounds of oxygen per horsepower-hour) in clean water under standard conditions.(c)Subsurface aeration equipment.1. Flexible tubing containing air release slits shall be provided across the lagoon bottom in accordance with the manufacturer's recommendations. Air tubing shall be securely anchored to prevent floating. To prevent clogging of the air lines, provision shall be made to accommodate cleaning.2. Air tubing and anchors shall be constructed of materials which resist corrosion.3. Air shall be supplied to the lagoon system at a rate sufficient to meet the oxygen requirements of par. (a) assuming an oxygen transfer efficiency of 7% in clean water under standard conditions.4. Tubular aeration units shall be provided in sufficient number to supply adequate air to the pond system based on a maximum transfer rate of 0.6 kilograms (1.25 pounds) of oxygen per unit per hour in clean water under standard conditions.5. Where data is presented to the department to justify oxygen transfer rates varying from the requirements of this paragraph the department may approve such design transfer rates.(d)Aeration systems.1. Multiple blowers shall be provided. Capacity of the blowers shall be sufficient to meet total air demands with one blower out of service.2. Diffusers and air piping shall be capable of supplying 200% of the average daily air demand.(7) HYDRAULIC STRUCTURES. (a)Materials. Influent lines, interconnecting piping, and overflow structures shall be constructed of materials suitable for underground gravity sewer construction.(b)Capacity.1. Influent lines to all lagoon systems shall be sized in accordance with s. NR 110.13(4).2. Overflow structures and interconnecting piping for continuous flow lagoon systems shall be sized in accordance with s. NR 110.13(4).3. Overflow structures and interconnecting piping for controlled discharge lagoon systems shall be sized to handle the anticipated interlagoon flow rates during periods of discharge.(c)Influent piping.1. 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.2. 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.3. 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.4. 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.Wis. Admin. Code Department of Natural Resources NR 110.24
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.