Section 123-5-005 - Wastewater Lagoons005.01 The seepage rate of wastewater lagoons will not exceed one-eighth inch per day at the design maximum water depth. A lower seepage rate, or zero seepage, will be required if the Department determines that additional ground water protection is required. Ground water monitoring wells will be required where the Department determines that monitoring is necessary.005.02 The liners of wastewater lagoons will be tested prior to the lagoon being placed into service. The test results will be submitted to the Department for review. Synthetic liners will be tested according to the manufacturer's instructions or other tests required by the Department. Soil liners will have the seepage rate measured by one of the following tests: 005.02A An independent soils testing laboratory will determine the coefficient of permeability from undisturbed core samples taken from the liner. The seepage velocity will be calculated using Darcy's Law at the design maximum water depth. Each permeability test swill pass the seepage test. Areas that do not pass will be reworked and retested. The minimum number of core samples thatwill be tested is listed in the following table. Permeability Testing Number of Core Samples per Lagoon Cell
Water Surface Area of Lagoon Cell (Acres) | Permeability Tests Required from Cell Floor | Permeability Tests Required From Side Slopes |
0-1 | 1 | 1 |
1-2 | 2 | 1 |
2-3 | 3 | 2 |
3-4 | 4 | 2 |
4-6 | 5 | 3 |
6-8 | 6 | 3 |
8-10 | 7 | 4 |
10-12 | 8 | 4 |
12-15 | 9 | 5 |
15-18 | 10 | 5 |
18-21 | 11 | 6 |
21-24 | 12 | 6 |
Greater than 24 acres | One per two acres | One per four acres |
005.02B The seepage rate will be tested directly by filling the cell with water and measuring the change of water level over time. The test will run at least 21 days. A control device must be used to measure the effects of rainfall and evaporation during the test. If the water depth during the test is less than the design depth, the test result will be adjusted to calculate the seepage rate at the design water depth of the cell. This test will be conducted under the supervision of a professional engineer. 005.02C Wastewater lagoons with a water surface area less than one acre may use a two-barrel test. One barrel, without a bottom, will measure the seepage rate and the other barrel, with a solid bottom, will be used as a reference to account for rainfall and evaporation. A professional engineer will supervise this test and verify the results. 005.02D Another method approved by the Department.005.03 The bottom elevation of soil liners for wastewater lagoons will be constructed at least four feet above the seasonal high ground water level, including the level of any perched ground water.005.04 Wastewater lagoons will not be constructed within 100 feet from any water well or within 1000 feet from a community public water supply well.005.05 Wastewater lagoons will not be constructed within 50 feet from a property line or within 200 feet from an existing dwelling, measured from the normal high water level of the lagoon.005.06 Wastewater lagoons will be designed and constructed to prevent storm water runoff from flowing into the cells and to prevent storm water runoff or surface water flow from eroding the earthen dikes.005.07 The top of wastewater lagoon dikes will be constructed at least one foot above the 100-year flood elevation at the site.005.08 The top of wastewater lagoon dikes will have a minimum width of eight feet to accommodate maintenance vehicles.005.09 Wastewater lagoons will be provided with influent flow measurement equipment capable of measuring the total influent flow. Elapsed time meters on lift station pump controls are acceptable to meet this requirement.005.10 Discharging wastewater lagoons will be equipped with an effluent sampling location and a primary flow-measuring device to measure the discharge flow rate. Primary flow devices include par flumes, palmer-boelus flumes, V-notch weirs, rectangular weirs, trapezoidal weirs or similar devices. Level monitoring equipment or flow meters will be included with the primary flow-measuring device for continuous discharge lagoons, but is not required for controlled discharge lagoons.005.11 All wastewater lagoons will be completely enclosed by a fence, unless exempted by the Department. The fencing will be at least 42 inches high and will include at least one lockable gate, a minimum of 10 feet wide.005.12 A warning sign will be posted on each side of a wastewater lagoon system. Sides longer than 500 feet will have one sign for every 500 feet or fraction thereof. The signs will be at least 12 inches by 24 inches in size and clearly show the words "No Trespassing, Wastewater Lagoon" or similar language.005.13 The organic loading rate of facultative lagoon systems will not exceed 30 pounds of five-day biochemical oxygen demand (BOD5) per acre per day for primary cells. The organic loading rate for the entire lagoon system will not exceed 25 pounds of BOD5 per acre per day.005.14 Facultative lagoons will have a maximum water depth of six feet in primary cells and eight feet in secondary cells. Greater depths may be approved if mechanical aeration is provided.005.15 Discharging wastewater lagoon systems will be designed with multiple cells that operate in series. Where two or more primary cells are provided, a control structure will be designed to split the flow proportionally or to divert the influent flow to either cell.005.16 The finished floor elevation of wastewater lagoons will not vary more than three inches from the design elevation or grade.005.17 After seepage testing is completed, newly constructed wastewater lagoons will be filled with two feet of water to protect the liner from damage and to reduce odors when the lagoons first receive wastewater. Lagoon cells that will not be placed into immediate service will follow the requirements of Chapter 11, 008.04.005.18 Rapid Infiltration (RI) Cells will be designed according to the following design standards. 005.18A RI cells will have at least 10 feet from the bottom of the cell to the seasonal high ground water level.005.18B RI cells will be designed to operate in a cycle consisting of a water application period followed by a drying period. The length of the drying period will be adequate to restore aerobic conditions to the soil and will not be shorter than the application period. The application period ill include all time that any standing water is visible in the cell. 005.18C RI systems that discharge to ground water will be designed to achieve a total nitrogen concentration of 10 milligrams per liter (mg/1) or less entering ground water. 005.18D Ground water monitoring wells will be required at all rapid infiltration systems.123 Neb. Admin. Code, ch. 5, § 005
Amended effective 9/4/2019