Section 58.01.16.493 - FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER TREATMENT OR DISPOSAL FACILITIES: WASTEWATER LAGOONS01.General.a. These rules pertain to all new and existing municipal wastewater lagoons, including discharging or non-discharging lagoons, municipal wastewater treatment lagoons, municipal wastewater storage lagoons, and any other municipal wastewater lagoons that, if leaking, have the potential to degrade waters of the state. Lagoons are also sometimes referred to as ponds. Section 493 does not apply to industrial lagoons or mining tailings ponds, single-family dwellings utilizing a single lagoon, two (2) cell infiltrative system, those animal waste lagoons excluded from review under Section 39-118, Idaho Code, or storm water ponds.b. Lagoons utilized for equalization, percolation, evaporation, and sludge storage do not have to meet the requirements set forth in Subsections 493.05 through 493.10, but must comply with all other applicable subsections.02.Seepage Testing Requirements.a. Existing Lagoons. All existing lagoons covered under these rules shall be seepage tested by an Idaho licensed professional engineer, an Idaho licensed professional geologist, or by individuals under their supervision by April 15, 2012 unless otherwise specified in a current permit issued by the Director.b. New Lagoons. As part of the construction process, all new lagoons must be seepage tested by an Idaho licensed professional engineer, an Idaho licensed professional geologist, or by individuals under their supervision prior to being put into service.c. Subsequent Tests. All lagoons covered under these rules must be seepage tested by an Idaho licensed professional engineer, an Idaho licensed professional geologist, or by individuals under their supervision every ten (10) years after the initial testing.d. Testing Due to Change of Conditions to Liner. Prior to being returned to service, lagoons must be seepage tested if a change of condition to the liner occurs that may affect its permeability, including but not limited to liner repair below the high water line, liner replacement, lagoon dewatering of soil-lined lagoons which results in desiccation of the soil liner, seal installation, or earthwork affecting liner integrity. A seepage test may be required after solids removal. Prior to performing activities that may affect liner permeability, the system owner must contact the Department in writing to determine if a seepage test will be required prior to returning the lagoon to service.e. Procedures for Performing a Seepage Test. The procedure for performing a seepage test or alternative analysis must be approved by the Department, and the test results must be submitted to the Department. If an existing lagoon has passed a seepage test before April 15, 2012 and submitted the results to the Department, the owner of that lagoon has ten (10) years from the date of the testing to comply with this requirement.03.Allowable Seepage Rates.a. Design Standard. Lagoons shall be designed for a maximum leakage rate of five hundred (500) gallons per acre per day.b. Operating Standard. The leakage rate for lagoons constructed after April 15, 2007 shall be no more than zero point one hundred twenty-five (0.125) inches (1/8 inch) per day, which is approximately thirty-four hundred (3400) gallons per acre per day. The leakage rate for existing lagoons constructed prior to April 15, 2007 shall be no more than zero point twenty-five (0.25) inches (1/4 inch) per day.c. For lagoons located over sensitive aquifers or near 303d listed stream segments, the leakage rate shall be no more than zero point one hundred twenty-five (0.125) inches (one-eighth (1/8) inch) per day, which is approximately thirty-four hundred (3400) gallons per acre per day. The operating standard may be considerably lower based on a ground water investigation considering fate and transport of contaminants to determine the effect of the seepage on the aquifer or stream segment and the best capability of measurement at the time of the investigation.04.Requirements for Lagoons Leaking Above the Allowable Amount. If a lagoon is found to be leaking at a rate higher than that allowed under Subsection 493.03.b., the owner of the lagoon, in accordance with a schedule negotiated with and approved by the Director, is required to:a. Repair the leak and retest for compliance;b. Re-line the lagoon and retest for compliance;c. Drain the lagoon in an approved manner and stop using the lagoon; ord. Determine the impact of the leaking lagoon on the environment based on ground water sampling and modeling. The procedure for performing ground water sampling and monitoring must be approved by the Department. Any impact must comply with IDAPA 58.01.11, "Ground Water Quality Rule," and IDAPA 58.01.02, "Water Quality Standards." If the impact does not comply with IDAPA 58.01.11, "Ground Water Quality Rule," and IDAPA 58.01.02, "Water Quality Standards," the owner of the lagoon must follow one (1) of the steps set out in Subsections 493.04.a. through 493.04.c.05.Location. a. Wastewater treatment lagoons shall be placed a minimum of two hundred (200) feet from residential property lines. In all cases, the design location shall consider odors, nuisances, etc. This distance is to the toe of the exterior slope of the dike or to the top of the cut for a lagoon placed into a hillside. More restrictive planning and zoning or other local requirements shall apply.b. Ground Water Separation. A minimum separation of two (2) feet between the bottom of the pond and the maximum ground water elevation shall be maintained.c. Bedrock Separation. A minimum separation of two (2) feet between the pond bottom and any bedrock formation shall be maintained.06.Basis of Design.a. Design variables such as climatic conditions, odor, pond depth, multiple units, detention time, and additional treatment units must be considered with respect to applicable standards for BOD5, total suspended solids (TSS), fecal coliform, dissolved oxygen (DO), pH, and other effluent requirements and limits.b. The preliminary engineering report shall include all design criteria for the development of the pond design.c. The reaction rate coefficient for domestic wastewater which includes some industrial wastes, other wastes, and partially treated wastewater must be determined experimentally for various conditions which might be encountered in the lagoons or actual data from lagoons in similar climates. Conversion of the reaction rate coefficient at other temperatures shall be made based on experimental data.d. Oxygen requirements generally will depend on the design average BOD5 loading, the degree of treatment, and the concentration of suspended solids to be maintained. If needed, aeration equipment shall be capable of maintaining a minimum dissolved oxygen level of two (2) mg/L in the ponds at all times. Suitable protection from weather shall be provided for electrical controls. Aerated cells shall be followed by a polishing cell with a detention time of a minimum of twenty-four (24) hours.e. See Subsection 490.02 for details on aeration equipment.07.Industrial Wastes as a Part of the Municipal Wastewater.a. Consideration shall be given to the type and effects of industrial wastes on the treatment process.b. Industrial wastes shall not be discharged to ponds without assessment of the effects such substances may have upon the treatment process or discharge requirements in accordance with state and federal laws.08.Number of Cells Required. a. A wastewater treatment pond system shall consist of a minimum of three (3) cells designed to facilitate both series and parallel operations. Two (2) cell systems may be utilized in very small installations of less than fifty thousand (50,000) gallons per day.b. All systems shall be designed with piping flexibility to permit isolation of any cell without affecting the transfer and discharge capabilities of the total system.09.Pond Construction Details. a. Embankments and Dikes. i. Material. Dikes shall be constructed of relatively impervious soil and compacted to at least ninety-five (95) percent Standard Proctor Density to form a stable structure. Vegetation and other unsuitable materials shall be removed from the area where the embankment is to be placed.ii. Top Width. The minimum dike width shall be ten (10) feet to permit access for maintenance vehicles.iii. Maximum Slopes. Inner and outer dike slopes shall not be steeper than one (1) vertical to three (3) horizontal (1:3).iv. Minimum Slopes. Inner slopes should not be flatter than one (1) vertical to four (4) horizontal (1:4). Flatter slopes can be specified for larger installations because of wave action but have the disadvantage of added shallow areas being conducive to emergent vegetation. Outer slopes shall be sufficient to prevent surface runoff from entering the ponds.v. Freeboard. Minimum freeboard shall be three (3) feet, except that for small systems of less than fifty thousand (50,000) gallons per day, two (2) feet may be acceptable.vi. Design Depth. The minimum operating depth shall be sufficient to prevent growth of aquatic plants and damage to the dikes, bottom, control structures, aeration equipment, and other appurtenances. In no case shall pond depths be less than two (2) feet.b. Pond Bottom. i. Soil. Soil used in constructing the pond bottom (not including the seal) and dike cores shall be relatively incompressible and tight and compacted to at least ninety-five (95) percent Standard Proctor Density.ii. Seal. Ponds shall be sealed such that seepage loss through the seal complies with Subsection 493.03. Results of a testing program which substantiates the adequacy of the proposed seal must be incorporated into or accompany the preliminary engineering report.c. Miscellaneous. i. Fencing. The pond area shall be enclosed with an adequate fence to prevent entering of livestock and discourage trespassing. This requirement does not apply to pond areas which store or impound Class A municipal reclaimed effluent.ii. Access. An all-weather access road shall be provided to the pond site to allow year-round maintenance of the facility.iii. Warning Signs. Appropriate permanent signs shall be provided along the fence around the pond to designate the nature of the facility and advise against trespassing. At least one (1) sign shall be provided on each side of the site and one (1) for every five hundred (500) feet of its perimeter.iv. Flow Measurement. Flow measurement requirements are provided in Subsection 450.06.e. Effective weather protection shall be provided for the recording equipment.v. Ground Water Monitoring. A ground water monitoring plan shall be submitted to the Department for review and approval as a part of the preliminary engineering report. An approved system of wells or lysimeters shall be required around the perimeter of the pond site to facilitate ground water monitoring.10.Closure. The owner shall notify the Department at least six (6) months prior to permanently removing any wastewater lagoon facility from service, including any treatment or storage pond. Prior to commencing closure activities, the facility shall: a. Participate in a pre-closure on-site meeting with the Department;b. Develop a site closure plan that identifies specific closure, site characterization, or cleanup tasks with scheduled task completion dates in accordance with agreements made at the pre-site closure meeting; andc. Submit the completed site closure plan to the Department for review and approval within forty-five (45) days of the pre-site closure meeting. The facility must complete the Department approved site closure plan.Idaho Admin. Code r. 58.01.16.493