(1) System storage ponds as described herein shall not be required where it is documented in the engineering report that an alternative system (e.g., permitted surface water discharge, deep wells) is incorporated into the system design to ensure continuous facility operation in accordance with the requirements of Fl. Admin. Code Chapter 62-600 If system storage is not required, provision of flow equalization or storage shall be evaluated in the engineering report to ensure that reclaimed water flows will match the demand pattern during a diurnal cycle.
    (2) Unless exempted by subsection 62-610.414(1), F.A.C., system storage ponds shall have capacities determined as follows.
    (a) System storage ponds shall have sufficient storage capacity to assure the retention of the reclaimed water under adverse weather conditions, harvesting conditions, maintenance of irrigation equipment, or other conditions which preclude land application.
    (b) Storage capacity or a limited wet weather discharge system shall be provided for wet weather conditions which preclude land application and shall be described in the engineering report and subject to Department approval. The system storage period shall be established by determining the volume of storage that would be required for a ten-year recurrence interval, using weather data that is available from, or is representative of, the area involved.
    (c) At a minimum, system storage capacity shall be the volume equal to three times that portion of the average daily flow of the reuse capacity for which no alternative reuse or disposal system is permitted.
    (d) Analytical means (water balance calculations or computer hydrological programs such as the Department’s LANDAP program) of determining system storage requirements shall be used and shall account for all water inputs into the system. Analysis shall be based on site specific data.
    (e) The methods and assumptions used for determining the system storage requirements shall be described and justified in the engineering report.
    (f) A minimum of 20 years of climatic data shall be used in storage volume determinations.
    (g) Irrigation efficiencies or rainfall efficiencies shall not be used in storage volume determinations.
    (3) System storage ponds and tanks shall be designed for continuous flow-through or off-line storage of the reclaimed water from the treatment plant. For continuous flow-through, the pond or tank shall be designed such that reclaimed water can be retained for the required storage period. For off-line ponds or tanks, the reclaimed water transmission system shall be designed such that all produced reclaimed water can be diverted to the pond or tank and retained for the required storage period under conditions which preclude land application.
    (4) System storage ponds shall be lined or sealed to prevent measurable seepage. The permeability, durability, strength, thickness, and integrity of the liner material shall be satisfactorily demonstrated for anticipated pressure gradient, climatic, installation and daily operation conditions. A quality assurance/quality control plan which substantiates the adequacy of the liner and its installation shall be incorporated into, or shall accompany the engineering report. Synthetic liners shall be installed in accordance with the manufacturer’s specifications and recommendations. Documentation of quality assurance and quality control activities on liner installation along with permeability or seepage test results shall be submitted with the notification that the facility will be placed in operation.
    (5) System storage ponds may be unlined if designed to provide both storage and percolation functions. When designed for percolation such ponds are subject to the provisions of Part IV of this chapter. System storage ponds may be unlined if high-level disinfection is provided.
    (6) Provisions for monitoring ground water quality adjacent to unlined system storage ponds shall be incorporated into the ground water monitoring plan.
    (7) System storage holding ponds shall provide a minimum three feet of freeboard. Holding ponds shall be provided with an emergency discharge or overflow device to prevent water levels from rising closer than one foot to the top of the embankment or berm. The overflow device shall have sufficient capacity to discharge excess flows. Disposition of the overflow discharge shall be identified in the engineering report.
    (8) Provisions for the control of algae shall be included in the design, operation, and maintenance and shall be described in the engineering report. Pond design shall also address the control of mosquito breeding habitat. Minimum pond depths (excluding freeboard but including the design operating range) of six feet, with inside bank side slopes steeper than 3:1 (horizontal to vertical), but no steeper than 1:1, are required to discourage growth of rooted aquatic weeds. Maintenance of a minimum pond water depth of 18 inches is required. Routine aquatic weed control and regular maintenance of pond embankments and access areas are required. The use of other depth criteria for mosquito control shall be justified in the engineering report.
    (9) Ponds shall be sited to avoid areas of uneven subsidence, sinkholes, pockets of organic matter or other unstable soils unless provisions are made for their correction. Ponds used to impound reclaimed water above natural grade shall be designed to prevent failure of the embankment due to hydrostatic forces, seepage or soil piping, wind and wave action, erosion, and other anticipated conditions. Results from field and laboratory tests from an adequate number of test borings and soil samples shall be the basis for computations pertaining to seepage and stability analyses.
Rulemaking Authority 403.051, 403.061, 403.087 FS. Law Implemented 403.021, 403.051, 403.061, 403.062, 403.085, 403.086, 403.087, 403.088 FS. History-New 4-4-89, Amended 4-2-90, Formerly 17-610.414, Amended 1-9-96, 4-1-21.