Rule 62-565.520. Off-spec Storage Requirements for Advanced Treatment Water Facilities

(1) For an ATWF for which there are alternative reuse or disposal systems permitted, those alternative reuse or disposal systems may be used for the management of off-spec water. For an ATWF for which there are no alternative reuse or disposal systems permitted, a separate, off-line system for storage of off-spec water shall be provided.

(2) For an ATWF connected to a public water system with the capability of treating to primary and secondary drinking water standards, the storage requirements are as follows:

(a) Off-spec storage ponds shall have sufficient storage capacity to assure the retention of the off-spec reclaimed water under adverse water conditions and maintenance of equipment. Off-spec storage ponds shall meet the following requirements:

1. A minimum of 30 years of recent climatic data determined by the National Centers for Environmental Information shall be used in storage volume determinations.

2. Off-spec storage ponds shall be designed in a manner which allows for the impoundment of rainfall equal to that of the 25-year, 3-day 24-hour storm event, as defined by the respective Water Management District, in which the facility is located.

(b) Analytical means of determining off-spec storage requirements shall be used and shall account for all water inputs into the system, including water balance calculations or computer hydrological programs. Analysis shall be based on site specific data.

(c) The methods and assumptions used for determining the off-spec storage requirements shall be included described and justified in the engineering report required in Rule 62-565.570, F.A.C.

(d) For off-spec storage ponds using non-synthetic liners, the permeability, durability, strength, thickness, and integrity of the liner shall be satisfactorily demonstrated for anticipated pressure gradient, climatic conditions, 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 the engineering report required in Rule 62-565.570, F.A.C.

(e) For off-spec storage ponds using synthetic liners, the 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 to the Department prior to the ATWF being placed in operation.

(f) For unlined off-spec storage ponds, a ground water monitoring plan prepared in accordance with Rule 62-520.600, F.A.C., shall be incorporated into the ATWF permit.

(g) Off-spec storage ponds shall provide a minimum freeboard of three feet.

(h) 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.

(i) Off-spec storage ponds shall be designed and maintained consistent with sound engineering practices to prevent the deliberate introduction of stormwater.

(j) The siting of the off-spec storage ponds shall be addressed in the engineering report in prepared under Rule 62-565.570, F.A.C. Off-spec ponds shall be sited to avoid areas of uneven subsidence, sinkholes, pockets of organic matter or other unstable soils. 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.

(3) For an ATWF that uses storage tanks for storage of off-spec water, the storage requirements are as follows:

(a) Off-spec storage tanks shall have sufficient storage capacity to assure the retention of the off-spec reclaimed water with a minimum of 1.2 times the design flow capacity of the ATWF.

(b) Off-spec storage tanks shall be designed and installed in accordance with the applicable American Water Works Association (AWWA) standard (adopted and incorporated by reference in Rule 62-555.330, F.A.C., effective May 5, 2014).

(c) Off-spec storage tanks shall be checked at least annually to ensure that hatches are closed, and screens are in place; shall be cleaned at least once every five years to remove bio-growths, calcium or iron/manganese deposits, and sludge from inside the tanks; and shall be inspected at least once every five years for structural and coating integrity by personnel under the responsible charge of a professional engineer licensed in Florida. Rulemaking Authority 403.861(9), 403.064(17) FS. Law Implemented 403.852(12), 403.861(7), 403.853(6), 403.861(17), 403.064(17) FS. History – New 2-26-25.