(1) Temporary use of the design freeboard. For purposes of this rule, the design freeboard shall mean the vertical distance from the water surface, when water levels are at the maximum design level, to the lowest elevation of the top of the surrounding dike.
    (a) Temporary use of the design freeboard of a perimeter earthen dike or a gypsum dike is authorized when the water level is at the design freeboard and when such use is necessary to prevent the release of untreated process water. Such use of the freeboard shall only be allowed when a third-party engineer has approved such use and when documentation demonstrating the continued safety and stability of the dike is submitted to the department. Such documentation shall include a listing of any operational limitations or constraints recommended by the third-party engineer as set forth in this section together with confirmation that the owner will comply with such recommendations. The third-party engineer shall base their recommendations on:
    1. An inspection of the facility,
    2. Dike design and construction information,
    3. Results of seepage and stability analyses (including monitoring of seepage pressures within the dike if such monitoring is deemed necessary); and,
    4. Wind surge and wave run-up analyses.
    (b) The report by the third-party engineer shall specify conditions under which such use may be undertaken so as not to jeopardize the integrity of the dike, such as:
    1. Acceptable wind speeds in forecast,
    2. Increased inspection frequencies; and,
    3. Weekly monitoring of piezometric levels within the mass of the dike, if and as needed.
    (c) The third-party engineer shall reevaluate the facility each time such action is proposed by the owner. The department shall be informed of the proposed use and the engineer’s recommendations prior to or within 24 hours of each such occurrence.
    (2) If the perimeter earthen dike of the phosphogypsum stack system is an above-grade earthen dike, the system may incorporate an emergency spillway to allow for the controlled release of process water during emergencies and avoid overtopping of the perimeter earthen dike. The spillway shall be located so as to minimize the environmental impact of any release to the extent practicable. This provision shall not be deemed to authorize a discharge from the spillway and shall not be construed to limit the department’s exercise of its enforcement discretion in the event that such discharge causes or contributes to a violation of applicable department rules.
    (3) Notwithstanding any provision of Fl. Admin. Code Chapter 62-673, the department is authorized to allow the temporary use of an emergency diversion impoundments (EDI) to receive and store discharges of process water through a spillway authorized by subsection 62-672.870(2), F.A.C., or by pumping where necessary to avoid or reduce the unpermitted discharge of process water to surface waters of the state. Following any such discharge, the owner of the system shall submit a plan within 30 days to the department and initiate all steps reasonably necessary to remove the process water from the emergency diversion impoundment as expeditiously as practicable but not to exceed 120 days following such discharge, or to otherwise mitigate the discharge to prevent violations of applicable department rules. Any department approval under this section or any other department approval of measures designed to mitigate impacts of emergency discharges of process water shall not be construed to limit the department’s exercise of its enforcement discretion in the event that such measures cause or contribute to a violation of applicable department rules.
Rulemaking Authority 403.4155 FS. Law Implemented Florida Statutes § 403.4155. History-New 6-28-99, Amended 7-19-06.