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Florida Administrative Code (Last Updated: October 28, 2024) |
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62. Department of Environmental Protection |
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D62. Departmental |
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62-672. Minimum Requirements For Earthen Dams Used In Phosphate Mining And Beneficiation Operations And For Dikes Used In Phosphogypsum Stack System Impoundments |
1(1) Design.
3(a) Site investigation. The general area desired for construction of a perimeter earthen dike shall be carefully inspected by the design engineer prior to selection of the exact location for the dike. Areas of uneven natural subsidence, sinkholes, pockets of organic matter, or other unstable soils shall be avoided, unless special provisions are made for their mitigation.
60(b) Soil testing. The requirements for soil testing set forth in paragraph 7262-672.300(1)(b), 73F.A.C., are adopted and incorporated by reference.
80(c) Cross section design. The design freeboard of an above-grade perimeter earthen dike shall not be less than five (5) feet unless a design freeboard of less than five (5) feet is justified based on results of seepage and stability analyses and wave run-up analyses. However, in no event shall the design freeboard of an above-grade perimeter earthen dike be less than three (3) feet. The crest on the top of the dike shall be graded toward the inside or the outside slope. If the dike exceeds 10 feet in height and crest runoff is directed toward the outside slope, runoff controls shall be used to protect the outside slope against erosion. Both inside and outside slopes shall be no steeper than two and one-half (2.5) horizontal to one (1.0) vertical. Seepage control shall be provided by means of a liner placed on the inside slope of the dike and constructed in accordance with Rule 23562-673.400, 236F.A.C. The top of the dike shall include a roadway which will permit wheeled vehicle traffic at all times. The design of the outermost earthen dike shall also incorporate an all-weather roadway near the downstream toe which will permit wheeled vehicle traffic around the perimeter of the dike for purposes of inspection of the slope, toe and natural ground beyond the toe, as well as maintenance.
302(d) Stability analysis. A seepage or flow net analysis shall be made, when applicable, for use in the stability analysis. The stability analysis shall consider the minimum fluid level as well as the fluid level at the design freeboard on the upstream slope of the dike, and possible fluctuations of the tail water level.
356(e) Design safety factors. The design safety factors set forth in paragraph 36862-672.300(1)(e), 369F.A.C., are adopted and incorporated by reference.
376(2) Site preparation. The site preparation requirements of subsection 38562-672.300(2), 386F.A.C., are adopted and incorporated by reference.
393(3) Material to be used. The requirements for materials to be used are set forth in subsection 41062-672.300(3), 411F.A.C., and are adopted and incorporated by reference.
419(4) Process water control design. Conveyance ditches, pumps, pipes, and hydraulic structures located within a phosphogypsum stack system shall have adequate capacity to circulate the process water stream(s), if applicable, and to contain or transfer runoff on the process watershed upstream of the water control structures resulting from a storm event generating 12 inches of rainfall in 24 hours while maintaining at the same time the design freeboard of the perimeter earthen dike. If provisions are made to contain some or all of the storm surge resulting from such event within the phosphogypsum stack system upstream from the conveyance system or water control structures, then the transfer capacity of the ditches, pumps, pipes, and related structures may be reduced accordingly.
539(5) Methods of construction.
543(a) Each new dike shall be constructed to meet or exceed the minimum safety requirements of the specifications and design for that dike. Appropriate earthmoving equipment shall be used to place materials in dike construction. The soil shall be compacted and density tests shall be performed to ensure that the designed densities are obtained. A representative of the third-party engineer shall be present on the site during construction of the dike and liner, and during construction and installation of spillways and penetrations through the dike or liner. The department shall be advised of the date on which construction of a new dike will begin so that a department representative can inspect the site.
656(b) Areas around any water level control structure pipe, any other conduit, or any surface of discontinuity between materials within the mass of the dike shall be carefully inspected to avoid potential concentration of seepages and to ensure that soils under and around a culvert are uniformly compacted and are in continuous contact with the external culvert surface. All penetrations through the liner on the upstream slope of the dike shall be made using water tight joints or connections and shall be capable of maintaining their integrity under anticipated in-use conditions. All pipes and joints in pipes or conduits extending through a dike shall be made leak proof and shall be constructed of materials suitable for the fluids carried and the load imposed. In order to avoid leaks associated with differential settlement, conduits through dikes shall not be rigidly supported by piles or piers. Backfill around conduits shall be of a density that is equal to or greater than those of the surrounding embankment. Particular attention shall be devoted to the lower third of the conduit.
832(6) Documentation. Applicable provisions of the documentation requirements set forth in subsection 84462-672.300(6), 845F.A.C., are adopted and incorporated by reference with the following exception. The owner shall furnish a certification of completion of construction within 30 days after completion of the dike. The remaining documents shall be submitted within six (6) months of placing the facility into operation.
890Specific Authority 892403.4155 FS. 894Law Implemented 896403.4155 FS. 898History–New 6-28-99, Amended 7-19-06.
