62-672.200. Definitions

(1) 100-Year Rainfall Event – A rainfall event which is characterized by a mean return period of one hundred years, i.e., a rainfall event which has a 99% probability for not being exceeded during any given year.

(2) 100-Year Annual Rainfall – The 100-Year rainfall event representing total annual rainfall of 76 inches.

(3) Abandoned dam – An abandoned dam is one associated with a settling area from which sufficient water has been removed to make the residue no longer a pollutional threat to surface waters or a hazard of any type to land areas.

(4) Above-Grade Perimeter Earthen Dike – A perimeter earthen dike that has its design freeboard above the adjacent ground surface.

(5) Active dam – An active dam is one associated with a settling area into which wastewater is being introduced for purposes of clarification or in which free water remains in contact with the dam.

(6) Auxiliary holding pond (AHP) – a lined storage pond, designated by the operator and approved by the department in accordance with Rule 62-673.320, F.A.C., typically used to hold untreated process water. AHPs are intended to increase system storage above that otherwise provided by cooling/surge ponds and are typically located within the footprint of a phosphogypsum stack system. An existing AHP may be unlined where it was authorized by a permit issued in accordance with Rule 62-673.320, F.A.C., to be in use as of July 19, 2006, or was otherwise subject to a demonstration provided in accordance with subsection 62‑673.650(2), F.A.C.

(7) Backup power – A secondary source of power not likely to fail simultaneously with the primary source.

(8) Beach or Delta – A gently sloping area of gypsum deposited within the settling compartment, above the process water level.

(9) Beneficiation – The processing of phosphate ore to separate the phosphate rock from the associated sand and clays.

(10) Berm – A shelf that breaks the continuity of the slope of an embankment in order to arrest the velocity of storm water flowing down the face and/or to enhance the stability of the embankment.

(11) Cast dam – A cast dam is one constructed of fill which was put in place by a dragline or other machine capable of free dumping, and is not mechanically compacted in progressive layers.

(12) Cooling/surge pond – impounded areas within the phosphogypsum stack system, excluding settling compartments atop the phosphogypsum stack, that provide cooling capacity, surge capacity, or any combination thereof, for the phosphoric acid process water recirculation system including phosphogypsum stack transport, runoff, and leachate water from the process watershed.

(13) Core – A zone of relatively impervious material within the dam to resist the flow of water through the dam.

(14) Cut-off-trench – An excavation into the foundation material to accept an extension of the core.

(15) Department – The Florida Department of Environmental Protection.

(16) Dike – A barrier to the flow of phosphogypsum and process water which is constructed of naturally occurring soil (earthen dike) or of phosphogypsum and which is a component of a phosphogypsum stack system.

(17) Drain – A material more pervious than the surrounding fill which allows seepage water to drain freely while preventing piping or internal erosion of the fill material.

(a) Blanket drain is a continuous horizontal drain layer within or beneath the downstream portion of the dam.

(b) Chimney drain is a continuous sloping drain layer within the downstream portion of the dam.

(c) Toe drain is a wedge-shaped drain supporting the downstream toe of the dam.

(18) Earthen dam or dam – A barrier to the flow of liquids which is constructed of naturally occurring soil and which is a component of a clay settling area.

(19) Earthen dike – A barrier to the flow of phosphogypsum and process water which is constructed of naturally occurring soil and which is a component of a phosphogypsum stack system.

(20) Emergency diversion impoundment (EDI) – a storage area designated in the facility’s site-specific water management plan to be used only when necessary to avoid an unpermitted surface water discharge resulting from dike overtopping or failure in accordance with subsection 62‑672.870(3), F.A.C. An EDI is typically located outside the footprint of a phosphogypsum stack system.

(21) Engineer – An engineer registered in the State of Florida in accordance with Chapter 471, F.S., and with experience in the design, construction, and operation of systems covered by this rule.

(22) Event Storage – The amount of rainfall occurring in a 24 hour period that can be stored within a phosphogypsum stack system, at or below maximum design levels, during the same 24 hour period through any combination of gravity flow or use of the emergency measures identified in the operation plan for the phosphogypsum stack system pursuant to subsection 62-672.780(7), F.A.C., but specifically excluding use of temporary measures identified in Rule 62‑672.870, F.A.C.

(23) Filter – A zone of material sufficiently more pervious than the dam or foundation so that free water will drain through the filter, but at the same time sufficiently fine grained to prevent piping of the fill material.

(24) Freeboard – The height of the lowest point on the dam or dike crest, excluding the emergency spillway, above the highest adjacent liquid surface within the impoundment.

(25) Gypsum dike – The outermost dike constructed within the perimeter formed by a starter dike for the purpose of raising a phosphogypsum stack and impounding phosphogypsum and/or process water. This term specifically excludes any dike inboard of a rim ditch, any partitions separating stack compartments, or any temporary windrows placed on the gypsum dike.

(26) Inside (upstream) slope – The face of the dam or dike which will be in contact with the impounded liquids.

(27) Log – A written record maintained by the owner of an earthen dam or a phosphogypsum stack system that contains a schedule of inspections of system components, the findings of such inspections, and any remedial measures taken in response to such findings.

(28) Maximum Design Level – the maximum process water elevation when the water level is at the operating design freeboard for an impoundment as determined using generally accepted good engineering practices, or the minimum freeboard allowed by paragraph 62-672.600(1)(c), F.A.C., for perimeter earthen dikes. For the purposes of this chapter, generally accepted good engineering practices for determining the permitted operating design freeboard includes, at a minimum, evaluation of wind surge, wave height, and wave run‑up analyses, erosion protection measures, and protection of dike integrity and inner rim‑ditch geometry.

(29) Maximum Potential Storage – the maximum amount of rainfall that can be contained within a phosphogypsum stack system, including AHPs and the top areas of phosphogypsum stacks, and temporary use of design freeboards in accordance with the provisions of subsection 62‑672.870(1), F.A.C.

(30) New perimeter earthen dike – A perimeter earthen dike which is the subject of a complete application for a department permit to construct or laterally expand a phosphogypsum stack system submitted to the department after June 28, 1999.

(31) Non-clay phosphate mining impoundments – Above-grade, non-clay phosphate mining/reclamation berms and impoundments such as:

(a) Units under reclamation receiving hydraulic fill;

(b) UInits constructed for impounding stormwater runoff;

(c) Structures located in mine cuts that could impound water above grade, and where a failure of such structure could result in a release of waters to waters of the state; and

(d) Perimeter ditch and berm systems that impound water above grade.

(32) Operation plan – The operation plan required by subsection 62-673.340(3), F.A.C.

(33) Outside (downstream) slope – The face of the dam or dike which will not be in contact with the impounded liquids.

(34) Perimeter earthen dike – The outermost earthen dike surrounding a phosphogypsum stack system that has not been closed or any other earthen dike the failure of which could cause a release of process water outside the phosphogypsum stack system.

(35) Phosphogypsum or gypsum – The definition of “phosphogypsum” set forth in subsection 62-673.200(13), F.A.C., is adopted and incorporated by reference.

(36) Phosphogypsum stack or stack – The definition of “phosphogypsum stack” set forth in subsection 62-673.200(14), F.A.C., is adopted and incorporated by reference.

(37) Phosphogypsum stack system – The definition of “phosphogypsum stack system” set forth in subsection 62-673.200(15), F.A.C., is adopted and incorporated by reference.

(38) Phreatic Surface – The upper surface of the water table within the mass of the dam or dike. It would be the elevation of the water surface if an open hole were dug into the dam.

(39) Piping – Progressive erosion of soil or solid material within the dam or dike, starting downstream and working upstream, creating a tunnel into the dam or dike. Piping occurs when the velocity of the flow of seepage water is sufficient for the water to transport material from the embankment.

(40) Process Water – The definition of “process wastewater” set forth in subsection 62-673.200(16), F.A.C., is adopted and incorporated by reference.

(41) Process Watershed  – the aggregate of all areas that contribute to or generate additional process water from direct precipitation, rainfall runoff, or leachate to a phosphogypsum stack, process water cooling/surge ponds, or any other storage, collection, or conveyance system associated with the transport of phosphogypsum or process water for a particular phosphogypsum stack system.

(42) Qualified Company Employee – An employee trained pursuant to Rule 62-672.800, F.A.C., specifically in the area of their job duties.

(43) Regional Holding Pond (RHP) – a lined storage pond typically used to hold untreated process water which is constructed for the purpose of temporarily storing process water from more than one facility and which is approved by the department in accordance with Rule 62-673.320, F.A.C.

(44) Retired dam – A retired dam is one associated with a settling area into which no additional wastewater is currently being introduced but which could be reactivated.

(45) Rolled dam – A rolled dam is one constructed of fill which is placed in layers which are mechanically compacted individually prior to placement of the next higher layer.

(46) Safety factor – A numerical value which represents the ration of the ultimate strength of a material or structure to the stress which will be applied to that material or structure.

(47) Settling area – A phosphate mining clay settling area surrounded by dams, embankments, or natural soil masses in which liquids are introduced for the purpose of separating suspended solid matter from water used for transportation of such matter.

(48) Starter Dike – The initial dike constructed at the base of a phosphogypsum stack to begin the process of storing phosphogypsum.

(49) System storage – the amount of rainfall that can be contained within a phosphogypsum stack system at or below maximum design levels, including AHPs and the top areas of phosphogypsum stacks.

(50) Tailwater level – The elevation of the water at the downstream toe of the dam or dike.

(51) Third-party engineer – An engineer who is not an employee of any entity that owns or operates a phosphate mine or phosphate fertilizer manufacturing facility.

(52) Toe – The toe of the dam or dike is the junction between the face of the dam or dike and the adjacent terrain.

(53) Wave height – the average height of the waves that may be determined for design purposes as a function of sustained wind speed, effective fetch length, and wind duration. Sustained wind speed shall be determined based on either an estimated 100-year return frequency wind speed adjusted to a sustained wind speed for a 10-minute duration, or a 110 miles per hour (mph) fastest-mile wind speed for locations within 25 miles of the seacoast and a 95 mph fastest-mile wind speed at other inland locations where the fastest-mile wind speeds are adjusted to a sustained wind speed for a 10-minute duration.

(54) Wave run‑up – the difference in vertical height between the maximum elevation attained by wave run up or uprush on a slope and the still water elevation at the inboard toe of the slope.

(55) Wind surge or setup – the vertical rise in base water-surface elevation, exclusive of the wave height, above the still water elevation, caused by wind‑induced stresses and mounding of the water surface in the leeward direction.

Specific Authority 403.061(22), 403.4155 FS. Law Implemented 403.061(22), 403.4155 FS. History–Revised 12-8-72, Formerly 17-9.02, 17-9.020, 17-672.200, Amended 6-28-99, 7-19-06.