62-673.610. Closure Plan Requirements

All closure plans shall address the following requirements, or shall contain an explanation of why the requirement is not applicable. Valid information on record in an existing permit or approved groundwater monitoring plan may be used to satisfy the applicable requirements of this rule.

(1) General information report. This report shall contain:

(a) Identification of the phosphogypsum stack system;

(b) Name, address and phone number of primary contact persons;

(c) Identification of persons or consultants preparing this report;

(d) Present property owner and phosphogypsum stack system operator;

(e) Location by township, range and section, and latitude and longitude of the phosphogypsum stack system;

(f) Total acreage of the phosphogypsum stack system and total acreage of the facility property;

(g) Legal description of the property on which the phosphogypsum stack system is located; and

(h) History of the phosphogypsum stack system, including construction dates and a general description of operations.

(2) Area information report. A report on the area in which the phosphogypsum stack system is located shall be included in the closure plan. The report may use verifiable information available from published documents. The term “area” means that area which may affect or be affected by the phosphogypsum stack system, and at a minimum includes the land within a one-mile radius of the phosphogypsum stack system. The report shall be supplemented by maps and cross-section drawings. The following topics shall be addressed in the report:

(a) Topography;

(b) Hydrology, including surface water drainage patterns and hydrologic features such as surface waters, springs, drainage divides and wetlands;

(c) Geology, including the nature and distribution of lithology, unconsolidated deposits, major confining units and sinkholes;

(d) Hydrogeology, including depth to groundwater table, groundwater flow directions, recharge and discharge areas used by public and private wells within one mile of the phosphogypsum stack system;

(e) Ground and surface water quality;

(f) Land use information. The report shall include a discussion and maps indicating:

1. Identification of adjacent landowners;

2. Zoning;

3. Present land uses; and

4. Roads, highways, right-of-ways, or other easements.

(3) Groundwater monitoring plan and site specific information. The closure plan shall include an approved groundwater monitoring plan containing site specific information which meets the criteria specified in subsection 62-522.600(3), F.A.C.

(4) Assessment of effectiveness of existing phosphogypsum stack system design and operation. Based on the area information report and the groundwater monitoring plan, an assessment shall be prepared which discusses the effects of the phosphogypsum stack system on adjacent ground and surface waters, and the phosphogypsum stack system area. Specific concerns to be addressed are:

(a) Effectiveness and results of the groundwater investigation; and

(b) Effects of surface water runoff, drainage patterns, and existing storm water controls.

(5) Closure plan performance standards. The closure plan and closure design plan shall be developed to meet the following performance standards.

(a) Closure plans for phosphogypsum stack systems shall be designed to:

1. Control, minimize or eliminate, to the extent necessary to protect human health and the environment, the post closure escape of phosphogypsum, process wastewater, leachate, and contaminated runoff to ground and surface waters;

2. Minimize leachate generation;

3. Detect, collect, and remove leachate and process wastewater efficiently from the phosphogypsum stack system, and promote drainage of process wastewater from the phosphogypsum stack;

4. Be compatible with any required ground water or surface water corrective action plan;

5. Minimize the need for further maintenance.

(b) Closure plans for phosphogypsum stacks shall include a final cover system designed to:

1. Promote drainage off the stack;

2. Minimize ponding;

3. Minimize erosion;

4. Minimize infiltration into the phosphogypsum stack;

5. Function with little or no maintenance.

(c) Closure plans for ponds and drainage conveyances storing process wastewater shall be designed to:

1. Treat or remove from the ponds and drainage conveyances all process wastewater as soon as practical, either through return of the process wastewater to the manufacturing process, transfer of process wastewater to another pond permitted in accordance with this rule, in-situ treatment, or by treatment and subsequent discharge of the process wastewater under an appropriate discharge permit;

2. Place any sludges removed from a pond or drainage conveyance into an active phosphogypsum stack permitted in accordance with this rule, or an inactive stack undergoing closure in accordance with this rule. The closure plan shall contain a detailed description of procedures for removing or treating the sludges, methods for sampling and testing surrounding soils, and criteria for determining the extent of removal required to satisfy the closure performance standards.

(6) Closure design plan. A closure design plan shall be prepared to meet the closure plan performance standards and shall be based on the area information report, groundwater monitoring plan, and assessment of the effectiveness of the existing phosphogypsum stack system design and operation. The closure design plan shall consist of engineering plans and a report on closing procedures which shall apply to the closing of the phosphogypsum stack system and the monitoring and maintenance during the long-term care period. The closure design plan shall include the following information:

(a) A plan sheet showing phases of site closing.

(b) Drawings showing existing topography and proposed final elevations and grades.

(c) For phosphogypsum stacks, final cover installation plans showing the sequence of applying final cover, including thickness and type of material that will be used. All phosphogypsum stacks shall have a final cover designed to meet the performance standards. Final cover shall be placed over the entire surface of the phosphogypsum stack. The final cover shall be vegetated with drought-resistant species to control erosion, whose root systems will not penetrate any low-permeability barrier layer. Water balance calculations, based on available climatic data, shall be prepared which estimate the rates and volumes of water infiltrating the cover systems, collected by any leachate control system, and migrating out of the bottom of the stack or liner system. Final cover may consist of synthetic membranes, soils, or chemically or physically amended soils or phosphogypsum.

1. Side slopes and all other grades shall be designed to minimize erosion of the final cover material. Such designs shall consider the erosion susceptibility of the material proposed for final cover relative to historical rainfall patterns for the area, the ability to establish and maintain vegetation and special maintenance procedures proposed to insure that infiltration and erosion are minimized. If the side slopes of any stack are steeper than a two-foot horizontal run to one foot vertical rise, the closure design plan shall include a stability analysis demonstrating the longterm stability of the area.

2. Top gradients of final cover on phosphogypsum stacks shall be designed to prevent ponding or low spots and minimize erosion.

a. The final cover on the top gradient shall consist of a barrier soil layer at least 18 inches thick, emplaced in 6-inch thick lifts. A final, 18-inch thick layer of soil or amended phosphogypsum that will sustain vegetation to control erosion shall be placed on top of the barrier layer. For unlined stacks, the barrier layer shall have a maximum permeability of 1 × 10-7 cm/sec; for lined stacks, the barrier layer shall have a maximum permeability of 1 × 10-5 cm/sec. If less permeable soils are used, the thickness of the barrier layer may be decreased to 12 inches provided that infiltration is minimized to an equivalent degree.

b. A geomembrane may be used as an alternative to the low-permeability soil barrier for a final cover, constructed to preclude rainfall infiltration into the stack. A geomembrane used in final cover shall be a semi-crystalline thermoplastic at least 40 mils thick, or a non-crystalline thermoplastic at least 30 mils thick, with a maximum water vapor transmission rate of 2.4 grams per square meter per day, have chemical and physical resistance to materials it may come in contact with, and withstand exposure to the natural environmental stresses and forces throughout the installation, seaming process, and settlement of the phosphogypsum during the closure and long-term care period. A protective soil layer at least 24 inches thick shall be put on top of the geomembrane. Material specifications, installation methods, and compaction specifications shall be adequate to protect the barrier layer from root penetration, resist erosion, and remain stable on the final design slopes. This layer shall include soils or amended phosphogypsum that will sustain vegetative growth.

3. The closure design plan shall describe provisions for cover material for long-term care erosion control, filling other depressions, maintaining berms, and general maintenance of the phosphogypsum stack, and shall specify the anticipated source and amount of material necessary for proper closure of the stack.

(d) The type of leachate control system proposed. The leachate control system shall be designed to prevent leachate from causing violations of water quality standards beyond the approved zone of discharge for the phosphogypsum stack system in accordance with Chapters 62-520 and 62-522, F.A.C.

(e) Compliance with groundwater protection requirements. The closure design plan shall show how the phosphogypsum stack system will meet the water quality standards of Chapter 62-520, F.A.C. The groundwater monitoring plan and sampling schedule may be adjusted for a phosphogypsum stack system where groundwater contamination is not evident or corrective measures have been taken to correct contamination.

(f) The proposed method of stormwater control. This shall include control of stormwater occurring on the phosphogypsum stack system. Stormwater or other surface water which mixes with leachate shall be considered to be leachate and shall be treated to meet the applicable water quality standards of Chapter 62-302, F.A.C., at the point of discharge. The stormwater control plan shall meet the requirements of Chapter 62-25, F.A.C.; however, nothing herein shall be construed to preclude application of the requirements of the appropriate water management district.

(g) The proposed method of access control. The closure design plan shall describe how access to the closed phosphogypsum stack system shall be restricted to prevent any future waste dumping or use of the phosphogypsum stack system by unauthorized persons. Restricted access shall remain in force until the phosphogypsum stack system is stabilized and there is no evidence that the property is being used as an unauthorized dump site.

(h) A description of any proposed final use of the phosphogypsum stack system.

(i) Closure construction quality assurance plan. A detailed construction quality assurance plan shall be developed for construction activities associated with the closure of the phosphogypsum stack system, including each component of the final cover system. The plan shall specify quality assurance test procedures and sampling frequencies. Records shall be kept to document construction quality and demonstrate compliance with plans and specifications. Upon completion of closure activities a final construction quality assurance report shall be submitted to the Department, prepared by a registered professional engineer. The final report shall include at least the following information:

1. Listing of personnel involved in closure construction and quality assurance activities;

2. Scope of work;

3. Outline of construction activities;

4. Quality assurance methods and procedures;

5. Test results (destructive and non-destructive, including laboratory results); and

6. Record drawings.

(7) Closure operation plan. A closure operation plan shall be included in the closure plan, and shall:

(a) Describe the actions which will be taken to close the phosphogypsum stack system, such as placement of cover, grading, construction of berms, ditches, roads, retention-detention ponds, installation or closure of wells and boreholes, installation of fencing or seeding of vegetation, protection of on-site utilities and easements;

(b) Provide a time schedule for completion of the closing and long-term care;

(c) Contain appropriate references to the closure design plan, area information report, groundwater monitoring plan, and other supporting documents;

(d) Describe the proposed method of demonstrating financial responsibility for the long-term monitoring and maintenance;

(e) Indicate any additional equipment and personnel needed to complete closure of the phosphogypsum stack system; and

(f) Describe any proposed use of the system for water storage or water management.

(8) Certification by registered professional engineer. Information, plans, and drawings presented in support of a closure plan shall be prepared under the direction of, and certified by, a registered professional engineer authorized to practice in the State of Florida in accordance with the provisions of Chapter 471, F.S. A letter of appointment shall be submitted by the proper company official confirming that the engineer is authorized to prepare plans and specifications. The professional engineer or another qualified engineer shall be required to make periodic inspections during the closing of the phosphogypsum stack system to insure closure is being accomplished according to the closure plan.

(9) Nothing in the section is intended to preclude the construction of a lined cooling pond on top of an inactive phosphogypsum stack, as long as the pond is constructed in accordance with the applicable provisions of this chapter, and as long as the design is included in the closure plan. Within such a cooling pond, the requirements for minimizing ponding and establishing vegetation cover are not applicable.

Specific Authority 403.061, 403.4154, 403.704 FS. Law Implemented 403.4154, 403.707 FS. History–New 3-25-93, Formerly 17-673.610.