62-673.400. Phosphogypsum Stack System Construction Requirements

(1) Minimum design standards. The requirements of this rule are the minimum standards for constructing a phosphogypsum stack system. Nothing in this rule shall be construed to prevent the Department from imposing more stringent standards if necessary to protect the environment and the public health and safety due to site specific conditions. An applicant whose system design meets the design standards of this rule will be presumed to provide reasonable assurance that the performance standards of subsection 62-673.340(1), F.A.C., will be met. This presumption may be overcome through a demonstration that site-specific or situation-specific circumstances require the imposition of stricter standards in order to provide such reasonable assurances.

(2) Liner and leachate control systems. Phosphogypsum stacks shall be constructed with composite liners and leachate control systems. Cooling ponds shall be constructed with composite liners.

(a) Liners shall be:

1. Constructed of materials that have appropriate physical, chemical, and mechanical properties to prevent failure due to physical contact with the phosphogypsum, process wastewater or leachate to which they are exposed, climatic conditions, the stress of installation, and other applied stresses and hydraulic pressures which are anticipated during the operational and closure period of the system. The supplier of materials for the liner components shall provide test information accepted by the engineer of record, that supports the capabilities of the materials to meet these needs;

2. Installed upon a base and in a geologic setting capable of providing structural support to prevent overstressing of the liner due to settlements and applied stresses;

3. Constructed so that the bottom of the liner system is not subject to fluctuations of the ground water so as to adversely impact the integrity of the liner system;

4. Designed to resist hydrostatic uplift if the liner is located below the seasonal high ground water table; and

5. Installed to cover all surrounding earth which could come into contact with the phosphogypsum, process wastewater or leachate.

(b) Liner design standards. The synthetic component of composite liners shall consist of a 60-mil or thicker geomembrane liner with a maximum water vapor transmission rate of .24 grams per square meter per day as determined by ASTM Method E96-80, procedure BW, “Test Methods for Water Vapor Transmission of Materials,” Sections 04.06, 08.03, and 15.09, which document is incorporated herein by reference. The other component of the composite liner shall consist of either of the following:

1. A layer of compacted soil at least eighteen inches thick, placed below the geomembrane, with a maximum hydraulic conductivity of 1 × 10-7 centimeters per second, constructed in six-inch lifts. The geomembrane liner component shall be installed in direct and uniform contact with the compacted soil component to retard leachate migration if a leak in the flexible membrane liner should occur.

2. A layer of mechanically compacted phosphogypsum at least 24 inches thick, placed above the geomembrane, with a maximum hydraulic conductivity of 1 × 10-4 centimeters per second.

(c) Any proposed composite liner design shall be accompanied by a detailed construction quality assurance plan prepared in accordance with the requirements of subsection 62-701.400(8), F.A.C., describing in detail how the design will be properly constructed in the field. For composite liners using compacted phosphogypsum, the quality assurance plan shall place particular emphasis on protection of the geomembrane during placement and compaction of the phosphogypsum, and on prompt placement of phosphogypsum on the geomembrane.

(d) The following liner design standards are adopted by reference and incorporated herein:

1. Paragraph 62-701.400(3)(d), F.A.C., standards for geomembranes, except for subparagraphs 2. and 3.;

2. Paragraph 62-701.400(3)(e), F.A.C., specifications for geosynthetic components. In addition, the synthetic liner material shall be subjected to continuous spark testing at the production facility prior to delivery to the site for installation. If the continuous spark testing detects any defect, the tested material must be rejected and not delivered to the site;

3. Paragraph 62-701.400(3)(f), F.A.C., standards for soil components;

4. Subsection 62-701.400(7), F.A.C., liner systems construction quality assurance; and

5. Subsection 62-701.400(8), F.A.C., soil liner construction quality assurance.

(e) Leachate control system standards.

1. A perimeter underdrain system designed to stabilize the side slopes of the phosphogypsum stack shall be installed above the geomembrane liner.

2. Perimeter drainage conveyances used in the leachate control system shall either consist of covered or uncovered ditches which are lined continuously with the phosphogypsum stack liner, or of chemically compatible leachate collection pipes. Covered ditches shall have maintenance manholes installed at appropriate intervals. Piped systems shall have manholes or appropriate cleanout structures at appropriate intervals. In the event that unusual site specific hydrogeologic or structural conditions exist, the Department reserves the right to impose stricter standards consistent with obtaining appropriate reasonable assurance that ground water and surface water quality standards will be met.

3. All toe drain or leachate collection systems must be constructed within the lined system.

(f) Liquid containment and conveyance systems.

1. Composite liners shall be used on all liquid containments and conveyances associated with phosphogypsum transport, cooling water, and return of process wastewater. Exceptions are pumped flow systems contained in pipes.

2. Pump and piping systems associated with the transport of phosphogypsum or process wastewater and which cross surface waters must be double contained with chemically compatible materials in a manner that assures that all materials under pumped flow are contained within a lined system in the event of a leak or piping system failure.

Specific Authority 403.4154, 403.704, 403.061 FS. Law Implemented 403.4154, 403.707 FS. History–New 3-25-93, Formerly 17-673.400.