62-701.430. Vertical Expansion of Landfills

(1) Applicability. Construction of a solid waste disposal unit on top of or against the side slopes of a previously filled landfill, whether active, closed, or inactive is considered vertical expansion of that landfill. Vertical expansion shall require either a modification of the landfill permit, or a new permit if the landfill has been closed. If a landfill has not been closed at the time of the vertical expansion, then the closure requirements of that landfill will apply at the time of closure of the vertical expansion, unless the closure requirements for the vertical expansion are more stringent. The following requirements shall apply:

(a) The vertical expansion shall not cause or contribute to any violations of water quality standards or criteria, shall not cause objectionable odors, and shall not adversely affect the closure design of the existing landfill.

(b) For vertical expansion over lined landfills, no interface liner is required between the old and new landfill slopes.

(c) For vertical expansion over landfills that were not constructed with a liner system or were not constructed in accordance with permit requirements, the vertical expansion shall comply with all the requirements of Rule 62-701.400, F.A.C., with the following exceptions:

1. Side slopes of six feet horizontal to one foot vertical rise or steeper require the installation of a single geomembrane slope liner overlain by a leachate collection and removal system;

2. The slope liner shall consist of a 60-mil or thicker HDPE geomembrane.

3. The liner shall be protected from physical damage by a 24-inch thick protective layer above the liner and a bedding layer below the liner at least 24 inches thick to protect against the calculated differential settlement.

4. In all vertical expansion construction, grades shall slope toward the new expansion area.

5. If the vertical expansion consists exclusively of construction and demolition debris, the expansion must comply with the requirements of Rule 62-701.730, F.A.C., as well as paragraph (a) of this subsection. If the vertical expansion consists exclusively of land clearing debris, the expansion must comply with the requirements of Rule 62-701.803, F.A.C., as well as paragraph (a) of this subsection.

6. If the vertical expansion consists of a composting operation, it must meet the requirements of Chapter 62-709, F.A.C., as well as paragraph (a) of this subsection.

7. If the vertical expansion consists of a Class III landfill, the provisions of paragraph 62-701.340(3)(c), F.A.C., apply.

(d) The provisions of subsection 62-701.610(1), F.A.C., are applicable to all operations, including recycling operations, conducted on top of closed landfills.

(2) Construction requirements. The design for the vertical expansion shall also provide calculations and supporting information on the following factors:

(a) Construction on the slopes of a filled landfill requires a determination of foundation stability in accordance with Rule 62-701.410, F.A.C., and calculations for the total settlement of the waste in the existing landfill and the waste that will be disposed of in the new disposal area to be constructed. Total settlement calculations shall address both compression and differential settlement and shall be based on worst case predictions. Total settlement calculations shall show the final elevations of the liner systems, that gravity drainage will be maintained, and that no other component of the design will be adversely affected.

(b) The vertical expansion design shall achieve a minimum factor of safety 1.5 using peak strengths for:

1. The liner system stability for liner systems installed over existing landfill slopes to prevent sliding along the interface between liner system components; and

2. Deep stability, to prevent sliding along all potential failure surfaces through the waste mass, along the liner systems, and through the foundation soils.

(c) Surface water management during construction of the vertical expansion over the slopes of an existing landfill shall be consistent with subsection 62-701.400(9), F.A.C., and shall require proper design of the drainageway at the interface between the existing slopes and vertical expansion area. The design shall;

1. Prevent infiltration into the existing and new landfills;

2. Minimize erosion of cover materials;

3. Carry the calculated flow; and

4. Comply with the cover requirements.

(d) A gas control system shall be installed to vent gas from the interface between the existing landfill slopes and the vertical expansion slopes to prevent accumulation of gas under the new liner system. Gas-venting shall include a gas-venting layer or system of gas collection wells under the entire slope that will be covered by the new liner system.

Rulemaking Authority 403.061, 403.704 FS. Law Implemented 403.702, 403.704, 403.707 FS. History–New 1-6-93, Amended 5-19-94, Formerly 17-701.430, Amended 5-27-01, 1-6-10, 2-15-15.