Leachate Management Plan Phases I-VI and The Capacity Expansion Area Southeast County Landfill Hillsborough County, Florida

Hillsborough County Solid Waste Management Department (SWMD) 332 N. Falkenburg Road Tampa, FL 33619

10150 Highland Manor Dr., Ste. 320 Tampa, FL 33610

813-621-0080

092260029.00 | April 2026

Section Page

Leachate Management Plan www.scsengineers.com Page i

Table of Contents

Leachate Management Leachate Generation Leachate Collection Systems

Phases I-VI Leachate Collection Capacity Expansion Area Leachate Collection

Section 7 Section 8 Section 9

Biosolids Composting Facility Leachate Collection Renewable Natural Gas Facility

Leachate Transmission Phases I-VI

Pump Station A (PS-A) Pump Station B (PS-B) Pump Station 2 (PS-2) Dewatering Wells

Capacity Expansion Area Section 7 – Pump Station 7 (PS-7) Section 8 – (No Pumping Systems) Section 9 – Pump Station 9 (PS-9)

Main Leachate Pump Station (MLPS) Leachate Storage Tank (T1)

T1 Secondary Containment System T1 Liquid Level Monitoring T1 Exterior and Interior Inspections

Leachate Treatment and Reclamation Facility (LTRF) Effluent/Leachate Storage Tank (T6)

T6 Secondary Containment System T6 Liquid Level Monitoring T6 Exterior and Interior Inspections Acid Mixer and Tank

Leachate Storage Tanks (T7 and T8) T7 and T8 Secondary Containment System http://www.scsengineers.com/

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Table of Contents

T7 and T8 Liquid Level Monitoring T7 and T8 Exterior and Interior Inspections

Leachate and Effluent Disposal Effluent/Leachate Storage Pond B Leachate Evaporator Facility Volume Reduction Leachate and Effluent Evaporation Via Truck-Mounted Spraying Effluent and Leachate Truck Loading Facilities

Truck Loading Procedures Wastewater Treatment Facilities

Leachate Flow Measurement, Data Collection, and Reporting General Leachate Flow Measurement

Effluent Quality Biosolids Quantity and Disposal

Phases I-VI Monitoring Flow Measurement PS-B Settlement Plates Bottom Liner Clay Evaluation LCRS Monitoring Locations

Capacity Expansion Area Monitoring Flow Measurement Leachate Detection Action Leakage Rate

Main Leachate Pump Station Leachate Treatment and Reclamation Facility

Maintenance and Inspection Leachate Collection System Schedule for Maintenance and Inspection Storage Tank Maintenance and Inspection RNG Facility

Contingency Plans Replacement of Flow Meters LTRF Storage Tank Secondary Containment Spill Countermeasures T7 and T8 Storage Tanks Secondary Containment Spill Countermeasures

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Table of Contents

Figure 3.1 Phases I-VI Leachate Collection Figure 3.2 Capacity Expansion Area Leachate Collection System Figure 4.1 Leachate Management System Schematic

Tables

Table 9.4.2 Private Leachate Treatment and Disposal Facilities Table 10.2.4 Liquid Levels Maintenance Schedule Table 11.2 Schedule For Maintenance

Appendices

Appendix A Leachate Reporting and Inspection Forms

Figures

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LEACHATE MANAGEMENT

The Hillsborough County Southeast County Facility (Facility) includes the Southeast County Landfill (SCLF), which is permitted by the Florida Department of Environmental Protection (FDEP) as a Class I landfill for Phases I-VI and the Capacity Expansion Area (CEA). This Leachate Management Plan (LMP) includes Phases I-VI and Sections 7, 8, and 9 of the CEA.

This plan gives SCLF employees a general understanding of the requirements for managing the leachate generated from the Class I landfill operations from the Phases I-VI and CEA disposal areas.

As defined in Rule 62-701.200(59), Florida Administrative Code (FAC), leachate is liquid that has passed through or emerged from solid waste and may contain soluble, suspended, or miscible materials. Leachate must be contained and kept separate from any groundwater or surface waters.

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LEACHATE GENERATION

One of the goals of the landfill design and daily operation is to minimize leachate production from the landfill to reduce the cost associated with leachate treatment and thus minimize the potential environmental contamination risks. The methods described in this section can be used separately or simultaneously to achieve leachate reduction.

Leachate is generated as water passes through solid waste or as liquids drain from solid waste materials. Water may be from stormwater infiltration, irrigation, groundwater, or other sources added to the waste material. Liquids from the solid waste include moisture from food or waste products and fluids disposed of in the waste. Water and liquids that drain through or from the waste materials eventually drain via gravity into the collection systems at the bottom of the Class I disposal areas.

Once collected, the leachate is pumped to various storage locations on-site including leachate storage tanks or the leachate/effluent storage pond (Pond B). From the storage tanks, the leachate can be conveyed to the on-site Leachate Treatment and Reclamation Facility (LTRF) for treatment or hauled off-site for treatment and disposal at a permitted wastewater treatment facility. Leachate may also be conveyed from Pond B to the Leachate Evaporator Facility (LEF) for volume reduction.

Liquids, including precipitation, collected on the LEF containment pad and liquid residuals from the volume reduction process will be treated as leachate.

In addition, leachate is generated in the form of condensate from the collection of landfill gas (LFG) from Phases I-VI and the CEA. Condensate is managed by several methods, including drainage back to the landfill or collection in sumps at low areas. Condensate produced at the Renewable Natural Gas (RNG) Facility is collected at the RNG Facility’s condensate sump and is transported back to the Leachate Collection and Removal System (LCRS) and removed for disposal via existing infrastructure and pump stations. While LFG condensate collection and transmission are not addressed in the Leachate Management Plan, condensate management is addressed within the Gas Collection and Control System (GCCS) Plan for the SCLF referenced as part of the SCLF Title V operating permit. This plan should be referenced for details regarding condensate management.

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LEACHATE COLLECTION SYSTEMS

The leachate collection system for Phases I-VI and the leachate collection and detection systems for the CEA are depicted in Figure 3-1 and Figure 3-2, respectively. Additional descriptions of these systems are provided in the following sections.

PHASES I-VI LEACHATE COLLECTION

Phases I-VI of the Facility were constructed directly above a waste clay settling area for a former phosphate mine known as Lonesome Phosphate Mine or Boyette Mine. The Phases I-VI landfill is approximately 162.4 acres. The settling area, also known as Settling Area No. 1, was built on natural ground with a perimeter dike constructed of sand borrowed from surrounding areas. As part of the phosphate mining operations, waste phosphatic clay and other soils were washed and phosphate minerals removed from the surrounding soils.

The washed waste phosphatic clays and soils were pumped to the settling areas and allowed to settle to the bottom of the settling ponds. The low-permeability waste phosphatic clays formed the bottom containment liner for the disposal of waste in the Phase I-VI area. A single layer of 36-mil chlorosulfonated polyethylene (CSPE) tied into the waste phosphatic clay layer as a side containment liner barrier.

The LCRS for Phases I-VI consists of crushed granite rock and tire-chip-filled trenches, 8-inch diameter perforated Schedule 80 polyvinyl chloride (PVC) pipes in granite rock-filled trenches, and 8-inch diameter perforated high density polyethylene (HDPE) pipes in granite rock-filled trenches. The gravel and tire-filled trenches drain to the 8-inch pipes which then drain to Pump Station B (PS-B) located in the Phase VI disposal area. PS-B was designed to be the ultimate low point for the entire footprint of Phases I-VI after final placement of waste material and loading of the waste phosphatic clays. As the waste phosphatic clays are loaded, the clays settle. Excess water from within the clays is squeezed out during the loading of the clays and enters the leachate collection system.

CAPACITY EXPANSION AREA LEACHATE COLLECTION

Section 7

Leachate Collection System

Section 7 of the CEA landfill is approximately 12.5 acres. The dimensions of Section 7 are approximately 750 feet long (southwest to northeast) and 800 feet wide (northwest to southeast).

Section 7 was designed with a double-liner system including one for leachate collection on the primary liner and the other for detection (secondary liner) of any leachate that may leak through the collection liner. A 300-mil bi-planar geocomposite was installed on the top of each of the 60-mil HDPE geomembranes to convey leachate toward collection trenches. Twelve inches of drainage sand and 12 inches of chipped tires were placed above the primary collection system to provide additional drainage collection and provide puncture protection of the underlying HDPE liners.

200'

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EFFLUENT TANK AT THE

LEACHATE TREATMENT

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WAGA RNG FACI LITY

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FIGURE 3-1. PHASES I-VI LEACHATE COLLECTION AND REMOVAL SYSTEM

APRIL 2026

HILLSBOROUGH COUNTY

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740.48'

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AND SECTION 9 RISER PUMP

LEACHATE SAMPLING POINT

007 (APPROXIMATE LOCATION)

18"Ø HDPE RISER PIPE

PUMP STATION 7

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FIGURE 3-2. CAPACITY EXPANSION AREA (SECTIONS 7, 8, AND 9) - LEACHATE COLLECTION AND REMOVAL SYSTEM

HILLSBOROUGH COUNTY

April 2026

1" = 200'

0 200100

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SECTION 7, 8, AND 9 BOUNDARY

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HDPE FORCEMAIN

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CEA SECTION PUMP STATION

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Leachate travels through the primary geocomposite and sand/tire-chip drainage layer and is collected in the leachate collection trench. This trench consists of 8-inch perforated HDPE leachate collection pipes and gravel wrapped in a geotextile to minimize migration of sand into the pipes.

Leachate that collects in the trench flows to a collection header and then toward a collection sump in the southwest corner of Section 7. The sump was designed as the lowest point in Section 7 and was filled with gravel. A riser pipe was installed in the gravel fill of the sump and contains a submersible pump for leachate removal.

Leachate Detection System

The leachate detection system of Section 7 consists of a bi-planar geocomposite between the primary and secondary geomembranes. The geocomposite drains leachate toward an 8-inch perforated HDPE pipe in a gravel-filled trench. The lateral pipes drain to a main header on the southwest end of Section 7. The main header drains to the low point of Section 7 containing a sump with gravel fill and a riser pipe. Leachate is removed from the Section 7 leachate detection system via the riser pipe using an above-grade pump.

During standard practices, the detection system is expected to collect a small volume of leachate.

Leakage rates collected in the detection system will be used to monitor the performance of the collection system. The action leakage rate (ALR) for the CEA is discussed in Section 10.3.2.

Section 8

Leachate Collection System

Section 8 of the CEA is approximately 6.8 acres. The dimensions of Section 8 are approximately 500 feet long (southwest to northeast) and 660 feet wide (northwest to southeast). Section 8 was designed with a double-liner system including one for leachate collection (primary liner) and the other (secondary liner) for detection of any leachate that may leak through the collection liner.

A 300-mil tri-planar geocomposite was installed on the top of each of the 60-mil HDPE geomembranes to convey leachate toward leachate collection trenches. Twelve inches of drainage sand and 12 inches of chipped tires were placed above the primary collection system to provide additional drainage collection and provide puncture protection of the underlying HDPE liners.

The design of Section 8 included connecting the leachate collection and detection system components to Section 7. Therefore, leachate travels through the upper geocomposite and sand/tire drainage layer and is collected in the leachate collection trenches in Section 8. These trenches consist of an 8-inch perforated HDPE leachate collection pipe and several feet of gravel wrapped in woven geotextile. Leachate that collects in the Section 8 trenches continues to flow though Section 7 trenches. Once in the Section 7 collection system, leachate drains to the sump in the southwest corner of Section 7 where it is removed from the sump by the submersible pump in the riser pipe.

Leachate Detection System

The leachate detection system of Section 8 consists of a tri-planar geocomposite between the primary and secondary geomembranes. The Section 8 tri-planar geocomposite was connected to the Section 7 bi-planar geocomposite. The geocomposite drains leachate to 8-inch perforated HDPE pipes in gravel filled trenches. The trenches flow through Sections 7 and 8. The lateral pipes drain to

Page - 7 a main header on the southwest end of Section 7. The main header drains to the leachate sumps in the southwest corner of Section 7 as described in previous sections.

During standard practices the detection system should collect a small amount of leachate. Leakage rates collected in the Section 8 detection system cannot be measured independently from Section 7;

however, since each system is connected, the total leakage measured in the Section 7 sump will be used to monitor the performance of the Sections 7 and 8 leachate detection systems.

Section 9

Leachate Collection System

Section 9 of the CEA landfill is approximately 15.2 acres. Section 9 is approximately 980 feet long (southwest to northeast) and 580 feet wide (northwest to southeast). The primary leachate collection system is composed of a combination of synthetic materials and natural granular materials. A geocomposite consisting of an HDPE geonet with the top and bottom sides bonded to a geotextile is directly above the primary 60-mil HDPE geomembrane. The geocomposite is overlain by a 12-inch-thick natural granular (sand) drainage layer and a 12-inch-thick chipped-tire drainage layer.

Leachate flows by gravity to a central leachate collection trench that conveys the leachate to the leachate collection sump on the south side of Section 9. The leachate collection pipe is a perforated 8-inch-diameter SDR 11 HDPE pipe surrounded by gravel and geotextile. From the sumps, leachate is pumped via a 6-inch SDR 11 HDPE forcemain to the LTRF located northeast of Sections 7 and 8.

As part of the construction of Tank 7 (T7) and Tank 8 (T8), the PS-9 forcemain was retrofitted to allow PS-9 to pump directly to the Main Leachate Pump Station (MLPS) located southeast of the Section 9 leachate collection sump.

Leachate Detection System

The leachate detection system for Section 9 includes a geocomposite consisting of a HDPE geonet with the top and bottom sides bonded to a geotextile installed between the primary and secondary geomembranes. Leachate entering the leachate detection system flows by gravity through the geonet to the leak-detection trench. The trench, constructed at a slope of approximately 0.75%, conveys leachate to a leachate-detection sump on the south side of Section 9. From the sump, leachate is pumped via a 6-inch SDR 11 HDPE forcemain to the LTRF or MLPS.

During standard practices, the detection system is expected to collect a small volume of leachate.

Leakage rates collected in the detection system will be used to monitor the performance of the collection system. The action leakage rate for the CEA is discussed in Section 10.3.2.

BIOSOLIDS COMPOSTING FACILITY LEACHATE COLLECTION

The SWMD operates a Biosolids Composting Facility (BCF) at the Facility. BCF operations are permitted under the Hillsborough County Falkenburg Road Advanced Wastewater Treatment Facility (WWTF) Domestic Wastewater Facility Permit Number FL0040614-022-DW1P/NR and is managed in accordance with the current Biosolids Composting Facility Operations and Maintenance Plan, which is maintained on-site.

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RENEWABLE NATURAL GAS FACILITY

The RNG Facility is located north of the Phase I-VI disposal area, and has the ability to independently accept LFG that meets minimum quality requirements for processing into RNG. The processed RNG is injected into a TECO pipeline to be sold as a renewable energy commodity. The RNG Facility is operated by WB Hillsborough LLC (WAGA), who maintains a separate RNG Facility specific Operations and Contingency Plan at the RNG Facility. Although the RNG Facility has the ability to operate independent from existing GCCS and Leachate Management System Infrastructure, LFG condensate is returned to the LCRS as a product of the landfill and is managed in accordance with the approved LFG Condensate Management Plan.

LEACHATE TRANSMISSION

A schematic of the leachate management system at the SCLF is shown in Figure 4-1. The following sections provide additional details for the transmission components of the leachate management system at the SCLF.

PHASES I-VI

Pump Station A (PS-A)

PS-A consists of an 8-foot inside-diameter below-grade concrete sump with a single submersible pump. From PS-A, leachate is pumped to the MLPS via forcemain. The pump operation is set with the “on” float at 30 inches from the sump bottom and the “off” float at 15 inches from the sump bottom.

If a high-level condition occurs, the PS-A sump control panel will shut down Pump Station B (PS-B). It will also transmit a signal, via a transceiver, with the sump condition to the telemetry control computer. If PS-A will be inoperable for more than 8 hours, leachate from PS-B will be pumped through the bypass line directly to the MLPS or Pond B.

Pump Station B (PS-B)

PS-B sump (located in Phase VI) is the primary leachate collection point for Phases I-VI. Upon consolidation of the phosphatic clay liner, the low point for the final collection and removal of leachate within the landfill is projected to be at the PS-B sump location. The LCRS for Phase I-VI was designed to drain to the PS-B sump.

PS-B sump consists of an 8-foot square (inside dimension) below-grade concrete vault. The vault has two 18-inch diameter HDPE horizontal access pipes, the main access pipe leading to PS-A, and an alternate access pipe leading toward the western perimeter of the landfill between cleanouts 4-1 and 6-1.

The primary pumps used to remove leachate from the PS-B sump are self-priming pumps each with a capacity of 150 gallons per minute (gpm). If the primary pumps fail, the operations contractor can obtain a secondary vacuum-assisted diesel pump that may be used as backup. PS-B sump is equipped with a level indicator located at the control panel near PS-A, and the SWMD monitors the liquid level daily to ensure that the levels noted below are maintained.

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PS-B pumps leachate to PS-A via a vacuum-assisted pump. The PS-B pump is controlled by a bubbler liquid level measurement system with an “on” sensor is set at the PS-B maintenance level reading of 30-inches, and the “off” sensor is set at 15 inches from the bottom. The PS-B maintenance levels and operational procedures are outlined in Table 10.2.4. The settings provide for free flow of leachate into the PS-B sump from the surrounding Phase I-VI disposal areas.

M

M

M

M

M

M

M

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M

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T6 TRUCK LOADING STATION

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T1 TRUCK LOADING STATION

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PS-7

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PS-9

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CAPACITY EXPANSION AREA

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T6 EFFLUENT/LEACHATE STORAGE TANK

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MLPS (240 GPM)

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PS-A (150 GPM)

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PS-B (150 GPM)

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MLPS TRUCK LOADING STATION

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T1 LEACHATE STORAGE TANK

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LTRF

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(PERMITTED WASTEWATER DISPOSAL FACILITY)

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PHASE I - VI

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PS-A BYPASS

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TRUCK SPRAY EVAPORATION ON WORKING FACE

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EFFLUENT/LEACHATE STORAGE POND B (236,000 GAL)

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PS-2

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PHASE I & PHASE II DEWATERING WELLS

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BIOSOLIDS COMPOSTING FACILITY

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(PERMITTED WASTEWATER TREATMENT PLANT)

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LEACHATE EVAPORATOR FACILITY

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(SEE NOTE 2)

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T7 LEACHATE STORAGE TANK

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T8 LEACHATE STORAGE TANK

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WAGA

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FIGURE 4-1. LEACHATE MANAGEMENT SYSTEM SCHEMATIC

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APRIL 2026

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HILLSBOROUGH COUNTY

AutoCAD SHX Text VALVE VALVE NORMALLY CLOSED PUMP METER FLOW ARROW PIPING TRUCKING SPRAY NOZZLES FOR EVAPORATION

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AutoCAD SHX Text NOTE: 1. NORMALLY CLOSED VALVES SHOULD ONLY BE OPENED UNDER THE NORMALLY CLOSED VALVES SHOULD ONLY BE OPENED UNDER THE SUPERVISION OF THE SITE SUPERVISOR. 2. VALVES WILL BE REMOTELY CONTROLLED TO ALLOW FLOW INTO VALVES WILL BE REMOTELY CONTROLLED TO ALLOW FLOW INTO POND B IN ORDER TO MAINTAIN LIQUID LEVELS FOR THE EVAPORATOR. 3. THIS SCHEMATIC IS SIMPLIFIED FOR NORMAL OPERATIONS AND DOES THIS SCHEMATIC IS SIMPLIFIED FOR NORMAL OPERATIONS AND DOES NOT INCLUDE EVERY VALVE, METER, AND PUMP.

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Pump Station 2 (PS-2)

Pump Station 2 (PS-2) consists of a vacuum assisted pump with a 3-inch HDPE suction line into the Phase II clean out 2-1 (CO 2-1). The PS-2 pump is controlled with a liquid level indicator located adjacent to the intake pipe, within the CO 2-1 header. The pump discharges via a 3-inch HDPE buried forcemain directly into the MLPS. The pump is operated by SWMD staff to supplement leachate removal from Phase II and the Phase II Cut-off Trench. The primary goal of this pump is to maintain the leachate level in Monitoring Port No. 2 (MP 2-2) and CO 2-1 below 30-inches. The CO 2-1 connection to the Phase II Cut-off Trench and the Phase II header allows PS-2 to influence the liquid level in MP 2-2. The leachate quantities pumped from CO 2-1 via the PS-2 pump are recorded by an electronic flow meter.

Dewatering Wells

Dewatering wells were installed to provide supplemental leachate removal from Phases I and II as part of the June 26, 2017 Corrective Action Plan. A well nest was installed in Phase I and in Phase II.

Each well nest consists of two 8-inch diameter HDPE well casings set within one 36-inch diameter borehole that spans from ground surface, through the waste, to 1-foot below the top of the clay liner.

Due to settlement and shifting within the waste surrounding the dewatering wells, some of the casings became pinched below the surface and a pump is no longer able to be removed or installed.

Each of the well casings that allow a pump to descend to the bottom of the casing can contain a pneumatic pump connected to a 3-inch diameter HDPE buried forcemain conveying the leachate to the MLPS. The wells are topped with an all-weather polyethylene dual extraction well cap and 2-inch LFG wellhead. The Phase I leachate extraction wells are designated DW 1-1 and DW 1-2, and the Phase II leachate extraction wells are designated DW 2-1 and DW 2-2. Pneumatic pump counters are used to estimate the leachate quantities pumped from the wells.

CAPACITY EXPANSION AREA

Section 7 – Pump Station 7 (PS-7)

The leachate collection and leachate detection system piping for Sections 7 and 8 drain to sumps in the southwest corner of Section 7 as shown in Figure 3-2. The leachate detection sump is pumped to the leachate collection sump by an above-grade pump located at PS-7. The leachate collection sump pumps leachate using a submersible pump in the sump to the MLPS or Pond B via an underground forcemain.

There are separate pumps for the leachate collection (submersible pump) and detection (above grade pump) sideslope risers. The levels in each sump are controlled with pressure transducers at the bottom of the riser pipes. These transducers are programmed for a high-level alarm at 48 inches, pump on at 24 inches, and pump off at 12 inches. All elevations are from the bottom of the Section 7 sump. Flow measurements are taken using readings from magnetic flow meters on each discharge line. Separate sampling ball valves allow separate leachate samples to be taken from either the collection or detection sumps.

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Section 8 – (No Pumping Systems)

Section 8 was constructed by connecting the leachate collection and detection systems to the Section 7 systems. No pumping systems are included in the Section 8 design. Section 8 uses the sumps and pumps for Section 7 to pump leachate to the MLPS or Pond B.

Section 9 – Pump Station 9 (PS-9)

The Section 9 area includes sideslope riser pipes—two for the primary leachate collection and one for the leachate detection systems—with submersible pumps. All the pumps for the Section 9 area are controlled by a separate control panel located on the south side of Section 9. Leachate is conveyed by a buried forcemain which connects to the existing forcemain on the south side of Section 7. The forcemain then continues to the leachate storage tank (T1) or effluent/leachate storage tank (T6) northeast of the CEA. As part of the construction of Tank 7 (T7) and Tank 8 (T8), the PS-9 forcemain was retrofitted to allow PS-9 to pump directly to MLPS.

The Section 9 pumps are controlled by a bubbler level sensing system at the PS-9 control panel. The standard practice bubbler settings for the leachate collection pumps from the bottom of the sump are high-level alarm at 36 inches, lag pump on at 33 inches, lead pump on at 27 inches, and low level alarm at six inches. The standard practice bubbler settings for the detection pump from the bottom of the sump are high-level alarm at 36 inches, pump on at 27 inches, and pump off at 21 inches.

In addition, the Section 9 pumps are deactivated when the leachate storage tank (T1) senses a high-level alarm. Similarly, Section 9 pumps will not convey leachate to the MLPS in the event of a high-level alarm at the MLPS.

MAIN LEACHATE PUMP STATION (MLPS)

The MLPS consists of a 7-foot-square (inside dimension) below-grade concrete sump with dual submersible pumps (i.e., one operating and one stand-by). Each submersible pump is rated to pump at a maximum discharge rate of 240 gpm. The operating pump is set for a 24-hour operation cycle with the “on” float at 48 inches from the sump bottom and the “off’ float at 24 inches from the sump bottom.

If a high-level condition occurs at the MLPS sump, the control panel will shut down PS-7, PS-9, PS-A, PS-B, PS-2, and all pneumatic pumps. It will also transmit a signal, via a transceiver, with the sump condition to the telemetry control computer. Maintenance and inspection of the MLPS pump are described in Section 11.0.

From the MLPS, leachate is pumped to the 575,000-gallon leachate storage tank (T1), the 575,000-gallon effluent/leachate storage tank (T6) [effluent/leachate storage tank (T6)—for emergency use only, as described in Section 7.0] at the LTRF, or to one of the 1,000,000 gallon leachate storage tanks located adjacent to the MLPS (T7 and T8).

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LEACHATE STORAGE TANK (T1)

Leachate from Phases I-VI and the CEA is currently stored in a 575,000-gallon (maximum capacity) glass-fused-to-steel aboveground raw leachate holding tank before being treated or hauled. The leachate level in the leachate storage tank (T1) is maintained to provide for the maximum storage capacity possible. The leachate storage tank (T1) is maintained with an average low level of six feet (as measured from the bottom of the tank) or 173,000 gallons to ensure that enough leachate is available for the LTRF to operate 3 days without interruptions. When the level in the leachate storage tank (T1) is below six feet, leachate hauling and spray evaporation will be temporarily reduced or stopped. Similarly, an action level is established for a high level of 11 feet (from bottom of tank) in the leachate storage tank (T1). A level of 11 feet provides a storage capacity in the leachate storage tank (T1) of 259,000 gallons (4 days’ storage) to allow continuous operation of the landfill pump stations. When levels are above 11 feet, treatment, hauling, and/or spray evaporation will be increased.

If a high-level alarm condition occurs (at 17.5 feet) in the leachate storage tank (T1), the LTRF will continue to operate, and the MLPS, PS-9, and the LTRF filtrate pumps will be shut down. A signal indicating the leachate storage tank (T1) condition will be sent to the control computer in the LTRF.

When a high-level alarm condition exists, additional hauling trucks will be used to transport the leachate to a WWTF, thus lowering the leachate level in the tank.

T1 SECONDARY CONTAINMENT SYSTEM

The LTRF leachate tank system is located within a concrete containment area. The secondary containment area has two sumps for stormwater drainage with 6-inch diameter HDPE pipes. The gate valves from the HDPE pipes are normally closed, in the event of an uncontrolled release. The gate valves are occasionally opened to release stormwater from the impoundment as needed. The LTRF secondary containment area was designed to hold 110% of the volume of the largest storage tank in case of failure of the tanks. Therefore, the concrete flooring and containment walls will be inspected weekly for cracks or structural deficiencies as discussed in Section 5.3. Any cracks will be immediately sealed using flexible concrete grout. Any structural deficiencies will be identified and corrective action taken to repair the walls.

T1 LIQUID LEVEL MONITORING

The leachate storage tank (T1) contains an overflow pipe. The overflow pipe is installed outside of the storage tank, with the tank sidewall penetration within 30 inches of the top of the sidewall of the tank. The tank is equipped with liquid level indicators that are float-operated with a direct readout.

The level gauge boards are mounted in a highly visible location on the exterior of the tank. The tank level is recorded daily on the leachate reporting forms. An example form is provided in Appendix A.

T1 EXTERIOR AND INTERIOR INSPECTIONS

The following describes the inspections of the leachate storage tank (T1) and procedures to be followed after the inspections:

• Overfill Prevention System: The overfill prevention system components will be inspected weekly. These components include level sensors, gauges, high-level alarm, and automatic shutoff controls.

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• Tank Exterior: The exterior of the tanks and the secondary containment system will be inspected weekly for adequacy of the impressed current cathodic protection system, leaks, corrosion, and maintenance deficiencies. The control panel for the impressed current cathodic protection system (located on the outside of the secondary containment walls next to the truck loading station) will be inspected to ensure that it is working properly. In addition, the inspection includes evaluating structural damage to the tank, damage to the coating system, loose connections, corrosion, visible leaks, and maintenance deficiencies. The inspector will also look for any structural damage to the concrete slab, peeling of the paint system, and visible leaks.

• Tank Interior: The interior of the tanks will be inspected whenever the tanks are drained or at least every three years. The inspector will look for any damage to the interior coating system, structural damage, cracking of the tank, visible leaks, and any accumulation of sludge.

• Procedures for Corrective Actions: If inspections reveal any deficiencies with the tank or the secondary containment system that could result in the system’s failing to contain the leachate, the SWMD shall take immediate action to correct the situation by assessing the problem and coordinating the required actions. Failures or damage to the tanks will be repaired by the tank manufacturer or a designated contractor. The SWMD shall notify the manufacturer or designated contractor of the situation; the tank manufacturer or designated contractor will remediate the tanks and prepare a detailed damage-assessment report. FDEP will be notified in writing of the situation and of the proposed corrective action.

Inspection Reports: Inspection reports and reports of any remedial action measures taken will be maintained at the SCLF and will be made available to FDEP upon request. The weekly inspection report form is provided in Appendix A. All reports will be maintained for the life of the tanks and the containment system.

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LEACHATE TREATMENT AND RECLAMATION FACILITY (LTRF)

In December 1994, the SWMD constructed an on-site LTRF. The LTRF system and operation are described in detail in the General Process and Operation Manual for the Powder Activated Carbon Treatment (PACT) System, Volume III, prepared by Zimpro Environmental, Inc. dated March 1994.

Process tanks and equipment are maintained in accordance with General Process and Operation Manual for the Powder Activated Carbon Treatment (PACT) PACT System, dated March 1994.

After treatment, the leachate is pumped through a 4-inch-diameter single-walled HDPE pipe to the effluent/leachate storage tank (T6) described in Section 7.0. The effluent from the LTRF must meet pre-treatment standards before being pumped to a tanker truck for transport to Hillsborough County’s WWTFs.

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EFFLUENT/LEACHATE STORAGE TANK (T6)

The effluent/leachate storage tank (T6) is a welded steel aboveground tank with a maximum capacity of 575,000 gallons. The effluent/leachate storage tank (T6) receives treated leachate (effluent) from the LTRF and stores the effluent for transport to Hillsborough County’s WWTFs or a permitted wastewater treatment and disposal facility listed in Table 9.4.2. If leachate must be stored in the effluent/leachate storage tank (T6) from the MLPS while the leachate storage tank (T1) is repaired or inspected, normal operations at the LTRF will stop. Once the leachate storage tank (T1) is repaired or inspected and the LTRF resumes leachate treatment operations, the leachate stored in the effluent/leachate storage tank (T6) will be pumped back to the leachate storage tank (T1). The effluent/leachate storage tank (T6) will be cleaned of leachate before effluent storage resumes.

The following standard and special setting conditions are applicable to T6:

1. Pump effluent from the LTRF to the effluent/leachate storage tank (T6) (standard practice).

2. Pump effluent from the effluent/leachate storage tank (T6) to the truck loading area (standard practice).

3. Pump leachate from the MLPS to the effluent/leachate storage tank (T6) (special condition).

4. Pump leachate from the effluent/leachate storage tank (T6) to the leachate storage tank (T1) (special condition).

T6 SECONDARY CONTAINMENT SYSTEM

The secondary containment system for the effluent/leachate storage tank (T6) can contain a minimum of 110% of the total volume of the tank. The effluent/leachate storage tank (T6) provides 575,000 gallons of maximum storage.

The secondary containment system consists of a 60-mil HDPE geomembrane lined basin. The tank is constructed at the bottom of the basin on a reinforced concrete pad and surrounded by a 6-inch thick reinforced concrete walkway. The lined basin is connected at the walkway slab and runs up 3H:1V sideslopes where it is anchored at a 12-foot wide berm.

The precipitation collected in the containment area is pumped into the adjacent stormwater management system via a horizontal submersible pump and sideslope riser. The sideslope riser system includes an additional camlock connection to be used for emergency effluent/leachate removal using an additional pump. Any spilled leachate and/or effluent that accumulates in the secondary sump is pumped to the leachate storage tank (T1) via a suction line originating from the horizontal centrifugal pump at the loading pad. The centrifugal pump is equipped with valves to operate in suction mode to remove any spilled effluent/leachate from the secondary sump. The submersible sump pump is manually operated to remove stormwater or used as an alternate for effluent/leachate removal.

Accumulated precipitation will be removed within 24 hours of observation. The precipitation will be pumped into the adjacent stormwater management system.

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Accumulated liquid in the trench drain that is not precipitation resulting from a recent storm event will be treated as effluent and pumped into the effluent/leachate storage tank (T6).

T6 LIQUID LEVEL MONITORING

The effluent/leachate storage tank (T6) contains an 8-inch overflow pipe. The overflow pipe is installed outside of the effluent/leachate storage tank (T6) with the tank sidewall penetration within 30 inches of the top of the sidewall of the tank. The tank is equipped with liquid level indicators that are float operated with a direct readout. The control panel is mounted in a highly visible location on the exterior of the tank. When the high-level alarm condition occurs (at 17.5 feet), a visual and audible alarm (a light and horn) located at the control panel to alert staff of a potential problem before overflow. The effluent/leachate storage tank (T6) level is recorded daily on the leachate reporting forms provided in Appendix A.

T6 EXTERIOR AND INTERIOR INSPECTIONS

The following describes the inspections of the effluent/leachate storage tank (T6) and steps to be followed after the inspections.

• Overfill Prevention System: The overfill prevention system components will be inspected weekly. These components include level sensors, gauges, high-level alarm, and automatic shutoff controls.

• Tank Exterior: The exterior of the tank and the secondary containment system will be inspected weekly for adequacy of the cathodic protection system, leaks, corrosion, and maintenance deficiencies. In addition, the inspection includes an evaluation of any structural damage to the tank, damage to the coating system, loose connections, corrosion, visible leaks, and maintenance deficiencies. The inspector will also look for any structural damage to the concrete slab or HDPE lining of the secondary containment system, peeling of the paint system, and visible leaks.

• Tank Interior: The interior of the tank will be inspected whenever the tank is drained or at least every three years. The inspector will look for any damage to the interior coating system, structural damage, cracking of the tank, visible leaks, and accumulation of sludge.

• Procedures for Corrective Actions: If inspections reveal any deficiencies with the tank or the secondary containment system that could result in failure of the system to contain the leachate, the SWMD shall take immediate action to correct the situation by assessing the problem and coordinating the required actions. Failures or damage to the tanks will be repaired by the tank manufacturer or a designated contractor. The SWMD shall notify the manufacturer or designated contractor of the situation; the tank manufacturer or designated contractor will remediate the tanks and prepare a detailed damage assessment report. FDEP will be notified in writing of the situation and of the proposed corrective action.

• Inspection Reports: Inspection reports and reports of any remedial action measures taken will be maintained at the SCLF and will be made available to FDEP upon request.

The weekly inspection report form is provided in Appendix A. All reports will be maintained for the life of the tanks and the containment system.

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ACID MIXER AND TANK

The acid dosing pumps at the effluent/leachate storage tank (T6) pump station inject sulfuric acid into the 4-inch effluent pipe. Landfill personnel monitor the pH by collecting grab samples from the sampling port or reading from the pH meter at the control panel, thereby allowing the acid dosing to be optimized and preventing large swings in pH. The acid dosing rate is controlled by an operator at the control panel using the pH readout to adjust the acid dose to achieve the appropriate pH range.

Also, the system includes controls between the acid dosing pumps and the pH meter to allow automatic acid dosing. The acid dosing pump controls are connected to the booster pump controls so acid dosing will only occur when the booster pumps are running. In addition, when the booster pumps are signaled off, the acid dosing pumps stop and the booster pumps continue to run for approximately 30 seconds to allow the piping system to be flushed of any residual acid.

LEACHATE STORAGE TANKS (T7 AND T8)

Leachate from Phases I-VI and the CEA may be conveyed to one of the 1,000,000-gallon (maximum capacity) welded steel aboveground leachate storage tanks before being treated or hauled for disposal at a permitted wastewater facility. Each of the tanks are 81-feet in diameter and 30 feet from foundation to the roofline. Each tank is fitted with an 8-inch overflow pipe 27 feet above the foundation to maintain a maximum capacity of 1,000,000 gallons. The leachate level within each of the storage tanks (T7 and T8) are maintained to allow for minimal disruptions to leachate collection and removal operations.

If a high-level alarm condition occurs (at 25 feet) in either of T7 and T8, the MLPS and PS-9 will be prevented from continuing to convey leachate to the high-level tank. A signal indicating the condition of T7 and T8 will be sent to the telemetry control computer. When a high-level alarm condition exists, additional hauling trucks will be used to transport the leachate to a WWTF, lowering the leachate level in the tanks. Leachate conveyance to T7 and T8 from Phase I-VI and the CEA pump stations will be suspended until the respective high-level alarm has been cleared.

T7 AND T8 SECONDARY CONTAINMENT SYSTEM

The T7 and T8 leachate tank system is located within a concrete containment area. The secondary containment area has a sump at the low point for stormwater drainage that is conveyed via sump pump to the MLPS. The valve from the sump discharge pipe is normally closed to reroute collected liquids back to MLPS for treatment as leachate, in the event of an uncontrolled release. The valve is occasionally opened to release stormwater from the impoundment to the site-wide stormwater management system as needed. The T7 and T8 secondary containment area was designed to hold 110% of the volume of the largest storage tank in case of failure. The concrete flooring and containment walls will be inspected weekly for cracks or structural deficiencies as discussed in Section 8.3. Any cracks will be immediately sealed using flexible concrete grout. Any structural deficiencies will be identified, and corrective action will be taken to repair the walls.

Accumulated precipitation will be removed within 24 hours of observation or when 10 percent of the secondary containment volume has been reached, whichever occurs first. The precipitation will be pumped into the adjacent stormwater management system after it is inspected to ensure no stormwater contaminated by leachate is released to the stormwater system.

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T7 AND T8 LIQUID LEVEL MONITORING

The T7 and T8 tanks each possess an overflow pipe. The overflow pipe is installed outside of the storage tank, with the tank sidewall penetration invert set at 36 inches below the top of the tank wall (beginning of roofline). The tank is equipped with liquid level indicators that are transducer-operated with a direct readout. The level gauge boards are mounted in a highly visible location on the exterior of each tank. The tank level is recorded daily on the leachate reporting forms. An example form is provided in Appendix A.

T7 AND T8 EXTERIOR AND INTERIOR INSPECTIONS

The following describes the inspections of the T7 and T8 and procedures to be followed after the inspections:

• Overfill Prevention System: The overfill prevention system components will be inspected weekly. These components include level sensors, gauges, high-level alarm, and automatic shutoff controls.

• Tank Exterior: The exterior of the tanks and the secondary containment system will be inspected weekly for adequacy of the impressed current cathodic protection system, leaks, corrosion, and maintenance deficiencies. The control panel for the impressed current cathodic protection system will be inspected to ensure that it is working properly.

In addition, the inspection includes evaluating structural damage to the tank, damage to the coating system, loose connections, corrosion, visible leaks, and maintenance deficiencies. The inspector will also look for any structural damage to the concrete slab, peeling of the paint system, and visible leaks.

• Tank Interior: The interior of the tanks will be inspected whenever the tanks are drained or at least every three years. The inspector will look for any damage to the interior coating system, structural damage, cracking of the tank, visible leaks, and accumulation of sludge.

• Procedures for Corrective Actions: If inspections reveal deficiencies with the tank or the secondary containment system that could result in the system’s failing to contain the leachate, the SWMD shall take immediate action to correct the situation by assessing the problem and coordinating the required actions. Failures or damage to the tanks will be repaired by the tank manufacturer or a designated contractor. The SWMD shall notify the manufacturer or designated contractor of the situation; the tank manufacturer or designated contractor will remediate the tanks and prepare a detailed damage-assessment report. FDEP will be notified in writing of the situation and of the proposed corrective action.

Inspection Reports: Inspection reports and reports of any remedial action measures taken will be maintained at the SCLF and will be made available to FDEP upon request. The weekly inspection report form is provided in Appendix A. All reports will be maintained for the life of the tanks and the containment system.

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LEACHATE AND EFFLUENT DISPOSAL

Leachate is disposed of at the SCLF by various methods, including treatment at the on-site LTRF, volume reduction at the LEF, hauling of raw leachate via tanker truck to a permitted WWTF, and truck-mounted spray evaporation of raw leachate within the contained working surface. Effluent from the on-site LTRF is disposed of by effluent evaporation or transporting effluent via tanker trucks to a permitted WWTF.

EFFLUENT/LEACHATE STORAGE POND B

The effluent/leachate storage pond (Pond B) provides 236,000 gallons of storage volume and is located west of the MLPS, as shown in Figure 3-1. Pond B was designed with one foot of storage for the 25-year/24-hour storm and one foot of freeboard. The pond was designed to store either raw leachate or effluent; however, Pond B’s primary use is for storage of effluent and leachate mixture for volume reduction at the LEF. The leachate and effluent mixture is pumped from Pond B to the LEF for volume reduction processing. Diversion of leachate from the MLPS to Pond B is controlled by a telemetry system that utilizes liquid level measurement devices and automatic valve controls to maintain the Pond B depth with at least one foot of freeboard.

Pond B was designed with an upper and lower 60-mil HDPE geomembrane. An HDPE geonet was installed between the two liners. The subbase for the lower geomembrane consists of six inches of soil with a saturated hydraulic conductivity of 1 x 10-5 centimeters per second or less, installed over the on-site soil which was cleared of vegetation and graded. Supplemental effluent evaporation in Pond B is provided using a spray evaporation system. The spray evaporation nozzle system was designed around the perimeter of the pond and consists of 30 nozzles, with an estimated flow capacity of 17-gpm per nozzle and a 510-gpm pump.

In general, the SWMD operates the spray evaporation system manually and only during the hours that the landfill is open. The spray evaporation system is not operated during windy conditions (i.e., over 10 miles per hour) to prevent overspray outside the limits of the pond liner system.

The following standard and special setting conditions are applicable at Effluent/Leachate Storage Pond B:

1. Effluent and leachate mixture storage and spray evaporation operation in Pond B (standard practice).

2. Effluent and leachate mixture storage in Pond B for conveyance to the LEF for volume reduction processing (standard practice).

The leachate reporting forms provided in Appendix A are…