The Zahle Landfill Project

Introduction:

In 2001, the Lebanese Government, through the Council of Development and Reconstruction (CDR) sought to contract with qualified firms for the operation of a newly constructed landfill in Zahle, Lebanon.  The project was initiated to improve the environmental conditions under which solid waste was being disposed by the municipalities in that region.  The World Bank provided funding through loans to the Lebanese Government to construct and operate a Controlled Landfill and to remediate the Old Dump.  SERDIM with its partners SCS engineers was honored to be selected by the Municipality of Zahle, Lebanon, The Council for Development and Reconstruction of Lebanon (CDR) and the World Bank to provide the services necessary to operate The Controlled Landfill in Zahle and to remediate Zahle’s Old Dump site.

The Controlled Landfill Before Commencement of Work

The Project:

The Zahle Landfill Project consisted of a variety of different coordinated tasks.  In general, SERDIM-SCS was responsible for completing construction of the new Controlled Landfill, operation of the Controlled Landfill and remediation of the Old Dump site.  The Controlled Landfill had been designed and partially constructed.

The Controlled Landfill:

Composite Liner System Installation

Composite Liner System:

The original design of the new Controlled Landfill provided for 3 independent disposal units or cells.  The bottom of each cell was lined with a composite liner consisting of 60 cm of compacted clay covered by a 1.0 mm high density polyethylene (HDPE) plastic geomembrane.  This liner system was constructed to prevent the infiltration of leachate through the underlying soil and into the water table.  Leachate is the strong contaminated liquid that is formed when water passes through solid waste. The combination of clay soil and plastic geomembrane liners has proven very effective in containing leachate within the disposal cell and thereby significantly reducing the potential for soil and groundwater contamination beneath the waste.

Leachate Collection System Installation

Leachate Collection System:

When a disposal cell is constructed to contain leachate, a system must be provided to remove the leachate in order to prevent release of the contaminant into the environment.  By removing the leachate from the cell, the potential for release is greatly reduced since the leachate cannot fill the cell and overflow or leak through any defects in the liner system.  The Zahle landfill uses a series of 4 submersible pumps to extract leachate from the cells and transfer it to a storage basin.  The storage basin is also lined with clay soil and geomembrane to contain the stored leachate.  Pipes were installed inside a sand and gravel layer that was placed over the liner system to allow the leachate to flow to the pumps.

Biogas Control System Destroying Landfill Gas

Biogas Control System:

Once solid waste is buried for disposal, it begins to decompose.  During the decomposition process a gas by product is generated.  The gas generated is commonly referred to as biogas or landfill gas (LFG).  Landfill gas is composed of primarily methane (CH₄) and carbon dioxide (CO₂) and other trace elements.  The methane constituent is of particular concern since methane is explosive when in certain concentration.  Therefore, Biogas or LFG can poses a serious safety problem when not monitored and controlled.   Additional, the components of LFG have been linked to ozone depletion and other environmental concerns. SERDIM-SCS installed and operated a modern LFG extraction and destruction system to address these safety and environmental concerns.  The system consists of a series of wells installed in the waste connected to a piping system.  A blower (air pump) that applies vacuum through the pipes to the extraction wells to remove the LFG from the waste mass. And, a flare that burns the LFG to destroy the harmful components contained in the LFG.  This collection and treatment process protects the citizens of Zahle and the environment.

Recyclable Materials Being Removed From Incoming Waste

Waste Placement & Compaction at New Controlled Landfill

Landfill Operations:

The new Controlled Landfill is an engineered facility that must be properly operated in order to be effective and efficient.  The SERDIM-SCS team established and implemented operational standards to ensure safety, public health and protection of the environment.  These standards included the proper placement and compaction of waste, covering of waste, housekeeping and litter control.  By properly performing these tasks, SERDIM-SCS successfully minimized the nuisances generally associated with landfills.  Odors, dust and noise were minimized to protect the neighbors  SERDIM-SCS accepted, processed. Sorted and disposed of over 39,000 Tonnes of new incoming waste from Zahle and and neighboring municipalities.

Weighing & Recording Incoming Waste

Data Collection:

The SERDIM-SCS team collected and analyzed data to evaluate the operations of the facility.  All new incoming waste was weighed and recorded with the origin, type of waste, hauler, truck etc.  Accurate records now exist for actual waste acceptance rates.  Additionally, SERDIM-SCS tracked operation costs and maintenance work performed.  This valuable information can be used to track trends that will benefit not only this facility but future solid waste projects in Lebanon. Monthly reports of landfill activities were submitted to the Municipality and the CDR.

ORIGINAL DESIGN

RECONFIGURATION TO MAXIMIXE CAPACITY

Landfill Evaluation & Design For Maximizing Capacity

Landfill Design:

The original design for the Zahle Controlled Landfill consisted of 3 separate disposal areas called cells.  Each individual cell was configured to be 14 m in height (from cell bottom) with 4v:1h side slopes.  SERDIM-SCS performed extensive analysis of the landfill design and determined that significant additional disposal capacity could be obtained by reconfiguring the cell design.  SERDIM-SCS engineers re-designed the original cells and combined all 3 cells into 1 large unit.  The height was increased to 24 m and the side slope grades changed to 3v:1h.  By making these design changes, SERDIM-SCS engineers determined that the capacity of the facility could be doubled using the same land area.  SERDIM-SCS doubled the capacity of the Controlled Landfill with no additional land use and minimal costs.  This is one of the many ways in which SERDIM-SCS made this project more efficient and effective.

The Old Dump:

Old Dump Before Remediation

Description:

For approximately the last 30 years, the Old Dump site was used for waste disposal for the Municipality of Zahle and other communities.  The site is approximately 15000 m² in area and was over 25 m in height (above original ground elevation).  The waste had been piled so high that it was spilling over onto adjacent properties. The waste was frequently burned in order to decrease the volume, resulting in many fires and “hotspots” contained within the waste pile.  A minimal amount of cover soil had been applied over the 20+years of use.

Excavation of Waste at Old Dump

Remediation:

The actual amount of waste disposed of at the Old Dump exceeded 225,000 m³.  The original contract required excavation and transfer of 103,000 m³.  One cell of the original design of the Controlled Landfill was to be dedicated to this waste.  Since SERDIM-SCS successfully increased the capacity of the Controlled Landfill, more space was available for waste from the Old Dump.  Through extensive analysis and study, SERDIM-SCS devised a method to remove over 225,000 m³ and return the Old Dump site back to original ground elevation.  Through its innovative approach, SERDIM-SCS was able to remove the vast majority of the waste and return the site to an open field ready for future beneficial uses.

Pest & Odor Control Being Applied

at Old Dump

Excavation & Transfer: 

In order to remediate the Old Dump site, SERDIM-SCS excavated and transported over 225,000m³ of waste from the Old Dump to the Controlled Landfill.  There were many challenges associated with the excavation of old waste from the site including:

• Fire Control (waste that was burned to reduce volume was still burning);
• Odor Control (Excavation of old waste can create obnoxious odors);
• Pest Control (Insects and rodents disturbed during excavation);
• Traffic Control (Numerous large trucks and equipment with limited access);
• Dust Control (Turbulence created by equipment and wind).

SERDIM-SCS effectively monitored and controlled each of these nuisances to minimize the impact on adjacent properties and neighbors.

Extracting & Destroying Biogas

at Old Dump

Environmental Monitoring and Control:

In order to protect the public safety and the environment during the Old Dump remediation, SERDIM-SCS performed several environmental monitoring and control tasks.  The two main areas for possible negative impacts from contaminants were air and water quality.  Leachate, the toxic liquid generated when water dissolves contaminants from waste, was monitored and controlled to prevent it from entering the river adjacent to the site.  Air quality was monitored and controlled by reducing smoke emissions from fires, minimizing dust from excavation and Biogas extraction and destruction.  Biogas is a byproduct generated by the decomposition of waste.  Biogas (also known as landfill gas) poses both safety and health concerns.  Because biogas contains sufficient amounts of methane, the potential for fire or explosion is high.  Furthermore, the long time exposure to biogas can lead to health concerns.  SERDIM-SCS designed, manufactured and installed a system to extract the biogas from the decomposing waste and burn it under controlled circumstances.  Destroying the biogas significantly reduces the potential for explosion and negative public health impacts.

Final Condition of Old Dump

After Remediation

The Final Product:

The Old Dump was renovated by SERDIM-SCS in a manner that will allow for the future beneficial use of the property.  The waste was removed to below ground level and a cap consisting of compacted fill was placed over the entire site.  The property is now available and suitable for future beneficial uses such as parks, playgrounds, sports fields or possibly a produce market.  The Zahle Old Dump that  once had significant negative environmental impact is now  valuable property and the waste was handled in an environmentally sound method by being disposed of in a modern, lined and controlled landfill.