Modern Landfills Are Not
What You Think They Are
Today’s engineered solid waste facilities are sophisticated infrastructure, designed from the ground up to protect groundwater, manage emissions, and return land to productive use. Understanding how they work is the first step to understanding what SHA does.
A Century of Change:
And Why It Matters
For most of human history, solid waste disposal meant finding a low-lying piece of land (a gully, a ravine, a former gravel pit) and filling it in. No liners. No drainage. No monitoring. Leachate migrated freely into surrounding soils and groundwater. Methane vented uncontrolled. Fires burned for years. These were open dumps, and they left lasting environmental legacies that communities are still managing today.
The shift began in the 1970s, when the environmental movement brought growing awareness of contaminated groundwater and public health impacts linked to uncontrolled disposal sites. In British Columbia, the Waste Management Act of 1982 marked a turning point, establishing for the first time that solid waste facilities required regulatory permits and environmental performance standards.
Through the 1990s and 2000s, BC’s regulatory framework matured significantly. The Ministry of Environment’s Landfill Criteria for Municipal Solid Waste (1993) established engineered containment as the provincial standard. Today, a permitted BC landfill is a highly engineered facility, designed, constructed, operated, monitored, and eventually closed under the oversight of qualified engineers and environmental scientists.
The Open Dump
- No liner: leachate migrates directly to groundwater
- No gas management: methane vents uncontrolled or burns
- No stormwater controls: runoff carries contaminants offsite
- No monitoring: contamination goes undetected
- No closure plan: site abandoned at end of use
- No financial assurance: cleanup costs fall to taxpayers
The Engineered Landfill
- Multi-layer liner system containing leachate at source
- Active gas collection: flaring or energy recovery
- Engineered stormwater diversion and management
- Ongoing groundwater and surface water monitoring
- Approved closure plan and post-closure monitoring program
- Regulatory financial assurance covering full closure costs
The BC Regulatory Journey
What’s Actually
Underground
A modern engineered landfill is far more complex than a hole in the ground. Scroll through the diagram to explore each layer, from the vegetated surface to the native geology below. Every component has a specific engineering purpose.
The Top of the Landfill Is Engineered as Carefully as the Bottom
The final cover system is the last major engineering task at a landfill, and one of the most consequential. It must manage stormwater, limit moisture infiltration into the waste body, support gas venting or collection, accommodate decades of settlement, and ultimately support a useable land surface.
A typical engineered final cover in BC includes multiple distinct layers: a vegetated topsoil layer that supports plant growth and sheds surface runoff; a protective barrier soil layer; a granular drainage layer that intercepts any moisture passing downward; a low-permeability geomembrane or geocomposite clay liner (GCL) that acts as the primary cap barrier; and a foundation layer that ties into the engineered slopes below.
Why this matters: A well-designed cover system reduces leachate generation, manages landfill gas migration to surface, and allows the site to support meaningful post-closure land use, from parks to solar farms. Cover system failures, by contrast, allow excessive moisture entry and uncontrolled gas release for decades.
The Gas Beneath the Surface Is Both a Problem and an Opportunity
As organic waste decomposes anaerobically (without oxygen) it produces landfill gas, primarily a mixture of methane (roughly 50%) and carbon dioxide (roughly 50%), with trace amounts of volatile organic compounds and other gases. Left unmanaged, this gas migrates laterally and vertically through the waste mass and can vent to the atmosphere, create odour impacts, and in extreme cases accumulate in structures or subsurface voids.
Modern engineered landfills include a gas collection system designed to intercept this gas before it reaches the surface. Vertical extraction wells (perforated pipes driven down through the waste at regular intervals) connect to a network of horizontal header pipes that convey the gas to a central collection point. From there, it can be flared (combusted to destroy methane and reduce climate impact) or utilized to generate energy.
BC regulatory context: The BC Environmental Management Act and associated permit conditions require landfill gas management at facilities above certain waste mass thresholds. The specific design (passive venting, active extraction, flaring, or utilization) is determined by facility size, waste composition, and regulatory requirements. SHA designs LFG systems for all scales of BC facility.
The Waste Itself Is Placed and Managed to Strict Engineering Standards
The waste body of an engineered landfill is not simply a pile, it is a carefully sequenced, compacted, and documented mass of solid material that must behave predictably over decades. Waste is placed in lifts (horizontal layers of defined thickness) compacted with specialized equipment to maximize density and airspace utilization, and covered daily with soil or alternative daily cover material to manage odour, pests, and blowing litter.
The geometry of the waste mass matters enormously. Cell sequencing (the order in which areas of the landfill are filled) determines how the facility ages, how settlement progresses, and how the gas and leachate collection systems perform over time. SHA’s landfill designs address all of these factors from the outset, not as afterthoughts.
Not all landfills receive municipal garbage. Dedicated facilities also exist for construction and demolition waste, industrial waste, contaminated soils, and biosolids, each with its own design requirements, liner specifications, and environmental management obligations.
Settlement: Organic material continues to decompose long after placement, and the waste mass compresses and settles over decades, often by a meaningful share of its original height. SHA’s designs account for this movement in the cover system, gas collection infrastructure, and any post-closure structures.
What Rainwater Becomes After Passing Through a Landfill
When precipitation or surface water infiltrates a waste mass, it picks up dissolved and suspended contaminants, organic compounds, heavy metals, ammonia, chlorides, and a range of other substances depending on what’s in the waste. This highly contaminated liquid is called leachate, and it is one of the most significant environmental risks associated with any solid waste facility.
In an engineered landfill, the primary liner system prevents leachate from migrating downward into native soils and groundwater. Above the liner sits the leachate collection system: a granular drainage blanket that allows leachate to flow freely toward low points, perforated collection pipes that convey it to a sump or collection point, and pumping systems that remove it from the facility for treatment and disposal.
SHA designs leachate collection systems as an integrated component of the overall landfill design, not as an afterthought bolted on at the end. The drainage layer geometry, pipe spacing, sump sizing, and pumping capacity are all calculated for the specific site conditions, waste characteristics, and BC climate.
Long-term generation: Leachate generation does not stop at closure. A closed landfill can continue generating leachate for 20–50 years or more. SHA’s closure plans include long-term leachate collection and treatment provisions sized for the post-closure conditions of the specific site.
The Last Line of Defence Between Waste and Groundwater
The liner system is the most critical environmental performance component of a landfill. It must prevent leachate from migrating downward into the native soils and groundwater below, and it must do this reliably for the full operational life of the facility and many decades beyond.
Modern composite liner systems typically include a high-density polyethylene (HDPE) geomembrane (a smooth or textured plastic sheet of defined thickness) placed over a low-permeability clay layer or geocomposite clay liner (GCL). The two materials work together: the geomembrane provides primary impermeability, and the clay layer provides a secondary redundant barrier. Between the two, a leak detection layer allows engineers to identify any liner compromise before contamination reaches native soils.
At larger or more complex facilities, a double-liner system with an independent leak detection zone between two liner components provides an additional level of protection. The specific liner design is determined by the hydrogeology of the site, the nature of the waste, and BC Ministry of Environment permit requirements.
Construction QA/QC: Liner installation is one of the most quality-sensitive construction activities in solid waste engineering. SHA provides construction quality assurance inspection for all liner installations on projects we design, ensuring that what is built matches what was engineered. A liner that looks right but is not properly installed provides false assurance.
What Lies Below the Liner Is as Important as What Lies Above It
The native geology beneath a landfill is not simply a foundation, it is an environmental resource that must be protected, characterized, and monitored for the lifetime of the facility and long afterward. Groundwater in the soils and bedrock below a landfill is the ultimate receptor for any liner system failure, and protecting it is the fundamental purpose of the containment system above.
Groundwater monitoring networks (arrays of monitoring wells installed at strategic locations around and beneath the facility) provide the ongoing evidence that the liner system is performing as designed. Samples are collected on a regular schedule, analyzed for indicator parameters and site-specific contaminants of concern, and reported to the Ministry of Environment under the facility’s operating certificate.
SHA designs groundwater monitoring networks from first principles, based on the hydrogeology of each specific site. The number, depth, screen interval, and location of monitoring wells are all determined by where groundwater flows, how fast it moves, and where a potential release would be detected first.
Post-closure monitoring: BC regulatory requirements typically mandate groundwater monitoring for a minimum of 25 years after closure, and sometimes much longer. SHA manages long-term monitoring programs for numerous closed facilities across British Columbia, providing continuity of environmental oversight that municipalities can rely on.
From Liability
to Asset
Methane (the primary component of landfill gas) is a potent greenhouse gas, approximately 80 times more effective at trapping heat than carbon dioxide over a 20-year period. Uncontrolled methane emissions from landfills are a significant source of anthropogenic greenhouse gas emissions globally, and managing this liability is both an environmental imperative and an increasingly regulated obligation for BC facility operators.
The good news is that the same gas that represents an environmental liability also represents a recoverable energy resource. Landfill gas can be collected, treated, and used to generate electricity, produce renewable natural gas (RNG) for pipeline injection, or simply flared to convert methane to the less potent CO₂. The appropriate management approach depends on the scale of the facility, the gas generation rate, and the available infrastructure.
SHA has designed landfill gas management systems for facilities ranging from small rural sites with passive venting to major regional landfills with active extraction, flaring, and energy recovery. The right solution for your facility is the one that meets regulatory requirements, manages environmental risk, and is proportionate to the scale and economics of the site.
Passive Venting
Perforated pipes installed vertically through the waste mass allow gas to migrate upward and vent to the atmosphere passively. Simple, low-cost, and appropriate for small or low-gas-generation facilities.
Small facilitiesActive Collection & Flaring
A blower creates negative pressure in the extraction network, drawing gas to a flare station where it is combusted. Converts methane to CO₂ and water, dramatically reducing climate impact. Required at larger BC facilities.
Medium & large sitesEnergy Recovery
Collected gas is treated and used to generate electricity via internal combustion engines or turbines, or upgraded to renewable natural gas for pipeline injection. Turns a liability into a revenue stream.
Large regional facilitiesProtecting What’s
Below the Surface
Leachate is arguably the most consequential environmental output of a solid waste facility. A liner breach or collection system failure that allows leachate to reach groundwater can contaminate a drinking water aquifer, render a stream uninhabitable for aquatic life, and create a remediation liability that persists for decades. Getting leachate management right is not optional, it is the core environmental engineering obligation of a landfill design.
Leachate characteristics vary widely depending on the age of the waste, the composition of the waste stream, and the rainfall regime of the site. Fresh leachate from an active landfill tends to be high in BOD (biological oxygen demand), ammonia, and dissolved organic compounds. Older leachate from a closed facility is typically more stable but may be high in ammonia and certain metals. Each presents different treatment challenges.
Treatment and disposal options for collected leachate include discharge to a municipal wastewater treatment plant (the most common BC approach), on-site biological or physical-chemical treatment followed by permitted discharge, recirculation into the landfill to accelerate decomposition, or spray evaporation. SHA evaluates the full range of options for each project and recommends the solution best matched to the site’s leachate characteristics and local receiving environment.
What’s In It
BOD & COD from organic decomposition, ammonia, heavy metals, chlorides, volatile organic compounds, pharmaceutical compounds, and microplastics, a complex mixture that changes over the facility’s life.
How It’s Collected
Granular drainage blanket above the liner conveys leachate to collection pipes and sumps. Active pumping removes it from the facility for treatment. Pipe spacing and sump sizing are engineered for site-specific conditions.
Treatment Options
Municipal WWTP discharge (most common), on-site biological treatment, physical-chemical treatment, constructed wetlands, evaporation, and leachate recirculation. Each approach has different cost and performance trade-offs.
Long-Term Generation
Leachate generation continues for decades after closure as moisture percolates through the aging waste mass. Post-closure leachate management must be planned for in the closure design, not retrofitted later.
Closure Is Not
the End of the Story
When a landfill reaches its permitted capacity and ceases accepting waste, the engineering obligation does not end, it enters a new and equally demanding phase. Closure is one of the most complex engineering projects in the lifecycle of a solid waste facility, and the decisions made at closure define the site’s environmental performance and community value for the next century.
Siting & Design
Site selection, environmental assessment, engineered design, regulatory approval. The decisions made here define everything that follows.
Construction
Liner installation, cell development, infrastructure construction. QA/QC inspection ensures the built facility matches the design.
Operations
Active waste filling, compaction, daily cover, leachate management, gas collection, ongoing monitoring and permit compliance.
Closure
Final cover construction, capping of gas wells, decommissioning of operational infrastructure, regulatory submissions and approvals.
Post-Closure
25+ years of environmental monitoring, leachate management, gas system maintenance, settlement monitoring, and annual reporting to the Ministry.
Closed Landfills Become Community Assets
A well-engineered and well-closed landfill does not have to be a permanent scar on the landscape. With appropriate final cover design and post-closure management, former landfill sites have been successfully converted into productive community uses across BC and beyond.
Parks & Green Space
The most common end use: rolling terrain, trails, and open space. The elevated topography of a former landfill can create distinctive parkland in otherwise flat urban areas.
Solar Energy Facilities
Closed landfill surfaces are increasingly being developed as solar farms, generating clean energy from land that has limited alternative use value.
Golf Courses & Recreation
The contoured topography of many closed landfills is well-suited to golf course development, providing recreational amenity while maintaining post-closure management access.
Sports Fields
Athletic fields, disc golf courses, and other low-intensity recreational uses are common on closed sites where surface settlement has stabilized sufficiently.
Wildlife Habitat
Native plant communities established on final cover systems can provide meaningful habitat in fragmented landscapes, with some sites managed specifically for ecological values.
Agricultural Use
In some cases, closed sites with appropriate final cover and monitoring have been returned to agricultural production, though this requires careful engineering and regulatory approval.
SHA Has Engineered Landfills
Across British Columbia for 30 Years
From initial siting through design, construction, operations support, closure, and post-closure monitoring, we provide the full range of engineering services for solid waste facilities in BC.