Featured Image text: "The Importance of Landfill Monitoring".

The Importance of Landfill Monitoring

Landfill monitoring is an important tool for evaluating the risk of a landfill to the surrounding environment. If through landfill monitoring over time a landfill is beginning to emit water pollution, or landfill gas is found to be migrating, action can be taken to prevent environmental damage before it occurs.

Solid Waste Landfill Monitoring and Reporting

Over time water enters landfills and re-absorbs various contaminants that pass through waste in the landfills. The leachate this creates contains a number of pollutants that can cause serious harm if released into the local water environment.

Deteriorating water quality can cause harmful effects, including animal and human diseases and vegetative stress. Groundwater monitoring programmes are the final line of defence as they help prevent contamination in the water that could be released into it.

Municipal solid waste landfills are now required to monitor air, surface water, and groundwater, by doing testing work which has become a significant component of a facility’s operating budget. The US Clean Air Act, Section 110 (CAA), the Clean Water Act, Section 402 (CWA), and other regulations posed significant challenges for landfill operators when introduced.

Why do landfills need to be monitored?

To assist in ensuring leachate controls prevent environmental pollution (using a pre-established baseline).

Closure and Post-Closure Care Requirements 1997 Final Rule Revisions to Criteria for Municipal Solid Waste Landfills from the US EPA website: The closure and post-closure care requirements for MSWLFs establish the minimum requirements that MSWLF owner/operators must comply with once the landfill stops receiving waste and begins closure. Owner/operators are also required to continue monitoring and maintaining the landfill during the post-closure care period.

A statistically significant increase in any of the contaminants monitored would indicate a possible release. Only water quality in different groundwater monitoring zones can be statistically compared. Groundwater monitoring programmes rely on consistent and reliable sampling methods, detailed field observations, and analytical techniques to produce a representative and comparable analytical data and detailed records.

Landfill leachate typically contains high ion concentrations and is discharged into groundwater or surface water with lower ion concentrations. Dilution occurs initially and when the leachate discharge is low in comparison to the receiving waters. As a result, the ion concentration decreases.

Featured Image text: "The Importance of Landfill Monitoring".

Why Monitor Landfills?

Monitoring, to keep a watch for pollution problems, is essential because landfills contain the potential to do massive damage to groundwater water sources which can render a groundwater drinking water source unsafe, or even an entire aquifer unusable. The economic, let alone the environmental cost, of polluting a water source can be enormous. It could also threaten the human health of those that drink it.

In fact, the decision-making process is more complicated because of the inherent variability in groundwater monitoring and because the treatment causes a non-steady-state in the aquifer.

Trend tests track the effectiveness of corrective action and forecast a termination date, which is usually not reached until comparisons of observation and action levels show favourable results.

Detection Monitoring

Once initial groundwater quality studies establish seasonal and temperature variations at a site, groundwater sampling continues in order to help detect changes in the “background” groundwater quality and flow directions related to constructing and operating the solid waste landfill. A statistically significant increase in the amount of any of the contaminants monitored would indicate a release might have occurred. 

The required number of wells, spacing, and depth of wells are site-specific and are determined by the aquifer thickness, groundwater flow rate and direction, and other geologic and hydro-geologic characteristics of the site. All groundwater monitoring systems must be certified by a qualified groundwater scientist and must follow the regulations’ sampling and analytical procedures.

What to Monitor for

The two main parameters to monitor within and around the perimeter of sanitary landfills are:

  • Water quality
  • Methane migration in permeable soils.

Landfill operators and those responsible for closed landfills should periodically collect water samples to determine the levels of contamination both within the landfill and at sensitive locations around the perimeter of every landfill.

Monitoring wells are typically positioned at the landfill perimeter downhill of any groundwater gradient across the landfill site. The landfill surface water drainage discharge point is also regularly sampled for monitoring purposes. Usually, this is directly adjacent to the discharge point.

It is also necessary to monitor the impact of a landfill on a local groundwater aquifer if a leachate contaminated groundwater pollution plume reaches an aquifer.

Surface springs and seeps should also be monitored to identify migration from beneath the landfill. Monitoring should occur quarterly because surface water quality is seasonal.

During high runoff, the impacts of landfills are relatively indistinguishable, and the likelihood of detection increases in dry weather.

Landfill leachate decomposes in three stages and decay begins immediately after wet deposition (heavy compaction of the landfill with night cover only delays the onset of decay).

How is Landfill Monitored?

To monitor groundwater, facility owners and operators must install a groundwater monitoring system capable of collecting samples from the uppermost aquifer (defined as the geological formation nearest the natural surface capable of yielding significant quantities of groundwater to wells or springs).

While most landfill monitoring methods include groundwater water quality sampling when contaminant levels are low identifying the background contaminant concentrations of contaminants can be challenging.

Facilities often use a monitoring station in an adjacent stream or lake. However, natural variations in groundwater chemistry can make it difficult to assess the impact of a landfill.

In such instances, a landfill perimeter monitoring point is needed for comparison. If the perimeter monitoring shows no evidence of a plume of contamination developing at the perimeter of the landfill site the landfill operator can show lake or watercourse pollution downstream is not caused by the landfill.

Soil Gas Monitoring

Landfills that are both open and actively being filled, and those that have been completed and closed to further tipping must all perform soil gas monitoring for methane migration. At worst methane migration can cause homes and other buildings to explode when the machine in landfill gas builds up in enclosed spaces.

Soil Gas Monitoring requires specialized instrumentation and trained staff. Unless the site operator/ owner has a deep knowledge of landfill science it is best for owners to hire experts.

Environmental Regulations Compliance and a Safe Working Environment

An expert landfill assessment team can help landfill owners and operators with monitoring duties to deliver both environmental regulations compliance and a safe working environment for the landfill staff and the site’s visitors.

From small landfills operated by remote communities to large urban projects, well designed and conducted landfill monitoring and risk assessment programs ensure that owners and operators minimize the environmental impact of landfill operations.

These programs are a vital part of ensuring a landfill meets all regulatory requirements. They are the first line of defence for any landfill.

Landfill Gas Monitoring

Landfill gas monitoring when used to measure the concentration of methane at the surface of the landfill can often, for unlined landfills, predict its migration. A portable gas monitor can give you the current concentration of methane at the landfill at any given moment.

Continuous gas monitoring may be needed where there is a risk of explosion. Installing a real-time landfill gas monitoring system for migrating gas concentrations is a much longer-term solution that can provide continuous data and identify anomalies in the emissions.

Monitoring of methane for employee explosion and asphyxiation protection is an essential part of landfill monitoring and helps keep landfill workers safe.

As a result, monitoring programs have become statutory requirements enforced in many jurisdictions with stiff penalties for non-compliance.

Comprehensive Landfill Gas Monitoring Programmes

A comprehensive monitoring program is an important part of landfill monitoring planning.

The location and configuration of sampling stations must be appropriate to the site conditions.

Landfills without gas extraction may require more frequent monitoring than landfills that do. The geology of the surrounding materials at any landfill site that is in contact with the waste may also require higher levels of monitoring.

Environmental monitoring data from older licenced landfills can be quite extensive.

Data from groundwater monitoring wells (water table observation wells and piezometers), leachate tanks and head wells, gas probes, gas extraction wells, sedimentation ponds, and surface water sampling points have been collected in some cases since the late 1970s.

When planning an environmental groundwater investigation, it is critical to consider permeability, gradient, geological medium, and groundwater flow direction to help determine piezometer installation details and location.

Choice of Sampling Locations

Another critical part of a landfill monitoring program is the choice of the sampling locations.

They must be representative of high gas migration and explosive potential areas. In addition to locating a sampling location, it is important to identify open flames and ignition sources. The monitoring also has to take into account properties that are separated from landfill gas.

Landfill Site Monitoring

There are different types of landfill monitoring to consider, as well as the factors that should be considered when reviewing the results of methane escape to air modelling.

While environmental health professionals seldom design a landfill monitoring program, they may be asked to review the plan and provide comments. In addition to reviewing the monitoring plan, they are also often asked to interpret the data obtained from the tests.

But, do note that there’s no need to choose just one type for landfill monitoring test. A number of test methods will usually be needed.

One of the main technology used for landfill gas monitoring is infrared (IR). The IR camera was invented by the founder of Edinburgh Instruments in 1976.

Since then, it has been widely used by leading landfill gas analyzer developers. However, this technology has not been thoroughly validated for use in landfills by some regulatory bodies. IR cameras can identify hot spots and emission points in landfills and can complement SEM.

There may also be other technologies available in the market that can provide the same, or similar, information.

Regulatory Requirements in Brief

Landfills with certain types of waste must submit their monitoring data to the local government environmental emissions regulatory department to be able to comply with local waste management and health authority regulations.

You can get guidance from the website of your environmental regulatory body or state and federal environmental compliance officials. Some professional bodies provide resource packs which may contain help documents that show you how to enter specific data.

For example, the Air Vapor Data Help Document provides instructions for entering measurements of soil gas in landfills. You can enter air samples into the Results Template. Soil gas measurements should be entered into the Air Vapour Database.

A Landfill’s Lifecycle

Landfill monitoring should be a part of every landfill’s lifecycle. The monitoring must assess the health risks posed by the landfills as well as the overall environmental impact of the site.

Professional monitoring services available to landfill operators include full interpretive annual reporting, groundwater contouring, time series, and piper and Schoeller analyses.

The Final Word – A Conclusion

A comprehensive monitoring plan should be prepared at the outset as its compliance is essential for ensuring acceptable low pollution levels from a safe landfill.

It is vital to ensure that all environmental controls are in place for the duration of the landfill’s contaminating life.


Specific tools and methods are available to monitor landfill operations, with special attention being given to methods for improving the monitoring of waste disposal practices.

Key monitoring parameters and methodologies covered include liquids such as water volume, depth, pressure and chemicals composition. The resulting waste product is the resulting biogas. The use of instruments within the dump for measuring the temperature, moisture, and pressure is not discussed here in any detail.


Waste Landfill. United States: N. p., 2000. Web. doi:10.2172/769335. Copy to clipboard Lindberg, JW, & Chou, CJ. Groundwater Monitoring Plan for the Solid Waste Landfill. The United States. https://doi.org/10.2172/769335 (Lindberg, JW, and Chou, CJ. 2000).

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