Groundwater monitoring at Waste Management landfills

Fact sheetAs the industry’s leading provider of wastemanagement and environmental services, Waste Managementoperates nearly 300 landfills across the United States andCanada. While these facilities vary greatly in size, location,materials accepted and surrounding geology and hydrology,environmental protection is a day-to-day concern at everyone of these facilities. A major component of the company’scommitment to environmental stewardship is the corporateGroundwater Protection Program, which uses innovative techni-cal practices and proactive programs that exceed regulatory andindustry leadership standards. This fact sheet describes howWaste Management protects groundwater at its landfills.

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Some terminology

Groundwater is water below ground that supplies wells andsprings. To prevent the contamination of groundwater bywaste, modern landfills are engineered to be closed systems,and incorporate a liner system designed to prevent the escapeof liquids. Generally, the foundation of this liner system is athick layer of compacted clay; above this is a synthetic“geomembrane” liner, usually in the form of a high-densitypolyethylene sheet. A third component of the liner system is a

Constituent - generally, a single component of a mixture. Ingroundwater monitoring, samples are analyzed for the levelsof specific constituents they may contain, for example heavymetals like lead.

Groundwater - water in the earth that supplies wells and springs.

Leachate - liquid that collects inside a landfill. It comes from thewastes deposited, as well as from precipitation that enters thelandfill.

Leachate collection system - a series of pipes and pumps thatcollect leachate from the bottom of a landfill (just above theliner), so that it can be removed and treated.

Liner system - - a barrier to the passage of liquids installed inthe “floor” and sides of a landfill. The typical liner system in amodern landfill consists of multiple layers (see the illustrationabove). At the top is one or more synthetic “geomembrane”layers that are impermeable to liquids, and below this is a thicklayer of compacted clay to contain liquids. Above these liners isa layer of porous material where the leachate collection systemis located.

Sampling - - the process of collecting small amounts of material orinformation that represent the whole from which they are taken.Variations in sampling techniques are one of the largest poten-tial sources of variability in groundwater analysis.

Leachate Collection LayerGravelPerforated Leachate Collection Pipe

Compacted Clay Liner

Prepared Subgrade(Underlying Soil)

Geomembrane Liner

Leachate CollectionSystem

LinerSystem

Filter Geotextile

network of pipes that collects leachate so that it canbe removed, treated and disposed of properly. This leachatecollection system is surrounded by porous material like gravel,so that leachate drains to the collection system.

When a landfill reaches its permitted capacity, it is closed.Closure involves installation of a relatively impermeable cap atthe top of the landfill to minimize entry of liquids into thewaste, thus decreasing the volume of leachate produced afterclosure. Cap components may vary by geographic regiondepending on precipitation; in general, the cap includes clay,geomembrane and topsoil layers. The topmost layer is soil,which is planted with grasses to prevent erosion, and in agrowing number of instances, to support such beneficialpost-closure uses as recreational areas.

This design uses two layers of protection—engineeredcontrol systems and natural geologic barriers. A groundwatermonitoring network provides a third level of protection tosafeguard human health and the surrounding environment, andto meet federal and state requirements. Groundwater testingprograms are mandated by federal and state requirementsto check for leakage. Managed by the U.S. Environmental

odern landfills and groundwaterM

A liner system includes multiple layersdesigned to prevent the escape of liquids from the bottom and

sides of the landfill. It also includes a system that automaticallycollects the liquids that accumulate at the bottom of the landfill.

rotecting groundwaterP

Protection Agency, state environmental agencies, and in manycases forming a part of the landfill owner’s operating permit,these requirements typically specify a list of contaminants tobe tested for, and also the frequency with which this testingshould be done.

©2008, Waste Management From everyday collection to environmental protection, Think Green.® Think Waste Management.

ow groundwater monitoringis performed

H

eeting and exceeding regulatoryrequirements

MWaste Management’s Groundwater Protection Program wasdesigned not only to address federal and state regulatory andpermitting requirements, but also to ensure that the companyupholds the highest standards of environmental responsibility.This program:â Observes stringent “chain-of-custody” procedures to ensure

accuracy of results and reporting.â Requires that groundwater samples be analyzed by an

independent laboratory.â Establishes comprehensive, formal guidelines for groundwater

sampling, including procedures, training requirements andformal audits.

â Exceeds requirements in many areas by analyzing for moreinorganic parameters than is required by the regulations orpermitting requirements of the landfill.

â Incorporates a remedial action system that specifies in detailthe actions to be taken should constituents be detected at alevel above the site and well-specific background values.

â Requires that every landfill have an employee who is respon-sible for groundwater monitoring and compliance with thesite permit in terms of notification and response actions.

On a schedule that is described in the site’s operatingpermit, samples are collected from our groundwater monitor-ing wells, sent to an analytical laboratory for analyses, andthe results are reported to both Waste Management and allappropriate regulatory agencies. All groundwater samplecollection and analyses are conducted at independentlaboratories.

Analytical testing results are compared to site-specificbackground levels to determine if a change has occurred.Federal and state regulations prescribe specific responses if anexceedance of a background value has been verified duringsampling; if this occurs, a notification is placed into theOperating Record and submitted to the regulatory authority.This system of monitoring occurs regularly throughout landfilloperation, and continues for many years following closure ofthe facility.

Sampling Cap

Seal

Highest SeasonalGroundwater Level

Lowest SeasonalGroundwater Level

Bottom Cap

Protection Post

Concrete Pad

SoilSoil

Seal

Monitoring Well Depth Varies.

Weep Hole

Varies

Slotted Casing

Protective Surface Casing

Gravel

Groundwater is monitored through a series of wells locatedaround the landfill on Waste Management property. The wellnetwork is certified by an independent qualified groundwaterscientist as being effective to detect a release of leachatefrom the landfill to shallow groundwater (or surface waterif more appropriate).

For more information contact Waste Management’s localgroundwater protection manager.

Groundwater is monitored by collecting samples of groundwater from aseries of wells located around the landfill.

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