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The 'go-to' guidance for many in the landfill sector in the UK is still the waste management papers produced in the mid and late 1990's: | The 'go-to' guidance for many in the landfill sector in the UK is still the waste management papers produced in the mid and late 1990's by the Department of Environment (now [[DEFRA]]): | ||
*Waste Management Paper 26B (WMP26B)<ref name="refB">Waste Management Paper 26B (WMP26B): Landfill Design, Construction and Operational Practice</ref> | *Waste Management Paper 26B (WMP26B)<ref name="refB">Waste Management Paper 26B (WMP26B): Landfill Design, Construction and Operational Practice</ref> | ||
*Waste Management Paper 26A (WMP26A)<ref name="refA">Waste Management Paper 26A (WMP26A): Landfill Completion</ref> | *Waste Management Paper 26A (WMP26A)<ref name="refA">Waste Management Paper 26A (WMP26A): Landfill Completion</ref> | ||
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The underlying geology and hydrogeology of a landfill is especially significant if there is an '''aquifer''' that is relied upon for drinking water or other extraction purposes. One definition of aquifer is from Freeze and Cherry (1979): “''An aquifer is best described as a saturated permeable geologic unit that can transmit significant quantities of waste under ordinary hydraulic gradients''”. | The underlying geology and hydrogeology of a landfill is especially significant if there is an '''aquifer''' that is relied upon for drinking water or other extraction purposes. One definition of aquifer is from Freeze and Cherry (1979): “''An aquifer is best described as a saturated permeable geologic unit that can transmit significant quantities of waste under ordinary hydraulic gradients''”. | ||
In the England and Wales, the [[EA]] categorize aquifers to be consistent with the [[Water Framework Directive]]. The categories are Principal Aquifer, Secondary Aquifer and Unproductive Strata. Previously the phrases major aquifer and minor aquifer were utilized. Similar arrangements exist in Scotland and are supervised by [[SEPA]]. | In the England and Wales, the [[EA]] categorize aquifers to be consistent with the [[Water Framework Directive]]. The categories are Principal Aquifer, Secondary Aquifer and Unproductive Strata. Previously the phrases major aquifer and minor aquifer were utilized. Similar arrangements exist in Scotland and are supervised by [[SEPA]]. In locating landfills, consideration is given to aquifers in terms of their Source Protection Zoning (see below). | ||
The relevance of the hydrogeological setting within which a landfill is located arises from the need to assess the technical precautions and engineering requirements for a landfill to be authorized such that unacceptable environmental impacts are prevented. This assessment is undertaken via a '''Hydrogeological Risk Assessment''' ('''HRA'''); this is submitted as supporting document to an [[Environmental Permit]] application and takes a risk based approach to the location of the landfill and the engineering required. Again, similar arrangements are in place in Scotland, Wales and Northern Ireland. | The relevance of the hydrogeological setting within which a landfill is located arises from the need to assess the technical precautions and engineering requirements for a landfill to be authorized such that unacceptable environmental impacts are prevented. This assessment is undertaken via a '''Hydrogeological Risk Assessment''' ('''HRA'''); this is submitted as supporting document to an [[Environmental Permit]] application and takes a risk based approach to the location of the landfill and the engineering required. Again, similar arrangements are in place in Scotland, Wales and Northern Ireland. | ||
In the case of Principal Aquifers, which are of the highest quality and use, it is unlikely that any HRA will come to the conclusion, even with extensive engineering, that a landfill will be able to be located above such an aquifer (see Landfill location below). | In the case of Principal Aquifers, which are of the highest quality and use, it is unlikely that any HRA will come to the conclusion, even with extensive engineering, that a landfill will be able to be located above such an aquifer (see Landfill location below). | ||
===[[Landfill Gas]]=== | |||
Another product of waste decomposition is [[Landfill Gas]]. This is a mixture of various components, principally methane and is a [[Biogas]] not dissimilar to that generated in an [[Anaerobic Digestion]] facility. | |||
Management of [[Landfill Gas]] consists of the prevention of build up by active removal of the gas from the waste mass by extraction and the prevention of migration and escape by the containment barrier/lining system and the restoration/capping systems. WMP27<ref name="ref27" /> deals with methods for management of landfill gas. | |||
===Landfill Engineering=== | ===Landfill Engineering=== | ||
Landfill engineering is a phrase used to describe the preparation and on-going engineering required to operate a landfill site, and overall design, approach and engineering solution is often referred to as a whole as a '''containment system'''. What is required at any particular site in the UK depends upon the proposals made by the permit holder to protect the environment as part of obtaining an [[Environmental Permit]] (with the HRA and the containment system and engineering design being a key part of any such submission) and any subsequent modifications agreed between the permit holder and the regulator ([[EA]], [[NRW]] or [[SEPA]]). | Landfill engineering is a phrase used to describe the preparation and on-going engineering required to operate a landfill site, and overall design, approach and engineering solution is often referred to as a whole as a '''containment system'''. What is required at any particular site in the UK depends upon the proposals made by the permit holder to protect the environment as part of obtaining an [[Environmental Permit]] (with the HRA and the containment system and engineering design being a key part of any such submission) and any subsequent modifications agreed between the permit holder and the regulator ([[EA]], [[NRW]] or [[SEPA]]). | ||
Notwithstanding the risk-based technical design of the landfill engineering, there are minimum requirements imposed by the Landfill Directive and subsequent UK legislation – [[The Landfill (England and Wales) Regulations 2002]] and the [[Landfill (England and Wales) (Amendment) Regulations 2005|Landfill Regulations 2005]]. | Notwithstanding the risk-based technical design of the landfill engineering, there are minimum requirements imposed by the Landfill Directive and subsequent UK legislation – [[The Landfill (England and Wales) Regulations 2002]], [[The Landfill (Scotland) Regulations 2003]] and the [[Landfill (England and Wales) (Amendment) Regulations 2005|Landfill Regulations 2005]]. | ||
The design will have been produced taking heed of the technical precautions required to satisfy the regulator that the site will not have an unacceptable impact upon the environment and that the approved design will comply with the requirements of the Landfill Directive. These precautions will have been validated against the various risk assessments required to accompany a permit application. | The design will have been produced taking heed of the technical precautions required to satisfy the regulator that the site will not have an unacceptable impact upon the environment and that the approved design will comply with the requirements of the Landfill Directive. These precautions will have been validated against the various risk assessments required to accompany a permit application. | ||
Usually the application will be accompanied by risk assessments of the hydrogeological impact of the site, the potential for | Usually the application will be accompanied by risk assessments of the hydrogeological impact of the site, the potential for [[Landfill Gas]] release and the stability of any engineering designs proposed. There will be additional risk assessments required for operational matters such as dust, noise and amenity impacts; these are largely managed by operational techniques, but occasionally there will be elements of mitigation required that constitute site engineering (e.g. the construction of noise bunds).<br> | ||
Sites which were authorised historically did not require engineering and such sites without an engineered lining system are commonly described as “'''dilute and disperse'''”. Notwithstanding the lack of site engineering, some evaluation of their pollution potential was undertaken. This mainly consisted of a simple evaluation of the ability of the surrounding geology to adsorb contamination to determine likely consequential pollution effects. This evaluation considered the ability of the ground to “'''dilute and disperse'''” the impact of the site, hence the common name. | Sites which were authorised historically did not require engineering and such sites without an engineered lining system are commonly described as “'''dilute and disperse'''”. Notwithstanding the lack of site engineering, some evaluation of their pollution potential was undertaken. This mainly consisted of a simple evaluation of the ability of the surrounding geology to adsorb contamination to determine likely consequential pollution effects. This evaluation considered the ability of the ground to “'''dilute and disperse'''” the impact of the site, hence the common name. | ||
Landfill engineering design evolved in the 1980s, such that new '''dilute and disperse''' sites became less likely to be granted consent by the regulator. At the time, this was not supported by the implementation of any new specific legislative drivers, the principal legislation remaining the [[Control of Pollution Act 1974]]. This required landfills to be licensed by local authorities. In assessing licence applications, local authorities were required to ensure the prevention of pollution to water and danger to public health. This requirement established a rationale for assessment and its implementation evolved over the period from 1976 onwards. With the introduction of subsequent legislation mentioned elsewhere on this page, the regulatory role moved from local authorities to the [[EA]] (and in due course the [[NRW]], [[SEPA]] and [[NIEA]]) and coincided with the Landfill Directive and Groundwater Directive which set minimum standards and requirements. | Landfill engineering design evolved in the 1980s, such that new '''dilute and disperse''' sites became less likely to be granted consent by the regulator. At the time, this was not supported by the implementation of any new specific legislative drivers, the principal legislation remaining the [[Control of Pollution Act 1974]]. This required landfills to be licensed by local authorities. In assessing licence applications, local authorities were required to ensure the prevention of pollution to water and danger to public health. This requirement established a rationale for assessment and its implementation evolved over the period from 1976 onwards. With the introduction of subsequent legislation mentioned elsewhere on this page, the regulatory role moved from local authorities to the [[EA]] (and in due course the [[NRW]], [[SEPA]] and [[NIEA]]) and coincided with the [[Landfill Directive]] and [[Groundwater Directive]] which set minimum standards and requirements). | ||
Landfill sites that incorporate engineered barriers are known as “'''containment facilities'''”. The design of such facilities has more than one form and can incorporate different numbers of layers and different designs. These layers are conventionally known as the “'''landfill lining system'''”.<br> | Landfill sites that incorporate engineered barriers are known as “'''containment facilities'''”. The design of such facilities has more than one form and can incorporate different numbers of layers and different designs. These layers are conventionally known as the “'''landfill lining system'''”.<br> | ||
The Landfill Directive sets out minimum requirements for site engineering. In simple terms, all sites require a "geological barrier" and some sites are additionally required to have an "artificial sealing liner". The most common manner in which these requirements are deal with is by having a clay liner of 1m metre thickness of low permeability engineered clay (permeability of less than 1x10-9 metres per second) overlain with 2mm thick welded HDPE (high density polyethylene) lining membrane. Typically, this would be further overlain with a geotextile protection layer and then a drainage layer of aggregate and pipework. | The [[Landfill Directive]] sets out minimum requirements for site engineering. In simple terms, all sites require a "geological barrier" and some sites are additionally required to have an "artificial sealing liner". The most common manner in which these requirements are deal with is by having a clay liner of 1m metre thickness of low permeability engineered clay (permeability of less than 1x10-9 metres per second) overlain with 2mm thick welded HDPE (high density polyethylene) lining membrane. Typically, this would be further overlain with a geotextile protection layer and then a drainage layer of aggregate and pipework. | ||
The design employed at any particular landfill would be informed by the outcome of the HRA which would assess the likely impact of a site upon the environment taking account of the design proposed. In general terms, the most sensitive sites would require the greatest degree of engineering. | |||
Landfills are constructed in discrete parts known as “[[Landfill Cell|landfill cells]]”. The sub-division into cells is undertaken so as to minimise the operating area and consequently minimise leachate generation and make the site more manageable in terms of odour and litter control. Sub-division also enables the site engineering to be constructed progressively as the site fills. | Landfills are constructed in discrete parts known as “[[Landfill Cell|landfill cells]]”. The sub-division into cells is undertaken so as to minimise the operating area and consequently minimise leachate generation and make the site more manageable in terms of odour and litter control. Sub-division also enables the site engineering to be constructed progressively as the site fills. | ||
==Landfill Location Policy in the UK== | ==Landfill Location Policy in the UK== | ||
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The requirements of the [[Landfill Directive]] are brought into UK guidance via various pieces of legislation and [[EA]] guidance, notably: | The requirements of the [[Landfill Directive]] are brought into UK guidance via various pieces of legislation and [[EA]] guidance, notably: | ||
* Environmental Permitting (England and Wales) Regulations 2010 | * [[Environmental Permitting (England and Wales) Regulations 2010]] | ||
* Regulatory Guidance Series, No LFD 1 - Understanding the Landfill Directive | * [[Regulatory Guidance Series, No LFD 1 - Understanding the Landfill Directive]] | ||
* Environmental Permitting Guidance - The Landfill Directive - For the Environmental Permitting (England and Wales) Regulations 2010 | * [[Environmental Permitting Guidance - The Landfill Directive - For the Environmental Permitting (England and Wales) Regulations 2010]] | ||
* Groundwater protection: Principles and practice (GP3) as updated by The Environment Agency’s approach to groundwater protection | * [[Groundwater protection: Principles and practice (GP3)]] as updated by The Environment Agency’s approach to groundwater protection | ||
===Source Protection Zones for Groundwater=== | ===Source Protection Zones for Groundwater=== | ||
In essence these policies rely upon a risk assessment of each proposed landfill location, set into the context of the site and whether or not it is within a '''Source Protection Zone''' ('''SPZ''') for a protected groundwater abstraction or within a Major Aquifer (as defined by the [[EA]]). | In essence these policies rely upon a risk assessment of each proposed landfill location, set into the context of the site and whether or not it is within a '''Source Protection Zone''' ('''SPZ''') for a protected groundwater abstraction or within a Major Aquifer (as defined by the [[EA]]). | ||
The relevant [[EA]] policy is as follows: | The relevant [[EA]] policy is as follows: | ||
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* ''For all other proposed landfill site locations, a risk assessment must be conducted based on the nature and quantity of the wastes and the natural setting and properties of the location.'' | * ''For all other proposed landfill site locations, a risk assessment must be conducted based on the nature and quantity of the wastes and the natural setting and properties of the location.'' | ||
* ''Where this risk assessment demonstrates that active long-term site management is essential to prevent long-term groundwater pollution, the Environment Agency will object to sites:'' | * ''Where this risk assessment demonstrates that active long-term site management is essential to prevent long-term groundwater pollution, the Environment Agency will object to sites:'' | ||
** below the water table in any strata where the groundwater provides an important contribution to river flow, or other sensitive receptors'' | |||
** within SPZ2 or 3'' | |||
** on or in a principal aquifer'' | |||
Source Protection Zones are defined and determined by the [[EA]] <ref>The locations of SPZs are shown on the [[EA]] "what's in my backyard" page of their website</ref><ref>[http://apps.environment-agency.gov.uk/wiyby/default.aspx What's in My Backyard]</ref>. as follows: | |||
* SPZ1 - also known as the Inner Zone - is any land within 50 days (groundwater) travel time from a groundwater source, with a minimum radius of 50 metres; | |||
* SPZ2 - also known as the Outer Zone - is any land within 400 days (groundwater) travel time from a groundwater source, with a minimum radius of 250 metres; | |||
* SPZ3 - also known as the Total Catchment - is defined as the area around a source within which all groundwater recharge is presumed to be discharged at the source. | |||
==Landfill Management== | ==Landfill Management== | ||
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Site operations and waste placement are usually carried out with various items of fixed and mobile plant, such as: | Site operations and waste placement are usually carried out with various items of fixed and mobile plant, such as: | ||
* weighbridge and associated site office | * weighbridge and associated site office | ||
* appropriate mobile plant to push the waste out into layers and provide compaction of the waste (this usually comprises bulldozer and/or wheeled compactor; these can be in multiple if the site has a large daily input) | * appropriate mobile plant to push the waste out into layers and provide compaction of the waste (this usually comprises bulldozer and/or wheeled compactor as shown in the picture at the top of this page; these can be in multiple if the site has a large daily input) | ||
* wheelwash to clean the wheels of road-going vehicles leaving the site to enter the public highway | * wheelwash to clean the wheels of road-going vehicles leaving the site to enter the public highway | ||
* various ancillary equipment to maintain dust suppression, surface water control and to deal with pests and birds/scavengers | * various ancillary equipment to maintain dust suppression, surface water control and to deal with pests and birds/scavengers | ||
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The engineered capping can be constructed in several ways and the design selected is evaluated in the same way as the landfill lining system, taking account of the various engineering constraints and impacts to be avoided at each site. The design also undergoes similar risk assessment to the lining system. The principle objectives of the engineering capping layer and restoration soils are: | The engineered capping can be constructed in several ways and the design selected is evaluated in the same way as the landfill lining system, taking account of the various engineering constraints and impacts to be avoided at each site. The design also undergoes similar risk assessment to the lining system. The principle objectives of the engineering capping layer and restoration soils are: | ||
*To contain | *To contain [[Landfill Gas]] within the waste | ||
*To repel/shed rainwater and surface water to reduce the production of Leachate | *To repel/shed rainwater and surface water to reduce the production of [[Leachate]] | ||
*To provide a barrier between the waste and the roots of vegetation growing in the soils | *To provide a barrier between the waste and the roots of vegetation growing in the soils | ||
*To provide an effective growing medium and afteruse for the site | *To provide an effective growing medium and afteruse for the site | ||
Commonly, the capping layer will consist of a compacted clay layer of 1 metre thickness, placed on the last levels of the waste (which is often a thicker layer of final cover to provide a uniform level for placement of the material). This capping layer can be replaced or supplemented by '''flexible membranes''' such as LLDPE (Linear Low Density Polyethylene) or GCL (Geo-synthetic Clay) in varying combinations. Flexible membranes can be laid over-lapped with no fused joints | Commonly, the capping layer will consist of a compacted clay layer of 1 metre thickness, placed on the last levels of the waste (which is often a thicker layer of final cover to provide a uniform level for placement of the material). This capping layer can be replaced or supplemented by '''flexible membranes''' such as LLDPE (Linear Low Density Polyethylene) or GCL (Geo-synthetic Clay) in varying combinations. Flexible membranes can be welded together (or fused) similar to engineering lining systems or laid over-lapped with no fused joints. | ||
Soil thickness will depend upon the proposed afteruse of the site; uses involving deep-rooted plants will require thicker soils to protect the engineered capping layer from root-penetration. | Soil thickness will depend upon the proposed afteruse of the site; uses involving deep-rooted plants will require thicker soils to protect the engineered capping layer from root-penetration. | ||
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===Settlement and Surcharge=== | ===Settlement and Surcharge=== | ||
As the waste mass decomposes, the waste infill material settles under its own weight to occupy less volume. This process is known as '''settlement'''. | As the waste mass decomposes, the waste infill material settles under its own weight to occupy less volume. This process is known as '''settlement'''. | ||
Settlement in landfilled waste occurs due to loading and other processes including chemical and microbial actions. These processes are time-dependent, and are controlled by factors such as leachate composition, pH, temperature and moisture. As a result, settlement in landfilled waste, especially long-term settlement, is complex and difficult to predict in both magnitude and timing. Notwithstanding that, reasonably accurate estimates are commonly used. | Settlement in landfilled waste occurs due to loading and other processes including chemical and microbial actions. These processes are time-dependent, and are controlled by factors such as leachate composition, pH, temperature and moisture. As a result, settlement in landfilled waste, especially long-term settlement, is complex and difficult to predict in both magnitude and timing. Notwithstanding that, reasonably accurate estimates are commonly used. | ||
Landfill sites operate under the terms of a [[Planning Permission]]. Amongst the matters controlled by the permission will be the final levels to which the site must be restored. As the waste ages and decomposes the final level will settle to a lower level. In order to ensure that the agreed final levels are achieved after the majority of the decomposition and related settlement have finished, it is common to agree that the final levels can be exceeded initially - known as '''surcharging''' | Landfill sites operate under the terms of a [[Planning Permission]]. Amongst the matters controlled by the permission will be the final levels to which the site must be restored. As the waste ages and decomposes the final level will settle to a lower level. In order to ensure that the agreed final levels are achieved after the majority of the decomposition and related settlement have finished, it is common to agree that the final levels can be exceeded initially - known as '''surcharging''' as part of a Landfill Surcharge Allowance]]. It is conventional to have two sets of [[Landfill Settlement Contours]] agreed with the planning authority - '''pre-settlement contours''' and '''post-settlement contours'''. | ||
It is conventional to have two sets of | |||
== Landfill Monitoring == | == Landfill Monitoring == | ||
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* Quantity and type of waste received including any assessments of suitability for acceptance at the site | * Quantity and type of waste received including any assessments of suitability for acceptance at the site | ||
* Daily activity and waste placement log | * Daily activity and waste placement log | ||
* Leachate volume and quality within the waste mass | * [Leachate]] volume and quality within the waste mass | ||
* Leachate volume and quality extracted from the site and disposed | * [[Leachate]] volume and quality extracted from the site and disposed | ||
* Landfill | * [[Landfill Gas]] quantity and quality within the waste mass | ||
* Presence of | * Presence of [[Landfill Gas]] outside the site perimeter | ||
* Emissions of | * Emissions of [[Landfill Gas]] from the surface of the site | ||
* Groundwater quality outside the perimeter of the site | * Groundwater quality outside the perimeter of the site | ||
* Surface water quality in nearby water bodies | * Surface water quality in nearby water bodies | ||
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===Reasons for Leachate, groundwater and surface water monitoring=== | ===Reasons for Leachate, groundwater and surface water monitoring=== | ||
The specific reasons for | The specific reasons for [[Leachate]], groundwater and surface water monitoring at landfills are: | ||
* to demonstrate that the landfill is performing as designed; | * to demonstrate that the landfill is performing as designed; | ||
* to provide reassurance that | * to provide reassurance that [[Leachate]] controls are preventing pollution of the environment (by reference to a pre-established baseline); | ||
* to meet the control and monitoring requirements of legislation and in particular Regulations 14 and 15, as well as Schedule III, of the Landfill Regulations, this includes the requirement for control monitoring; | * to meet the control and monitoring requirements of legislation and in particular Regulations 14 and 15, as well as Schedule III, of the [[Landfill (England and Wales) (Amendment) Regulations 2005]], this includes the requirement for control monitoring; | ||
* to demonstrate compliance with the Groundwater Control and Trigger level requirements of Schedule 3 of the Landfill Regulations; | * to demonstrate compliance with the Groundwater Control and Trigger level requirements of Schedule 3 of the [[Landfill Regulations]]; | ||
* to indicate whether further investigation is required and, where the risks are unacceptable, the need for measures to prevent, reduce or remove pollution by | * to indicate whether further investigation is required and, where the risks are unacceptable, the need for measures to prevent, reduce or remove pollution by [[Leachate]]; | ||
* to identify when a site no longer presents a significant risk of pollution or harm to human health (to enable an application for a certificate of completion to be made, and thereby formally end the licensing or permitting process and the legal duty to monitor). | * to identify when a site no longer presents a significant risk of pollution or harm to human health (to enable an application for a certificate of completion to be made, and thereby formally end the licensing or permitting process and the legal duty to monitor). | ||
{| class="wikitable" | {| class="wikitable" | ||
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| [[File:Dip tape.png|400px|center|Dip Tape]]|| [[File:Monitoring well.png|300px|center|Monitoring well head]]|| [[File:Sampling well.png|300px|center|Well sampling]] | | [[File:Dip tape.png|400px|center|Dip Tape]]|| [[File:Monitoring well.png|300px|center|Monitoring well head]]|| [[File:Sampling well.png|300px|center|Well sampling]] | ||
|- | |- | ||
| Measurement Equipment || Well head for groundwater || Sampling from | | Measurement Equipment || Well head for groundwater || Sampling from [[Leachate]] well | ||
|- | |- | ||
| [[File:Gas monitoring.png|300px|center|Monitoring Multiple Gas Extraction wells]]|| [[File:Well monitoring.png|300px|center|Monitoring single gas well head]]||[[File:Gas well heads.png|300px|center|Gas well extraction system]] | | [[File:Gas monitoring.png|300px|center|Monitoring Multiple [[Landfill Gas]] Extraction wells]]|| [[File:Well monitoring.png|300px|center|Monitoring single gas well head]]||[[File:Gas well heads.png|300px|center|Gas well extraction system]] | ||
|- | |- | ||
| Monitoring Multiple Gas Extraction wells || Monitoring single | | Monitoring Multiple [[Landfill Gas]] Extraction wells || Monitoring single [[Landfill Gas]] well head || [[Landfill Gas]] well extraction system | ||
|} | |} | ||