Landfill: Difference between revisions
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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 Department of the Environment produced a series of Waste Management Papers (WMP)<ref name="refB" /><ref name="refA" /><ref name="ref27" /> over the period from the late 1970s to 1997. WMP 26B contains a review of the types of designs. The design employed at any particular design 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. | The Department of the Environment produced a series of Waste Management Papers (WMP)<ref name="refB" /><ref name="refA" /><ref name="ref27" /> over the period from the late 1970s to 1997. WMP 26B contains a review of the types of designs. The design employed at any particular design 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 Gas=== | ===Landfill Gas=== | ||
Another product of waste decomposition is landfill gas. This is a mixture of various components, principally methane. WMP28B<ref name="refB" /> also contains a useful review of the generation and evolution of 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. WMP28B<ref name="refB" /> also contains a useful review of the generation and evolution of landfill gas. | ||
Landfill gas needs to be managed to prevent build-up | Landfill gas needs to be managed to prevent build-up such that it migrates off site through the surrounding soils and rock (where it can accumulate and create explosive conditions) or is released into the atmosphere (as it is a significant potential contribution to greenhouse gases). | ||
Management of landfill gas consists of the prevention of build up by active removal of the gas from the waste mass by extraction (and subsequent destruction by high temperature flare or via the creation of energy for subsequent use on site or for export ot the national grid) 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. | |||
<ref name="ref27" /> deals with methods for management of landfill gas | |||
==Landfill Location Policy in the UK== | ==Landfill Location Policy in the UK== | ||
The basic criteria for suitable landfill locations are set out in the Landfill Directive, which says in Annex 1: | ===Landfill Directive=== | ||
The basic criteria for suitable landfill locations are set out in the [[Landfill Directive]], which says in Annex 1: | |||
''1.1 The location of a landfill must take into consideration requirements relating to: | |||
''(a) the distances from the boundary of the site to residential and recreation areas, waterways, water bodies and other agricultural or urban sites;''<br> | ''(a) the distances from the boundary of the site to residential and recreation areas, waterways, water bodies and other agricultural or urban sites;''<br> | ||
''(b) the existence of groundwater, coastal water or nature protection zones in the area;''<br> | ''(b) the existence of groundwater, coastal water or nature protection zones in the area;''<br> | ||
''(c) the geological and hydrogeological conditions in the area;''<br> | ''(c) the geological and hydrogeological conditions in the area;''<br> | ||
''(d) the risk of flooding, subsidence, landslides or avalanches on the site;''<br> | ''(d) the risk of flooding, subsidence, landslides or avalanches on the site;''<br> | ||
''(e) the protection of the nature or cultural patrimony in the area.''<br> | ''(e) the protection of the nature or cultural patrimony in the area.''<br> | ||
''1.2. The landfill can be authorised only if the characteristics of the site with respect to the | ''1.2. The landfill can be authorised only if the characteristics of the site with respect to the aforementioned requirements, or the corrective measures to be taken, indicate that the landfill does not pose a serious environmental risk.''<br> | ||
<br> | |||
===UK Implementation of Landfill Directive=== | |||
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 | |||
* Groundwater protection: Principles and practice (GP3) as updated by The Environment Agency’s approach to groundwater protection | |||
===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]]). | |||
Source Protection Zones are defined and determined by the [[EA]] 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. | |||
''• 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'' | |||
The locations of SPZs are shown on the [[EA]] "what's in my backyard" page of their website<ref>[http://apps.environment-agency.gov.uk/wiyby/default.aspx What's in My Backyard]</ref>. | |||
The relevant [[EA]] policy is as follows: | |||
''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:'' | * ''The Environment Agency will normally object to any proposed landfill site in groundwater SPZ1.'' | ||
* ''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:'' | |||
==Landfill Management== | ==Landfill Management== | ||
The management of a Landfill not only encompasses the engineering and and monitoring to ensure permit compliance, but also encompasses the receipt and placement of the waste while the site is open/operational. In general terms, the following day to day activities take place and are further detailed in WMP26B <ref name="refB" />and ISWA's Guidelines<ref>ISWA's LANDFILL OPERATIONAL GUIDELINES (2nd Edition 2010 ISWA WORKING GROUP ON LANDFILL)</ref>: | |||
Landfill | |||
In general terms, the following activities take place: | |||
* waste is received at the site and the vehicle and contents weighed | * waste is received at the site and the vehicle and contents weighed | ||
* all paperwork is checked to ensure that the received materials are acceptable for disposal at the site | * all paperwork is checked to ensure that the received materials are acceptable for disposal at the site | ||
* a visual check is made of the waste at the weighbridge to confirm that the material has been correctly described | * a visual check is made of the waste at the weighbridge to confirm that the material has been correctly described | ||
* the vehicle is dispatched to the tipping area where its | * the vehicle is dispatched to the tipping area where its content are discharged | ||
* site waste is pushed out into a working area and the nature of the waste checked to confirm that it has been correctly consigned and is acceptable for disposal at | * site waste is pushed out into a working area in the operational/active landfill cell and the nature of the waste checked to confirm that it has been correctly consigned and is acceptable for disposal at the site prior to final placement and compaction | ||
* the vehicle leaves the working area and is re-weighed at the weighbridge (empty) and an appropriate receipt given to the driver | * the vehicle leaves the working area and is re-weighed at the weighbridge (empty) and an appropriate receipt given to the driver | ||
The working area utilised on each day is kept to a minimum area and waste is tipped in relatively thin layers. This practice is maintained to minimise the area open to the atmosphere and the potential attraction to avian scavengers. At the end of every day a layer of suitable inert material is spread over that day's input to minimise wind-blown litter and prevent birds and rodents from accessing the tipped waste. | The working area utilised on each day is kept to a minimum area and waste is tipped in relatively thin layers. This practice is maintained to minimise the area open to the atmosphere and the potential attraction to avian scavengers. At the end of every day a layer of suitable inert material is spread over that day's input to minimise wind-blown litter and prevent birds and rodents from accessing the tipped waste. | ||
Site operations and waste placement are usually carried out with various items of fixed and mobile plant, such as: | |||
* 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) | |||
* 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 | |||
==Landfill Restoration, Closure and Aftercare== | ==Landfill Restoration, Closure and Aftercare== | ||
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Landfill sites are generally restored (finished) to green space, such as agriculture, forestry or (less often) public open space. | Landfill sites are generally restored (finished) to green space, such as agriculture, forestry or (less often) public open space. | ||
The final engineering structure | The final engineering structure is an '''engineered capping layer''' on top of the final layer of waste. Sub-soil and then top soil is placed on to the engineered capping layer, often termed the restoration levels or horizon. Landfill sites are usually restored progressively in phases as the waste mass reached final levels. The final restoration is usually defined in the [[Planning Permission]] for the site. | ||
The | 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 landfill gas within the waste | |||
*To repel/shed rainwater and surface water to reduce the production of Leachate | |||
*To provide a barrier to root growth in the soils from the waste | |||
*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. This can be replaced or supplemented by flexible membranes such as LLDPE (Linear Low Density Polyethylene) or GCL (Geo-synthetic Clay) in varying combinations. Membranes can be laid in an over-lapped with no fused joints or can be overlapped and welded together similar to lining systems. | 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 can be replaced or supplemented by flexible membranes such as LLDPE (Linear Low Density Polyethylene) or GCL (Geo-synthetic Clay) in varying combinations. Membranes can be laid in an over-lapped with no fused joints or can be overlapped and welded together similar to lining systems. | ||
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. | ||