Landfill operators: environmental permits

Jul 15, 2023

The design requirements that you need to meet in your environmental permit application and how to comply with your permit.

As the site operator you must design and build your landfill to protect the environment. This guide explains the design requirements that you need to meet when you apply for an environmental permit.

You need to carry out risk assessments when you apply for or change an environmental permit. You must submit your risk assessments to the Environment Agency as part of your permit application.

Check what information to include in your hydrogeological risk assessment.

Your risk assessments must show that you have designed your site to manage the environmental risks from your activity. This must include the:

The Environment Agency will only issue a permit if it’s satisfied that your proposed engineering design meets the necessary requirements. Your permit will include conditions that you must meet when constructing your landfill site.

Before you start constructing any new cell, development area or infrastructure you must submit your construction proposals to the Environment Agency. The Environment Agency will confirm whether it’s satisfied with your proposals.

You should also read the guide for how the Environment Agency makes decisions on landfill engineering.

You must have construction quality assurance (CQA) for the construction of all aspects of landfill engineering and infrastructure.

Engineering proposals at all landfill sites must:

You may be able to demonstrate that a geological barrier or artificial sealing liner may not be needed if it would add little or nothing to protect soil and water. You must demonstrate this through a hydrogeological risk assessment.

You must submit your risk assessment to the Environment Agency as part of your permit application.

You must follow design, construction and quality assurance procedures for each element of your landfill engineering and infrastructure. These are:

You must construct each element of your landfill engineering and infrastructure to recognised industry best practice.

The Environment Agency encourages the development and use of new methods and materials where it results in improved or equivalent environmental protection. Find out more about how the Environment Agency makes decisions on landfill engineering.

For earthworks, the design and specification must follow the guidance for the specification for highway works. This guidance sets out the acceptability of materials, characterisation testing, layer thickness and compaction for general fill.

You must also follow the guidance for earthworks in landfill engineering (LFE4) which explains the design and construction of earthworks at a landfill site.

You must have a geological barrier that meets the standards in earthworks in landfill engineering (LFE4).

Where the natural geology around your site does not provide enough protection for soil and water, you can artificially enhance the geological barrier. An artificially enhanced barrier must be at least 500mm thick. This prevents the sole use of a geosynthetic layer to enhance the geological barrier.

The geological barrier must:

Your groundwater risk assessment must demonstrate that the proposed geological barrier will provide sufficient attenuation to prevent a potential risk to soil and groundwater. Attenuation means the reduction in the contamination concentration or flux through biological, chemical and physical processes.

You may be able to show through a groundwater risk assessment that the geological barrier will provide little or no additional benefit.

Check what information to include in your hydrogeological risk assessment.

Where you need to construct a geological barrier you must follow the requirements of both the:

You must:

Your design specification must be the same as in your site-specific risk assessments.

Your proposal must include a risk assessment by the design engineer. It must demonstrate that any temporary structures will not damage the permanent works.

The Environment Agency will normally accept the use of natural clays or mudrocks for the construction of the geological barrier. You may need to process mudrocks before you incorporate them into the geological barrier. Your source evaluation report must confirm whether you need to process the material you will use to construct the geological barrier.

You may also use bentonite enriched soil for this purpose. You must follow the guidance in using bentonite enriched soils in landfill engineering (LFE10).

Your CQA plan must include the pass criteria for the proposed geological barrier.

You must describe how you are going to construct the geological barrier to meet your design specification.

Landfills for hazardous and non-hazardous waste must have a leachate collection and sealing system unless collecting leachate is not necessary. Find out how to manage the leachate produced by the waste in your landfill.

If you think you do not need to collect leachate you must demonstrate this to the Environment Agency. You must base this on a risk assessment that considers the location of the landfill and the waste types it will accept. The Environment Agency must confirm that it is satisfied that you do not need to collect leachate.

The leachate collection and sealing system consists of:

You do not need to collect leachate at landfills for inert waste.

Your landfill design must include an artificial sealing liner if you need to collect leachate. The artificial sealing liner should normally extend up the side walls.

If you do not consider this necessary, you must justify this through a site-specific risk assessment. This risk assessment must consider landfill gas as well as potential leachate emissions.

If you want to increase leachate levels in your site you must have adequate engineered containment up the side walls.

Landfills below the water table do not need an artificial sealing liner if both of the following are met:

The design of the artificial sealing liner must be based on your risk assessment and must consider the overall landfill design. This must demonstrate that there is no likelihood of unacceptable discharges from the landfill over its entire lifecycle.

The Environment Agency will only accept mineral artificial sealing liners where there is a substantial natural geological barrier. The requirement for an artificial sealing liner is most likely to be met by a geomembrane or a dense asphaltic concrete (DAC) liner.

As well as being very low permeability, your artificial sealing liner must be stable, durable and resistant to chemical attack, puncture and rupture.

Your stability risk assessment must consider the interactions between the multiple layers in the lining system.

You must assess the chemical compatibility of the materials to be used to construct the artificial sealing liner with the probable waste, leachate and gas composition and temperature.

You must consider the effect of potential weaknesses or imperfections in the materials to be used on the performance of the artificial sealing liner.

You must protect geomembranes with suitable materials against:

Suitable materials include geotextiles and mineral materials.

You must carry out a cylinder test to show that you will use suitable material to protect the geomembrane.

Where you use a mineral (such as clay) as the artificial sealing liner, you must protect it against erosion, weathering, desiccation, vegetation and penetration. You must protect the liner with a suitable weather protection layer. You must place a geotextile separation layer between the upper surface of the mineral liner or weather protection layer and the leachate drainage layer.

Where you use a mineral as the artificial sealing liner, you may provide protection by increasing its thickness.

Where you use minerals to protect your geomembrane they must be:

Where you use a geotextile protection layer you must follow the guidance for using non-woven protector geotextiles in landfill engineering (LFE7).

You must make sure the placement of the protection layer does not damage or overstress the liner.

You must have an effective leachate collection and drainage system to manage the risk to groundwater and surface water.

You must be able to:

You must use geophysical leak detection on all cells where the artificial sealing liner is a geomembrane. This is to check for defects after the leachate drainage layer has been installed and before depositing waste.

Read guidance for leak location surveys – geophysical testing of geomembranes used in landfills in the industry code of practice (LGG 113).

You must include details of the geophysical leak detection survey you propose to use in your CQA plan.

You must include the results of the geophysical leak detection survey in your CQA validation report. This must include:

You must include scaled plans of the survey area. Plans must be accurate to 100mm and include the:

Your risk assessment may indicate that the lining system needs a leak interception layer. In this case, you must divide the system into compartments to help find significant leaks.

You must monitor your leak interception system.

You must specify the geosynthetic products you intend to use.

You must follow the guidance for the materials that you propose to use:

Your engineering design must assess the stability of the lining configuration for the design life of your site.

Your design must specify the required tensile strength of any geosynthetic material you propose to use. You must verify this strength in accordance with your CQA plan.

You must:

Read guidance on geosynthetic interface shear resistance testing in the industry code of practice (LGG 115).

You must describe how you are going to install the geosynthetic materials to meet your design specification. You must:

Where you use plant machinery to place the soil protection layers or the leachate drainage and collection layer, your CQA plan must confirm that the method of placement will not damage the underlying geosynthetic material.

Where you propose to use a geosynthetic material as a capping layer, your CQA plan must also:

A GCL may be used as part of an artificially enhanced geological barrier or to provide the sealing layer to a cap.

You must meet the design requirements for:

Needle punched (reinforced) GCLs must normally be used due to their internal shear strength. If you use unreinforced GCLs you must demonstrate their suitability.

You must confirm the total permeability and flux for your design.

The clay in a GCL must have an active sodium montmorillonite content of more than 70%.

You must consider the performance of the product you are proposing in relation to free swell and shear strength.

You must specify the:

Products must be tested in the factory to detect needle fragments. You must only use products where all needle fragments have been removed before they leave the factory. You must provide evidence from the manufacturer that needle detection has been carried out and all needle fragments have been removed.

You must minimise the number of seams and the amount of patching. Seams must run down a slope or be on a flat base.

Your CQA plan must include the pass criteria for the proposed geomembrane material. The pass criteria must meet the requirements described in using geosynthetic clay liners in landfill engineering (LFE3).

You must describe how you are going to install the GCL to meet your design specification.

Your CQA plan must include the following GCL specific requirements:

Geomembranes are flexible polymeric sheets that can be welded together.

You may use a geomembrane to meet the requirement for an artificial sealing liner or the sealing layer to a cap.

You must follow the design requirements for:

The liner you choose must be resistant to a wide range of chemicals over long periods of exposure.

You must carry out tests to determine the effects of leachate chemistry on the physical properties of the proposed geomembrane material for chemicals where there is no manufacturer’s data.

You must design leachate monitoring and extraction points so they spread the anticipated loads and do not overstress or puncture the geomembrane. Your design engineer must provide detailed design calculations and engineering drawings to show these structures will not damage the geomembrane throughout its design life.

You must consider potential desiccation of mineral liners beneath geomembranes.

Your CQA plan must include the pass criteria for the proposed geomembrane material. The pass criteria must meet the requirements described in using geomembranes in landfill engineering (LFE5).

You must describe how you are going to install the geomembrane to meet your design specification.

You must describe how you will determine the proposed panel layout for the geosynthetic materials before you install the geomembrane.

Your CQA plan must state that only suitably qualified, trained and experienced staff install the geomembrane liner. This must include both of the following:

You must use a company that is accredited, or working towards being accredited, to the BGA accreditation scheme for geomembrane installers.

You must minimise the number of welds and the amount of patching. Welds must run down a slope or be on a flat base.

Before using the geomembrane and at the start of each shift, you must carry out trial seams. This is to confirm that the set-up of each piece of seaming equipment is suitable for the conditions in which the geomembrane will be installed.

You must:

For geomembranes, you must select a suitable material beneath the leachate drainage material to provide protection. A range of materials, including geotextiles and mineral materials, can provide appropriate protection.

You must carry out a cylinder test to show the material you propose to use will protect the geomembrane.

Where you use a mineral material, you must specify the method of placement together with the thickness and particle size of this material.

Where you use a geotextile you must follow the design requirements for:

You must place the geotextile to the manufacturer’s recommendations.

No plant machinery must pass directly onto the exposed geotextile.

You must specify the minimum thickness of material that is required between any plant machinery that is placing the protection layer and the underlying geomembrane within your design.

You must make sure the method you use to place the protection layer will not damage the geomembrane.

Your CQA plan must include the pass criteria for the proposed geomembrane protection material. The pass criteria must meet the requirements described in using non-woven protector geotextiles in landfill engineering (LFE7).

Geotextiles must be manufactured from non-woven polypropylene or polyethylene fibres. This guidance does not cover woven geotextiles as they are not commonly used as protectors.

Where you propose to use a geotextile protection layer you must describe how you are going to install the geotextile to meet your design specification.

You must not use geotextiles made from post-consumer or post-industrial recycled materials.

Geotextile products must be tested in the factory to detect needle fragments. Needle fragments must be removed before the product leaves the factory. You must provide evidence from the manufacturer that needle detection has been carried out and all needle fragments have been removed.

You can meet the requirement for an artificial sealing liner by using a DAC liner system.

When designing a DAC liner you must consider:

You must produce a mix design report containing the source evaluation testing for the materials and specific mix design for a dense asphaltic lining.

You must produce a field trial report when you have completed your trial and send it to the Environment Agency. Your report must confirm or refine the mix design and proposed method statement for the actual construction.

Your CQA plan must include the pass criteria for the proposed DAC material.

You must include details of how you will undertake a trial liner on site to verify your mix design. Before the trial you must specify the:

You must describe your process for mixing and transporting the DAC layer and the asphaltic binder layer materials.

You must describe how you are going to construct the DAC in accordance with your design specification, including:

You must specify the type and frequency of CQA for each of the following elements of the DAC liner:

Your permit will include a compliance limit for leachate levels to minimise the rate of leachate emission through the base of the site.

To manage leachate you must:

If you want to use an alternative method for monitoring the level of leachate you must justify this through a site-specific risk assessment. You must include details of how you will calibrate any assumptions you have made.

The drainage system must cover the entire base of the cell. The perimeter side slope drainage system must transmit leachate to the base of the site. The side slope drainage system must be the subject of a risk-based design and may be different from the basal drainage system. The design of the side slope drainage system must consider both the management of leachate and landfill gas.

The Environment Agency will accept a 300mm thick granular drainage layer combined with an engineered slotted or perforated pipework system if you meet the following minimum design and installation criteria:

Such site-specific issues include:

The Environment Agency will accept carbonate minerals as part of leachate drainage blankets for non-hazardous waste sites. Carbonate minerals include limestone and dolomite derived aggregates.

You must confirm the grading of the drainage material using particle size distribution testing on the material after placement. The amount of fines may increase with handling on site. Therefore, an additional allowance of 2% of material passing the smallest sieve is acceptable.

Where the design uses a geomembrane, you must carry out a cylinder test to assess the actual performance of the proposed system.

The Environment Agency will accept other types of drainage material but you must demonstrate they are suitable. To do this, you must assess them for:

You must assess the stability of the drainage material on any slope together with the stability and integrity of both the sub-grade and the liner.

Where you need to use a filter geotextile, it must achieve the standards set out in the following filter geotextile standards table.

Your CQA plan must include details of the:

Where you place a geotextile well in advance of waste, you must provide test results to demonstrate adequate performance before the waste covers the geotextile. For example, if test results show it will be 6 months before the onset of ultraviolet degradation, you can leave the filter geotextile exposed for that period without further testing. If after 6 months it is still uncovered you will need to take further samples and retest to demonstrate compliance before you cover with waste.

The geotextile is an important part of the drainage system. You must provide full time third party independent CQA supervision when you install it. This includes at the time of cell construction or in phases as waste is placed. This must be adequately addressed in the CQA plan.

You must include the manufacturer’s quality assurance data in your validation report if you can match it to the specific rolls of geotextile used. If you cannot match it, you must carry out on site CQA testing and include it in your report.

You must:

If you use an alternative method to determine the suitability of the drainage aggregate, you must justify your method.

Where a geomembrane liner forms part of the barrier system, you must carry out a geophysical leak location survey once you have placed the drainage and collection layers. This is to make sure you find any damage so you can repair it.

You can use used tyres as an alternative form of drainage materials. They can be loose tipped or baled whole and shredded used tyres.

You can use whole or shredded used tyres known as ‘used tyre derived aggregate replacements’ (UTDAR) as an engineering material if you can show they are suitable for the required service life of the leachate drainage and collection system.

The Environment Agency will not normally agree you can use UTDAR where your landfill site is in a sensitive groundwater setting.

Sites in a sensitive groundwater setting include:

Check the Magic map to find out if your site is in a sensitive groundwater setting.

In these sensitive settings you will need to provide groundwater, stability and landfill gas risk assessments. These risk assessments need to confirm that the protection of the environment is not affected by the control of leachate levels within the waste.

Your design will need to address:

You must use a final equivalent thickness of 500mm where you want to use UTDAR, either as the entire drainage blanket or as a constituent part of it. You must specify the required initial thickness of the whole or shredded tyres and this must take account of the long-term compression of the UTDAR.

You must specify the design of the side slope drainage system. This must consider the management of both leachate and landfill gas.

For all size reduced materials you must specify the:

The Environment Agency does not consider 300mm rough shred to be suitable for use as UTDAR. There is no current evidence to characterise its performance after it has been placed and covered with waste.

The non-tyre elements of the drainage installation must meet the design and CQA requirements for a granular leachate drainage layer.

You do not need to apply for a permit for the storage and subsequent use of whole or shredded used tyres if you include these details in your construction proposals in accordance with your permit’s ‘engineering’ condition.

You can only store and use whole or shredded used tyres once the Environment Agency has approved your construction proposals in writing. You must provide details on:

You can provide this information to the Environment Agency separately or within the overarching CQA plan for the containment system.

A competent person must prepare the specification and CQA plan and supervise the storage and use of UTDAR.

You must provide a written statement to prevent, detect, contain and mitigate fires. This must include:

You must not store:

Where you cannot comply with these requirements you will need to apply for an environmental permit, or apply to vary your landfill permit.

All whole used tyres received for use as UTDAR must have been removed from their wheels.

All whole used tyres must be free from debris, inner tubes, foreign matter and contaminants.

Used tyres must show no signs of partial consumption or charring by fire.

All supplies must be accompanied by the material safety data sheet.

Your CQA engineer must carry out:

Where a geomembrane is part of your design, you must be able to carry out a leak location survey. It’s unlikely that you will be able to carry out a leak location survey after you have placed the full thickness (more than 500mm) of the UTDAR drainage blanket.

If you intend to carry out a walk-over geophysical survey, you may either:

You must specify the material you propose to use for your leachate collection pipework.

Your design must consider the:

Pipework must be bedded on suitable pipe bedding material and covered with mineral drainage material to a minimum thickness of twice the external pipe diameter.

The required open area in the drainage pipe is a balance between hydraulic conductivity and crush resistance. You must justify the range.

To get a good filter around the pipe you need to retain approximately 85% of the gravel surround. D15 is the particle size above which 85% will be retained.

The pipe can be slotted, perforated fully or perforated for two-thirds of its circumference. The maximum size of the slots or perforations must be chosen according to the D15 value.

You must specify the method of joining the pipework.

All sections of pipes must be firmly fixed together using butt fusion or electro-fusion welding techniques. You must not use simple push-fit couplings or hand welding techniques.

Pipe diameter must be a minimum nominal internal diameter of:

You must specify the pipe spacing. It must be a maximum of 30 metres or calculated using the approach used within ‘Barrier systems for waste disposal facilities’ (2004) by Rowe, Quigley, Brachman and Booker (ISBN 9780419226307).

You must provide the manufacturer’s quality control testing and all design calculations within the validation report for the works.

You must survey the as-placed pipework to confirm it has been placed to the required gradient and minimum spacing.

Where you use a separation geotextile as part of your design, you must specify the material you propose to use and show it will provide suitable separation.

Where you use a geotextile you must, where applicable, follow the design requirements for geosynthetic materials. You must refer to BS 8661 to demonstrate that your separation geotextile is suitable.

You must only use a geotextile product that is manufactured under factory control guidelines set out in BS EN 13257.

You must refer to the functional characteristics and relevant test methods.

Separation geotextiles must be manufactured from polypropylene or polyethylene fibres. This can be woven, non-woven or a combination of both.

You must define the pass criteria for the proposed separation geotextile.

You must describe how you are going to install the separation geotextile to meet your design specification.

You must remove leachate from the drainage collection system by:

You must install a ‘target pad’ in preparation for retro-drilling to replace a failed extraction well or monitoring point. The design of the target pad will be site specific but must be present near to all leachate extraction and monitoring points.

You must design leachate monitoring infrastructure to prevent ingress of perched leachate.

You must design leachate extraction wells to ensure the abstraction of leachate for the design life of your site.

Your leachate extraction wells must have:

You must be able to measure leachate levels with appropriate dip meters.

The layout of your leachate collection and monitoring wells must allow access for monitoring and abstraction.

Side slope risers must allow access for CCTV or jetting and for inspection. For this, and for pump access, your side slope risers must be at a continuous gradient over their length and must not follow any intermediate benches in the landfill side slope.

You must assess the effects of the side slope riser on the stability of the adjacent liner system, together with the need for additional protection.

You must seal side slope risers near the surface. This must be within the top 2 metres of the pipe length within the waste, to prevent air entering the landfill and landfill gas escaping.

Your design must use permanent buried pipework, as soon as is practicable, to carry leachate from the removal manholes to the treatment or disposal facility.

You must install foundations that adequately support the weight (including settlement pressure) of any built structure, to keep it vertical and to avoid damage to underlying materials.

For structures sited directly on the site base, you must have a level, load-bearing foundation.

For structures sited at higher levels within waste, less stringent engineering measures may be acceptable. It depends on the depth of waste below the structure and the final height of the structure.

In all cases, you must provide engineering calculations to confirm the load-bearing capability of the structure and its long-term stability. Where you propose to install side slope risers, you must also meet the design requirements for leachate drainage pipework.

Where you propose to progressively raise any leachate monitoring or extraction point at the same time as waste is landfilled, your design and installation method must ensure it stays vertical during and after construction.

To keep pipework vertical you can:

Your design must consider:

You must adopt CQA procedures to document the design, construction and maintenance of the extraction or monitoring point.

You must use suitably qualified, trained and experienced staff to install leachate extraction and monitoring pipework. At least one crew member must be accredited to the CSWIP standard level for pipe welding. All other welders must be accredited to the CSWIP entry level scheme for pipe welding or an alternative scheme where you can demonstrate its equivalency to the Thermal Welding Institute scheme.

You must include the maintenance of the structure in the monitoring plan.

Where you are only constructing the base of the leachate extraction or monitoring point, you must carry out CQA as part of the cell construction work.

A third party CQA engineer must supervise the installation and drilling of retrofitted leachate extraction and monitoring wells.

Where the leachate extraction or monitoring point is to be extended later, all work must be subject to CQA procedures. This will need to be validated as each section is completed.

All leachate transfer pipework must be designed and installed to maintain the integrity of the pipework. This is the pipework that transfers leachate from each cell or phase of your site and to on site leachate storage tanks prior to off site removal.

You must have third party CQA for the construction of the discharge pipework.

You must carry out frequent inspections, monitoring and maintenance for all discharge pipework to make sure it remains fit for purpose. You must agree the frequency of inspections, monitoring and maintenance with the Environment Agency.

You must develop landfill gas extraction and monitoring systems based on your site-specific risk assessment.

You must:

When you design your gas control system you must consider the:

Your gas management plan must specify the layout of your gas collection system. It must include:

You must:

You must demonstrate in your gas management plan how you will minimise point source emissions at the interfaces with the containment system around the perimeter of the site and at engineered features in the cap. This includes at gas monitoring and leachate collection wells. You must incorporate appropriate methods of monitoring and maintain the performance of these features after they are installed.

Your landfill gas collection pipework and extraction system must adequately manage the predicted volume and flow-rate of landfill gas produced.

You must lay your collection pipework at an appropriate fall. This will allow condensate to drain freely and prevent blockage or restriction of gas flow within the transmission pipework.

Your design must allow the system to drain condensate back into the waste mass or leachate treatment system by gravity or a pumped system. You must not drain condensate across the restored surface of the landfill site. You must make sure migration control is not compromised by landfill gas utilisation.

Your gas management plan must specify your well designs considering:

Your layout design must allow for:

You must consider whether you require a gas collection layer beneath the cap. Where your design uses a gas collection layer, you must consider its compatibility with other elements of the gas control measures in relation to:

Your design must consider possible failure modes, for example:

Where you need to use temporary measures to collect gas until you can install a permanent system, you must set out your temporary system design in your gas management plan.

You may use methods such as sacrificial horizontal gas collection systems or sacrificial percussion (pin) wells when filling a waste cell.

You must describe how you will collect gas generated while you are filling a cell in your gas management plan.

You must install temporary or sacrificial gas extraction:

You must review the effectiveness of temporary gas collection measures regularly. You must incorporate measures to protect these temporary arrangements from damage.

You must provide access for monitoring, maintenance, adjustment and flow monitoring.

You must prepare a specification and CQA plan for all elements of the landfill gas collection and monitoring systems.

You must use suitably qualified, trained and experienced staff to install landfill gas extraction and monitoring pipework where joints are required. At least one crew member must be accredited to the CSWIP standard level for pipe welding. All other welders must be accredited to the CSWIP entry level scheme for pipe welding or an alternative scheme where you can demonstrate its equivalency to the TWI scheme.

A competent person must prepare the specification and CQA plan.

Your specification must cover the:

Your CQA plan must cover:

Your plan must confirm the proposed drill depths and length of the stand-off between the base of each borehole and the base and sidewalls of the site. Where you propose to drill above a sidewall you must consider any potential deflection of the borehole during the drilling works.

Your site emergency plan must include a generic CQA plan for any works set out in your site emergency plan or carried out as emergency measures.

If you are retro-drilling wells within the waste or installing wells where there is a significant level of risk of damaging the basal, sidewall or capping liner, you must have a contingency action plan to remediate any damage to the containment system. This work must be supervised by a suitably experienced third party CQA.

You must:

A competent person, in consultation with the Environment Agency, must supervise the installation works.

A third party CQA engineer or inspector must supervise the installation and drilling of permanent gas wells and sub-surface pipework. This is to make sure that you do not damage the landfill containment system.

Landfills for hazardous and non-hazardous waste will normally need a permanent surface sealing layer. This is also known as a permanent or final cap.

If you consider that a cap would add little or nothing to protect the environment, you must show this through a groundwater risk assessment and landfill gas risk assessment.

Caps are built structures that prevent gas emissions from the waste, and rainwater infiltration into it.

Read guidance on the design of capping systems in the industry code of practice (LGG 111).

Temporary capping means any cap that is not a final cap (or intermediate cover) that will remain in place for more than 12 months.

Intermediate cover is a landfill cover that is expected to remain effective until the temporary or permanent cap has been installed.

You must keep uncapped areas to a minimum. You must cap as soon as possible after the end of waste disposal in an area of the site.

You must have either a final or temporary cap where you need to:

Your final cap must include:

You may need a regulating layer between the final layer of waste and the cap. The regulating layer is the sub-grade or foundation layer on which the cap is placed. If so, you must specify the thickness and nature of this layer.

You must base the design of the final cap on your groundwater risk assessment and landfill gas risk assessment.

The Environment Agency will not accept that a site is ‘definitely closed’ until all final capping works on site are complete and you have submitted a validation report to them.

Where you need either a final or temporary cap, you must design it to the following relevant standards:

You must design your final or temporary cap to:

You must consider the impacts of climate change, for example wetter winters and drier summers.

You must consider interactions between all the elements of the capping system in your stability risk assessment.

You must also consider:

Where you include a drainage geocomposite, read the guidance in the industry code of practice (LGG 114) – Using drainage geocomposites in landfill engineering.

You must install a temporary cap where you:

You must:

Where the temporary cap is not controlling gas emissions, odour or leachate levels you must replace it or repair it within a timescale agreed in writing with the Environment Agency.

A temporary cap must cover any exposed waste slopes including internal flanks.

Your permit normally requires you to install a temporary cap with approved construction quality assurance (CQA).

Where you install a temporary cap without approved CQA you must submit a CQA validation report to the Environment Agency to confirm the standard you installed it to.

Where the temporary cap has not been installed with approved CQA and is not controlling gas emissions, odour or leachate levels, you must replace it with a temporary cap installed with approved CQA within a timescale agreed in writing with the Environment Agency.

You may have installed a temporary cap that does not meet the standards for a final cap or with less CQA compared to that required for a final cap. For example, with part-time supervision. If so, the Environment Agency will normally ask you to follow one of the following 3 approaches:

You must complete the replacement of any temporary cap with a final cap within 2 years of the end of waste disposal within an area of the site or within a timescale agreed in writing with the Environment Agency.

You must maintain access for inspection, monitoring and maintenance, and to assess and maintain stability of the temporary cap until you install the final cap.

Providing the temporary cap has been designed to allow access for inspection, monitoring and maintenance, and is adequately controlling gas emissions, odour and leachate levels, a final cap must be installed within 2 years or within a timescale agreed in writing with the Environment Agency.

This is only when you have no definite plans to re-open the site, as this is like permanent cessation. You may maintain a temporary cap for up to 5 years where you have confirmed in writing to the Environment Agency that you plan to re-open the site. If you have not reopened the site after 4 years, you must install a final cap within the 5-year period.

You may maintain a temporary cap providing it remains stable, you have designed it to allow access for inspection, monitoring and maintenance, and it is adequately controlling gas emissions, odour and leachate levels.

Where the temporary is not controlling gas emissions, odour or leachate levels, you must replace it with a temporary cap installed with approved CQA within a timescale agreed in writing with the Environment Agency.

In all 3 cases, you must install a final cap as soon as is reasonably practicable. This must be within 2 years of the end of waste disposal within an area of the site or within a timescale agreed in writing with the Environment Agency where:

You do not need third party CQA for:

For temporary works, the installation must be subject to in-house management system control. The Environment Agency considers 10 metres to be a reasonable stand-off.

For temporary systems, such as installing shallow probes and pin wells, you must describe your CQA measures in your CQA plan.

You do not need to describe your CQA measures where your temporary works are associated with maintenance of systems, such as the temporary disconnection and re-connection of surface pipes.

You must agree the nature and extent of any maintenance with the Environment Agency before you start work. This includes agreeing whether these works require third party CQA.

You do not need third party CQA for pipework and extraction systems where you must carry out emergency works. However, your site accident and incident management plan must provide a generic CQA plan for foreseeable emergency works and you must submit a CQA validation report for all emergency works as soon as practicable.

Where you propose to carry out drilling into waste on your landfill, you must consider:

You must provide your construction proposals and a CQA plan to the Environment Agency that outlines the work you propose to carry out. You must not begin construction until the Environment Agency has confirmed that it is satisfied with your construction proposals.

You must:

A zonal drilling approach must normally include:

The low risk zone is well above the predicted base of the waste. You can use standard drilling operations. Drilling can advance in 3 metre increments.

The intermediate risk zone is within 2 metres of the predicted base of the waste. You must reduce drilling increments to 300mm. You must inspect the drill arisings for each increment.

The high risk zone is within 1 metre of the predicted base of the waste. You must relate the drilling increment to the accuracy of the drilling method. It must be less than the target layer - for example if a 300mm layer of gravel is the target, increments must be 200mm. As you approach the base, you must use 150mm or 100mm increments, dependent on risk. You must check the drill arisings carefully for signs of drainage material.

You must include an action plan and remediation strategy in your CQA plan in case you penetrate the containment system or base or sidewalls of your site.

Where you are replacing a structure such as a leachate extraction or monitoring point you must follow these design hierarchy steps:

You must use calculations to demonstrate how you have considered the following:

The design for each borehole must include the:

You must review your landfill gas management plans and odour management plans for the site. You must include in your CQA plan:

You must:

The CQA personnel must be experienced with rotary drilling techniques.

The Environment Agency will not accept CQA inspectors with only basal lining and capping supervision experience.

Your CQA inspector must:

You must submit a validation report to the Environment Agency within 4 weeks of completing the works, or other time period agreed in writing with the Environment Agency.

You may use waste in any engineered structure where it satisfies the minimum engineering standards. For example, using waste as an artificially established geological barrier for an inert waste landfill or in a landfill cap.

Landfill permits do not normally include a recovery code (for example R5) to cover this activity as you can use suitable inert waste on the basis that the engineering is an integral part of the permitted disposal activity.

Where you propose to use waste in an engineered structure and want to do this as a recovery activity (under an R code) you must follow the deposit for recovery guidance and apply to include that activity in your permit. You must complete a waste recovery assessment when you deposit waste that does not provide an engineering function. See the guidance for raising the base of a landfill.

You do not need a separate waste recovery plan where the proposal relates directly to the landfill containment system. However, the Environment Agency must make sure you are recovering waste based on information that you include in your construction proposals and CQA plan. This includes assessing the suitability and quantity of waste proposed.

To be a recovery activity, waste material must be replacing non-waste material that would otherwise be used. Factors that may indicate that non-waste would be used for the proposed works are outlined in the Waste recovery plans and deposit for recovery permits guidance.

The Environment Agency will only approve the construction proposals if the material is suitable for its intended purpose.

The Environment Agency will need to confirm that you are using the minimum amount of waste necessary to achieve the intended purpose.

All engineering works must be covered by third party CQA and be completed to an appropriate, approved standard.

For more guidance on waste recovery permits, plans and engineering, see the deposit for recovery operators guidance.

Where you want to raise the base of a landfill before starting construction of any part of the landfill, such as an artificially enhanced geological barrier, the Environment Agency does not consider it is an integral part of the landfill operation.

You can raise the base by constructing the sub-grade or sub-base layer with non-waste material or waste as a recovery operation. For the Environment Agency to accept that waste is being recovered before a subsequent disposal operation takes place, you must satisfy the recovery test outlined in the deposit for recovery operators guidance. You must include information to satisfy the recovery test in your construction proposals and CQA plan, or in a separate waste recovery plan.

See guidance on raising the base of a site when you propose to deposit waste into water.