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:

stability of the lining and capping system, wastes and underlying geological strata

effectiveness of the leachate collection system – including the drainage layer, pipework, pumps and abstraction chambers

effectiveness of any groundwater control systems – including the drainage layers, pumps and abstraction points

ability to maintain operational and management control of the leachate and groundwater systems

ability to effectively collect landfill gas and prevent the migration of gas

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: design requirements

Engineering proposals at all landfill sites must:

meet the design requirements set out in this guide

prevent unacceptable discharges to ground and surface water and emissions over the entire lifecycle of the landfill

be structurally and physically stable over the entire lifecycle of the landfill

Demonstrate little or no additional benefit

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.

Design your landfill engineering and infrastructure

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

leachate collection and sealing layer

geosynthetic clay liners (GCL)

dense asphaltic concrete (DAC) lining systems

leachate drainage and collection systems

leachate drainage pipework

leachate extraction and monitoring systems

leachate transfer and discharge pipework

landfill gas extraction and monitoring

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.

Earthworks

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.

Geological barrier

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:

extend along the base and up the sides of the landfill

provide a barrier to contaminant emissions

prevent soil and groundwater pollution

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.

Geological barrier: design

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

specification for highway works

earthworks in landfill engineering (LFE4)

detail your proposed specification and methodology in your method statement and quality assurance and control procedures

provide a detailed specification for all mineral layers used for building or protecting engineering structures

assess chemical compatibility during the feasibility and trial liner stage, not as part of routine CQA testing

design permanent and temporary bunds, support slopes and ramps so they are stable in geotechnical terms and do not overstress, strain or puncture the lining system

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. Read the guidance on using bentonite enriched soils in the industry code of practice (LGG 110) which is hosted by the Environmental Services Association.

Geological barrier: construction quality assurance

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.

Leachate collection and sealing system

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:

an artificial sealing liner

a leachate drainage layer

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

Artificial sealing liner

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:

they are hydraulically contained

you can show in your risk assessment that the containment system will perform as well or better without a liner

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 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.

Artificial sealing liner protection

You must protect geomembranes with suitable materials against:

thermal and localised stress and stress concentrations that can lead to stress cracking

Suitable materials include geotextiles and mineral materials.

You must carry out a cylinder test for each cell you construct 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:

covered by a separation geotextile and leachate collection drainage layer

Where you use a geotextile protection layer, read the guidance on using non-woven protector geotextiles in the industry code of practice (LGG 107) which is hosted by the Environmental Services Association.

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

Leachate collection and drainage system

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

abstract leachate from the drainage layer over the entire lifecycle of the landfill

collect and control leachate on the base and sides of the site

manage landfill gas emissions from any sidewall drainage layer to prevent, or where that is not practicable, minimise methane emissions and odours

prevent, or where that is not practicable, minimise air or surface water ingress into the waste from any sidewall drainage layer

monitor leachate on the base of the site

Leak detection

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) which is hosted by the Environmental Services Association.

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 i…