Manage leachate

How to manage the leachate produced by the waste in your site.

You must manage the leachate produced by the waste in your site.

You must take appropriate measures to prevent leachate having an impact on soils, groundwater or surface water. Check how to complete a groundwater risk assessment for leachate.

You must consider the guidance in Monitoring landfill leachate, groundwater and surface water: LFTGN 02 in your permit application or permit variation application.

Check how to monitor landfill leachate before you apply.

You must normally actively manage leachate at landfills for hazardous or non-hazardous waste. You do not normally need to actively manage leachate at landfills for inert waste.

Actively manage means that you must extract and dispose of the leachate your site produces. You may also need to treat your leachate before you dispose of it.

You must propose maximum leachate levels in your permit application. Leachate levels must be based on your groundwater risk assessment. Your proposals must also consider how you manage landfill gas.

Where leachate levels will be above the level of the surrounding ground surface (for example, at land raise sites), you must consider the impact on slope stability.

The Environment Agency will review your proposal and set compliance limits in your permit that tell you the maximum level of leachate you are allowed.

You must develop and maintain a leachate management plan.

Develop new methods to manage leachate

Where you propose to use a new method to actively manage or monitor leachate, you must provide the Environment Agency with evidence to support its use. You must send this to your local Environment Agency officer as an amendment to your leachate management plan. The amount of evidence you provide must be proportionate to the risk of pollution from the proposed new method.

Your evidence must include:

• a literature review
• laboratory testing and modelling
• field trials
• site comparisons
• research and development projects

You need to allow time for the Environment Agency to assess any new method. They will charge you by the hour for the time they spend assessing your proposals.

Increase leachate levels

To increase leachate levels at your site you must:

1. Apply to change (vary) your permit.
2. Include a groundwater risk assessment with your variation application.

Your groundwater risk assessment must show no unacceptable emissions to groundwater or surface water or other increased risk of pollution (for example, by emissions through a sidewall or leachate over-topping).

For more information read the groundwater protection guidance.

Include the following in your proposals to increase leachate levels:

1. Predicted impact on groundwater quality

Use existing, representative groundwater and leachate quality data to show the predicted impact on groundwater quality. This must cover all cells that may be affected by higher leachate levels. You must include a conceptual site model with details of your proposed leachate catchment area, with your groundwater risk assessment.

The leachate catchment area is the area of the site subject to a particular leachate level. This will allow the Environment Agency to assess your proposals for a larger area than a single cell, for example where increased levels overtop inter-cell bunds.

The Environment Agency will not accept increased levels where there is evidence of existing groundwater pollution due to leachate from the cells or phases where you propose to increase levels. You must take appropriate action to reduce this impact.

Your groundwater risk assessment must assess the impact of redundancy within the leachate management system, due to the clogging of the leachate collection blanket or failure of the leachate collection pipework. It must include the theoretical long term effect this will have on the effective management of leachate levels.

2. How you will maintain the revised level

Use evidence to show that all cells and leachate catchment areas affected by higher leachate levels have adequate containment and leachate drainage and extraction systems to maintain the revised level. This must be to an appropriate height up the sidewall – see dilute and disperse cells.

For cells and phases that are hydraulically contained you must follow the guidance for sub-water table landfills.

The Environment Agency will only accept applications to increase leachate levels where they are satisfied that your leachate extraction and monitoring infrastructure is fit for purpose.

Where you propose to use a new method for leachate monitoring, you need to include details of how you will calibrate any assumptions made.

3. Site-specific plans, drawings and cross sections of the existing basal liner, cell and phase separation bunds referenced to ordnance datum.

If you have already provided this information to the Environment Agency, you must provide them with reference to that information.

4. Site-specific leachate flow calculations

Show that the leachate collection system in all affected cells can transport leachate to the extraction sumps, both before and after the increase in leachate level.

5. Maximum leachate level

Provide a maximum leachate level and justified stand-off to prevent overtopping of any inter-cell bund into cells where there would be an impact on groundwater or off site.

For example, if bunds to an adjacent unlined or lesser standard cell or off site are 3 metres high, the Environment Agency may only accept leachate levels up to 2 metres.

6. Evidence of landfill gas management

Provide evidence that you have designed your leachate extraction, monitoring and treatment infrastructure to enable landfill gas emissions to be managed after the increase in leachate level.

7. Evidence of stability

Provide evidence that your proposed leachate levels will not have a negative impact on the stability of the basal liner, cap, waste or leachate and landfill gas infrastructure. You must confirm this with stability and settlement risk assessments.

8. Existing monitoring data

Provide evidence from existing monitoring data that you have maintained levels below the compliance limit. This is to show that the leachate extraction infrastructure can maintain the proposed leachate level across the whole leachate catchment area.

Find out how to monitor landfill leachate.

Sub-water table landfills

Where the leachate level is based on groundwater levels outside the site (for example, in sub-water table landfills), you must show that you can maintain an inward hydraulic gradient. This gradient must be sufficient to prevent an emission of leachate by diffusion or advection. This must be maintained where your site presents a pollution risk. Groundwater and leachate levels must be measured close to the site boundary.

You must agree appropriate monitoring locations with the Environment Agency. You can agree these with your local Environment Agency officer where your site has a monitoring and extraction point plan (MEPP). If your site does not have a MEPP, you must apply to change your permit.

Dilute and disperse cells

For cells designed as dilute and disperse, there will be no basal engineering or leachate drainage. The Environment Agency will not normally allow increases to leachate levels in these cells.

Recirculating leachate

If you want to recirculate leachate at your site you must describe this in your leachate management plan.

You must show that:

• there is an effective leachate drainage and extraction system within all cells where you propose to recirculate
• there is appropriate and effective leachate monitoring infrastructure within all cells where you propose to recirculate
• leachate levels are and will continue to be effectively managed and will comply with all relevant permit conditions
• landfill gas is and will continue to be effectively managed

You must show that the proposed recirculation of leachate will not have an unacceptable impact on:

• the stability and integrity of the engineered containment system and infrastructure
• the stability of the waste
• odour emissions
• surface water
• the management and extraction of landfill gas
• the water balance calculations for the site

If you can demonstrate that you have an effective leachate drainage and extraction system, you must confirm that there will be no unacceptable risk to soil, groundwater and surface water.

Your proposed design must include:

• objectives of the proposed scheme
• confirmation that there is sufficient leachate to allow leachate recirculation
• the method of leachate recirculation, including its suitability for your site
• the design of leachate recirculation infrastructure
• examples of where the proposed method has been used previously, including details of how successful the method was, any problems encountered and how you resolved those problems
• the duration of the proposed scheme

Where you propose to use a new method to recirculate leachate, you must provide your local Environment Agency officer with evidence to support its use.

Recirculation: assess the risks

Your assessment of the potential operational risks must include:

• confirmation that the proposed scheme will not have a negative impact on the effective operation of the site
• the extent of the anticipated settlement of the waste, including confirmation that the settlement will not have a negative impact on the landfill, leachate recirculation, landfill gas and capping infrastructure
• how you will maintain the effective management of landfill gas during the proposed recirculation works
• confirmation that your leachate management infrastructure is able to deal with leachate with an increased pollution potential
• how you will manage potential odours and amenity issues
• how you will prevent any perched leachate seepages
• how you will prevent waste instability
• how you will prevent oxygen from entering the waste, and what measures you will take if this occurs and causes internal waste fires
• how you will prevent ground and surface water contamination

Recirculation: leachate management plan

Your leachate management plan must include the following for your recirculation scheme:

• as-built drawings
• how you will monitor the operational performance of the proposed scheme
• how you will monitor the performance of the proposed recirculation and existing landfill infrastructure

Your plan must include the monitoring that you will do during and after the proposed recirculation works. You must include the monitoring you will carry out to:

• assess the impact the recirculation scheme will have on the quality of the leachate
• assess the potential odour impact of the scheme
• assess the stability of the containment system and waste
• assess the impact of the scheme on the management of both leachate and landfill gas
• make sure the proposed scheme is having no impact on soil, groundwater and surface water

Store and treat leachate

Your leachate management plan must consider the need for storing the leachate your landfill produces.

You must ensure the leachate meets the required standard before you dispose of it to the water environment. You must treat your leachate where you must:

• meet the requirements of a consent to discharge
• satisfy a statutory water undertaker’s authorisation to discharge to the sewerage network

Where you treat leachate at your landfill site and that activity is above the threshold in schedule 1 to the Environmental Permitting Regulations (EPR) 2016, Part 2, Chapter 5, section 5.3 or 5.4, you must comply with the best available techniques reference document on the treatment of waste (2018).

For new leachate treatment facilities above the EPR schedule 1 threshold, you must comply with the associated emission levels in the best available techniques conclusions (BAT AELs). Contaminants in discharges must be below the higher value in:

• table 6.1 for direct discharges
• table 6.2 for indirect discharges

Your discharges must meet the limits for water based liquid waste.

If you have an existing leachate treatment plant above the EPR schedule 1 threshold, the Environment Agency will change (vary) your permit to include the limits.

Where your treatment activity is below the EPR threshold, you must still treat and store leachate safely to prevent pollution. You can achieve this by complying with best available techniques (BAT).

You must provide secondary containment for your leachate storage and treatment facility unless you use other appropriate measures to minimise leaks and spills from your primary containment.

Where you provide secondary containment you must follow the guidance in CIRIA 736: Containment systems for the prevention of pollution: secondary, tertiary and other measures for industrial and commercial premises (2014).

Store and treat leachate: construction quality assurance (CQA) plan

You must provide independent third party CQA for the construction of your leachate storage and treatment facility. This includes secondary containment measures. You must submit a CQA plan to your local Environment Agency officer outlining the work you propose to carry out.

You must not begin constructing your leachate storage and treatment facility, including your secondary containment measures, until the Environment Agency has confirmed they are satisfied with your proposals.

Your CQA plan must include:

• the location and design of all tanks (including raw and treated leachate storage, chemicals and other liquids or powders for treatment)
• the maximum capacity of the primary tanks
• the location of all pipework
• the materials you will use to construct the storage tanks and the secondary containment
• the CQA supervision you will provide during construction
• the conformance testing you will carry out
• the post construction integrity testing you will carry out
• the structural calculations for tanks and basal containment
• the design and capacity of all secondary containment
• confirmation that all material will be resistant to the liquid being stored
• the design of any leak detection system

Where your secondary containment consists of a geomembrane, your CQA plan must state that this be installed by suitably qualified, trained and experienced staff. This must include both of the following:

• a lead technician and a foreman accredited to at least standard level (level 1) of the BGA/TWI/CSWIP welding standard (developed by the British Geomembrane Association (BGA), Thermal Welding Institute (TWI) and the Certification Scheme for Personnel (CSWIP))
• all welders accredited to a minimum of entry level (level 2) of the BGA/TWI/CSWIP welding standard

Design of pre-manufactured glass lined steel tanks

Design specific requirements for pre-manufactured glass lined steel tanks include:

• details of all penetrations and secondary skins
• manufacturer’s testing to show it complies with the appropriate mark for the market in Great Britain
• proof of thickness of side walls
• date of production
• details of compliance testing you will carry out on site

Design of manufactured on site glass lined steel tanks

For glass lined steel tanks manufactured on site, you must include the design specific requirements and:

• bolt and fastening arrangements to individual panels and the base
• joint designs and locations
• proof of thickness of steel lining
• details of tank cladding
• location, height and material for structurally independent baffle-boards to prevent jetting
• details of all geosynthetics – including product specification and on site testing

Design of pre-cast concrete tanks

Design specific requirements for pre-cast concrete tanks include:

• grade of concrete
• a cross section of individual sections showing the thickness of the concrete and cavities
• details of steel cables tied to tension the sections together
• details of all wall penetrations and interaction with steel cables
• details of your method of sealing between separate sections

Design of cast in-situ concrete tanks

Design specific requirements for cast in-situ concrete tanks include:

• grade of concrete
• thickness of concrete walls, including the tolerances
• casting joint details
• design and specification of reinforcement
• requirement for concrete curing
• specification for concrete cube testing
• details of penetrations and seal details
• details of all geosynthetics, including product specification and on site testing

Design of leachate lagoons

Where you propose to construct a leachate lagoon you must provide a hydrogeological risk assessment to confirm your design will not cause unacceptable emissions to groundwater or other increased risks of pollution. Your CQA must be to the same standard you use for your landfill engineering.

Validation report

You must submit a CQA validation report to your local Environment Agency officer within 4 weeks of completing the construction and testing of your leachate storage and treatment facility and secondary containment (or other time period agreed in writing with the Environment Agency).

Inspection and maintenance

You must provide a plan of how you will inspect and maintain all elements of your leachate storage and treatment facility. You must use a suitably qualified and experienced chartered civil, structural or geotechnical engineer where appropriate to carry out the inspection.

Dispose of leachate

You have a number of options for the disposal of leachate off site:

• discharge to the sewerage network
• by tanker to a waste water treatment works that is authorised to accept it
• discharge to the water environment, including through passive treatment systems like reed beds

Any discharge to the sewerage network must be authorised by the statutory water undertaker.

Any discharge to the water environment must be authorised by a consent to discharge. You can apply to vary the activity into your landfill permit.

Leachate is mirror entry waste – waste code 19 07 02* or 19 07 03. Read chapter 2 of waste classification technical guidance (WM3). Where you remove leachate by tanker, you must classify it.

The Environment Agency will normally apply controls over any treatment process prior to discharge to water. They must apply controls where the activity has the capacity to treat more than 50 tonnes of non-hazardous waste a day.

Where required by your permit, you must send your Environment Agency local officer annual data showing how you have managed the leachate produced by your site.

Where your method of leachate treatment produces sludges, you must ensure you dispose of these appropriately.

Leachate deposits on land

You cannot dispose of leachate to land, on grassland or crops. This is liquid waste disposal, banned by the Landfill Directive.

You can recover treated leachate on land for agricultural benefit or ecological improvement, providing you can show that the activity is for waste recovery.

You can apply for a separate recovery permit, or apply to vary to add the activity to your existing landfill permit.

Application of treated landfill leachate to short rotation coppice (SRC)

A short rotation coppice (SRC) system is normally a secondary (or tertiary) leachate treatment activity. Leachate will normally need initial treatment to reduce the concentration of contaminants. It can then be irrigated to a crop as a source of water and nutrients to produce biomass – normally reeds or willow. You may not need initial treatment for leachate with low contaminant concentrations.

Regulating SRC activities

The SRC system will be an installation if it has the capacity to treat more than 50 tonnes of non-hazardous waste a day (EPR 2016, schedule 1, section 5.4). Below that threshold, it will be a waste operation.

If you propose an SRC system on a landfill site that is an installation, for example an operational landfill for non-hazardous waste, it may also be part of that installation as a directly associated activity to the landfill.

Installations have additional requirements. These include the assessment of BAT.

The BAT reference document on the treatment of waste (2018) sets out indicative standards for operation and environmental performance of leachate storage and treatment facilities.

SRC: apply for a permit

The main product of the treatment will be biomass. The SRC may be an enclosed system or include a discharge to the water environment. The Environment Agency will need to regulate any water discharge activity.

Your application must be supported by a site specific environmental risk assessment.

SRC: soil quality

You must analyse the soil in the SRC to find out the background concentration of substances in the soil. Submit the results with your application. You must sample and analyse your soils in accordance with BS 18400; soil quality.

The Environment Agency will normally include the background concentrations in your permit. This is to provide a baseline to compare future analysis to ensure you are not polluting the soil in the SRC in the long term.

The process must not contaminate the soil significantly above the background concentration, as that would be a disposal activity. You must monitor the soil throughout the life of the operation to show that pollutants are not accumulating in the soil.

SRC: leachate management

You must not allow hazardous substances, non-hazardous pollutants and persistent bio-accumulative and toxic substances to enter the SRC system. You must only allow the application of substances necessary for normal plant growth, for example, water, nitrogen, potassium, phosphate and other micro-nutrients.

You must ensure that where you apply an initial leachate treatment process, it removes unnecessary substances to minimise their take up by plants. Where the initial treatment cannot achieve this, the Environment Agency is unlikely to accept leachate irrigation to a coppice as an appropriate treatment activity.

You must sample and analyse the treated leachate before you apply it to the SRC and keep a record of the results.

You must have an alternative route for leachate disposal available for periods when you cannot use the SRC (for example, wet weather or low soil moisture deficits). You must include these in your leachate or SRC management plan.

SRC: reports

Your permit will tell you how often you must send data on soil and treated leachate quality to the Environment Agency. Your permit will normally require a summary each year in your annual report. You must also provide a more detailed review every 3 years. That review must consider the total quantity of treated leachate you have applied. It must consider the cumulative effect the substances in the treated leachate have had on soil quality within the SRC.

SRC: permit application summary

As a minimum, and on a site specific basis, your application will need to satisfy the Environment Agency that:

• leachate is being treated and not disposed of
• the environmental risk and consequences of the activity at the specified location are acceptable
• the plant species you have selected are suitable for the purpose
• the process will not cause deterioration to background soil quality
• you will treat the leachate to an appropriate standard before application to the coppice
• the quality of the treated leachate is appropriate for the plants you intend to grow
• you have indicators for monitoring the performance (both success and failure) of the process, based on background soil and treated leachate analysis
• the SRC process is contained and will prevent the uncontrolled escape of leachate from the system – there will be an engineered barrier and a surface water management system to prevent percolation and horizontal migration (including over-topping)
• where you discharge final effluent to controlled water, you have included an application for a discharge consent
• your leachate or SRC management plan will ensure that you only apply leachate when there is a soil moisture deficit, and at an appropriate rate to prevent over-topping of the system or leaching of the treated leachate
• where the SRC is on a landfill cap, you will maintain the integrity of the cap so that it is not damaged by roots or pipework, and you can maintain access for monitoring and managing the landfill activity

You need to monitor before and throughout the life of the activity to provide representative analysis of the main performance indicators, including:

• soil moisture deficit
• soil infiltration rates
• slope
• treatment capacity
• leachate quality before irrigation
• application rates
• soil quality during and after operations