Guidance

Cemeteries and burials: groundwater risk assessments

How to carry out a groundwater risk assessment for human or animal burials.

You need to follow this guidance if you are examining the potential or current effect of burials in a cemetery or individually, as part of a risk assessment.

You will need to do a risk assessment, for example:

  • as part of a planning application or condition
  • when altering existing facilities
  • following a pollution incident
  • when ongoing environmental management of the site is needed, for example disposal of grey water

These principles also apply to pet cemeteries and the emergency burial of animal carcasses.

You need to submit your risk assessment to the Environment Agency or your local authority, depending on who has requested it. Your assessment will need to be approved before you begin or continue your activity.

Human burials are not currently controlled through the permitting system under the Environmental Permitting (England and Wales) Regulations 2016. However, we will introduce permitting controls for high risk cemeteries once the coronavirus (COVID-19) pandemic is over.

You should use the principles for a groundwater risk assessment to make sure you do not cause pollution. You may still need a permit if you dispose of any water from the site. Check the guidance Discharges to surface water and groundwater: environmental permits.

You need to check if you are in a sensitive location for groundwater and what restrictions apply. Use the interactive groundwater maps to find out if you are in a sensitive location. You must also find out about private water supplies by contacting your local council.

Read the restrictions in the Environment Agency’s groundwater position statements for more information:

  • section L – on the development of new cemeteries or the extension or redevelopment of existing cemeteries
  • section M – for emergency disposal either on-farm or in similar locations and circumstances

In your risk assessment you will need to make different calculations for green burial sites. You must give green burials additional environmental and sustainability considerations over more traditional burials. Examples include:

  • using a shroud or coffin made from materials that are locally or sustainably sourced and degrade more easily than a wooden coffin
  • using a ‘natural’ burial ground that is managed in an environmentally or ecologically responsible way, for example meadow or woodland sites
  • not using preservatives in body embalming or coffin construction

Source, pathway and receptor

You should use a source-pathway-receptor approach to follow this guide’s principles.

For groundwater risk assessments relating to burials the:

  • source is the buried human or animal remains
  • pathway is the subsoil or other medium through which substances from the source permeate and travel
  • receptor is the groundwater

Groundwater receptors can include:

  • any boreholes, wells and springs used for drinking supplies
  • groundwater-dependent ecosystems (such as wetlands) or other identified conservation sites that may be at risk (such as Sites of Special Scientific Interest)

To assess the risk at a site you will need a realistic estimate of the yearly maximum number of burials that take place or will take place, and whether these involve human or animal remains.

You must make sure any subsurface investigation of the soil and rock is at least 1 metre below the deepest the grave.

You should use site specific hydrogeological data.

Tiered approach to risk assessment

You must not pollute groundwater. You need to carry out a risk assessment to show that:

You should use a tiered approach for risk assessments. The cost, time and effort of doing an assessment is proportional to the effort or measures required to make the risks from the activity acceptable.

For all tiers you need to develop a conceptual model.

Tier 1 assessment: risk screening

For a tier 1 assessment, you need to do a desk study and a qualitative risk assessment. You can then assess the overall risk of the proposal as low, medium or high. For high and medium risks you need to do a more detailed tier 2 or 3 risk assessment.

Tier 2 and 3 assessments: detailed risk assessments

For tier 2 and 3 assessments you need to build on the information you gathered in your tier 1 assessment and refine your conceptual model.

If your risk assessment shows pollution or a risk of pollution you need to work with your local authority and the Environment Agency on how to address this. At existing cemeteries you will have to stop burials until you have an agreed plan of action.

Tier 2 and 3 minimum risk assessment requirements

For tier 2 and 3 assessments you need to supply the following minimum information.

Site description

Your risk assessment must show for:

  • tier 2, a local survey to supplement Ordnance Survey maps
  • tier 3, an accurate site survey based on location, area and topography – mark any landscaping included in the proposal

Number, type and sequence of burials

Your risk assessment must show for:

  • tier 2, projections on which annual numbers are based – provide with supporting data and explanations
  • tier 3, the tier 2 projections and a plan of the proposed sequence of burial area use – indicate expected progression over time

Meteorological factors

Your risk assessment must show for:

  • tier 2, long-term average data on local rainfall and Met Office Rainfall and Evaporation Calculation System soil moisture data
  • tier 3, analysis of available data to find out the monthly mean, maximum and minimum effective rainfall, and soil moisture data for bare soil, short-rooted vegetation and deep-rooted vegetation

Soil and subsoil characteristics

Your risk assessment must show for:

  • tier 2, soil survey maps and possible site investigation and percolation tests
  • tier 3, site survey with augering and trial pits

Geology (including superficial) and hydrogeology

For tier 2, you must show geological and hydrogeological maps and histories. You may also need to include:

  • limited site investigation (like trial pits and drilling)
  • groundwater vulnerability
  • source protection zones
  • an assessment of the aquifer characteristics from published data

For tier 3, you need to provide the tier 2 information, plus:

  • rock and soil characteristics
  • presence of shallow groundwater
  • variations in water table recorded for at least 1 year of monthly measurements

Any boreholes you use must be appropriately designed to define the physical conditions of the surrounding groundwater. Gather data and carry out any suitable investigations (for example, to estimate permeability based on falling head test, bailing test, tracer tests).

You must have at least 3 investigation boreholes – 1 on the up-gradient side of the site and 2 close to the down-gradient boundary. You should be able to work out the groundwater flow direction from your investigation boreholes.

Monitoring

Your risk assessment must show:

Proximity to water source or resource

Your risk assessment must show for:

  • tier 2, Environment Agency records of licensed abstractions and local authority records of private water supplies (include surface and groundwater supplies)
  • tier 3, as tier 2 plus any additional water features including all groundwater, drainage, flood risk and surface water features (read more about water features surveys)

The area of the water features survey will depend on the size of the site, proposed abstraction rate and the aquifer type. The Environment Agency will determine the radius of the survey.

Data assessment

Your risk assessment must show for:

  • tier 2, simple pollutant flux and water balance calculations, such as dilution at the water table
  • tier 3, possible use of more sophisticated models to assess attenuation (reduce the effect of)

Proximity to housing or other developments

Tier 2 and 3 risk assessments must check local, regional or national planning authority for potential:

  • residential, educational, commercial or industrial developments
  • roads, rail and mineral extractions

Monitoring groundwater

You do not need to monitor sites where the risk assessment shows that the risk to groundwater is low. You will need to monitor other sites – the frequency will depend on the degree of risk.

Follow the groundwater monitoring principles and the technical guidance for monitoring groundwater.

You may also need to carry out monitoring outside the burial boundary. For example, if burials are close to the perimeter of cemetery grounds.

You need to carry out monitoring to:

  • define the baseline water quality and physical conditions in surrounding groundwater and surface waters before development
  • identify all vulnerable receptors and help identify potential pathways
  • provide an early warning of adverse environmental impacts

If your monitoring identifies pollution, you must stop further burials, investigate, and stop the pollution before you can start burials again. You must tell the Environment Agency.

Minimum monitoring requirements

You may need to consider what parameters you are monitoring on a site-specific basis. For example, you may need to include formaldehyde, organics, hazardous substances and bacterial indicators.

Where you need to monitor groundwater, you must meet the following minimum requirements for pre-development and ongoing burials.

Minimum number of boreholes

You must have at least 3 investigation boreholes – 1 on the up-gradient side of the site and 2 close to the down-gradient boundary. You should be able to work out the groundwater flow direction from your monitoring boreholes.

Minimum borehole monitoring period

You should monitor:

  • 1 year before the site is developed
  • for a period of 3 years after the first burial

For higher risk sites, the Environment Agency may require you to increase the monitoring frequency, both before development and longer term. This will depend on the sensitivity of the site – the results can be reviewed accordingly.

Surface water monitoring points

For surface waters that are at risk you should have 1 monitoring point upstream and 1 downstream. You should ensure they are monitored on a monthly basis.

Baseline conditions

The minimum frequency for monitoring baseline conditions and the monitoring suite (the determinands) before development is either quarterly or 6 monthly.

Minimum frequency Suite of determinands
Quarterly water level, pH, temperature, electrical conductivity, dissolved oxygen, ammonium, nitrogen, chlorine
6 monthly sulphate, total oxidised nitrogen (nitrate and nitrite), total organic carbon, biological oxygen demand, chemical oxygen demand, alkalinity, sodium, potassium, calcium, magnesium, iron, manganese, cadmium, chromium, copper, nickel, lead, zinc, phosphorus, formaldehyde (if allowed at the burial location), mercury

Long-term monitoring

The frequency of monitoring and suite of determinands for long-term monitoring once the site is in use (indicators of pollution) is 6 monthly.

Minimum frequency Suite of determinands
6 monthly water level, pH, temperature, electrical conductivity, dissolved oxygen, total oxidised nitrogen (nitrate and nitrite), total organic carbon, biological oxygen demand, chemical oxygen demand, ammonium, sulphate, chlorine, sodium, potassium, calcium, magnesium, iron, phosphorus, formaldehyde (if allowed at the burial location), mercury

You may also need to increase the frequency of monitoring for higher risk sites or decrease it to annual monitoring if monitoring shows stable conditions.

Pollutant release from body decay

You can use the following information to calculate the potential release of pollutants from the decomposition of a typical human body.

Composition of the human body:

Composition % weight
Water 64
Protein 20
Carbohydrate 1
Mineral salts 5
Fat 10

Elemental composition of a human body based on a 70kg body:

Element mass (g)
Oxygen 43,000
Carbon 16,000
Hydrogen 7,000
Nitrogen 1,800
Calcium 1,100
Phosphorus 500
Sulphur 140
Potassium 140
Sodium 100
Chlorine 95
Magnesium 19
Iron 4.2
Copper 0.07
Lead 0.12
Cadmium 0.05
Nickel 0.01
Uranium 0.00009
Total body mass 70,000

Factors affecting the rate of decomposition

Decomposition relies on the rate of activity of degrading organisms and on the rate of the biochemical reactions involved. Factors which could influence the degradation rate include:

  • age at death
  • body mass index
  • cause of death
  • integrity of the corpse
  • burial depth
  • preservatives

Site related factors include:

  • geological and hydrogeological characteristics of the soil, including soil type, permeability and porosity
  • microbiological characteristics of the soil
  • mechanical, structural and resistance parameters of the soil
  • coffin or other container construction
  • land cover – land cover and topography will affect infiltration and water logging which will delay decomposition
  • climate
  • depth of unsaturated zone

How these factors interact can be complex. In 80% of cemetery burials, complete skeletonisation of the body would be within an interval of:

  • 10 years for soil burial
  • 30 years for entombment

Decay and dissolution

Bone dissolution is a slow process and will depend on the acidity of the surroundings. Skeletal materials may be expected to show faster dissolution in acid soils than more neutral soils.

When you model the decay and dissolution of a human corpse, you should consider the following:

  • skeletonisation of a buried corpse may take 10 years to complete
  • embalming with formaldehyde may delay decay but quantifiable effects data are not available – assume the same rates of decay for embalmed and unembalmed bodies
  • assume the same decay rates for ‘green’ and conventional burial sites
  • initial in-grave decomposition conditions are usually aerobic but the body rapidly reaches an anaerobic state

You also should assume a constant linear rate for degradation of the body, with delays for components known to be resistant or shielded in some way. For example:

  • not all components will be readily degraded or solubilised during the skeletonisation process – phosphorus and calcium are mainly present in bone – estimate bone dissolution to take around 10 years after burial
  • tissue degradation by aerobic processes will be limited by oxygen availability – expect it to occur at a constant rate in relation to depth, partial pressure or recharge rate, once the initial oxygen in the grave has gone
  • degradation by anaerobic processes will be limited by availability of electron acceptors and controlled via recharge – expect it to occur at a constant rate
  • tissue degradation by fermentation will be limited by microbial access to tissue surfaces – expect a linear degradation rate

The time it takes for a body to completely disappear, including the skeleton, is unclear and variable. A typical time period for ‘time to dust or removal’ is often modelled as 100 years.

Contaminant decay rates and timings

Contaminant Mass per(g) Available mass for release(g) Release start year Release end year Kinetic release model Release rate per burial (g yr-1)
Calcium 1,100 1,100 10 100 zero-order 12.22
Carbon 16,000
+
10,000a
14,800b
+
10,000a
0 10 zero-order 2,480
Carbon 1,200 1,200b 10 20 zero-order 120
Nitrogen 1,800
+
500a,d
1,400c
+
500a,d
0 10 zero-order 190
Nitrogen 400 400 10 20 zero-order 40
Mercury 3 3 0 2,600 zero-order 1.12x10-3
Phosphorus 500 500 10 100 zero-order 5.55
Formaldehyde 180 180 0 0.25 as a single event N/A
Formaldehyde 500d 500d 0 10 zero-orderd 50

Notes

  • a – assumes a 15,000g coffin mass
  • b – assumes that in a 16,000g body, 1,200g is collagen (in bone and so forth) – this is degraded after skeletonisation and so lost over 10 years
  • c – assumes that in a 1,800g body, 400g is collagen (in bone and so forth) – this is degraded after skeletonisation and so lost over 10 years
  • d – relies on catalytic hydrolysis of resin in situ

Typical infiltration rates

The numbers and proximity of the buried in a cemetery or natural burial ground will vary.

When you do a risk assessment for green burials you must consider:

  • lower burial densities
  • whether trees or shrubs are planted on the grave – this will alter the biological and recharge conditions through the grave

The time it takes for pollutants to flush from a buried body relates to effective rainfall and the infiltration rate through the soil and grave. When you do your risk assessment you will need to consider infiltration rates and adjust your calculations accordingly.

Estimate the possible average composition of effluent reaching the water table beneath the burial ground by dividing the pollutant release by the total annual infiltration.

This table gives an estimate of water infiltration (litres per year) through a typical grave plot:

Grave cover Surface infiltration (1yr-1) Infiltration from grass surrounds (1 yr-1) Total (1 yr-1)
Chippings 750 500 1,250
Grass 500 500 1,000
Green burial 250 760 1,010

This table is based on an average annual rainfall of 650mm and typical evapotranspiration losses. Each grave and surrounding area is considered to be centred on:

  • 5.06 square metres for a typical municipal cemetery with 1,976 graves per hectare
  • 6.32 square metres for green burial sites with 1,580 graves per hectare

Potential groundwater pollutants from human burials

The end products of body degradation will occur as:

  • volatile gaseous products such as carbon dioxide, methane and ammonia – these will migrate up to the surface by diffusion and advection
  • soluble and suspended components such as ammonium and micro-organisms – these will migrate down through the subsurface with recharge

The soluble and suspended components risk polluting groundwater. They include:

  • ammoniacal nitrogen
  • formaldehyde (used in embalming fluid and coffin manufacture)
  • mercury (as amalgam in dental fillings)
  • other metals (mostly of medical or jewelry origin)
  • pathogens (including bacteria and viruses)
  • phosphorus and calcium (from bone)

Attenuation (reduce the effect) of pollutants from burial sites

Pollutants from burial sites may migrate into the:

  • soil zone surrounding the burial
  • unsaturated zone of the underlying aquifer
  • saturated zone of the aquifer

Different degradation processes will occur in each zone. The depth of grave and depth of soil underneath a grave will affect how pollutants transform and degrade.

For example, in shallow soil zones or deep graves, the attenuation of pollutants from a burial will rely more on the processes in the unsaturated zone and saturated zone. Soil zone processes will be less important.

After a burial the main processes of attenuation are in the:

  • soil zone – intense chemical and biochemical degradation, filtration and sorption (there is usually enough air for rapid oxidation of pollutants unless the soil is waterlogged)
  • unsaturated zone – sorption and filtration but reduced chemical and biochemical degradation
  • saturated zone – dilution and dispersion (the extent of filtration depends on the nature of the aquifer; chemical reactions depend on the groundwater chemistry)

There is less chemical and biological activity below the soil, in the unsaturated zone. Oxygen diffusion from the surface is low and low oxygen (anoxic) conditions may develop. However, chemical and biochemical reactions may continue to attenuate (reduce the effect of) pollutants. Filtration and sorption may continue to de-mobilise particulates and some dissolved pollutants.

Micro-organisms and pathogens

Potential micro-organisms and pathogens from decomposing bodies could include:

  • multicellular organisms such as worms
  • unicellular organisms and their resting stages such as giardia and cryptosporidium
  • bacteria, fungi and their spores
  • viruses

Only bacteria present a realistic threat of increasing after burial. Viruses cannot replicate without a living host cell.

The transport of micro-organisms and pathogens in groundwater depends on their size, shape and how they travel through the aquifer – for example through the subsurface pores of aquifer systems as opposed to fractures.

The potential for the aquifer matrix to remove micro-organisms and pathogens by filtration depends on its nature. Where the major route for groundwater flow is through a porous intergranular matrix, like sandstone aquifers, there is a high filtration potential.

Aquifers where fractures are the main flow route, like chalk aquifers, have limited potential for filtration.

Water abstracted from a shallow depth has a shorter travel time within the aquifer. Therefore it is more likely to be at risk of transporting micro-organisms and pathogens than water abstracted from a greater depth, which has a longer residence time.

Because of the short travel time, many springs and shallow wells are more vulnerable to microbial pollution problems than deep wells or boreholes.

Published 14 March 2017
Last updated 11 June 2020 + show all updates
  1. We have updated the information about the decay process and the pollutants that are released from a decaying human body. We have also updated the information about infiltration rates.

  2. 1. You will need to do a risk assessment for on-going environmental management, for example grey water disposal. 2. If you dispose of water at a human burial site then you must check if you need an environmental permit for that activity.

  3. Corrected the effective grave area. 5.06 metres squared for typical municipal burials. 6.32 metres squared for green burials.

  4. First published.