Background
The C4SL research project (Phase 1) provided technical guidance to support Defra's revised Statutory Guidance (SG) for Part 2A of the Environmental Protection Act 1990 (Part 2A). Part 2A was originally introduced to ensure that the risks from land contamination to human health, property and the environment are managed appropriately, with the revised SG being designed to address concerns regarding its real-world application. The revised SG presents a new four category system for classifying land under Part 2A, ranging from Category 4, where the level of risk posed is acceptably low, to Category 1, where the level of risk is clearly unacceptable.
Phase 1 Project
The Phase 1 project produced, demonstrated and communicated a methodology for developing C4SLs which represents as wide a consensus as possible in the field of land contamination risk assessment. The C4SLs represent a new set of generic screening levels for 6 contaminants which are more pragmatic (but still strongly precautionary) compared to the existing soil guideline values (SGVs) and other similarly derived numbers. The C4SLs consist of cautious estimates of contaminant concentrations in soil that are still considered to present an acceptable level of risk, within the context of Part 2A, by combining information on human health toxicology, exposure assessment and normal ambient levels of contaminants in the environment. Within the Phase 1 Defra publication, it was emphasised that further work to expand C4SLs for other contaminants would need to be led by industry.
Phase 2 Project
The Soil and Groundwater Technology Association (SAGTA) is leading a collaborative industry initiative which started formulating and developing a project framework in 2015. Funding for this phase has been secured from SAGTA members, with in kind contribution from a number of consultants and a financial grant from the Society of Brownfield Risk Assessment (SOBRA) www.sobra.org.uk. The project officially started in 2018. Phase 2 will develop 19 C4SLs for a range of contaminants which have been selected following a consultative process choosing the contaminants which would be most useful to industry. Subsequent funding has been received from Environment Agency in 2023 to develop the 20th substance for PFAS.
The full list of contaminants that C4SLs are being derived are as follows and those in green are now available to download (as pdf):
|
Vinyl Chloride |
Cis-1,2-Dichloroethene | Free Cyanide | Toluene | Vanadium |
|
Trichloroethene |
Trans-1,2-Dichloroethene | Complex Cyanide | Ethylbenzene | Nickel |
| Tetrachloroethene (PCE) |
1,2-Dichloroethane (Ethylene Dichloride) |
Inorganic Mercury |
Xylenes |
Methyl tertiary butyl ether (MTBE) |
| Naphthalene | 1,1,1-Trichloroethane | Beryllium | 1,2,3-Trimethylbenzene, 1,2,4- Trimethylbenzene &1,3,5-Trimethylbenzene |
PFAS |
The project is being delivered by a consortium of partners which include the following:
Project Manager: CL:AIRE supported by Simon Firth (Firth Consultants Ltd) and Naomi Earl (Freelance Consultant)
Tier 1 Toxicologists: Sarah Bull (TARA Consulting); Camilla Alexander-White (MK Tox & Co Ltd) and George Kowalczyk (GK Toxicology Consulting).
Tier 2 Toxicologists: Natasha Glynn (Atkins); Gareth Wills (WSP); Jo Wilding (Independent); Laura Aspinall and Andrew Fellows (RSK); Melinda Evans (Soilfix); Adam Symonds, Duncan Grew & Peter Sheppard (Worley) and Kate Baker (Antea Group UK).
Exposure Modellers: Dave Brooks (Sirius); Gareth Barns (Geosyntec); Robert Reuter (Wardell Armstrong LLP); Catherine Cussell (RSK); Lucy Burn (Advisian) and James Lymer.
Steering Group
The project is being overseen by a Project Steering Group, led by Hannah White on behalf of SAGTA and consists of representatives from the following organisations:
SAGTA, Defra, Welsh Government, UKHSA, Public Health Wales, Foods Standards Agency, Environment Agency, Natural Resources Wales, Homes England, Lancaster City Council, YALPAG, Wiltshire Council, Welsh Contaminated Land group, Mole Valley District Council, SoBRA, NHBC, AGS, EPUK, EIC and HBF.
Programme
The project will endeavour to deliver the C4SLs in a timely manner. However as this project is relying on a lot of industry goodwill and until we know the exact hurdles that we may face, we will provide updates to industry as to how the project is progressing through the National Brownfield Forum minutes (www.claire.co.uk/brownfieldforum) and CL:AIRE News (https://www.claire.co.uk/home/news).
This section contains notes issued by Defra which will be of interest to those involved with contaminated land in both public and private sectors.
The files listed below are published in Adobe Acrobat Portable Document Format (PDF).
CLAN 1/02: Withdrawal of ICRCL Guidance Note 59/83 (2ND Edition) (15 KB)
CLAN 2/02: Contaminated Land Supplementary Credit Approvals 2003-04 (45 KB)
CLAN 3/02: Withdrawal of ICRCL Trigger Values (30 KB)
CLAN 1/03: An introduction to CLARINET (30 KB)
CLAN 1/04: 2004/05 Capital Programme Guidance Note (60 KB)
CLAN 2/04: Defra questionnaire on progress with land contamination - summer 2003 (10 KB)
CLAN 3/04: Section 86 of the Water Act 2003 (10 KB)
CLAN 4/04: Contamination of Agricultural Land & Part IIA of the EPA 1990 (52 KB)
CLAN 5/04: Ground waters & section 86 of the Water Act (10 KB)
CLAN 6/04: Update on the Soil Guideline Values Taskforce (16 KB)
CLAN 1/05: 2005/06 Capital Programme Guidance Note (57 KB)
CLAN 2/05: New advice on SGVs (24 KB)
CLAN 1/06: 2006/07 Capital Programme Guidance Note (209 KB)
CLAN 2/06 Best Value Performance Indicators (BVPI) Q&A (122 KB)
CLAN 3/06: Soil Guideline Values Taskforce (26 KB)
CLAN 4/06: Defra update on SGVs (24 KB)
Soil Guideline Values (SGV) and supporting technical guidance are intended to assist professionals in the assessment of long-term risk to health from human exposure to chemical contamination in soil.
There are different SGVs according to land-use (residential, allotments, commercial) because people use land differently and this effects who and how people may be exposed to soil contamination.
SGV are 'trigger values' for screening-out low risk areas of land contamination. They give an indication of representative average levels of chemicals in soil below which the long-term health risks are likely to be minimal. Exceeding an SGV does not mean that remediation is always necessary, although in many cases some further investigation and evaluation of the risk will be carried out.
SGV should not be used where they are not representative of the site under investigation. They do not assess other types of risk to human health such as fire, suffocation, explosion, or short-term and acute exposures. They also cannot be used to assess risks to controlled waters, property, pets and livestock, or ecological receptors.
SGV are available only for a limited number of chemical substances. However, the framework reports and software provide a starting point for the assessment of a much wider range of chemicals.
Professionals and regulators assessing risks to health from land contamination are not required to use SGV and the supporting technical guidance. Alternative approaches can be used provided that they satisfy the legislative requirements.
Framework Reports
The principles and method used to derive SGV is described in two main framework reports:
- Human health toxicological assessment of contaminants in soil (Science Report Final SC050021/SR2) (PDF, 718KB)
This report describes the technical principles and framework the EA use to derive Health Criteria Values. - Updated technical background to the CLEA model (Science Report Final SC050021/SR3) (PDF, 1.60MB)
This report describes the technical background to the CLEA model. It also sets out the underlying assumptions that the EA have made to predict exposure for three standard land use scenarios (residential, allotments and commercial).
Professionals should be familiar with the information in these reports before using SGV in site assessments.
SGV and TOX Reports
The EA published SGV Reports and TOX Reports for a small number of soil contaminants. TOX Reports describe the toxicology of specific chemicals or groups of related chemicals including a summary of expert group evaluations. They also set out the recommended health criteria values (HCV) used in SGV derivation.
SGV Reports discuss the available evidence for the presence of specific chemicals in soil and their fate and transport in soil systems. In addition to the SGV themselves, the SGV Reports contain other useful information to assist risk assessors.
CLEA Software
The EA published the calculations for deriving SGV as described in the framework reports as a spreadsheet for use by professionals in conjunction with the wider guidance. The CLEA software is written using Microsoft Excel and uses VBA macros to support functionality. In addition, a specific spreadsheet has been published to support the assessment of dioxins in soil.
- CLEA software v 1.071
- CLEA software v 1.06
- CLEA Licence Agreement
- CLEA handbook v 1.05
The CLEA software version 1.05 handbook is still relevant to version 1.06 and 1.071 and has not been changed.
FAQs
The Environment Agency compiled a list of the most frequently asked questions (PDF, 121KB).
SGV Reports and supplementary information for specific chemicals and groups of chemicals are available for download below.
It is recommended that professionals using SGV Reports are familiar with the information in the framework reports (see below). SGV Reports published before 2009 have been withdrawn. They were prepared using previous framework guidance (R&D Publications CLR7 – 10) published in 2002, which have been superseded.
Introduction to Soil Guideline Values
- Human health toxicological assessment of contaminants in soil (Science Report Final SC050021/SR2) (PDF, 718KB)
This report describes the technical principles and framework the EA use to derive Health Criteria Values. - Updated technical background to the CLEA model (Science Report Final SC050021/SR3) (PDF, 1.60MB)
This report describes the technical background to the CLEA model. It also sets out the underlying assumptions that the EA have made to predict exposure for three standard land use scenarios (residential, allotments and commercial).
Heavy metals and other inorganic compounds
- Soil Guideline Value for arsenic in soil (PDF, 385 KB)
- Soil Guideline Value for nickel in soil (PDF, 139 KB) This report has been withdrawn
- Soil Guideline Value for mercury in soil (PDF, 220 KB) This report has been withdrawn
- Soil Guideline Values for selenium in soil (PDF, 150 KB)
- Soil Guideline Values for cadmium in soil (PDF, 188 KB)
BTEX
- Soil Guideline Value for benzene in soil (PDF, 365KB)
- Soil Guideline Value for toluene in soil (PDF, 437KB)
- Soil Guideline Value for ethylbenzene in soil (PDF, 363KB)
- Soil Guideline Value for xylene in soil (PDF, 740KB)
Dioxins
Other organic compounds
Supplementary information for the derivation of SGVs
Heavy metals and other inorganic compounds
- Supplementary information for the derivation of SGVs for arsenic (PDF, 2.33 MB)
- Supplementary information for the derivation of SGVs for nickel (PDF, 2.4 MB) This report has been withdrawn
- Supplementary information for the derivation of SGVs for mercury (PDF, 2.41 MB) This report has been withdrawn
- Supplementary information for the derivation of SGVs for selenium (PDF, 2.36 MB)
- Supplementary information for the derivation of SGVs for cadmium (PDF, 2.39 MB)
BTEX
- Supplementary information for the derivation of SGVs for benzene (PDF, 2.32 MB)
- Supplementary information for the derivation of SGVs for toluene (PDF, 2.32 MB)
- Supplementary information for the derivation of SGVs for ethylbenzene (PDF, 1.03MB)
- Supplementary information for the derivation of SGVs for xylene (PDF, 2.35 MB)