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Development of Category 4 Screening Levels for assessment of land affected by contamination - SP1010

The aim of this research project is to provide technical guidance to support Defra¡¦s recently 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. The Impact Assessment (IA) which accompanies the revised SG explains this system in more detail and identifies a potential role for Category 4 Screening Levels (C4SLs) in providing a simple test for deciding that land is suitable for use and definitely not contaminated land.

The proposed project will produce, demonstrate and communicate a methodology for developing C4SLs which represents as wide a consensus as possible in the field of land contamination risk assessment. The proposed C4SLs will represent a new set of generic screening levels which are more pragmatic (but still strongly precautionary) compared to the existing soil guideline values (SGVs) and other similarly derived numbers. The C4SLs will 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. The development of C4SLs is expected to yield significant benefits to home owners, regulators, the regulated community and the general public, by helping to address historically overly-cautious / uncertain / inconsistent decision-making and costly unnecessary remediation, while ensuring that risks to home owners and the general public remain acceptably low.

As a consequence, Defra anticipates that specific economic benefits will accrue from the C4SLs. In order to deliver the objectives of the project, a critical review of the basis upon which the existing SGVs have been derived will be undertaken. Following the review, recommendations will be made regarding the options for a new risk-based methodology and model, which will incorporate scientifically and technologically sound aspects of existing approaches together with novel risk assessment approaches, akin to those used in the risk assessment of other media, such as food or consumer products. Considerable efforts will then be made to gather opinions and achieve consensus on a final methodology from the contaminated land practitioner community, via the use of a Steering Group and a Stakeholder Group.

The primary output of the project will consist of a report which describes the C4SL methodology and provides guidance on appropriate computer modelling approaches for deriving them. It will also contain substance-specific annexes which illustrate the application of the methodology / model to six agreed substances, likely to comprise benzo(a)pyrene, benzene, arsenic, chromium (VI), cadmium and lead. Three external presentations about the work will also be delivered.
The primary objective of the project is to develop a novel risk-based methodology and model for the development of C4SLs. Once developed, the approach will be demonstrated on selected substances and feedback obtained from as wide a group of relevant stakeholders as possible during the process of development. The methodology ultimately proposed will meet the requirements for defining C4SLs as pragmatic (yet still precautionary) levels in the context of the new four category test specified in the revised SG. The new C4SLs will aim to deliver the usefulness (and potential economic benefits) described in the IA of the revised SG.

Work package objectives are as follows:
> Design of methodology for determining C4SLs (Work Package 1 ¡V WP1)
> Develop agreed methodology using 2 test substances (Work Package 2 ¡V WP2)
> Determine C4SLs for 6 substances using the principles of the new methodology (Work Package 3 ¡V WP3)

Research Project Proposal Specific evidence objectives

Inception Meeting: Project inception meeting to set goals and agree scope of the project.
Measure: Milestone 1: Attend inception meeting, set goals and scope and provide minutes and action points from the meeting.
Target: Deliver minutes one week after inception meeting.

WP1: Design of methodology:

Objective 1.1: To design methodology with which to determine C4SLs
As part of designing the methodology we will review existing approaches and new options for developing a risk-based model, and make recommendations for a model design that best incorporates:
i) Modelling of human exposure scenarios
ii) Interpretation of human toxicology & epidemiology data
iii) Measurements of the actual levels of contaminants at a site of investigation iv) Evaluations of the impact of the results from DEFRA project SP100811 re: normal levels of background contaminants, in the context of interpreting levels of relative risks to health. v) Considerations of uncertainty in the model
Measure: Milestone 2. Delivery of Draft WP1 report outlining the options for risk-based modelling and the proposed recommendation for the development of more detailed methodology in WP2.
Target: At least one week before the October Steering Group meeting

Objective 1.2: To consult on the proposed approach and receive comments on the WP1 report.
Measure: Comments obtained from Defra and stakeholders to be able to refine the proposed approach and confirm the substances for which C4SLs will be developed in WP2 and WP3.
Target: CL:AIRE to provide Defra's Steering Group with a proforma sheet to use when commenting on the draft reports. Defra to forward comments to CL:AIRE on the draft report before the steering group meeting.
Completion of WP1 report 3 weeks after the stakeholder workshop. The stakeholder workshop to be held in October 2012. End WP1.
Measure: Milestone 3. Organising and delivery of Workshop 1.
Target: Delivery of 1st workshop in October 2012.
Measure: Milestone 4. Delivery of Final WP1 report.
Target: Delivery of final report 23rd November 2012.

WP2: Develop methodology using at least 2 substances

Objective 2.1: To develop methodology for at least 2 test substances
Measure: Milestone 5. Draft WP2 report outlining the model to be used to develop C4SLs
Target: At least one week before the January Steering Group meeting ¡V 11th January 2013. CL:AIRE to provide Defra¡¦s Steering Group with a proforma sheet to use when commenting on the draft reports. Defra to forward comments to CL:AIRE on the draft report before the steering group meeting.

Objective 2.2: To carry out consultation on the model
Measure: To obtain comments from the consultation on the proposed approach and organise and deliver Workshop 2. Milestone 6.
Target: The stakeholder workshop to be held in January/February 2013.

Objective 2.3: To refine the model based on stakeholder comments
Measure: A revised WP2 report outlining the amended model (if necessary) to be used to develop C4SLs. Milestone 7.
Target: Completion of WP2 report 3 weeks after the stakeholder workshop. End WP2.

WP3: Determine C4SLs for 6 substances:

Objective 3.1: To determine C4SLs for 6 substances
Measure: Milestone 3. Draft final report outlining the C4SLs for the chosen 6 substances. Milestone 8
Target: At least 2 weeks before the April Steering Group meeting

Objective 3.2: To carry out consultation on the C4SLs derived
Measure: Comments and feedback on project outputs from Defra and stakeholder workshops WP3 and issue a revised draft final report. Milestone 9
Target: The stakeholder workshop to be held in April/May 2013.
Overall Objective

Objective 4: To complete a final report describing the work from all 3 work packages, culminating in an agreed risk-based model and proposed C4SLs for the chosen 6 substances
Measure: Milestone 10. Submission of the final report to Defra.
Target: Before 31st May

Objective 5: To present project results at several contaminated land meetings/events in 2013
Measure: Milestone 11. Presentation of results at external conferences and workshops
Target: To be agreed with Defra as project progresses

In terms of interdependence, the success of WP2 is largely dependent on the ability to design a methodology during WP1 and stakeholder engagement to agree a way forward regarding the risk-based model proposed. Similarly, WP3 is reliant on the development of an agreed model in WP2 and buy in from stakeholder groups in order to refine the model.

Project Documents
• FRP - Final Report : SP1010 Development of Category 4 Screening Levels Main Report   (2653k)
• ANX - Annex : SP1010 Appendix A - Sensitivity analysis parameters   (488k)
• ANX - Annex : SP1010 Appendix B - Probabilistic Modelling   (544k)
• ANX - Annex : SP1010 Appendix C - Arsenic   (1638k)
• ANX - Annex : SP1010 Appendix D - Benzene   (1544k)
• ANX - Annex : SP1010 Appendix E - BaP   (1973k)
• ANX - Annex : SP1010 Appendix F - Cadmium   (2899k)
• ANX - Annex : SP1010 Appendix G - Chromium VI   (1585k)
• ANX - Annex : SP1010 Appendix H - Lead   (2204k)
• ANX - Annex : SP1010 Appendix I - Statistics Review   (263k)
• INF - Information Leaflet : SP1010 Policy Companion Document   (324k)
• INF - Information Leaflet : SP1010 Project Erratum - December 2014   (160k)
• OTH - Other : Peer Review - Professor Alan Boobis   (222k)
• OTH - Other : Peer Review - Robert Scofield   (57k)
• OTH - Other : SP1010 Stakeholder Report   (1018k)
Time-Scale and Cost
From: 2012

To: 2013

Cost: £181,111
Contractor / Funded Organisations
Contaminated Land: Applications in Real Environments