ENVIRONET Conceptual Site Model

Transcription

1 ENVIRONET Conceptual Site Model Peter Booth Senior Technical Director 17/04/2012

2 Definition The conceptual site model (CSM) can be seen as; A representation which sets out the critical pollutant linkages of concern for a particular land contamination problem The CSM provides an understanding of what needs to be undertaken to achieve risk management, and from this point appropriate remediation techniques for any set risk management goals can be chosen. 2

3 Environmental Risk Assessment Environmental risk assessment is often used to support the decision making process for environmental remediation projects. Environmental Risk can be defined as a quantitative or qualitative combination of the probability of a defined hazard causing an adverse consequence at a receptor, and the magnitude of that consequence. Environmental Risk assessment can be defined as the process of identifying and quantifying a risk, and assessing the significance of that risk in relation to other risks. 3 Definitions sourced from the UK s Environment Agency

4 Source Pathway Receptor Source The actual cause or source of the contamination requires identification. For example, a source might be a leaking building, waste tank, waste disposal site or ground and groundwater that has already become contaminated. The location of any such contamination needs to be identified, and may reside in the soils, deeper ground or surface waters. 4

5 Source Pathway Receptor Pathway The pathway is essentially the route along which a particle of water, substance or contaminant moves through the environment e.g. the route contaminants are transported between the source of landfill leachate and a water receptor. In other words, the pathway is the route the source takes to reach a given receptor. Pathways may include air, water, soil, animals, vegetables and ecosystems. 5 Definition sourced from the UK s Environment Agency

6 Source Pathway Receptor Receptor An entity/organism, material property or any existing or potential active or passive use of water that is being or could be harmed by a potential pollutant, including groundwater or surface water resources, amenity uses or abstraction points. If contamination is to cause harm, it must reach a receptor. A receptor may be a person, animal, plant, eco-system, property or a controlled water. Each receptor must be identified and their sensitivity to the contaminant must be established. 6 Definition sourced from the UK s Environment Agency

7 Source Pathway Receptor Understanding the existence of this information allows a conceptual site model to be created. Such a model displays all these potential sources, pathways and receptors for the site in question. Conclusions can then be drawn about the potential risks caused by the source of contamination. Conceptual site models are often used to help design site investigations and prioritise the type of data required as well as its spatial location. The conceptual site model therefore can assist determining the most optimal remediation strategy. A pollutant linkage occurs when a source, pathway and receptor exist together. 7

8 Where does CSM fit into the site investigation process? Site investigation work is expensive Before any expensive work is undertaken you need to collate all available information through; Desk studies. Walk over surveys. Interviews with previous site personnel. CSM produced Qualitative risk assessment undertaken If significant pollutant linkages occur there will generally be a requirement for an intrusive site investigation. The CSM therefore helps drive and prioritise the expensive site investigation programme. 8

9 CSM Data Requirements Information relating to the historical use of the site and its surrounding area. Geological information including sediment types, structural features, geomorphology. Climatic data including precipitation rates, air temperature, prevailing wind speeds and direction. Hydrogeological data including. Aquifer characteristics Hydrologic budget Recharge rates precipitation, artificial recharge. Discharge rates evaporation, transpiration, groundwater pumping. Groundwater flow Hydraulic gradient groundwater elevations, flow direction. Flow velocity (travel time). Information related to the known contamination. 9

10 The Conceptual Site Model (CSM) A well developed CSM can be utilised to support the decision making process associated with the management of contaminated land and groundwater. The CSM allows you to simply visualise and then organise all the available information pertaining to a specific site, in turn allowing you to identify any data and information gaps. Further data can be prioritised, acquired and integrated within the CSM, allowing its revision and refinement. The development of a CSM is therefore an iterative process, with the new information revising your understanding of the various sources, pathways and receptors. 10

11 Once the CSM is established it can be used to: Estimate site conditions that may lead to unacceptable risks and warrant further study, therefore supporting the design and scope of any required site investigation. Develop site specific sampling designs and procedures for sample collection and analysis. Identify sources of contamination at the site, potential chemicals of concern, and the media (soil, groundwater, surface water, structures) affected. Provide a detailed description of the site and its setting. Quantify how contaminants may be migrating from the sources and the media and pathways through which migration and exposure of potential human or environmental receptors could occur (including possible air releases). Support the clean up actions and/or decision making process that might be required to meet pre-determined criteria for the future utilisation of the land. 11

12 An example of a CSM 12 Diagram sourced from The International Network for Acid Prevention (INAP)

13 An example of a CSM 13 Diagram sourced from the ATSDR Public Health Assessment Guidance Manual

14 Summary A CSM can almost be regarded as a cartoon visualisation of what you know about the site. It allows available information to be brought together pictorially, thus allowing; Information gaps to be seen. Potential areas of concern to be noted. Provision of an early view of how contaminants might be moving across the site. Relationships between sources, pathways and receptors to be better understood. Without a CSM where would you prioritise site investigation? The CSM can help focus the site investigation in terms of; Where you require data (spatially). The kind of data you may require (soils, groundwater, contaminant types). 14

15 Thank you for Listening - Any Questions? Staff Photo Here Peter Michael Booth Senior Technical Director T. +44 (0) E. peter.booth@wspgroup.com 15

16 CSM exercise based on the Painful Site The aim of the exercise is to draw a conceptual site model similar to the examples provided, but based on the information of the Painful Site highlighted during this course. The conceptual site model should depict the site setting and show some sources, pathways and receptors. Please note there is no right or wrong answer! 16

17 Things to consider! What are the primary contaminant sources on the site? Are there potential pathways for contamination to leave the site boundary? What are the key receptors for any residual or migrating contamination? What should the spatial extent of our assessment be? What other types of information might we want to pursue (other than collecting samples)? What environmental media might currently be contaminated? 17

18 Things to consider! What are the potential exposure pathways of concern? How might contaminants have moved once they were released to the environment? 18