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Point source pollution: prevention and management

Point source pollution: prevention and management. Gordon Lethbridge, Environmental Section, HSE Consultancy Group, Shell Global Solutions, Cheshire Innovation Park, Chester, UK CH1 3SH. Overview of presentation. Groundwater protection strategies for large networks of sites

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Point source pollution: prevention and management

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  1. Point source pollution: prevention and management Gordon Lethbridge, Environmental Section, HSE Consultancy Group, Shell Global Solutions, Cheshire Innovation Park, Chester, UK CH1 3SH

  2. Overview of presentation • Groundwater protection strategies for large networks of sites • Groundwater protection strategies for large facilities • The role of risk assessment in groundwater protection • Groundwater protection measures • Industry – regulator partnerships • Conclusions

  3. Prioritisation of sites in large networks: Network Environmental Risk Assessment (NERA) • GIS based desktop site prioritisation tool • Ranks sites in terms of potential environmental risk (SIV) • Groundwater usage, distance to abstraction wells, depth of abstraction, groundwater vulnerability • Not restricted to risks to groundwater • Ranks sites in terms of the condition of the assets (CIV) • Type and age of tanks and lines, corrosion prevention measures, corrosivity of soil • SIV and CIV can be integrated to get an overall assessment of potential risk • Process remains evergreen • Risk ranking may change over time as circumstances change

  4. Site classification using NERA CIV Poor condition High risk C Low Risk A Medium risk B Good condition SIV Low sensitivity High sensitivity No action Priority action Monitor

  5. Potential applications of NERA • Prioritise sites for investigation of soil and groundwater contamination • Prioritise sites for upgrading of facilities • Match containment and leak detection facilities to the level of risk posed by a site • Rapidly assess potential environmental liabilities of sites acquired from third parties • Identify any sites that pose an unacceptably high risk even with the most sophisticated containment and leak detection systems in place • Aid decision making in location of new sites

  6. Examples of groundwater protection measures at retail filling station sites: containment • Double walled tanks • Double walled pipeline • Coated walls • Corrosion resistant materials in aggressive soils • Tank overfill protection • Provision of spill collection capacity at tank fill points • Leak proof pavement • Leak proof drainage system

  7. Examples of groundwater protection measures at retail filling station sites: leak detection and monitoring • Wet stock management • Reconcile deliveries with sales and stocks • Monitor trends over time • Interstitial monitoring in double walled tanks and pipelines • External electronic leak detection • Groundwater monitoring

  8. Groundwater protection at large facilities

  9. Groundwater protection at large facilities • Risk-based product storage • Match products with tanks • High risk products in low risk tanks • Low risk products in high risk tanks • Risk-based approach to primary and secondary containment • Risk-based tank inspection • Inspect a high risk tank more frequently than a low risk one

  10. Risks to groundwater from point sources: some observations • Major leaks and spills are very rare (emergency response) • Vast majority of leaks are minor. • Underground pipelines are a greater source of leaks than underground tanks • Problems with UST often due to sub-standard manufacture or poor installation technique • Spills can be minimised through use of appropriate technology and procedures

  11. Groundwater protection following a spill or leak • Monitored Natural Attenuation (MNA) • Permeable reactive barriers • Source treatment / removal • Aggressive groundwater plume treatment

  12. The life cycle of a BTEX plume in groundwater Red = contaminated groundwater Blue = clean groundwater 1. Expanding 2. Stable Time 3. Shrinking 4. Exhausted = source

  13. 90% of BTEX plumes in groundwater are < 100 metres in length Based on 604 sites Source: API, 1998

  14. Groundwater protection: industry – regulator partnerships • Recognition of need to develop solutions in partnership between the Environment Agencies and industry organisations such as SAGTA and Institute of Petroleum • Research projects • Workshops • Reciprocal review of technical guidance • Examples • Groundwater vulnerability at retail filling stations • MtBE in groundwater • Monitored Natural Attenuation

  15. Conclusions • Risk assessment is the key to cost-effective groundwater protection • Large number of facilities requires site prioritisation • Match the level of containment, leak detection, inspection monitoring, SI and remediation to the level of risk posed by the site • When groundwater impacts do occur natural attenuation processes have great potential to mitigate risks • Industry – regulator partnerships are key to developing solutions which meet the needs of all parties

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