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IES Webinar: Land & Groundwater Remediation Options & Scoping - The Decision Process - Martin Westwood

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Model Procedures provide a framework for making decisions about land contamination risks and are a useful resource which offer a lot of detail leading up to, and after, remediation. The remediation stage is often a significant and complicated financial commitment for any project, however the design and delivery of a project gets minimal attention in CLR11. There is a wealth of guidance on specific remediation techniques, some of which is outdated. Therefore, the process can be fraught with uncertainty and a lack of evidence on how the remediation strategy was developed can lead to a lack of confidence in it. This process needs to be open and transparent and stakeholders need to be fully engaged throughout the entire process.

During this webinar, Martin presents an overview and worked examples of the process when undertaken in accordance with best practice principals.

Publicada em: Meio ambiente
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IES Webinar: Land & Groundwater Remediation Options & Scoping - The Decision Process - Martin Westwood

  1. 1. Model Procedures : Framework for decision making about land contamination risks (CLR11). Despite the remediation stage of a project often being a significant and complicated financial commitment, the design and delivery gets minimal attention in CLR11, albeit is a key process. Discussion of how to comply with an navigate model procedures and undertake remediation options and sustainable implementation. Martin Westwood Environmental Scientist BSc (Hons) CEnv 7th August 2018 “Remediation Action taken to prevent or minimise, or remedy or mitigate the effects of any identified unacceptable risks” (Contaminated Land Report 11)
  2. 2. Safety Moment
  3. 3. Content 1. Model Procedures 2. Remediation Process 3. Remediation Options Appraisal 4. Pilot Trial 5. Remediation Strategy Development 6. Detailed Design/Implementation 7. Costing /Cost Benefit 8. Licences / Permits/ Material Management Plan 9. Verification of Remediation 10.Four Case Studies
  4. 4. Model Procedures for the Management of Land Contamination, CLR11(2004) 1. Remediation Options Appraisal 2. Remediation Strategy Development 3. Implementation Plan 4. Design / Implementation / Verification of Works How did you design the method? How did you carry out the works? How can you show the success of the works?
  5. 5. Remediation Process- The basics There are three main ways to reduce or control unacceptable risks Remove or treat the (source) of pollutant(s); Remove or modify the pathway(s); Remove or modify the behavior of receptor(s). Ex-situ – where contaminated material is removed from the ground prior to above-ground treatment or encapsulation and/or disposal on or off-site. The main advantage of ex-situ techniques, compared with in situ, is that contaminants, being brought up to the surface, are made more accessible to treatment processes In-situ – where contaminated material is treated without prior excavation (of solids) or abstraction (of liquids) from the ground. The main advantages of in-situ methods are that they can often avoid excessive environmental impacts and costs associated with excavation and abstraction and they can typically be implemented on operational sites. Hybrid /combined options -one or more appropriate remediation options Normally for different contamination phases or different receptors. CIVIL ENGINEERING BIOLOGICAL CHEMICAL PHYSICAL STABILISATION AND SOLIDIFICATION THERMAL METHODS
  6. 6. Remediation Options Appraisal Document and Record Everything and set out clearly from first principals The SuRF-UK framework draws on existing methods with the aim to develop a robust and streamlined framework for assessing sustainable remediation that is compliant with legislative requirements
  7. 7. Remediation Options Appraisal
  8. 8. Pilot Trails Encouraged for all remediation process except civil engineering methods Can be expensive, but so is failure Always best to measure than model Laboratory tests Field Trials Specialist contractor should have a method to assist that they have adopted previously Case studies (on line) CL:AIRE case studies
  9. 9. Remediation Strategy Development
  10. 10. Detailed Design/Costing
  11. 11. Cost Benefit Analysis Guidance allows for continual review of the process of remediation Consideration of costs and benefits of remediation with time Is remediation sustainable? How does the environmental benefit from continued operation correlate with other factors as Timescales, financial, socio- economic, energy use, noise etc Get an economist and cost manager on board- this is formal process not just cost cutting
  12. 12. Licences and Permits/Material Management Plan https://www.gov.uk/guidance/check-if-you-need-an- environmental-permit#what-you-need-a-permit-for Waste operation Mobile plant licence Land and groundwater Deployment Water discharge / activity/ abstraction Work near controlled water Foul sewer discharge consent Other i.e. ecological, air, waste etc
  13. 13. Verification As specified by CLR11, prepare a Remediation Implementation Plan that sets out in detail the methodology for the design, preparation, implementation, verification, monitoring and maintenance of the remediation. The Implementation Plan should include a Verification Plan which sets out what information should be obtained during the development of the site (and when) so that a permanent record exists of the remediation actions completed to address the identified RPLs. The Implementation Plan should be agreed prior to undertaking any works on site. Typical verification criteria for in-situ remediation: Reduction in contaminant concentrations to below assessment criteria Reduction in contaminant distribution Asymptotic conditions for remediation system Stable contaminant concentrations in verification monitoring wells Typical verification criteria for ex-situ remediation: Contaminant concentrations laboratory analysis
  14. 14. Case Studies Under Model Procedures
  15. 15. In-situ Vacuum Enhanced Free Product Recovery- Gas Oil (1)
  16. 16. EA policy is remediation was required to remove the free phase gas oil. 24m3 of free-product in the ground to be removed Remediation options evaluation undertaken Chosen method: In-situ Vacuum Enhanced Free Product Recovery (Venturi effect) under licence Delineation During Contract Free phase product and soil vapour are extracted simultaneously from a network of wells using a vacuum pump Free-product is separated for storage and disposal off-site at an appropriate licensed facility (waste management) Waters and condensate pass through a treatment system prior to discharge to the sewer (discharge consent) 200 extraction wells over 3000m2 Recharge rate very slow (80% yield) 4 week recharge Near Asymptotic Conditions 300 days operation 18m3 of gas oil In-situ Vacuum Enhanced Free Product Recovery- Gas Oil (2)
  17. 17. Reed bed- Free phase Relict Creosote (PAHs) • Perched groundwater management/ exploitation of existing ground conditions • Free phase (DNPAL) management and collection system • Wetland / reed bed (biological water treatment (3 month capacity) • Representative TPH CWG concentration: 12 mg/L. • 70 % COC removal /35m3 per day • Treatability Trial) • Piped water outfall to River under SWDC • Facility to construct further treatment steps (if required) • Temporary water management and treatment was significant cost • Verification- testing groundwater into and out of reed bed and compliance at discharge point • Post Completion Environmental Management System / maintenance plan
  18. 18. Permeable Reactive Barrier (PRB) Chlorinated Solvents • PRB in aquifer • In-situ: Activated carbon /hydrogen release compound /in situ anaerobic bioremediation or • Ex-situ: Additional treatment step (Groundwater pump and treat)
  19. 19. Avenue Coking Works- Tar sediment, Soils and Dry Wastes (1) Technique Designs Volume Final / Forecast Treatment (m3) Thermal desorption 270,300 257,266 Soil screening /sorting 237,600 203,485 Bioremediation 74,000 181,206 Total 581,900 641,497 Off-Site Disposal (Tonnes) Asbestos 2352 913 Metal 3000 550 Other waste 4600 2470 Recovered Timber 1450 10,000 Tar 0 19,000 Total 11, 402 32,020 Groundwater and Surface Water Treated 650,000 All Earthworks (m3) Total Material volume (cut) 1,883,377 2,244,989 Total Material volume (Fill) 1,934,896 2,178,20 Total 3,818,273 4,423,189 Material Import to Create Landform 0 80,000 Groundwater and Surface Water Treated ?? 650,000
  20. 20. Information Sources
  21. 21. Conclusions Follow Model Procedure Framework Adapt the methodology (but be clear if there is a deviation or amalgamation) The remediation and model procedures should be proportional to the scheme complexity Each step is iterative (but try to think holistically) Design sustainably and to minimise resource (cost benefit) Document everything /all decision (undertaken in tabular format) Consult with client, regulators and contractors at all stages Get contractor on board at earliest opportunity Undertake a remediation plot trial Expect the unexpected and try to accommodate it When you prepare the contract documents make sure the relevant technical uncertainties are covered in case of unforeseen conditions (the contractor wont look at your technical report) Make sure that the verification requirements are documented in contract Update the risk assessment based on changes in contaminant mass/distribution Thank You. Any Questions