For M&E contractors and real estate professionals, understanding the complexities of underground oil tank decommissioning is crucial for project success and environmental compliance. In this complete guide, we’ll explore the primary decommissioning methods, environmental assessment procedures, and key considerations for industry professionals to highlight how tanks can be taken out of service correctly.
Understanding Decommissioning Options
When it comes to underground fuel tank decommissioning, professionals have two primary methods at their disposal: complete removal or in-situ decommissioning through foam or concrete filling. Each approach has its specific applications and considerations that must be followed to ensure a safe removal.
Complete Tank Removal
Complete removal represents the most thorough decommissioning solution as it refers to all components being taken away at the same time. This process consists of three key steps which must be carried out in the correct order to ensure safety is maintained.
1. Site preparation and safety measures
Firstly, the work area must be secured in line with health and safety standards. Once the tank and surrounding parameter has access only limited to approved personal, utility marking and verification can take place. The initial stage also includes the implementation of soil erosion controls which ensure the surrounding grounds remain in good condition.
2. Tank preparation
To prepare the tank for decommissioning, all remaining oil products must be removed, followed by a deep clean and purging. Once complete, vapour testing is essential to ensure safe working conditions for the next steps.
3. Excavation and removal
Although a full clean and vapour test is required before this stage, all exposure to the tank must be handled carefully. The removal then involves disconnection of all associated piping followed by extraction using appropriate heavy equipment. Professional transport must also be arranged to eliminate any onward travel risks.
Complete removal offers of oil tanks is advantageous as it:
- Allows for comprehensive site assessment
- Eliminates future liability concerns
- Provides definitive documentation of tank condition
- Enables thorough soil inspection and remediation if necessary
In-Situ Decommissioning: Foam and Concrete Filling
Although a complete removal is often preferred, the reality is that it’s simply not feasible in all scenarios. In situations where removal isn’t practical or necessary, in-situ decommissioning presents a viable alternative. This method involves:
1. Tank preparation
The tank must be inspected for structural integrity, drained of all remaining product and professionally cleaned including a full degassing.
2. Filling process
- For foam filling:
- Installation of fill pipes at strategic points
- Introduction of expanding foam material
- Monitoring for complete cavity filling
- For concrete filling:
- Strategic placement of concrete delivery points
- Controlled filling to ensure void elimination
- Verification of complete solidification
Benefits of in-situ decommissioning:
- Minimal site disruption
- Lower cost in many scenarios
- Reduced risk when tank is under structures
- Shorter project timeline
Environmental Assessment Procedures
Professional environmental assessment forms a critical component of any decommissioning project. This ensures that all safety criteria are met and that spaces are left safe once the decommissioning has been completed.
The process typically includes both a site historical review and a full site survey as part of the pre-decommissioning assessment. The Site history review looks at previous usage patterns, all records and testing, plus any documentation created as a result of leaks or repairs. Once the past information has been assessed, the site survey can take place to assess the surface conditions, identify potential contamination indicators, and provide a full evaluation of the surrounding infrastructure.
Environmental Testing Protocol
Professional environmental testing typically includes:
- Soil Analysis
- Strategic sample collection
- Testing for Total Petroleum Hydrocarbons (TPH), Volatile Organic Compounds (VOCs) and/or Semi-volatile Organic Compounds (SVOCs)
- Groundwater Evaluation
- Determination of groundwater depth
- Assessment of flow direction
- Testing for contamination if warranted
Documentation Requirements
Proper documentation is essential for ensuring the entire decommissioning process is managed in line with environmental considerations.
This means documents should include detailed site assessment reports, test results and analysis, photographic documentation, chain of custody for samples, decommissioning method certification plus the final site condition report.
Professional Liability Considerations
Understanding and managing liability is crucial for all professionals involved in tank decommissioning projects.
Key Liability Areas
- Professional Responsibility
- Adherence to industry standards
- Proper documentation maintenance
- Clear communication with all stakeholders
- Environmental Liability
- Compliance with local regulations
- Proper handling of contaminated materials
- Long-term site monitoring if required
- Best Practices for Liability Management
- Maintaining comprehensive insurance coverage
- Detailed record-keeping
- Clear communication of procedures and findings
- Professional certification maintenance
Successful underground oil tank decommissioning requires careful attention to method selection, environmental assessment, and professional liability management. The choice between complete removal and in-situ decommissioning should be based on site-specific factors, regulatory requirements, and client needs.
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