Overview
A major oil terminal operator engaged OTECSA Consulting Ltd to review an existing DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) risk assessment relating to the demolition of crude oil a storage tank at one of its terminal sites.
The client had previously completed demolition work on a storage tank that already had a detailed DSEAR assessment in place for that activity. Two additional tanks were scheduled for demolition under a tight project timeline, and the client required confirmation that the existing assessment and safeguards remained suitable for the new scope of work.
OTECSA was commissioned to carry out a focused technical review to determine whether the previous assessment could reasonably be applied to the demolition of the additional tanks, while identifying any new risks, gaps, or additional safeguards required.
The Challenge
The earlier demolition project involved a tank with a partially collapsed internal roof and remaining crude oil inventory. In contrast, the new tanks had already been emptied and water-flushed, leaving only residual sludge material at the base of the tanks.
As the composition of the sludge was not fully known, a conservative approach was taken, assuming that potentially flammable vapours could still be present during demolition activities.
The project also presented several practical challenges:
- Demolition activities were already being planned on a short timescale
- Large demolition equipment and cranes had been mobilised
- One of the tanks shared a bund with a live operational storage tank, introducing potential “domino effect” risks
- The client required a clear and practical review rather than a completely new assessment
OTECSA therefore needed to provide a pragmatic, technically robust review within a short turnaround period.
OTECSAs Approach
Rather than producing a completely new DSEAR assessment, OTECSA adopted a structured review methodology based on the existing assessment for the previously demolished tank.
The review included:
- Examining each demolition activity and determining whether it remained applicable to the new tanks
- Reviewing existing safeguards and mitigation measures
- Assessing whether previously identified ignition sources were still relevant
- Reviewing actions from the original assessment to determine whether they should also apply to the new demolition works
- Identifying any additional recommendations specific to the new tanks and site conditions
The assessment also considered the differences in demolition sequence due to the intact floating roofs present on the new tanks.
Throughout the project, close communication with the client ensured information could be reviewed quickly and efficiently to support project timelines.
Key Risk Considerations
The main hazard considered during the review was the potential release and ignition of flammable vapours from residual crude oil sludge remaining within the tanks.
Key risk controls reviewed included:
- Gas detection and lower explosive limit (LEL) monitoring
- Use of ATEX-certified equipment where required
- Permit-to-work arrangements
- Control of ignition sources
- Emergency response arrangements
- Safe access and egress planning
- Workforce communication and contractor awareness
OTECSA also identified additional considerations specific to the project, including the need to assess interactions between demolition activities and a nearby live storage tank located within the same bunded area.
Recommendations
The review concluded that many of the safeguards and actions from the previous demolition project remained relevant and should continue to be implemented.
Additional recommendations included:
- Communicating hazards and control measures clearly to all personnel and contractors involved in the demolition works
- Reviewing potential “domino effect” scenarios involving adjacent live equipment
- Confirming equipment temperature controls and ignition prevention measures
- Sampling and analysing residual sludge material to better understand any remaining flammability risks
Outcomes
OTECSA concluded that, provided all safeguards, control measures, and recommended actions were implemented prior to demolition, the residual risk associated with the new tank demolition activities could be considered broadly acceptable.
The review provided the client with:
- Confidence that the existing assessment could be applied to the two tanks to be demolished
- Additional project-specific recommendations
- A practical and efficient route forward without requiring a full new assessment
- Support for safe decision-making under a demanding project schedule
The project also demonstrated the value of adapting and reviewing existing risk assessments for similar operations, helping to deliver a proportionate and practical safety solution while maintaining robust DSEAR compliance.
Key Takeaways
This project highlighted the importance of combining practical engineering judgement with structured risk review processes. By building upon an existing assessment and focusing on operational differences, OTECSA was able to provide the client with a clear, efficient, and safety-focused solution tailored to the realities of a live industrial environment.