Tanks Under Scrutiny: An On-Site Fuel Storage Audit for UK Depots

On-site fuel storage rarely attracts attention until something goes wrong. A tank that has served the yard quietly for years can become a pollution incident, an enforcement notice or an insurer’s exclusion after a single overfill or a bund drain left open. For fleet managers in 2026, the business case for tighter controls is not only environmental; it is financial and operational.

Why the audit matters

Fuel stored on site is convenient, but it creates a pollution risk that ordinary fuel-card controls do not address. The regulatory position differs across the UK, and commercial premises with tanks above the relevant thresholds must meet oil storage rules. In England, the Oil Storage Regulations apply to many commercial and institutional premises; Scotland, Wales and Northern Ireland operate their own regimes. The common principles are sound containment, secure pipework, safe delivery procedures and evidence of maintenance.

Insurers increasingly ask for that evidence during risk surveys. A clean inspection log, a stocked spill kit and a clear delivery procedure are not paperwork for its own sake; they show that the site is managed. A pollution incident can lead to clean-up costs, enforcement action and reputational damage that dwarf the value of the fuel lost.

The audit checklist

1. Containment and bunding

Check that the bund has the required capacity. For a single tank, the common benchmark is 110% of the tank’s capacity. For multiple tanks, it is usually 110% of the largest tank or 25% of the aggregate capacity, whichever is greater. Confirm that bund walls are intact, joints are sealed and the base is stable. The drain valve should be closed and locked, with a controlled procedure for removing rainwater. Pipes and fill points should be within the bund where required, and the tank should be labelled with its contents and hazards.

A frequent failure is a bund drain left open or a valve that can be opened by anyone. Another is rainwater accumulating until the bund has little or no spare capacity. Both turn secondary containment into a false comfort.

2. Tank and pipework condition

Inspect the tank shell, seams, vents, fill points, sight gauges and locks. Look for corrosion, staining, weeping joints and impact damage. Drip trays should be in place under vulnerable connections. Delivery hose couplings should be compatible and protected from damage. Drums and intermediate bulk containers need their own containment and should not be left outside bunded areas.

3. Inspection routines

A documented routine is more useful than an informal glance. Daily visual checks should cover leaks, odour, security and evidence of spillage. Weekly checks can cover bund condition and rainwater. Monthly inspections should be recorded, signed and filed, with defects raised and closed out. Inspections should also take place after every delivery and after severe weather. A competent person should own the routine, and cover should be arranged for absence.

4. Spill kits and response

A spill kit should be close to the tank, protected from weather and suitable for diesel. It should contain absorbents, drain seals, PPE and clear instructions. Stock levels should be checked monthly, and used items replaced. Staff should know where the kit is and how to use it. The emergency plan should identify who to call, how to stop a leak and how to prevent fuel reaching drains or watercourses. A short spill drill is more valuable than a folder nobody has read.

5. Deliveries and access

Deliveries should be supervised and made against a written procedure. The fill point should be secure and clearly marked. Dip or gauge the tank before and after delivery, record the volume and reconcile it with the delivery note. Drivers should be inducted on site rules, including parking, coupling and emergency arrangements. Unattended filling and uncontrolled overfill are common causes of avoidable incidents.

6. Records and insurer evidence

Keep an asset register for tanks, bunds, pipework and spill equipment. Retain inspection logs, maintenance records, delivery notes, training records and spill drill notes. Photograph defects and repairs. Insurers may ask for this evidence at renewal or after a claim. Records also help with stock reconciliation: unexplained fuel loss can indicate a leak, theft or a metering problem.

7. Security and housekeeping

Fencing, lighting, locks and signage should deter interference and make leaks easier to spot. Keep vegetation cut back and remove incompatible materials from the bund area. Ensure that access routes allow a tanker to reach the fill point without reversing into vulnerable equipment.

Common failures and what they cost

• A bund drain left open, eliminating secondary containment.
• No spill kit, or a kit that has been emptied and not restocked.
• Inspection logs that stop three months before the insurer’s survey.
• Unlabelled tanks and unidentified pipework.
• Deliveries made without supervision or reconciliation.
• Rainwater and debris reducing bund capacity.

These failures rarely cost much to fix in advance. After an incident, the cost can include fuel loss, clean-up, specialist waste disposal, enforcement action and increased insurance scrutiny.

Making the business case

An on-site storage audit should take hours, not weeks. Assign an owner, set a quarterly calendar and budget for the simple items: labels, locks, spill kit replenishment and bund repairs. Integrate the findings with fuel management by reconciling deliveries, tank stock and fuel-card transactions. Tighter storage controls reduce loss, support insurance renewals and protect the depot’s licence to operate.

Conclusion

Start with a walk-round and the checklist above. Fix the open drain, the missing kit and the absent log first. Document what has been done, photograph it and review it quarterly. The tank may be out of sight at the back of the yard, but it should not be out of mind in the fleet’s cost and compliance controls.