Guide
Leaking oil tank: contamination, testing and what it can cost
Updated
This is the page that matters. Everything else on this site is a few hours of work; a contaminated ground problem is a different order of expense and it does not go away by itself.
Why oil in the ground is a serious problem
Heating oil moves. It travels through soil, along drainage runs and service trenches, and it can reach groundwater or a watercourse a long way from where it escaped. A small persistent weep from a fitting can put more oil into the ground over a year than a single visible spill. Once oil is in the ground the questions are how far it has gone, what it has reached, and what has to be done about it, and answering them costs money before any remediation starts.
Signs worth taking seriously
- A persistent smell of oil in a room, a cellar, a drain or the garden.
- Oil consumption that has risen without a change in the weather or in usage.
- Staining, dead vegetation or a rainbow sheen on standing water near the tank.
- Oil appearing in a drain, ditch, stream or land drain.
- A tank base that is cracked, a bund holding oily water, or corrosion at the bottom of a steel tank.
What happens next
- Stop the source if you safely can: isolate the supply, and contain what is escaping.
- Report it where oil has reached, or may reach, a watercourse, a drain or groundwater. Pollution incidents are reported to the environmental regulator for your country, and doing it early is treated very differently from doing it late.
- Get an assessment. Soil sampling and, where needed, groundwater investigation establish how far the oil has travelled. The gov.uk guidance on managing land contamination sets out the framework (gov.uk).
- Tell your insurer. Some home and business policies cover oil escape and the resulting clean-up, and many require prompt notification. This is the single most valuable phone call in the whole process.
- Remediate to whatever the assessment concludes: excavation and disposal of contaminated soil is the common route on domestic sites.
The cost reality
Nobody can give you a number for this without an assessment, and anyone who does is guessing. What is reliable is the shape: investigation costs are modest compared with remediation, remediation costs scale with how much material has to come out and where it has to go, and the total can be many times the cost of the tank work that triggered it. That is precisely why testing before or during removal, on any tank with a hint of a problem, is a cheap decision.
Contaminated soil and oily water are waste. They leave site with a registered carrier, and you should keep the documentation, which you can cross-check on the public register of waste carriers (Environment Agency public register).