Diesel Spill at School
There was a theft of diesel oil from a 1400 litre oil tank located in a shed in the grounds of the school. Thieves left the fuel line pulled from its mounting and fuel running to ground. The spill occurred only 10 metres from stream that is a tributary of a major sea loch. The Environment Agency visited the site and identified that oil had already reached the tributary. They installed containment booms and absorbents.
A site survey was undertaken to assess the extent of the contamination. Oil impaction was found in the soils in and around the shed, the adjacent shed and in the walls and floors of the two sheds. Soils around two rainwater drains were oil impacted, and they were discovered to discharge to the stream. Oil was found to have already entered the stream at points beyond the containment booms.
To mitigate the immediate risks of further migration through soils and along the drainage channels to the stream an interception trench was dug close to the shed with a pump installed to remove oil for licensed disposal. Containment booms were placed further downstream to address oil reaching the stream beyond the current booms.
Risks and Remediation
There was a risk of future migration of oil to the stream from oil impacted soils, via leaching by rainwater and flow in soils and along drainage channels. Due to the water contained in bioremediation and chemical treatments these were ruled out due to the risk of causing leaching of oil. Source removal was proposed and agreed. The sheds were demolished. Approximately 150 tonnes of oil impacted soils were excavated and sent to licensed disposal.
Validation was undertaken utilising field monitoring and submission of soil samples for analysis to a UKAS accredited laboratory with and agreed by the Environment Agency.