Discharge tanks are ancillary to pipes and are used to prevent the risk of overpressure and water hammer.

At around 9:00 p.m., an alarm sounded after a 2,000 m³ discharge tank overflowed at an oil terminal. A 500 m³ mixture of crude oil and water spilt into and around the tank’s bund. The operator implemented the tank’s emergency plan and the nearby oil terminal implemented its internal emergency plan after a gas detection alarm went off.

Firefighters sprayed foam to prevent the risk of ignition. Gas measurements were negative and nearby railway traffic was halted. The overflow was pumped by a specialist company and treated as waste. The area surrounding the bund was cleaned and the contaminated ground was stripped. Due to a problem with the bund’s integrity, it was feared that the soil had been polluted.

The operator conducted an investigation to determine the causes of the accident. The spill occurred after a new product lighter than crude oil was transferred. This operation entailed heating the pipe and sending water through it to flush out stuck-on remnants. In addition, the facilities were more than 50 years old.

The inspection authorities for classified facilities asked the operator to:

• monitor the quality of the groundwater;
• inspect the tank and its roof;
• determine the causes of the accident (operation and relaying of the level alarms to the control room).