Supernatant diesel fuel was found in manholes of the fuel tanks of a service station at 2:10 p.m. during an unloading operation. A total of 3 m³ of a mix of water and oil was pumped out. The tanks and pipes were tested for leaks. The operator tested the soil and groundwater at the site since for the possibility of seepage. He installed three piezometers, replaced three shut-off sensors on the diesel tank, checked the tightness of the pipe flanges, drained the oil separator and repaired the float gauge. A total of 600 l of diesel from a 24,000-l tank spilt from the gauge well.

The incident occurred during a fuel delivery. The excess diesel flowed out of a gauge well. The fuel receipt procedure was not followed. In particular, the volumes available in the tanks were not checked prior to unloading. One of the shut-off sensors was found to be defective. The operator assumed that it had not been properly fitted. The inventory monitoring system was not available. Some of the leak detectors were defective. The pipes were single-walled.

During another fuel delivery two weeks later, fuel was found on the leak detector canister.

Following these accidents, the operator reminded his crews and the carrier of the fuel receipt procedure. The manholes are now visually inspected and the observations are recorded in a log. Two tanks and single-walled pipes were replaced. The operator drew up an HSE alert sheet and distributed it to all employees and carriers to raise their awareness of properly managing fuel receipts and deliveries:

• check and certify the volume available in the tanks before commencing unloading;
• check and ensure that the gauge wells are closed after each operation;
• explain the unloading plan to drivers on the delivery note or on the loading ticket;
• unload a complete compartment in a single tank;
• avoid using the shut-off sensors;
• halt fuel dispensing at the pumps;
• immediately give the alert if an accident occurs.