CHEVRON PIPE LINE CO

Incident Narrative

TANK 207 HAS AN EXTERNAL FLOATING ROOF DESIGN TO MINIMIZE VAPORS. THIS FLOATING ROOF COLLECTS RAIN AND SNOW AND MUST BE DRAINED FOLLOWING EACH STORM TO PREVENT THE ROOF FROM SINKING INTO THE PRODUCT. THE ROOF DRAIN HOSE CONNECTS AT THE ROOF AND RUNS INSIDE THE TANK AND PRODUCT AND OUT THE SIDE OF THE TANK THROUGH A VALVE. WHEN THE TANK ROOF IS AT IT LOW LEVEL LIMIT THE ROOF DRAIN HOSE IS COILED UP ON THE TANK FLOOR. WHEN THE HOSE IS IN THIS POSITION IT TRAPS WATER INSIDE AND CANNOT BE FULLY DRAINED. DURING THE 10 DAYS OF TANK 207'S LOW LEVEL BOISE EXPERIENCED VERY COLD TEMPERATURES RANGING FROM 10F TO 30F NEVER GETTING ABOVE FREEZING. THE PRODUCT TEMPERATURE AT THIS TIME WAS 15F, FREEZING THE WATER THAT WAS TRAPPED IN THE ROOF DRAIN HOSE THAT LAY ON THE TANK FLOOR. ON 1/26 AND 1/27 THE TANK LEVEL HAD RISEN AND THEREFORE WITH THE FROZEN WATER INSIDE THE HOSE IT HAD LOST ITS FLEXIBILITY, AND WAS PULLED OFF OF THE FITTING INSIDE THE TANK. THE FROZEN WATER HAD ALSO DAMAGED THE VALVE AT THE END OF THE SYSTEM. THIS CREATED A RELEASE POINT FOR THE TANK PRODUCT. ON THE MORNING OF THE 28TH THE STATION OPERATOR FOUND THE RELEASE OF 15BBLS OF DIESEL FUEL TO THE GROUND AROUND THE TANK.