COLONIAL PIPELINE CO

Incident Narrative

TANK 316 WAS SCHEDULED FOR AN API 653 INSPECTION IN 2010. DUE TO ISSUES ASSOCIATED WITH SURFACE WATER UNDER THE TANK FLOOR, IT WAS DETERMINED THAT THE TANK SHOULD BE ELEVATED AND THE FLOOR REPLACED. REMOVAL OF FLOOR PLATES BEGAN ON 4/22/10 AND BY 4/26/10 THE ENTIRE FLOOR WAS REMOVED. A PRELIMINARY ASSESSMENT CONDUCTED ON 4/26/10 FOUND CONTAMINATED SOIL IN THE VICINITY OF THE TANK SUMP AND NEAR AN 11-INCH FLOOR CRACK. THE PATTERN OF THE IMPACTED SOIL UNDER THE TANK INDICATED THAT THE CONTAMINATION RESULTED FROM A RELEASE FROM THE 11-INCH CRACK. ANALYSIS DETERMINED THAT THE SUMP FLOATED DUE TO POOR DRAINAGE OF SURFACE WATER AROUND THE TANK. A METALLURGICAL ANALYSIS DETERMINED THAT THE LEAK WAS CAUSED BY FLEXING OF THE TANK BOTTOM CAUSED BY FLOTATION OF THE SUMP. CORROSION ON THE SOIL SIDE AND PRODUCT SIDE OF THE FLOOR PLATES PROVIDED STRESS CONCENTRATORS FOR THE FATIGUE TO AFFECT. THIS COMBINATION OF DEGRADATION MECHANISMS PRODUCED CORROSION FATIGUE AND A THROUGH-WALL CRACK. THIS REVISED FINAL REPORT IS SUBMITTED TO REVISE THE APPARENT CAUSE TO CORROSION RATHER THAN OTHER, AS SUGGESTED BY PHMSA REVIEWERS. CORROSION IS CONSIDERED A BETTER CATEGORY SINCE IT IS ONE OF THE SPECIFIC CAUSE CATEGORIES ON THE ACCIDENT REPORT AND THE REPORT DOES NOT ALLOW MULTIPLE CAUSES TO BE SELECTED. APPROXIMATELY 442 TONS OF SOILS WERE EXCAVATED AND REMOVED FOR TREATMENT. THE GA EPD CASE MANAGER FOR THE SITE WAS PROVIDED A COURTESY NOTIFICATION OF THE RELEASE ON 5/4/10. NO FORMAL NOTIFICATIONS TO THE GA EPD OR THE NRC WERE REQURED. (THE ORIGINAL REPORT WAS INADVERTENTLY SUBMITTED AS A 100 BARREL SPILL RATHER THAN 100 GALLONS OR 2.38 BBLS.)