TRANSCANADA NORTHERN BORDER INC — Gas transmission and gathering — incident on 2011-07-20

Gas transmission and gathering incident in GILLETTE, CAMPBELL County, WY. Reported cause: MATERIAL FAILURE OF PIPE OR WELD. Reported consequences: 0 fatalities, 0 injuries, 50555 NATURAL GAS released, $4,280,685 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20110294.

Operator ID: 32487.

Reported incident date: 7/20/2011 19:30.

Location detail: 16.2

Cause detail: DESIGN-, CONSTRUCTION-, INSTALLATION-, OR FABRICATION-RELATED

Cause detail: THE BISON PIPELINE EXPERIENCED A RUPTURE FAILURE AT APPROXIMATE MILEPOST 16.2 IN CAMPBELL COUNTY, WYOMING, AT ABOUT 1930 HOURS ON JULY 20, 2011. THERE AREA OF THE FAILURE WAS REMOTE FROM ROADS OR STRUCTURES RESULTING IN DAMAGE RESTRICTED TO THE PIPELINE RIGHT-OF-WAY. THERE WERE NO INJURIES OR FATALITIES. PRELIMINARY EXAMINATION OF THE PIPE IN THE FIELD AND LABORATORY HAS INDICATED THAT THE FAILURE MAY HAVE BEEN THE RESULT OF MECHANICAL DAMAGE INCURRED DURING PIPELINE INSTALLATION. THE RESULTS OF THE STUDIES HAVE BEEN FINALIZED AND HAVE BEEN SUBMITTED UNDER SEPARATE COVER, AS PART OF THE CORRECTIVE ACTION ORDER.

PHMSA trend classification: significant incident, not serious.

PHMSA standardized cause: MATERIAL FAILURE OF PIPE OR WELD — CONSTRUCTION, INSTALLATION OR FABRICATION-RELATED.

PHMSA indexed costs: $6,700,000 reported total cost, $3,662,863.71 in 1984 dollars, $8,657,226.221 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.