NUSTAR PIPELINE OPERATING PARTNERSHIP L.P.

Incident Narrative

NUSTAR CONFIRMED THE RELEASE AT 16:30 ON JUNE 8, 2020. THE PIPELINE WAS SHUT DOWN AT 17:15 ON JUNE 8, 2020. THE REPAIRS INCLUDED PUTTING A CLAMP AROUND THE PINHOLE AT 20:18 ON JUNE 13, 2020. THE PIPELINE WAS RESTARTED AT 20:18 ON JUNE 13, 2020. 48-HOUR NRC UPDATE #1279309 SUPPLEMENTAL: THE LEAK/RELEASE OCCURRED AT A LOCATION ON THE PIPE THAT HAD A LACK OF FUSION AREA AT THE ERW SEAM BOND LINE. DURING OPERATION, OUTER SURFACE PITTING HAD OCCURRED IN THE SAME GENERAL AREA. THE LEAK OCCURRED AT THE LACK OF FUSION LINE WHERE THERE WERE ALSO SEVERAL CORROSION PITS ON THE EXTERNAL SURFACE OF THE PIPE. THIS IRREGULARLY SHAPED PIT WAS COINCIDENT WITH THE BOND LINE AND THE LACK OF FUSION AREA, WHICH ACTED AS A CREVICE. CREVICES ARE KNOWN TO ACCELERATE CORROSION AND THE PITTING WIDENED THE LACK OF FUSION, EVENTUALLY RESULTING IN A CONNECTION BETWEEN THE OD AND ID. THE PITTING CORROSION IS TYPICAL OF WHAT WOULD OCCUR IN SUBMERGED SERVICE WHERE THE COATING WAS EITHER NOT PERFECT WHEN MANUFACTURED OR WAS DAMAGED IN USAGE. THERE WERE TWO STRAP MARKS STRADDLING THE PITTED AREA THAT MAY HAVE DISTURBED THE COATING LOCALLY. THE EXTERNAL SURFACE PITTING AREA WAS GENERALLY IN LINE WITH THE ERW WELD SEAM AT THE 6:30 O'CLOCK LOCATION (NEAR THE BOTTOM). THE COINCIDENCE OF THE LACK OF FUSION (LOF) AND THE CORROSION AT THAT LOCATION CREATED A THROUGH HOLE 0.070-INCH LONG AND 0.040-INCH WIDE ON THAT SECTION OF PIPE.