ExxonMobil Silvertip Pipeline Crude Oil Release into the Yellowstone River in Laurel, MT on 7/1/2011 [open pdf - 8MB]
"On July 1, 2011, at approximately 10:40 p.m. mountain daylight time (MDT), a failure occurred on ExxonMobil Pipeline Company's (EMPCo) Silvertip Pipeline in Yellowstone County, Montana, resulting in the release of approximately 1500 barrels of crude oil into the Yellowstone River. The river flows eastward from the release site through the City of Billings and eventually discharges into the Missouri River. The failure occurred in the vicinity of the city of Laurel, Montana just downstream of the Highway 212 Bridge. The failure was reported to the National Response Center on July 2, 2011, at approximately 12:19 a.m. MDT. The leak was detected by ExxonMobil controllers in Houston, Texas. Controllers shut down the pumps and valves at the beginning of the line (Silvertip Pump Station) within 10 minutes. The remote controlled valve, #4462, just upstream of the Yellowstone River, however, was not closed for an additional 46 minutes. The cause of the release was determined to be a severed pipeline near the south shore of the Yellowstone River that occurred after a prolonged period of high runoff and flooding. Debris caught on the pipe over time increased the stresses until ultimately the critical stress of the pipe was exceeded."
United States. Pipeline and Hazardous Materials Safety Administration: http://www.phmsa.dot.gov/