An oil spill on the Key­stone pipe­line in north­east­ern North Da­ko­ta this week is the se­cond sig­nifi­cant leak in two years on a crude oil pipe­line that op­ened less than a dec­ade ago.

The Key­stone pipe­line, which trans­ports oil from Al­ber­ta to the Midwest, ap­pears to have rup­tured on Tues­day and has since spilled an estimated 383,000 gal­lons of crude near the town of Edinburg, ac­cord­ing to the North Da­ko­ta Department of En­vi­ron­men­tal Quality.

The Cal­ga­ry-based com­pany that op­er­ates the pipe­line, TC Energy, said in a state­ment that the leak has af­fect­ed a­bout 22,500 square feet of land, or a­bout a half-acre. The com­pany said it's work­ing to dis­cover the leak's cause, as well as cleaning up the spill and repairing the pipeline.

State en­vi­ron­men­tal regu­la­tors say the spill en­croached on wet­lands a­bout 3 miles out­side of Edinburg, which is a­bout 70 miles north­west of Grand Forks.

In No­vem­ber 2017, the Key­stone pipe­line ruptured near Am­herst, S.D., spill­ing 407,000 gal­lons of oil, though initial estimates pegged the leak at 210,000 gallons.

The prob­able cause of that spill was a "fa­tigue crack" from me­chan­i­cal dam­age dur­ing the pipe­line's con­struc­tion, the National Transportation Safety Board con­clud­ed last year. A metal-tracked ve­hi­cle like­ly caused the crack, which grew over time un­til the pipe­line rup­tured.

"It's a valid ques­tion, two cracks on a fair­ly new pipe­line — geez what's going on?" said Rich­ard Kuprewicz, pres­i­dent of Accufacts, a Wash­ing­ton state-based pipe­line safe­ty con­sult­ing firm.

Still, he cau­tioned that "age is not a pre­dic­tor of pipe­line fail­ure. I have seen new pipe­lines that have re­al­ly been abused and I have seen old pipe­lines that look like new."

The Key­stone pipe­line is one of three large trans­na­tion­al pipe­line sys­tems that trans­port a par­tic­u­lar­ly thick crude from Al­ber­ta's oil sands, also called tar sands. The larg­est such sys­tem is run by Cal­ga­ry-based En­bridge, and its main cor­ri­dor of pipelines runs through north­ern Min­ne­so­ta to Su­pe­ri­or, Wis.

En­bridge is in the midst of a years­long bat­tle to build a new pipe­line to re­place its ex­ist­ing Line 3, which is ag­ing, cor­rod­ing and op­er­at­ing at only 51% ca­pac­i­ty. Min­ne­so­ta pub­lic utili­ties regu­la­tors ap­proved new Line 3 last year. But the pipe­line — fierce­ly op­posed by en­vi­ron­men­tal groups and some Ojib­we tribes — is still wait­ing for oth­er per­mits.

The Key­stone pipe­line, which fer­ries oil to ter­mi­nals in Oklahoma and southern Il­li­nois, op­ened in 2010. TC Energy is try­ing to ex­pand the Key­stone sys­tem with its con­tro­ver­sial Key­stone XL pipe­line, which would run from Al­ber­ta through Mon­tan­a and South Da­ko­ta to Steele City, Neb.This week's North Da­ko­ta leak would rank in the Top 10 larg­est U.S. on­shore oil spills since 2010. In that year, an En­bridge pipe­line rup­tured in south­west­ern Mich­i­gan, spill­ing 834,000 gal­lons of Ca­na­di­an crude. En­bridge's last ma­jor spill in Min­ne­so­ta was in 2002 when Line 3 failed near Cohasset, re­leas­ing 252,000 gal­lons of oil.

Mike Hughlett • 612-673-7003