CALGARY — TransCanada Corp. has shut down its massive Keystone oil pipeline for the second time in less than a month after detecting a small leak at a pumping station in Kansas, the energy and pipeline giant said.

TransCanada Corp. shut down its Keystone pipeline May 29 because of a leak at a pumping station for an undetermined length of time. The 591,000 barrel per day line ships Canadian crude oil to key U.S. pricing point Cushing, Oklahoma. (Photograph by: SHANE BEVEL, BLOOMBERG NEWS) The 591,000-barrel-per-day line was shut down over the weekend after a half-inch fitting broke, spilling approximately 10 barrels of oil at the Severance, Kansas pumping station, the Calgary-based company said Tuesday.

“The team is putting together a restart plan and they’re hoping to get the system up and running as soon as possible but it will probably be a few days,” spokesman Terry Cunha said.

Keystone, which started operations June 2010, has had 11 such breaks along its line at pumping stations on the United States side of the system.

The most recent occurred May 7 when a -inch fitting broke at a North Dakota pumping station spewing approximately 500 barrels of oil on TransCanada line and into a neighbouring field.

The Hardisty, Alberta to Cushing, Oklahoma line was shut down for six days after the event while TransCanada replaced the fittings at the pipeline’s 47 pumping stations. Cunha said all the fittings were working properly at the time, including the -inch fittings.

TransCanada’s announcement on Tuesday comes at a critical time for the company’s plans to extend Keystone to refiners in the U.S. Gulf Coast.

Keystone XL faces fierce opposition from environmental groups as well as federal and state legislators concerned with the threat of oil leaks and increased greenhouse emissions from expanded oilsands production.

The protests increased after last year’s BP oil spill in the deepwater U.S. Gulf of Mexico, and the Enbridge oil spill into Michigan waterways last April. Lobby groups were successful in calling for additional environmental scrutiny of the Keystone XL project, which has been delayed almost a year.

A 45-day public comment period on supplemental environmental analysis on the pipeline wraps up next week. A decision on a key presidential permit is expected by the end of the year, although supporters of the project have lobbied to have a decision handed down by November.

Keystone is a key feed for the Cushing oil storage hub, the pricing point for the New York Mercantile Exchange’s benchmark crude contract.

Another shut down along likely is supporting higher oil prices in the region, analysts said.

Crude oil futures traded up $1.52 US per barrel to $102.12 US in New York Tuesday early afternoon.