A Houston-based company is buying easements to build an oil pipeline from Ten Mile Terminal in Mobile to the Chevron Oil Refinery in Pascagoula, and a portion of their planned route runs right through the watershed draining into Big Creek Lake, Mobile's drinking water supply.

The high-capacity, 24-inch pipeline will be capable of moving 150,000 barrels of oil per day, according to Alabama Public Service Commission records. Early last year, the PSC approved a request from Plains Southcap for a "Certificate of Industrial Development" for a right of way in Mobile County.

To put the size of the pipeline in perspective, the Macondo blowout caused by the explosion of Deepwater Horizon gushed oil at less than half that flow rate. When oil is coursing through Plains Southcap's 45-mile-long pipeline at maximum capacity, a rupture would result in a spill of 6,250 barrels in one hour.

That could be 262,500 gallons of oil on land sloping toward Big Creek Lake.

Charles Hyland, director of the Mobile Area Water and Sewer Service, said the water system has asked Plains Southcap to find another route that does not go through Big Creek Lake's watershed. Meanwhile, MAWSS has hired engineering firm KBR (formerly Kellogg, Brown & Root) to assess the risk posed by the pipeline, and Plains Southcap has agreed to pay the cost of that study.

"We take any threat to our watershed extremely seriously," Hyland said. "And we want to make sure we have all of the relevant information so the board can make an informed decision."

Plains Southcap did not return phone calls made Wednesday and Thursday by the Press-Register/AL.com seeking comment. According to a story we published last year, oil bound for the pipeline first will be extracted from Canadian tar sands, processed in Canada to remove the heavy contaminants, then shipped to Mobile in railroad tanker cars.

David Underhill, conservation chair of the Mobile Bay Sierra Club, discovered the proximity of the pipeline to Big Creek Lake while examining Plains Southcap's application to the PSC. He brought it to light earlier this week at a Sierra Club meeting that was open to the public.

In approving the application last year, the PSC found the project to "be in furtherance of industrial development in the state of Alabama." In their order, the PSC exults about the $45 million cost of the pipeline, which includes construction of two vast oil storage tanks at Ten Mile Terminal.

But once the tanks and pipelines have been constructed, few jobs will be associated with the largely automated process. If it is built as planned, the mostly buried pipeline will come within about 3,000 feet of the easternmost finger of Big Creek Lake, and will have to cross Hamilton Creek, which empties into the lake. Before reaching the Chevron refinery it will also have to cross the Escatawpa River basin.

Plains Southcap is a subsidiary of Plains All America Pipe Company headquartered in Houston. Another Plains All America subsidiary, Plains Midstream Canada, has had two notable pipeline failures in the past few years. The largest occurred April 29, 2011, when a pipe burst near Little Buffalo in Alberta and 28,000 barrels of oil spilled before the flow was shut down. Plains Midstream Canada was reprimanded for operational failures by Alberta's Energy Resource Conservation Board. They've also been charged with three counts of violating environmental protection laws in connection with the spill.

Is the Alabama Public Service Commission doing us a public service by approving projects like this one? Surely the PSC members should have noted the threat to the source of drinking water for most of Mobile County.

Contamination of Big Creek Lake would result in anything but "a furtherance of industrial development in the state of Alabama." Our state's second largest city would shrivel up and die of thirst.

(This editorial was written by Mike Marshall, director of statewide commentary, for the Mobile/al.com editorial board. You can reach him at mmarshall@al.com.)

Updated July 1, 2013 to correct the spelling of Plains Southcap.