Picture a line of boulders, up to 4 feet in diameter, against a 50-foot-wide dirt right of way overlying an underground natural gas pipeline. Also picture fences, timber debris, signs and pipe barriers along the route.

Those measures will be at least part of Kinder Morgan Energy Partners' access-control strategy to keep illegal border crossers and smugglers, among others, from using a proposed pipeline route to navigate through the desert.

That's if the federal government approves the company's plan for the 59-mile Sierrita pipeline through the Altar Valley southwest of Tucson to Sasabe. The measures are outlined in a document Kinder Morgan filed with the feds earlier this month.

More access-control plans are coming, although it's not clear that they'll be made public. They're under review by the federal Customs and Border Protection agency.

A top Kinder Morgan official says these strategies have worked for gas pipeline projects in Oregon, Utah and Wyoming.

"That's why we feel very comfortable they would work here," despite this region's different terrain, said Lynn Christensen, Kinder Morgan's Sierrita pipeline project manager.

Despite that, Altar Valley ranchers who oppose the pipeline said they're still dubious the control measures will work against border crossers here.

Kinder Morgan would build the pipeline in a 50-50 partnership with MGI, a subsidiary of Pemex, the Mexican state energy company, and Mitsui Corp., a Japanese company that is financing a gas pipeline into Mexico that would connect with the Kinder Morgan pipeline at the border.

Company's pledge

At a public meeting in Tucson last week, Kinder Morgan officials said they'll work hard to prevent public access to the pipeline so planned revegetation work will survive. The federal Energy Regulatory Commission, which must approve the pipeline route, requires revegetation of grasses and cacti that Kinder Morgan will clear.

"The intent is to make this right of way not driveable," said Nicole Pedigo, Kinder Morgan's environmental project manager. "There's nothing to prevent foot traffic from a pipeline right of way. ... The intent is to make it inaccessible to all vehicles, including ATVs if possible."

When residents and county officials asked how Border Patrol vehicles pursuing immigrants and smugglers can be kept out, Pedigo said, "All bets are off. ... They are going to use every single access road that they have. At road crossings of the pipeline, we will take extra care to keep them out, using rocks and boulders."

Christensen told the crowd that the company would consider a compensatory mitigation package to offset permanent habitat damage that might occur from the pipeline.

Afterward, Pat King, an Altar Valley rancher, dismissed boulders as unworkable. King pointed to a chair in the meeting room and said, "Here's a boulder, now get on our bike and ride around it. I'm sure that's what they'll do. They (Kinder Morgan officials) don't live in this area. They don't experience the illegal traffic of both people and drugs, and therefore the necessary impact of the Border Patrol" on the land.

In an interview later, Christensen said boulders would be most likely installed within six miles of the border, where officials expect to encounter rock, with large mesquite trees and other materials installed farther north.

Boulders a BP idea

Allen Fore, a Kinder Morgan spokesman, said the boulders were suggested by the Border Patrol, and the company expects a more detailed list of Border Patrol suggestions later. But it's not clear if those suggestions will be made public due to security concerns, said officials of Kinder Morgan and Customs and Border Protection, the Border Patrol's parent agency.

"We've asked them multiple times to put together a list of what things would be helpful for us to do," Christensen said. "We're still waiting for that list. ... I guess there's a pretty high level of concern about even telling us what they think would be helpful for us to help them."

A pipeline border-security plan is being reviewed in Washington, D.C., said Andy Adame, a CBP spokesman. A release date isn't known, Adame said, although the parent agency says it can adapt to the pipeline's presence.

"Whether the pipeline is constructed or not, CBP has the detection technology and response capability necessary to counter identified threats or vulnerabilities occurring along this border region," CBP said. "CBP is an all- threats organization with the capability to rapidly shift resources."

Oregon plan works

As a past success, Christensen cited the Ruby project, a 680-mile pipeline across the northern Rockies into Oregon, built in 2011 by a subsidiary of El Paso Natural Gas Co., which Kinder Morgan acquired last year. The company laid boulders along 150 miles of the line, after the Forest Service and the Bureau of Land Management had asked it to block public access.

Since then, a Forest Service office has asked the company to reinforce a section of line, and from that, Christensen assumes the rest has worked, he said.

While Southern Arizona's landscape is different and border traffic is intense, he said, "we're talking about the same kind of all-terrain vehicles - big, four-wheel- drive vehicles.

"Boulders are boulders," he said. "The boulders I'm talking about are big enough that they can't be rolled out of the way by hand."

Altar Valley rancher Mellissa Owen responded: "I wonder how much illegal traffic they have to deal with in Oregon. It's a whole lot different if someone wants to get a pickup carrying 15 people who paid $3,000 to get across the border, versus someone going for a joyride on an ATV. I would say their motivations are a lot different."

Altar Valley probably gets more foot and vehicle traffic than Ore-gon, added rancher Walter Lane.

"They can put in a line of rocks and that's all fine and well, but how long will that line of rocks be? Do you make it two miles so they can't drive around it?" he asked.

Contact reporter Tony Davis at tdavis@azstarnet.com or 806-7746.