With some 12 million illegal immigrants already living in the U.S. and as many as 500,000 crossing the border each year, Congress recently authorized the construction of a wall at the Mexican border. Will it stem the flow? 

Why build a wall now?
Efforts to get comprehensive immigration reform through Congress collapsed last year due to fierce opposition by conservative Republicans, who insisted that the federal government first secure the U.S. border with Mexico. Under intense political pressure, Congress passed the Secure Fence Act, which called for 700 miles of new fencing along the 1,952-mile U.S.-Mexico border. The Bush administration then set a goal of completing 300 miles of barriers by the end of 2008, and Congress authorized $1.2 billion for the effort. The project got off to a slow start, with construction bogged down by environmental assessments, land acquisition delays, and design issues. But in recent weeks, the pace of building has accelerated.

What, exactly, is being built?
It’s not really a continuous “wall” in any strict sense of the word. Extending from Tecate, Calif., to Laredo, Texas, the new barrier will consist of a variety of obstacles, depending on the terrain. In some places, the wall will be a 15-foot-high sheet of metal; in others, mesh fencing. In some areas, the wall will be solid concrete. For about half the 300 miles, the only barrier will be a new system of cameras, underground sensors, light towers, and radar set up to catch people sneaking north through the remote Sonoran and Chihuahuan deserts.

How’s it going?
By the end of September, the Department of Homeland Security, which is overseeing the effort, had completed about 145 miles of barriers along the border in California, New Mexico, and Arizona. In some places, contractors are installing barriers at the pace of a half-mile a day. In Arizona’s Altar Valley, the busiest illegal immigrant corridor in the country, a 15-foot-high steel-tube fence is rising. In Calexico, Calif., fencing is now blocking a seven-mile stretch where smugglers have had easy access to launch boats across the All American Canal into California. It remains to be seen whether the professional “coyotes” who smuggle people across the border will eventually find a way to go around or over the new barriers, but for now, they appear to be working. “For the first time,” said U.S Border Patrol Chief David Aguilar, “we’re getting ahead of the criminal organizations,” including both drug smugglers and illegal immigration rings.

Aren’t there already some fences at the border?
Yes. There is currently 106 miles of fence, mostly along cities that abut the border, including San Diego; El Paso, Texas; and Nogales, Ariz. It’s been fairly effective in stopping people from crossing at these points, but the flow of immigrants has simply detoured around it. Now the fencing is going up in the remote rural areas where much of the illegal traffic has shifted. A new, 15-foot steel-mesh barrier now stretches for about 32 miles from San Luis, Ariz., to the Tinajas Atlas Mountains. That barrier is now the longest on the border, more than twice the length of the 14-mile fence separating San Diego from Tijuana. “This is going to be a rude awakening for the crowds [of illegal immigrants] that come in the fall,” said Welby Redwine, a Boeing engineer overseeing some of the work. “When they see it, they’re going to say, Wow, what happened?” Critics of the wall say that until Mexico has an economy that can sustain the desperately poor peasants now heading north in search of work, they will find a way into the U.S.—the wall notwithstanding. “Show me a 50-foot wall,” said Arizona Gov. Janet Napolitano, “and I’ll show you a 51-foot ladder.”

Have border communities welcomed the new barriers?
No, since plans call for fences to cut through private property, farms, and ranches. About 70 miles of fence is to be built in the Rio Grande Valley, at the southernmost tip of Texas. Government documents show that the fence in this region will be placed about two miles north of the Rio Grande River, the traditional border between the U.S. and Mexico. That would leave parts of several communities in a no-man’s land between the fence and the river. The fence would actually cut through the campus of the University of Texas at Brownsville and leave some local landmarks and the district office of a state representative on the “Mexican side” of the barrier. Some stretches would cut farmers off from prime farmland near the water. “This is going to seriously affect the farmers,” said Mike Allen, a local economic development official. “They will not have access to water. It’s just going to create bedlam.”

What will these people do?

Right now they’re hoping to stop—or relocate—the fence. Several Texas mayors have denied access to parts of their city’s property to Homeland Security workers assigned to begin surveys and other preliminary work on the fence. The city of Eagle Pass has flatly denied a request from federal officials to build a portion of the wall within its borders. Negotiations with the federal government are underway, and while Homeland Security officials say they are sensitive to local concerns, they also say that national security must come first. Don’t forget, said department spokeswoman Laura Keehner, that “this wall is used to keep out potential terrorists as well as illegal immigrants.”