I am profoundly skeptical that a physical barrier is the best approach to border security, but what if, instead of a wall, the nation constructed infrastructure that would generate electricity and help address other environmental concerns? A consortium of engineers have proposed just such an idea: an Energy, Water, Industry and Education Park (FEWIEP) that would enhance border security while providing energy and water to the border region. Among other things, the plan anticipates that such a project, once built, would help pay for itself through the generation of electricity.
Here's how Scientific American describes the idea:
Instead of an endless, inert wall along the U.S.–Mexico border, line the boundary with 2,000 miles of natural gas, solar and wind power plants. Use some of the energy to desalinate water from the Gulf of Mexico and the Pacific Ocean and ship it through pipelines to thirsty towns, businesses and new farms along the entire border zone. Hire hundreds of thousands of people from both countries to build and run it all. Companies would make money and provide security to safeguard their assets. A contentious, costly no-man's-land would be transformed into a corridor of opportunity. . . .
The border region receives boundless solar energy, and has significant natural gas and wind resources. It's also suffering from extreme drought, and water shortages are predicted to get worse. Farming is exceedingly difficult. And jobs are often scarce—in part because of lack of water and power. If an energy and water corridor were built, the facility owners would protect their properties. Transmission, gas and water lines would be monitored by companies, states and federal agencies, as many elsewhere are now. And the plants could be integrated with security walls or fences.
I'm skeptical of parts of the plan, particularly the emphasis on water desalination. The problems of water scarcity in the western US are more a policy problem than a problem of physical supply. The expansion of water markets and real water pricing would do much to rationalize water use (and also help address the consequences of climate change).
That said, much of the US-Mexico border would be an ideal place to expand solar power, and such installations would provide something of a physical barrier (insofar as some folks think such a barrier is desirable). Solar power doesn't work well everywhere, but there are parts of the country to which it's quite well suited. And if we're going to have something of a wall -- and Mexico is not going to pay for it -- wouldn't it be a consolation if the "wall" could pay for itself?