(FORTUNE Magazine) – Seven decades of dam building, canal digging, and highway construction have given the U.S. Army Corps of Engineers a reputation as an enemy of the environment. Think again, says Lieutenant General Henry Hatch, chief of engineers: The Corps is doing an about-face. In response to government directives and public concern about the environment, Hatch intends to turn the world's largest public-service engineering organization into a friend of the snail darter and the tidal flat. Welcome to the new paradigm. A recent Corps staff paper notes that the world's population is expected to double by 2100. To support all those people, the global economy will have to expand five to ten fold, with potentially catastrophic results for the environment. As Hatch observes, ''It doesn't take a rocket scientist to realize that environmental engineering represents a major area of potential growth.'' The transformation began under Hatch's predecessor, Lieutenant General E. R. Heiberg, who in 1985 called a meeting of some 75 senior leaders to discuss the Corps's purpose, values, and direction. Hatch, then director of civil works, was put in charge of strategic thinking. ''Many of us in those days couldn't spell 'environment,' much less say what it meant,'' he admits. Now, however, the Corps is turning its attention to endangered wetlands in areas like the Mississippi Delta and Chesapeake Bay. Recently, for example, it helped to secure a $2 million levy against Wall Street whiz kid Paul Tudor Jones II for illegally filling in wetlands on his 3,272-acre Maryland hunting retreat. For internal presentations, shaman-consultant Jim Channon has superimposed the Corps's red-castle insignia on a blue-green depiction of spaceship earth to symbolize the Corps's new mission: assuring humanity's future. Far from being a ''soft'' value, says William Robertson, a civilian aide to Hatch, environmentalism is ''hard, practical reality -- and not just for the Corps, but for the planet.''