The Portland, Ore., Bureau of Environmental Services and Salem, Ore.-based contractor Emery & Sons Construction Inc. on a recent project needed precision to bore a new sewer line beneath two trolley tracks near an existing steam vent in downtown Portland. They turned to an up-and-coming technology: laser-guided boring. Photo Courtesy Of Emery & Sons The laser-guided boring system allows crews to precisely place materials and work in tight spaces. Using a Pella, Iowa-based Vermeer AXIS tool, the laser system provides near-exact placement of a bored tunnel and then pulls the pipe back through when complete—“a marvelous machine,” says Bill Theiss,
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.