While a demolition contractor clears debris and stabilizes the site of what the owner claimed was the largest sloped green roof in North America, a forensics team is investigating why the structure suddenly collapsed on the afternoon of Feb. 13. Photo: Courtesy Aquascape Freeze-thaw cycle following major snowfall apparently triggered collapse of large green roof near Chicago. Related Links: Ice, Snow Take Toll on Northeast Roofs, But Engineers Say Codes Are Adequate The 700-ft by 50-ft area of roof that collapsed was attached to a warehouse. There were no injuries or inventory damage, said Ed Beaulieu, vice president at Aquascape,
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.