Project experts give an update on the main dam at Chimney Hollow Reservoir, which is currently about 285 feet tall, just 65 feet shy of the ultimate 350-foot-tall height. The main dam is a hydraulic asphalt core with a rockfill embankment, only the second of its kind in the United States and by far the tallest. As winter nears, crews are preparing for the narrowing of the top of the dam, which will make the area more congested for heavy equipment operations.