CROWN POINT, N.Y. — The Lake Champlain Bridge linking New York and Vermont crashed into the lake Monday, December 28, 2009, as controlled explosions brought down the unsafe 80-year-old span that was the first of its kind used for highway traffic and a design that was duplicated on numerous other bridges.

Snow fell and a small group of onlookers watched as the 2,184-foot-long link between Crown Point, N.Y., and Addison, Vt., was dropped into the water and ice at the narrow south end of the lake Monday morning.

There was a sharp concussion followed by billowing smoke as steel and concrete fell, with a section of pavement at the arched center of the bridge teetering and then falling into the channel below.

The decades old bridge was closed Oct. 16, when engineers deemed it wasn’t safe because of severe erosion in its concrete piers.

The implosion was the start of a nearly two-year project to replace the bridge. The demolition conducted by Coeur d’Alene, of the Idaho-based Advanced Explosives Demolition, was originally scheduled for Wednesday, Dec 23rd, but cold and ice delayed preparations.

AED’s crew spent more than a week placing 800 pounds of explosives packed into more than 500 charges that brought the bridge down in sections. Another crew was to begin removing the tons of bridge debris from the channel, a task that’s expected to be completed by the spring when construction of the new span is set to begin.

The new bridge is expected to open in the summer of 2011.

Opened on Aug. 26, 1929, with a ceremony attended by then-Gov. Franklin D. Roosevelt, the Lake Champlain Bridge was the nation’s first long-span continuous truss bridge for highway traffic, and its steel girder arch design was used on numerous other spans.

The ruins of two 18th-century forts are just off the Crown Point approach to the bridge, along with a newly renovated visitors center at the adjacent historic site. A few hundred yards east of the bridge stands the Champlain Memorial Lighthouse. It also was recently refurbished, and crews used plywood to protect a bronze bust created by French sculptor Auguste Rodin that is mounted on the front of the 100-year-old memorial facing the bridge.