By afternoon, the machine below the bridge had bitten off most of the northbound lanes, leaving jagged edges and metal rods zigzagging from the bridge.

“Those things are remarkably powerful,” said Clark County Public Works spokesman Jim Gladson as he peered over yellow caution tape at the machines parked on the creek’s empty bed.

Friday’s demolition was an early step in a series of plans to replace the bridge. The span was closed last December when inspectors deemed it unsafe after years of turbulent high water had undermined the bridge’s support piers. A new bridge, which will not touch the creek, will open in late October.

Workers plan to have the structure demolished by the end of the weekend, temporarily leaving nothing but a cavity where a bridge has stood for decades.

On Friday, as many as 25 people worked on the bridge at a time. Onlookers milled about on the north side, gawking at the sight.

Contractors discussed many ways to demolish the old bridge, but decided that using machines to bite into chunks would be best.

“There’s a lot of ways to bring down a bridge, but the one they chose was the one they thought would be most efficient and the best way to handle the debris,” Gladson said.

Taking down the concrete slab was no easy business. Before they started, crews placed barriers in the creek with pipes to drain water, diverting Salmon Creek underground through the project. Then, they lined the work area with filter fabric to prevent falling debris from harming the streambed, said Linda Small, Clark County Public Works project manager.

As they removed the old bridge, crews also worked on the new bridge by inserting metal rods 45 feet into the ground on each side of the span. The rods will serve as the base for the future bridge supports. Construction of the bridge gets under way next week, Small said.

Highway 99 will remain closed until the new bridge is finished, so this weekend’s work won’t further disrupt traffic.

The new $9.2 million bridge will have four traffic lanes, bike lanes, wider sidewalks and lighted scenic overlooks. The old one was built in sections with support piers placed in the creek; the new crossing will be a single span reaching from bank to bank.

Laura McVicker can be reached at 360-735-4516 or laura.mcvicker@columbian.com.