Between 2:40 and 3 p.m. on Jan. 11 -- the 23rd consecutive day of rain -- two large landslides occurred in Des Moines near the bridge construction site on Marine View Drive.

The first landslide went onto Des Moines Memorial Drive about 100 yards north of the bridge; the second, which occurred within 10 minutes, was on the northwest corner of the bridge.

The northbound lane of Des Moines Memorial Drive was shut down because the slide took out the right shoulder of that lane.

Debris from the bridge landslide washed up against an excavator that was working in Des Moines Creek.

Des Moines City Manager Tony Piasecki declared an emergency after the Public Works Department assessed the slides and determined the compromised level of safety.

It was the first emergency that he has declared in four years as city manager.

With an emergency declaration, the city manager can award a bid to a contractor right away, and then bring it to the city council. Except in an emergency, bids for work are submitted, then reviewed by lawmakers who select a contractor.

“We had to take some action to deal with the slides that were occurring,” said Piasecki. “When there is life safety involved it’s necessary to declare an emergency.”

Barriers were set up along Des Moines Memorial Drive and water was diverted directly into Des Moines Creek, said Leo Stapleton, project manager with Condon Johnson and Associates.

Loren Reinhold, Des Moines assistant city engineer for surface water management, said a geotechnical engineer inspected the slide areas and provided the city with recommendations to open the roadway.

“They were able to pump water from the storm drain directly to the creek so that water doesn’t go into the slide area,” he noted.

Current construction on the bridge has not been delayed due to the slides.

It’s estimated that the bridge still will open by June, with final construction work completed in July, Reinhold said.

He considers it lucky to have a contractor on site.

Stein Straume, a worker at the bridge construction site, was walking up a trail used by workers at the northwest corner of the bridge about 15 minutes before the slides occurred.

Others were walking up the trail five minutes before the slides.

Straume didn’t see the first slide, but was standing on the bridge when the second slide occurred 10 minutes later.

“It sounds like a rush of water,” Straume said. “To watch dirt and liquid come down is pretty amazing.”

The location of the landslides is an area that’s experienced many slides before.

Des Moines Memorial Drive is an ancient slide zone and over time people have built homes on and it and roads have been built over it, said Reinhold.

The Puget Sound area is famous for the amount of landslides, observed Dr. Eric Baer, geology professor at Highline Community College.

The region is more susceptible because of the amount of rain, the steep slopes, the geologic makeup of the slopes and the population in the region, said Baer.

“All factors are significant, and they all play a role in slides,” Baer said.

Puget Sound-region hills are formed from layers of different rock. The top layer is clay and with large amounts of rain, it becomes saturated and slippery.

In most slides there is a human element, Baer added.

Many of the region’s roads are built along stream valleys. To build these roads, workers cut into the hill to flatten an area for the roadway.

“This makes a moderately steep slope into an even steeper slope,” said Dr. Baer. “It’s goes steep, flat, steep.”

Des Moines Memorial Drive was built into a hill and, over time, the road has settled into areas that have slid.

The road has warped down and settled and patchwork has been needed to repair the settling, said Reinhold.