Efforts to recover bodies following a Washington state mudslide that killed at least 29 people could be hampered in the coming weeks if melting snow runs into a clogged river at the disaster site, officials said.
Over the past two days, workers at the mud pile in the foothills of the Cascade Mountains, northeast of Seattle, have taken advantage of sunny skies and receding water, but more rain is expected from Thursday through Sunday.
The official death toll from the mudslide, based on the number of victims' remains sent to the coroner's office, rose to 29 on Wednesday, up from 28 a day earlier, the Snohomish County Medical Examiner's office said. On Tuesday, 20 people were still listed as missing.
The March 22 slide was triggered when a waterlogged hillside caved in above the Stillaguamish River. A torrent of mud roared over the riverbanks and across state Highway 530, engulfing some three dozen homes on the outskirts of the town of Oso.
The mudslide clogged the Stillaguamish River, which in the following days cut a slow-moving channel through the mud and debris. But snow melting on the Cascade Mountains is expected to pour through that channel, possibly flooding the mud-pile site.
Sections of the slide area, already under 25 feet of water and believed to contain human remains, could be submerged by more than 100 feet of water within three to four weeks without a channel to divert the partially dammed river, said Mike Asher, an area fire chief acting as the head of operations for the east side of the disaster zone.
"There's a lot of snow left on the mountains surrounding the valley," Asher said. "We're going to start facing runoff issues from that in the very near future."
The US Army Corps of Engineers is working on a plan to dig a river channel, likely to be accompanied by levies, to keep the muddy, contaminated disaster site cordoned off, Asher said.
If the diversion goes wrong, the river could flow west down Highway 530, flooding both the road and homes alongside it, he said.
Meanwhile, no sign of life has been detected since the day of the slide, when eight injured people were rescued.
"Where we find a lot of log jams and that type of area, that's where we're finding the human remains," recovery team supervisor Steve Harris told reporters on Tuesday, referring to places where much of the debris had collected after trees and logs crashed through homes.
The search-and-recovery force included a mix of firefighters, National Guard troops, US Army soldiers and civilian volunteers, some from the local community, in an area that supervisors have mapped out in a three-dimensional grid.
The Snohomish County Medical Examiner's Office said 22 of the confirmed fatalities have been identified, including a 4-month-old girl and two other children aged 5 and 6.