Mudslides create messes on Washington interstates

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Mudslides created messes and traffic delays on Washington interstates Thursday, most notably on Interstate 90 and Interstate 5. 

Mudslide on I-5

A mudslide blocked northbound I-5 near Woodland, which is about 20 miles from the Washington-Oregon border. Chopper video showed one truck stuck in the debris around 5 p.m. 

Some semi trucks were able to drive over a part of the slide a little later, but backup remained as of 6 p.m. 

Mudslide on I-90

A mudslide blocked all lanes of westbound I-90 in Issaquah disrupting traffic for hours on Thursday,

It reopened mid-afternoon. 

Trees, rocks and mud came down from a hillside at about 4:45 a.m. near the Highpoint Way exit Thursday, disabling as many as a dozen vehicles. One car was high-centered on a rock, according to the State Patrol.  No injuries were reported.

PHOTOS: Mudslide closes WB I-90 in Issaquah

Debris went across all four of the westbound lanes. 

Mud was a few inches in some places and a little deeper in others. Large rocks and one or two trees were across the road.  After clearing debris, the Washington State Department of Transportation reopened the left lane. 

WSDOT recommends drivers use the Preston Fall City Road to SR 202 to avoid I-90. 

According to a WSDOT spokesman, the slide was caused by a combination of last week's heavy snow melt, heavy rain over the past 36 hours and a water source somewhere above the slide area.

>> Find Seattle's slide-prone area map here

>> Find King County's slide-prone area map here

Officials don't know if the water is coming from an overflowing reservoir or retention pond, a broken water line or a property owner's drainage pipe.

Workers have been digging trenches above the slide area to disperse the water more evenly, so it doesn't wash down the area where the slide occurred.

WSDOT is also working with the City of Issaquah to determine where the water is coming from.

Meanwhile, engineers have been instructing workers how to shore up the hillside. They've been removing loose material and back filling with some boulders.

They are also considering taking out some trees to remove the danger of them falling onto I-90.