EVERETT — Railroad officials say they’ve narrowed down the worst trouble spots for mudslides that have forced cancellation of an increasing number of passenger train trips between Everett and Seattle the past few years.

Six slide-prone hillsides, spanning from just south of downtown Everett to the southern part of Mukilteo, are targeted for extensive repairs and reinforcement, say officials with BNSF Railway and the state.

The goal is to begin at least some of the work this summer, said David Smelser, who oversees the Amtrak Cascades trains for the state Transportation Department.

“We need relief,” he said.

The federal government recently granted $16 million to the transportation department for mudslide prevention throughout the state. The stretch between Everett and Seattle has been by far the most troublesome in recent years and all of that money will be funneled into work in the six targeted areas, Smelser said.

Officials from the Federal Railroad Administration visited the slide areas last month with personnel from the railway and the transportation department, Smelser said.

The state also has begun working with cities along the route to pinpoint areas where poor drainage control might be eroding slopes above the tracks, and eventually to see what measures could be taken there.

“You might have some very expensive fixes if you don’t work on the root cause,” Smelser said.

So far this winter, slides have forced cancellations of 170 Sounder commuter trips between Everett and Seattle, according to Sound Transit. The previous high for cancelled Sounder trips in one winter was 72 in 2010-11. Service began in 2003.

Just during this winter’s rainy December, 34 Amtrak train trips were cancelled on the stretch between Everett and Seattle. Both Amtrak’s Cascades and Empire Builder trains travel the tracks.

The railway owns the tracks and imposes a 48-hour moratorium on passenger service as a safety precaution when tracks are blocked by a mudslide.

Both Amtrak and Sound Transit provide replacement bus service when the trains aren’t running. Still, mudslide disruptions make the commuter service less reliable and have been cited as a factor in low ridership on the line.

On Dec. 17, a slide bowled over several cars in a freight train as it moved below the bluffs near the Port of Everett. No one was injured.

This spot, just southwest of the downtown Everett waterfront, is one of the six targeted areas for repairs, said Gus Melonas, spokesman for BNSF Railway in Seattle.

Otherwise, state and railway officials aren’t giving specific locations for the slide-prone slopes. Smelser said more detailed geotechnical and environmental work lies ahead before exact construction locations will be determined.

Work could include terracing of hillsides and installation of drainage pipelines, holding ponds and retaining walls, depending on the conditions at each location.

The railroad already has spent “millions” on similar measures, Melonas said, without providing details. The state spent $100,000 on preliminary fixes last year.

Because of the environmental and design work needed, some of the planned projects might not get under way this year, Smelser said.

While the slope work is expected to help, in the long run the best solution might be to improve drainage in neighborhoods above the slopes, Smelser said.

Judy Oberg, who with her husband, Dick, has lived above the tracks in Everett for 32 years, says they’ve noticed more water running through their neighborhood the past few seasons.

“Every time they pave a road or a shoulder of the road it’s less places for the water to go,” she said.

There was a slide on the bluff below her neighbor’s property two years ago, Oberg said.

Ryan Sass, Everett city engineer, said city officials in January and February were hearing of new landslides below neighborhoods “on an almost daily basis.”

Smelser said aerial photos and rainfall data are among the tools that will be used to study drainage issues, and the information will be correlated with where slides have happened.

“We are looking at all the components of slides — geology, storm- and surface-water controls, vegetation management,” said Larry Waters, public works director for Mukilteo.

One possible measure is a development ban in sensitive areas, though this would be up to local jurisdictions, Smelser said. Another element to come out of the study could be educating homeowners on ways to reduce the amount of water running off of their property, officials said.

“Winters that result in deep soil saturation, leaking pipes, or homeowner activities such as placing lawn clippings on these slopes can contribute to the instability,” Sass said.

Bill Sheets: 425-339-3439; sheets@heraldnet.com.