MUKILTEO — The long wait for the opening of the second Sounder train platform is over.

Service on the new platform is scheduled to start Monday with the arrival of a train at 4:47 p.m.

Construction on the $18.1 million project began in January 2014. It involved building a second platform at the Mukilteo station and a tower structure for a pedestrian bridge over the railroad tracks to connect the north and south platforms.

“I’m excited to celebrate the long-awaited opening of the full platform,” said Mukilteo Mayor Jennifer Gregerson.

The new platform was originally scheduled to open in September 2014. But there were multiple delays.

BNSF Railway had restrictions on construction work over its tracks. “Constructing a project in the middle of an active freight right-of-way presented very unique challenges,” said Kimberly Reason, a Sound Transit spokeswoman.

With flaggers needed to help direct train traffic through the construction site, “it made the timeline for the project more extended than we planned,” she said. BNSF instituted moratoriums on construction from Oct. 1 to Dec. 31, their busiest time of year for freight traffic, she said.

There were issues with new elevators at the station as well. In October, inspectors from the state Department of Labor &Industries identified problems on two elevator cars. It’s common for more than one inspection to be needed for the elevator system to be certified, Reason said. “It’s a multistep inspection process, and typically not just one visit,” she said.

There also were design changes that required some reworking, Reason said.

New artwork by Whidbey Island artist Linda Beaumont will be displayed in the station. Two installations, called “Earth Canoes” have been displayed in the north platform. “Sky Canoe” is suspended in the pedestrian overpass, with eel grass, plants and leaves layered into its fiberglass. The works are a tribute to the area’s tribal canoe cultures.

The Mukilteo station’s first platform opened in 2008. It has been the only Sounder station with one platform. Monday’s opening of the south platform means all Sounder stations will use two tracks and two platforms. Sounder light rail service runs from Everett to Seattle.

Gregerson said the opening of the second platform marks “the first part of the redevelopment of our waterfront, restoring access and enlivening an area that has been off limits to Mukilteans for decades.”

For years, the waterfront was dominated by a former U.S. Air Force tank farm. Although the fuel storage tanks were removed in 1999, the area remained fenced, and the lots weedy, with some abandoned buildings remaining.

There’s only one operating building on the site, the Northwest Fisheries Science Center. Plans call for the aging wooden building, which once served as military barracks, to be replaced by a $33 million, 26,000-square-foot building that could open in 2020.

A new $129 million ferry terminal adjacent to the Sounder platform is scheduled to open in mid-2019. Last year, the Mukilteo-Clinton route was the busiest in the state ferry system, used by 2.23 million cars and trucks, or 21.3 percent of the ferry system’s vehicle traffic. The new facility is replacing the current 60-year-old terminal.

The city also has plans to transform waterfront property from Edgewater Beach to Lighthouse Park. They include construction of a nearly mile-long promenade between the beach and the popular city park, as well as adding other parks, a scuba diving site, and providing more places to access aquatic activities such as kayaking and fishing.

Sharon Salyer: 425-339-3486; salyer@heraldnet.com.