SEATTLE -- The Transportation Department is warning drivers to expect congestion delays in August on northbound lanes of Interstate 5 through downtown Seattle.

Construction work is reducing capacity by about half for 19 days starting Monday.

Officials said 65,000 drivers a day will have to find a new way north into Seattle or risk backups that could stretch all the way to Tacoma.

Several lanes will be closed around the clock, leaving only two or three lanes open to handle all of the northbound traffic, even during rush hours.

The project stretches from Spokane Street to the Interstate 90 interchange.

Crews are replacing expansion joints and resurfacing lanes.

Meanwhile, many commuters may avoid the I-5 closures by taking the Sounder train to work. Sound Transit has added one extra train to accommodate the high numbers of travelers expected during the construction. Despite that, the trains may be filled to capacity.

Officials said that on an average day, 6,800 people board the train and head to Seattle.

Now, due to the I-5 construction, the train has become a top choice for commuters.

Sound Transit officials said they expect the train to be standing room only during the closures and for those planning on leaving their cars at the stations, parking is expected to be at a premium.

Extra parking will be made available at various train stations.

In Auburn, the city arranged to have 45 more parking spaces open for commuters, which are generally used by merchants and residents in the area.

In Renton, the stretch of Rainier Avenue South between South Fourth Place and South Seventh Street in Renton cannot be used to get around I-5. Crews are tearing down an old railroad bridge that runs over the street, allowing Rainier to be widened, providing an additional lane in each direction.

The work is expected to be finished on Wednesday.

Washington State Ferries have added sailings to try to help ease the I-5 slowdowns.

Starting Monday morning, extra weekday sailings will be added for the passenger-only runs between Vashon and Seattle.

From August 13 to 27 there will be additional departures at 5:50 a.m. from Vashon and 6:25 a.m. from Seattle.

In the afternoon there will be extra sailings leaving Seattle at 3:35 p.m. and Vashon at 4:10 p.m.

The west Seattle water taxi has added an early morning sailing.

Boats will leave for downtown every 40 minutes starting at 6:10 a.m. with five morning departures in all.

Officials said ridership is up 27 percent this year.