Get ready, Sunset and Ingleside commuters.

After celebrating its hundredth birthday in February, the Twin Peaks Tunnel will be shut down for a good chunk of the summer starting in late June to make some already-delayed improvements, the SFMTA has announced.

For two of the lines that run through the tunnel — the L-Taraval and the M-Ocean View — buses will replace regular Muni metro service for the duration of the 60 day shutdown. The buses are scheduled to run every 5 minutes during peak hours and at 8 to 15 minute intervals during midday and evening hours.

The K-Ingleside line will operate along a modified route. Trains will operate between the Sloat-St. Francis and Balboa Park stations, continuing on the J-Church line after Balboa Park. Riders can also transfer to the shuttle buses at Sloat-St. Francis or to BART at Balboa Park. A map of the routes is available here.

The improvements theoretically will allow trains to move more quickly through the tunnel, which serves an estimated 80,000 people per day.

It's part of the $40 million Twin Peaks Replacement Project. The tunnel will receive a full track replacement along with seismic reinforcements and improvements to its drainage system, according to the SFMTA.

As a dry run for the service changes, officials expect the tunnel will be closed and shuttle buses run instead on Memorial Day, according to SFMTA Director of Transportation Ed Reiskin.

Commuters along these lines have already been dealing with more limited service than usual. The tunnel and adjacent stations began closing early on Friday and Saturday nights in mid-March so prep work for the summer construction could be done, and those early closures are scheduled to last until the full closure begins in late June.

Filipa Ioannou is an SFGATE staff writer. Email her at fioannou@sfchronicle.com and follow her on Twitter.