BANGOR, Maine — The Bangor Public Library has resumed work on a multimillion dollar construction project to restore the facility and create more room for modern uses.

Director Barbara McDade said Friday that the excavation work at the library is for the two-story atrium, which will be built onto the 1997 addition.

Also, she said, work on the third floor will create a children’s room, an expanded young adult section and an art gallery that will feature work by local artists. The library’s lecture hall also will be updated.

Tentatively, library officials expect the interior work to be completed in September.

Other plans for the library include the addition of a small-business center for startup businesses to use high-end business machines and software.

McDade said the entire project is tentatively scheduled for completion in March 2016.

The library has completed the estimated $3 million repair to the library roof, including replacement of the copper dome.

“I think people are going to be very pleased,” McDade said of the coming changes. “They’ll still be able to find the books that they want, but there will be more spaces to do other things, there will be more reading space.”

The updates and repairs come after a $9 million fundraising campaign, with $3 million donated by the Stephen and Tabitha King Foundation, $3 million coming from city bonds and the rest coming from private donations throughout the community.

McDade estimated about $1 million of that would go toward the library’s endowment fund, which pays for library operations. Approximately 40 percent of the library’s annual budget comes from the endowment with the rest coming from the city, she said.

To reduce space taken up by the library’s approximately 500,000-volume collection, compact shelving has already been installed in the library basement.

The library also culled about 20,000 books that weren’t being used from its collection. McDade said they attempted to donate them to the Portland Public Library, but they were too worn.

They also offered them for the Friends of the Library book sale, but they were judged unsellable.

“So we did end up trashing them, I’m sorry to say,” McDade said, adding that they made sure all culled books were either available at another library in the state or available for free online.

Follow Evan Belanger on Twitter at @evanbelanger.