CLEARWATER, Fla. — Almost 15 years after it began construction, the Church of Scientology plans to open its massive Flag Building in downtown Clearwater on Oct. 6 with a dedication ceremony it says will draw 10,000 Scientologists.

One month later, the International Association of Scientologists’ Anniversary Weekend, a signature Scientology event usually held in England, will be moved to Clearwater and conducted in an enormous tent that will seat most of the 8,000 people expected to attend.

The IAS is a powerful fundraising arm of the church, and the money it collects helps fund Scientology’s social betterment programs. The annual anniversary celebration often is used by church leader David Miscavige to review the church’s successes and announce initiatives.

Church representatives met with Clearwater city staff Friday to discuss a tentative special event plan submitted to the city on Friday and obtained by the Times.

Scientologists are thrilled with the coming events, said Pat Harney, a church spokeswoman.

“We are enthusiastically preparing for both the Opening of our Flag Building and the annual International Association of Scientologists Anniversary Celebration,” she wrote in an email.

Harney didn’t directly respond to a list of questions about the October dedication and the Nov. 8-9 anniversary event. “As we get closer to the events, we will have further details,” she wrote.

The Flag Building is also known as the “Super Power” building because it reportedly will be the only place where a highly classified Super Power program, first advanced by church founder L. Ron Hubbard in the 1970s, will be conducted.

Hubbard said the Super Power program would awaken spiritual beings occupying human forms to empower them to clear the planet of its many perils. Participants would be spun on a gyroscope-like wheel, spend time in a sound chamber, sniff vials emitting fragrances and experience changes in gravitational pull.

In August 2011, church fundraiser Lauri Webster told Scientologists in Clearwater that the “out-of-this-world machines” in the Super Power building “would make any science fiction buff marvel.”

Construction of the building, begun in 1998, dragged for years without explanation, eventually drawing daily fines from the city for missing deadlines. In 2011, the church paid $413,500 in fines to Clearwater.

A 2011 Times analysis showed that the church had raised $145 million for the massive seven-story structure, which covers an entire city block.

A federal lawsuit filed in January by former parishioner Luis Garcia alleges that the church entity that was responsible for raising funds for the Super Power project purposely kept the building incomplete “to use it as a shill to induce further payments from members.”

The church paid $290,000 in taxes on the property from 1999 to 2011. The property is now fully tax-exempt. It has been valued at just over $80 million by Pinellas County appraisers.

For the upcoming events, the church has made some requests of the city, including temporary street closings and removing trees around downtown’s Franklin Street area to accommodate the huge pre-fabricated tent it will ship to Clearwater from England, said Paul Bertels, the city’s traffic operations manager.

City planners will discuss with the church the idea of temporarily removing trees, Bertels said, but he said it is unlikely that any trees would be permanently removed.