SPRINGFIELD -- A Westfield developer is planning a multi-million dollar renovation of the historic Masonic Temple on State Street as the future "dream" site of the Springfield Conservatory of the Arts School.

Frank A. DeMarinis and his firm, Sage Engineering & Contracting Inc., were selected by the city under a 10-year lease agreement for the magnet school that serves students in grades 6-12. The school, now split at two rented locations in Springfield, is slated to open at the refurbished site in September 2018, officials said.

"It's going to be absolutely beautiful once it's completed," said Lydia Martinez, assistant superintendent of Springfield Public Schools. "This is an amazing dream come true to actually be able to have a school (at one site) that infuses the arts for our students."

DeMarinis, who owns the property, said this week the renovation task is extremely challenging.

"On a scale of 1 to 10, this is is an 11," DeMarinis said. "I think it's a great project for the city. It's a great project for us. It's a win-win for everybody."

The Masonic Temple, which was built in the 1920s and dedicated in 1926, is on the National Register of Historic Places. It cost $1 million to build, made possible by a fund drive by local Masons. It was "erected by Masons, for Masons and dedicated to the interests and welfare of Masons," according to its historical summary.

Some of the unique features in the vacant building include a 1,500-seat auditorium on the third floor with a stage, balcony and pipe organ. The building also features a banquet hall and commercial kitchen, two former chapels, a former robing room for lodge members and an art gallery.

Martinez said that one large area will double as a gymnasium and dance studio, and the auditorium will be refurbished. There also will be new science labs, classrooms and a library area, and the grand foyer will be kept as a grand foyer to include some student exhibits.

DeMarinis said his renovation project could cost anywhere from $5 million to $20 million to complete. He purchased the property for $100,000 at foreclosure auction in 2014. It had most recently served as a church.

Mayor Domenic J. Sarno praised the school plans, saying it serves the students well, and will "bring back to life a beautiful, historic building."

The city is finalizing the 10-year lease agreement with DeMarinis, with the option of two five-year extensions, said Theo G. Theocles, the city's deputy procurement officer.

The conservatory school, created in 2014, describes itself as "offering an arts-infused curriculum grounded in academic inquiry, collaborative small-group instruction, and professionally guided arts training."

However, in order to fit all students now, the middle school grades are located at the former Immaculate Conception School on Kopernick Street in Indian Orchard and the high school grades are located at the former Our Lady of the Rosary School on Franklin Street.

The Masonic Temple site provides ample space for all grades, with enrollment expected to total 420 students, Martinez said.

That fits in with the original vision of having the conservatory at one site, close to the downtown arts and entertainment assets, Martinez and Sarno said.

"As we know, the arts are an integral part of student success if we are truly going to educate the whole child," Martinez said.

The city in seeking proposed locations stated that it wanted a large facility with many specialty rooms and spaces, preferably close to the city's performing arts venues such as Symphony Hall, CityStage and the MassMutual Center.

In the first year, the lease will cost the School Department $1,457,800, equating to $19.70 per square foot, according to the agreement. An interior parking area is not included in the lease area (74,000 square feet).

The lease will rise in increments to $1,742,205 by year 10, equating to $23.54 per square foot, according to the agreement. The lease will be renegotiated if the assessed value of the building exceeds $3.5 million after renovations are complete, the agreement states. The building's assessment now is $807,500.

Under the lease, DeMarinis is responsible for the cost of all renovations, improvements, taxes, major utilities, repairs and other expenses.

Martinez said the cost will be offset by the savings that will occur when the department stops renting the two former Catholic schools in 2018.

DeMarinis and Sage Engineering have begun with a major cleanup inside the building, occurring in recent weeks, that will be followed by the removal of materials containing asbestos, he said.

A new roof will be installed and the interior of the building will basically be gutted and improved, DeMarinis said.

The improvements include all new utilities including electrical and plumbing, new lighting, new bathrooms, a new heating-ventilation-air conditioning system, a new fire alarm system, new bathrooms, measures to make the building fully handicap-accessible, and extensive interior work, DeMarinis said.

The exterior of the building, now in good condition, will be preserved in keeping with historic preservation, DeMarinis said.

DeMarinis was previously involved in construction of the Riverbend Medical Building and the Roots Aquatics and Fitness Center in Westfield, among other projects.

Martinez said city officials have been very supportive of the plans, and the project helps restore a building instead of letting it continue to sit vacant and deteriorating.