ACCOUNTING and consulting firm BDO Seidman just leased 121,441 feet to become the anchor tenant at 100 Park Ave.

Sources tell us the space on the ninth through 11th floors will become its New York headquarters.

The firm will move in January and expand by 10,000 feet from its current digs at 330 Madison Ave.

This is the 15th-largest deal of the year. The space had an asking rent of $82 a foot.

The building, located on the western blockfront between 40th and 41st streets, is completing a $72 million capital improvement program that will earn it a Silver LEED certification.

The certification signifies leadership in energy efficiency and is becoming more important in leasing circles as companies seek to brag about reducing their own carbon footprints.

One of the fastest ways to score green brownie points is to move to new or retrofitted office towers.

Chicago-based Howard Ecker of Howard Ecker & Co. brought the tenant to building owner SL Green Realty Corp., which had Steve Durels working in-house with a Cushman & Wakefield team of Paul Glickman, Tara Stacom, Mitti Lieberson, Alexander Chudnoff, Diana Biasotti and Jonathan Tootell.

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We just toured the 60-story Silver Towers at 42nd Street and Eleventh Ave. that is still under construction.

The project is being developed by Silverstein Properties on the eastern end of a block that Larry Silverstein bought about 23 years ago and which already has his River Place on the western end.

The 1.2 million foot complex will have 1,359 rental units, a fitness center with a 75-foot swimming pool, spa, lounge, library, 194 car garage, tenant breakfast facilities and more than 20,000 feet of retail.

The towers will be topped out this week at 645 feet and are scheduled to open next spring.

The project is being built “first class,” a proud Silverstein told us while gazing at the shimmering curtain walls.

Citi Habitats is the leasing agent for the studios, one- and two-bedroom units.

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Frank Sciame purchased an additional 110,000 feet of air rights for the 80 South Street parcel along the East River.

The additional air power will bring the project, once slated for a Santiago Calatrava-designed townhouse cube tower, to 300,000 feet.

“It opens up a lot of possibilities,” Sciame said, excited at the prospect. “We’re considering developing it ourselves and have some international interest. We believe in the site and it makes it a much more viable building.”

That’s because it could have a much larger base more suited to a hotel, for instance.

“We have views now protected to the north, south and the East River,” Sciame added.

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Basketball City is finally getting its home on the Pier 36 range after two long years of negotiations with the city.

The 21-year deal with two 10-year renewals was hammered out with the city’s Economic Development Corp. for 129,689 feet of the old Chiquita Banana Pier on the Lower East Side, just north of the current Manhattan installation of the Olarfur Eliasson waterfall.

The Basketball City folks, however, claim it’s a 64,000 foot deal and no one from EDC returned our calls.

Basketball City had a previous location in Chelsea but closed it and now runs its programs for inner city youth and corporate teams at various gyms.

“Once we have a facility we will be able to give back more,” said Basketball City’s Bruce Radler.

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