One of the largest and most imposing structures in New Haven — and the site of some of its biggest entertainment events — will soon be consigned to the scrap heap.

The Veterans Memorial Coliseum closed on Aug. 31 after city administrators determined that the 31-year-old facility was too expensive to keep running, costing as many as 75 employees their jobs.

The city has entered the preliminary stages of applying for a $10 million state grant to pay for the structure’s demolition. In October, the city’s Coliseum Authority will hire an engineering firm to prepare the demolition plans and the bidding for the destruction contract will begin. The earliest demolition date would be after New Year’s Day.

That will leave Yale’s John J. Lee Amphitheater in the Payne Whitney Gymnasium as New Haven’s largest indoor sporting venue. The Lee Amphitheater seats just 2,800, while the Coliseum held 11,171.

As a result, shows such as the Coliseum’s final event, World Wrestling Entertainment’s Tour Defiance, which took place on Aug. 26, may never return to New Haven. Several officials said the city has no plans to construct a new arena. Instead, the city is considering two main possibilities for replacing the massive structure that still dominates a 4.5 acre site south of the New Haven Green.

Officials have proposed relocating the Long Wharf Theatre downtown to expand the city’s theater district that stretches along Chapel Street. Another possible use for the site could be a conference center for hosting trade shows.

“There’s a niche in the market for that type of thing,” said Tony Bialecki, a New Haven business services officer.

City officials added that the Coliseum site is large enough to accommodate both a conference center and theater, either of which could employ many more workers than the Coliseum.

And while discussion of the site’s future continues, closure and demolition plans are going forward. The city, which owns the Coliseum, will take inventory and auction off the building’s assets on Sept. 19.

“By the end of September, it will all be moth-balled,” Bialecki said.

The Coliseum first opened in 1971 as a state-of-the-art facility, one of only a handful of arenas in the state. But as the structure aged and new, more modern arenas sprung up statewide, events began to look at other venues.

City officials said renovating the Coliseum to make the arena competitive would cost $30 million, three times the cost of the demolition. The facility was last renovated in 1997 when minor upgrades to the concession stands and restrooms were made.

That same year, the city hired SMG to manage the Coliseum. SMG runs hundreds of arenas nationwide and brought several high-profile acts to New Haven, including rapper Snoop Dogg’s Puff Puff Pass tour last autumn.

Until 2011, the city will continue to pay $1.9 million annually on bonds that were issued in 1971 to pay for the Coliseum’s construction. Of the approximately $1 million the city receives annually from the state’s hotel tax, 75 percent was allocated to the Coliseum’s operations. The rest went to the Visitor’s and Convention Bureau. City officials are uncertain where the Coliseum’s share will now go.

Late last year, SMG confronted the city with the need for an additional $600,000 to keep the Coliseum open. That request sparked a study of the Coliseum’s economic impact.

At Monday night’s New Haven Board of Aldermen meeting, Alderman Brian Jenkins proposed a referendum to allow New Haven voters to determine the Coliseum’s fate. But the proposal failed to achieve unanimous consent from the board and was discarded.

The 2,300-space parking garage that towers above the arena will remain open through at least December. About 800 parkers use the garage daily, most of them commuters at nearby Union Station. Shuttle buses between the train station and the Coliseum will continue as long as the garage is open.

But once the garage closes, parking south of the New Haven Green could become tight. City officials are already planning for new parking facilities, in addition to future uses of the Coliseum’s parcel.