A speculative flex industrial building in Marlborough has been driven onto the rocks by a brutal commercial downturn and will likely meet its end at a foreclosure auction tomorrow morning.

Barring a last-minute bankruptcy filing, Wells Fargo will foreclose on the half-finished South Street Business Park, brainchild of FCM Builders President David Franchi, along with 14.55 acres of land. Paul E. Saperstein Co. is the auctioneer.

Franchi attempted to put a 145,000-square-foot building at 413-417 South St. into service in the face of the worst commercial downturn in two decades, and without any tenants in place. He planned to follow that by building a 75,000-square-foot office property next door. The South Street Business Park targeted renewable energy manufacturing, pharmaceutical manufacturing and technology firms.

The project was originally financed with a $6.5 million loan from Middlesex Savings Bank. Franchi’s firm paid off that loan in early 2008, replacing it with a $9.55 million mortgage from Wells Fargo. That loan went into default last year, before construction was completed. The building shell now sits, half-finished, behind a fence.

"We got on site after the bank had declared a default, but we never got a notice of default," said Michael Landry, an attorney for AA & D Masonry, a subcontractor suing Franchi over $409,000 in unpaid work. And Landry’s client isn’t alone: Subcontractors have filed liens against the project totaling $771,000 in unpaid work.

"There weren’t any red flags," Landry added. "We did the work, and we didn’t get paid. He ran out of money. We’ve sent in repeated requests for payment, and they haven’t been responded to."

The submarkets around Route 495 have been hit the hardest by the current commercial downturn, as many buildings had yet to fully recover from the dot-com bust. Total availability in the 495-MassPike market stood at 27.5 percent at the end of 2009, according to data from Jones Lang LaSalle. Asking rents were averaging around $19 per-square-foot, and falling.