Only about 275 vehicles a day have been parking at Western Pennsylvania's biggest and most under-utilized parking garage -- seven floors and 2,200 spaces at Port Authority's Light Rail Transit station at South Hills Village.

Business in the 13 months it's been open has been so lousy that the top four floors of the $21 million structure in Bethel Park are blocked off.

But business is about to pick up.

The authority board has agreed to lease up to 300 spaces to a nearby Giant Eagle for employee parking for up to $56,000 a year, starting July 1 with 225 spaces.

While the move will free spaces for customers at an overcrowded parking lot at the supermarket, it'll hike the occupancy rate above 25 percent at the South Hills Village garage about a half-mile away.

Moreover, riders who now park for free at the 600-space "upper lot" at the T station will likely have to park elsewhere or shift to the garage and pay in the not-too-distant future.

Proposals are due Monday afternoon from developers interested in leasing what a Port Authority official called "probably the most valuable piece of property we own." The existence of the garage now makes it possible for the financially challenged transit agency to remove cars from the area known as the upper lot, market the site and profit from it.

Eleven individuals or developers picked up informational packets about potential development, including Simon Property Group, which owns South Hills Village mall.

"It could be residential, condos, apartments, businesses or a combination," authority spokesman Bob Grove said. "We don't limit proposals. We're looking for the best one."

In October, the authority sold 2.6 acres of vacant land along Brookside Boulevard next to the South Hills Rail Center for $160,000 for residential development.

It bought that property and the land where the parking garage sits in 1971 as part of a 44-acre purchase for what was to be a "Skybus" facility. Instead, the site houses the South Hills Village T Station, a light-rail storage and maintenance facility, an operations-communications center and park-n-ride facilities.

The Port Authority charges $2 a day to park in its garage, whose walkway connects directly to the T station. Pass holders are eligible for a discount that lowers their cost to $1 a day.

Meanwhile, the authority board has extended a lease with Jefferson Regional Medical Center for $1,250 a month for employee parking at the Large Park-n-Ride lot along Route 51 in Jefferson Hills.