Despite the many concerns about the massive parking garage being built behind the North Shore casino, developer Don Barden doesn't appear to have a lot of good options available to change the design of the garage.

As critics complain about the garage's potential impact on the city skyline, gambling industry consultants say the 3,800 spaces Mr. Barden is planning aren't out of proportion. And while some have suggested that Mr. Barden bury part of the structure underground, as his original plans showed, that could double its cost, experts say.

The size is necessary to accommodate the size of the casino and the other amenities it will be offering.

"That strikes me as reasonable to the size of the project he's developing. If you can't accommodate your drive-in guests, you will be unsuccessful," said Joseph Weinert, senior vice president of Spectrum Gaming Group, an industry consultant.

It would be expensive to build part of the garage underground because of its proximity to the Ohio River.

"I think that's a very legitimate concern. If I were building that structure, I'd probably have the same concern," said John Dorsett, senior vice president of Walker Parking Consultants, an Illinois firm that has helped in the design of more than 3,000 parking structures across the country, including some in Pittsburgh.

The 10-level garage proposed by Mr. Barden has been an issue since summer. Some fear its height, nearly twice that of the casino itself, will mar the city skyline and the developing North Shore riverfront.

In a deal with the city and Allegheny County, Mr. Barden, at a cost of $1 million, agreed to install decorative screening on the south side of the garage facing the river to try to address concerns.

But that did little to appease critics. Last month, the Riverlife Task Force challenged the city planning commission's approval of the casino and garage design before the state Supreme Court.

It asked the state Supreme Court to vacate the decision and halt building permits for the garage or appoint a special master to decide if the structure complies with city zoning laws.

"The issue with this project is that the casino has become a garage and the structure is truly one of the largest to be built on the riverfront in decades with the exception of Heinz Field," Riverlife Executive Director Lisa Schroeder said.

Some critics have suggested that Mr. Barden simply cut the number of spaces in the garage to reduce its size. But industry experts said the 3,800 planned doesn't appear to be excessive for a casino with 3,000 slot machines starting out, restaurants and other amenities, and expansion in its future.

Nor do the number of spaces appear to be out of line with what competitors for the Pittsburgh license proposed or what other stand-alone casinos in Pennsylvania plan to offer.

In Pittsburgh, Forest City had plans for a 2,200-space garage on the west side of Station Square, plus 800 valet spaces in two levels underneath the casino, to supplement existing parking. Isle of Capri was considering another 3,000 spaces beyond available parking near Mellon Arena.

The two proposed stand-alone casinos in Philadelphia, both on the riverfront, also have built in a lot of parking. One has plans for a 4,200-space garage, plus 300 surface spaces. The other will start with a 2,400-space garage, then expand to 4,250 spaces, according to the Pennsylvania Gaming Control Board.

Three Atlantic City casinos have more spaces than the proposed Majestic Star garage: The Borgata Hotel Casino & Spa with 7,100 spaces, plus a speed ramp to whisk visitors in and out; the Trump Taj Mahal at 6,734: and Caesars at 5,569. The Showboat has 3,400 spaces. Two others have fewer, the Hilton with 2,806 spaces and Resorts with 1,686.

Paul Girvan, managing director of The Innovation Group, a gambling consultant, said the "very, very loose rule of thumb" in the industry is one parking space per slot machine.

The reason is convenience: Casinos want to make it as easy as possible for people to get into the property and onto the gambling floor.

"The closer the parking to the gaming floor the better. You don't want people to walk a long distance," Mr. Girvan said.

In determining the spaces needed, casinos not only factor in those guests playing machines at any given time, but also must take into account those at bars or restaurants or watching entertainment, as well as those in transit from the casino to the parking garage or vice versa. If there's a hotel, there's generally a spot for each room.

"3,800 would seem to be ... a pretty good sizing [for the Pittsburgh casino]. You have to build a parking garage for Easter Sunday, actually," Mr. Girvan said. "You build it for your weekends, your peak day and your peak month."

In St. Louis, the new Lumiere Place casino, with 2,000 slot machines, 49 tables, a poker room and a 295-room hotel, has 2,350 parking spaces, including 1,355 in a garage.

Todd George, the casino general manager and vice president, said it's not uncommon for the spaces to fill or reach near capacity at peak times, particularly Friday and Saturday evenings. He does not believe the 3,800 Mr. Barden is planning is unreasonable.

"I think it's always better to have too many than too few, honestly. It's one of those things where going in you want to be successful. The goal is to drive as many people as possible as often as possible. If you have enough parking to satisfy them, that takes one variable out of the equation," he said.

Ed Fasulo, the Majestic Star general manager in Pittsburgh, said ease of access and attached parking are always among the top amenities patrons look for in a casino based on marketing and customer service surveys.

Majestic Star officials estimate that at any given moment 10 percent to 20 percent of cars will be in transition, meaning they are either coming into the garage or leaving it. Mr. Fasulo said he expects the garage to be full at peak times.

"Believe me, we would not build and spend money on a garage we did not need," he said. "It's amazing how everyone is an operator. Each situation is different. You can't say there is a hard and fast formula."

But Ms. Schroeder said there could be alternative ways to generate the number of spaces Mr. Barden needs without having to build such a large garage. They could include shared parking plans, similar to those employed at SouthSide Works to reduce demand, satellite lots and other creative arrangements.

"All means of accommodating and sharing parking can and should be considered before building to maximum capacity a parking structure for one facility at its highest use," she said.

Ms. Schroeder also noted that two levels of underground parking were included in Mr. Barden's original proposal and presumably were part of the original budget for the project.

"It's no more expensive now to put it underground than it was then," she said. "We still think it's important to hold him to the proposal."

Mr. Fasulo said, however, the original proposal was crafted before officials learned that they would run into the water table going two levels underground.

To continue with the plan, he added, would have led to a sizeable increase in cost. "I know it was substantial. The comment was that it would be more than double," he said.

Experts in garage construction tend to concur. They said underground garages generally are more expensive than those above ground. The costs go even higher when there's water involved.

Dilip Nandwana, chief executive officer of International Parking Design in Los Angeles, said the walls in such garages must be heavily reinforced because of the water pressure and then waterproofed to prevent leaks. The added work can increase the cost of the garage by 80 percent to 100 percent or even more, he said.

"The cost really goes up," he said.

"To go below grade you are probably looking at twice the cost and potentially more than double the cost," Mr. Dorsett added. "Given the river bed, it may not be physically feasible to do that."

Nonetheless, Ms. Schroeder believes there is still a need to explore alternatives. As it stands, Riverlife believes the structure violates the zoning code "in its size and scale and structure. It was proposed as an accessory and is now a garage two football fields long and 10 stories high.

"I think the question still remains what is the impact of a structure of that size and scale on a primary riverfront parcel with high visibility and dwarfing the casino structure," Ms. Schroeder said.