Asked about the biggest challenge in building the enormous Water Gardens complex in Santa Monica, developer Jerome Snyder doesn’t hesitate: parking.

“We had to figure out how to get 3,000 people in there within a half-hour in the morning and back out in the evening,” Snyder, a principal at J.H. Snyder & Co., said in describing the complex’s cavernous underground parking garage. “Everything hinged on that.”

When it comes to developing a successful office, retail or residential building, much rests on the seemingly mundane matter of parking design. It’s such an important aspect of the project that Snyder said he personally designs the ones his firm builds.

“In 50 years, I think I’ve figured it out,” he said.

For every project, Snyder has scale models made of the proposed parking layouts while each garage is still in its design phase.

He then takes an appropriately scaled model car and with his finger pushes it through the maze of ramps, aisles and parking stalls to make sure it’s designed properly.

“It takes a lot of time and effort,” he said. “But there’s no better way to figure it out than if you can drive a car through there.”

No matter what the methods, parking garage design can be an obstacle course for designers and engineers. The price of land is high, availability is low, and the cost of constructing underground garages is driven up by a variety of geological factors. A high water table, the occasional methane spurt and soil contamination are only a few of the challenges, both economic and practical.

“You want a garage that is easy to use rather than complicated, a garage that has a simple layout rather than a complex one,” said Jeff Okyle, vice president of business development for parking lot operator Standard Parking, which acts as a consultant on construction projects. “The challenge is meeting those goals and at the same time creating a space that is very efficient for the developer without lots of wasted space.”

Because of a water table less than 10 feet below the surface in some spots, projects along Wilshire Boulevard often are forced to use “slurry construction” involving extra-thick concrete walls reinforced with steel rebar and pumps running continuously to keep leaks from invading the underground garages.

In the Miracle Mile district, along Wilshire between La Brea and Fairfax avenues, developers are sometimes faced with the task of venting explosive methane gas and deposits that remain from a bygone era when the region was covered in fields of oil derricks.

Then there’s soil contamination from past industrial users, which despite the availability of federal and state grants can eat up half a project’s budget, depending on the scope of the cleanup required.

Snyder is facing all three conditions in a mixed-use project at the corner of Hauser and Wilshire boulevards. It calls for 60 underground parking spaces on two levels, but because of the low water table and methane gas complications, the cost per stall jumped to $35,000 per space, Snyder said. The price tag will climb if complications arise during construction.

Coming up with a plan for easy access and exits without bottlenecks is tougher, Okyle said. The design process is more “common sense” than “rocket science,” he said, but nonetheless is one of the more important design aspects of a building.

Snyder agrees and marvels at how often developers fail to get the parking right. “There are a lot of bad designs out there,” he said.