Randy Stenger's hunch that people would pay to play with full-size bulldozers or excavators — actually driving and operating them — has grown into a business reality.

It's been about 18 months since Stenger, a self-described "kid at heart," opened Extreme Sandbox, a 10-acre playground of sorts in Hastings.

When he found the site — ideally suited because it was open and full of sandy soil — he asked the city for leeway on zoning rules to test the attraction to see whether it would actually succeed.

"We didn't want to build something permanent until we knew it was viable," he said.

The attraction has exceeded his expectations, Stenger said, with bookings for parties and corporate events as well as individuals in search of an offbeat way to have fun. Videos of people maneuvering the equipment through Extreme Sandbox's obstacle course or scooping up sand have popped up on YouTube. The attraction has earned a universal thumbs-up from TripAdvisor.com, the widely read travel website, and flattering testimonials on Facebook.

The success has prompted Stenger to move ahead with plans to solidify Extreme Sandbox's presence in Hastings. He recently got approval from the city for a permanent facility at its site at 1901 Glendale Road and is in the process of buying the 10-acre parcel. He plans to pave the gravel parking lot and put up a 6,200-square-foot building to replace the trailer he has used for offices and a training center for customers.

Stenger said he hopes the building will be completed by the end of the year. In addition to giving him more space for an area to be used for reception, training and spectators, it will provide indoor storage for his stable of equipment — two excavators, a bulldozer, a skid steerer and a firetruck.

Stenger said he would like to expand Extreme Sandbox's group and corporate event business. Customers so far have included Land O'Lakes and Northern Tool and Equipment.

Fidelity Bank's Women in Business networking group recently had its annual outing at Extreme Sandbox. Steve Stoup, senior vice president of marketing at the Edina bank, said he had learned about the Hastings attraction by word of mouth.

"The main goal of these events is to network, have fun and maybe do something you would not do otherwise," he said. After a successful outing last year to the Minnesota Horse and Hunt Club in Prior Lake that involved shooting clay pigeons, Stoup said he concluded "that the women liked doing something with some testosterone in it."

Stoup said the 35 women who went to this year's event loved it. He likes to find different things for the women's group to do every year, but adds, "Would I find another reason to go out there again? Absolutely."

Extreme Sandbox is the only attraction of its kind in the Midwest; Stenger says the only other one he knows of is in Florida. He said he's been inundated with calls from people across the country wanting to operate an Extreme Sandbox as a franchisee. That's something he's considering in the future, but not before he opens a second one of his own in some other large metro area, like Chicago.

The lengthy search for a site that led to Hastings makes Stenger believe that finding a second location won't be easy. Stenger said he found the ready-made sandbox in Hastings after "a whole lot of driving around the metro area." Even after he found it, he wasn't sure city officials would embrace his far-out business idea.

He already had approached other cities where he had found possible sites, without success.

"It's not that they said no. It's just that they thought it was going to be too much of a struggle to get approved."

Stenger said the reaction in Hastings was different, with city planners recognizing the economic potential of the new venture.

"An entrepreneur comes forward with an idea, and we want to be able to be accommodating when we can," Community Development Director John Hinzman said. "This is a situation where we could, and it worked out great."

Extreme Sandbox requires all its customers to go through training from Stenger and other employees before operating the equipment. Other safety measures include staff-operated remote-control turnoff switches and not allowing kids younger than 14 on the equipment, even as passengers.

But Stenger says he has learned that older teenagers are the most adept at working the switches and levers that control the huge playthings. "They're much better than adults," he said. "The reason is video games."