Skyline Eco-Adventures, the first company to offer zip line tours in the U.S., has made a $1 million investment to open its first zip line on Kauai in May and to add its first side-by-side line to its Maui course this summer.

"We spent three years in development and then began constructing the Kauai site in January," said 35-year-old Danny Boren, who serves as president of the company that he owns with his father, Buck.

"We’re going to open in mid-May. We don’t have a start date yet, but we’ll probably open reservations in the next three weeks," the younger Boren said.

The new course, which will be called Skyline Poipu, will feature eight zip lines that offer valley, mountain and ocean views.

It supplements the company’s zip line offerings in Maui and Hawaii island. The Borens, who hail from Maui, opened the nation’s first zip line tour course in 2002 when they debuted one just minutes from Haleakala National Park.

"Zip lines have been used in military training and camps for years and then later became popular adventure attractions abroad, but we were the first to bring the concept to the U.S. as a tourist activity," Boren said.

Boren, who had experienced a zip line as a high school student at Seabury Hall in Makawao, said he experienced his first zip line tour in Costa Rica.

"My dad came down to visit me and we went to the mountains in Monteverde and tried a zip line," he said. "We loved it and began talking about it as a business idea."

The concept was so unusual that the Borens had to privately fund it.

"I took a job teaching at Seabury for six months while I worked on the funding," Boren said. "We only had six paying guests the first month. Luckily, it grew from there."

As the concept took off, the Borens launched a second location high above Maui’s Kaanapali Resort, which they followed by opening Skyline Akaka Falls, which goes over a waterfall near Akaka Falls on Hawaii island’s Hamakua Coast.

"We’ve put a guest on a zip line more than 2 million times," he said, adding that the company’s latest expansion will add about 15 jobs, taking them to about 85 employees companywide.

Tickets for the Kauai course will be $139, with a 25 percent discount for kamaaina and military. The price includes a guided tour and access to eight ziplines. The entire experience will last about two and a half to three hours.

Even as Skyline tours have grown, so too has the competition. Boren estimates that there are about 400 zip line tour companies operating in the U.S., with about 21 of them in Hawaii.

"We constantly have to upgrade our zip lines," Boren said, adding that the company also plans to add new lines to its Haleakala course this summer.

"We are adding our first side-by-side zip line," Boren said. "People really seem to enjoy those."

In addition to entertaining the public, Skyline focuses on education, safety and giving back to the community, he said.

During the past decade, Skyline has given more than $600,000 to state and national nonprofits, he said. The company was named Hawaii Eco-Tour Operator of the Year in 2004 by the Hawaii Eco-Tourism Association and this month was voted the state’s top land adventure tour by Hawaii Magazine readers, Boren said.

Sue Kanoho, executive director of the Kauai Visitors and Convention Bureau, said Skyline Poipu will be the sixth zip line course to open on Kauai.

Kanoho said there were not any zip lines on Kauai until after 2002, when the TV show "Amazing Race" featured a segment in which contestants dropped 160 feet from Wailua Falls into the water.

"After that segment ran, we started getting phone calls from people asking to do that tour," she said. "We didn’t have a tour yet, but I think it planted the seed for activity operators to see the potential."

This latest zip line will follow last year’s opening of Koloa Zip line, Kanoho said.

The industry has worked well with the island," Kanoho said. "It’s a fun experience that lets visitors see a different view than they normally might see. We think it’s a good match for Kauai."