Bridgton’s own Great Adventure Challenge – a triathlon combing kayaking, mountain biking, and trail-running – returns for its ninth go-round this Saturday, Aug. 20.

Rob Knowles, who founded the charity event alongside Ed Rock, general manager at Shawnee Peak, predicts a respectable turnout. But the surging popularity of triathlons, road races and mud-runs has cut into participation, these past few years.

“The Challenge was at its biggest around 2010 and 2011,” said Knowles. “Since then, there’s been a huge influx of events … 5Ks all over. I hope to put 100 kayaks on the line. This would entail 70 individuals and 30 teams. But it’s unlikely I’ll reach this; more like 65 and 18. It’s hard (to be sure), because lots of folks hold out registering till the end.”

Originally, the Challenge benefited Good Neighbors Inc., a Bridgton outfit dedicated to assisting Mainers with disabilities where Knowles worked for 25 years. But when the Scarborough-based Morrison Center, which provides similar educational, therapeutic and support services, acquired Good Neighbors, it naturally became the race beneficiary.

“We generate between $7,000 and $8,000 a year for the [Morrison Center],” said Knowles. “This year, I’m hoping for $6,500 to $7,000; our biggest year was $9,000. All registrations go to the agency and sponsors support all costs; no one receives any monetary compensation for anything and never has.”

Knowles has had most of the same sponsors for all nine years. Some Maine giants – namely, Hannaford, Shawnee Peak and Poland Springs – contribute regularly to the event, as do several smaller business like Premier Physical Therapy, Lake Region Photography and Skydive New England. Individuals and families also provide financial support.

On race day itself, a battalion of more than 70 generous volunteers man the front lines, coordinating the action and attending to athletes’ needs. Volunteers receive a T-shirt, a lunch and “a lot of satisfaction,” as Knowles put it.

Momentum, out of Casco, provides a range of support services to the disabled. It has five teams registered, with a client or two on every team. “They’ll compete as any other entrant, with absolutely no handicap: For one day, they’re simply athletes competing on an even playing field and if they excel, they will be recognized,” Knowles said.

One lucky competitor each year walks away with a new kayak, paddle and life vest from Saco Bound, and 24 racers in eight different age/gender groups earn trophies. Everyone wins a T-shirt and lunch for themselves and a supporter. There’s free ice cream all day for kids and a jazz band scheduled to play from 10:30 a.m.-1 p.m.

Knowles describes the course itself: “The race starts in the water and covers a 2.5-mile closed course. It can be seen from the Route 302 causeway on Moose Pond. It transitions to bike at the beach and has a short road segment to off-road – then, no more tar. The off-road varies from double-track dirt roads to loose sand roads to single-track. There are two significant sections: One downhill over a rock brook – only 100 yards or so, but tough – and Pratt’s Hill, 700 feet uphill. Everyone, except two people in the past nine years, either carries or pushes [their bike at these spots.]”

The triathlon closes with its “run” stretch, two miles round-trip, up and down Pleasant Mountain. “The run is straight up the face of the mountain and under the chairlift,” said Knowles. “No one runs up; several run down.”

The course largely covers public roads, but three landowners do allow Knowles the use of their property on a yearly basis. Knowles emphasized the tender loving care with which the course is treated. “The trail is very well-marked, in excess of 100 directional signs in 16 miles. We sweep the course and pick up all the signs and discarded water bottles.”

Registration is $60 dollars per individual, $150 dollars per team. The Challenge is online at www.maineadventureracing.com. The Morrison Center can be found at www.morrison-maine.org.

A school of kayakers sets out on the 2.5-mile paddle leg of last year’s Great Adventure Challenge.

Photo courtesy of Lake Region Photography, via Rob Knowles.