Clutha district youth co-ordinator Daniel Maze said 10 teenagers worked on the fitness course as part of Making A Difference (Mad), a leadership programme he runs.
The teens, all years 12 and 13 pupils at Lawrence Area School, spent more than 200 hours over 14 weeks restoring the course.
Mr Maze said the assault course was built by the New Zealand Army in 1990, but had not been used for several years.
"Some Lawrence people were surprised to find it there after all this time. I think a lot of people didn't even know it was there," he said.
The course starts with the "gut buster", a steep 75m incline, then continues with obstacles ranging from a set of tyres, to high and low hurdles, to a 2m climbing wall.
The group and some volunteers from the community worked to clear overgrown tracks, fix old obstacles, make new ones, and create signs and maps.
The project had been well supported through volunteer labour and donated gravel, bark chips, and wood stain. The group was also given $1500 by the Lawrence-Tuapeka Community Board from the Kate Leslie Fund to purchase signs.
Mad programme member Kelly Tweed said she was surprised how much work had been needed to get the course back into shape.
"It's been a lot of hard work but the course will be good for sports training, and even the fire brigade and police could use it."
The course will be officially opened by Clutha Mayor Bryan Cadogan at 11am this Sunday, followed by tours of the course, and a sausage sizzle.
