An army of teenagers put the finishing touches Friday on a two-year, all-volunteer project in Hawthorne Park that is transforming 200 yards of Bear Creek frontage from an riparian nightmare into an environmental asset.

An army of teenagers put the finishing touches Friday on a two-year, all-volunteer project in Hawthorne Park that is transforming 200 yards of Bear Creek frontage from an riparian nightmare into an environmental asset.

Students from South Medford High School and St. Mary's School planted native trees and shrubs along a strip of the creek that two years ago was an impenetrable wall of invasive Himalayan blackberries in soils polluted from petroleum-laced runoff spewed from Interstate 5's viaduct.

The runoff now is filtered naturally by the roots of strategically placed plants that cumulatively improve more than the image of this stretch of downtown creek and the water quality for native salmon.

It also serves as one large life lesson for the teens who weathered blackberry thorn scrapes and sore backs to make a little corner of their world better.

"Everybody's told us that it's a really big deal to take care of the environment," says Bobbi Reierson, a South Medford senior who spent the past five months working on the project. "But working on this, it suddenly made sense."

It also makes sense for the project not to grow beyond the park's banks for now, says Jim Hutchins, who organized the effort through his Oregon Stewardship program he teaches in local schools.

The man his volunteers know as "Hutch" says the project is best suited by having regular groups of teens hand-water the native plants to ensure their survival while also vigilantly removing every returning blackberry shoot that, if ignored, could eventually regain its grip on the creek bank.

"We're not going to do any more," Hutchins says. "We're just going to try to maintain what we have."

The project began two years ago when a Southern Oregon University student helped Hutchins create the first "bioswales" there to filter viaduct runoff that otherwise would simply flow out of pipes and into the ground next to the creek bank.

The insidious sloughing of petroleum products straight into urban streams is a nationwide problem that is exacerbated at places such as the viaduct, where storm water had nowhere to go but through pipes leading straight to Bear Creek, which is a major salmon and steelhead tributary in the Rogue River basin.

Around the swales, blackberries were replaced with more than 1,000 snowberry, spirea, Oregon ash and other plants.

They eventually will growing to create a natural canopy that will help reduce summer temperatures in the creek that now are unhealthy for young salmon in the summer.

South Medford kids logged more than 1,000 hours and St. Mary's students added another 200 hours pulling blackberries, planting trees and keeping the thirsty elements watered.

Hutchins says the hand-watering and other TLC from volunteers have created a 93 percent survival rate among the new upland plantings. Planted willow chutes, however, have seen a 50 percent survival rate, with those closest to the creek faring best.

"It's mainly all kid labor," Hutchins says. "And it's incredible."

The final 300 plants found fresh dirt Friday as work parties from both schools took turns working the soil as well as visiting learning stations that included a display of hides and skulls of native animals like deer, beaver and cougars.

In all, several waves of teen volunteers have worked on the project and Reierson says future generations of Oregon Stewardship students will continue to tend to this highly visible — and increasingly healthy — stretch of creek along the Bear Creek Greenway running through downtown.

"It's been like a torch that people have passed," Reierson says. "Hopefully, someone else will take it when we all leave."

Reach reporter Mark Freeman at 541-776-4470, or email at mfreeman@mailtribune.com.