ASHLAND — Dirk Patterson and Sam Dodenhoff pore over Gary Spence's trailer and powerboat, looking for signs of aquatic plants or dangerous snails hitchhiking their way into Oregon on the boat or trailer.

ASHLAND — Dirk Patterson and Sam Dodenhoff pore over Gary Spence's trailer and powerboat, looking for signs of aquatic plants or dangerous snails hitchhiking their way into Oregon on the boat or trailer.

Spence, of Ashland, had been fishing at nearby Howard Prairie Lake, and his boat was clean, just like all 275 boats the pair studied last summer at their boat-inspection station at Interstate 5's Port of Entry near Ashland.

As they fill out paperwork verifying Spence's boat as clean, drivers of two pickups pulling powerboats that may or may not have been harboring hidden quagga mussels ignore the inspection sign.

"About 50 percent of them don't stop, and that's on a good day," Patterson says. "There's nothing we can do. All we can do is watch them go by.

"It's not the ones who stop that you worry about," he says. "It's the ones who don't."

That might change as early as this summer under a bill winding its way through the Oregon Legislature that would beef up the state's fledgling fight against invasive aquatic species by making these volunteer stations mandatory.

After last year's poor showing, in which nearly three out of four boats buzzed past inspection stations, organizers say the threat of getting pulled over and receiving a $90 ticket for noncompliance is needed to ensure that invasive species stay out of Oregon waterways, saving millions in cleanup costs and avoiding environmental disasters suffered in other states.

"Being voluntary is the weak link in the whole program," says Rick Boatner, the aquatic invasive species coordinator for the Oregon Department of Fish and Wildlife and head of the inspection program.

"Last year we had a 27-percent compliance rate," Boatner says. "That's pretty poor."

The bill, labeled House Bill 3399, has a hearing Tuesday in the House Ways and Means Committee. It previously passed out of the House Agriculture and Natural Resources Committee.

It would give inspectors like Patterson and Dodenhoff authority only to check for aquatic species and not use them like police roadblocks to weed out drunken drivers.

"It'll be pretty specific, but it would give us the tool we need," Boatner says.

The Legislature in 2009 created $5 invasive species boat permits to fund a coordinated effort to ensure that environmental wrecking balls like zebra and quagga mussels don't enter Oregon on boats coming from infected waters.

Some invasive species can thrive in local waters because they would be safe from predators or diseases seen in their native habitats, allowing them to reproduce exponentially and out-compete native fish for food and space.

Zebra and quagga mussels do all that and more. The mussels filter zooplankton, altering ecosystems much the way tui chubs did in Diamond Lake last decade. They also can ruin boat engines, jam steering equipment, clog water pipes and cloak a lake bed.

In its strongest attempt yet to keep Oregon quagga-free, the state's two-year-old "Clean Launch Law" makes it illegal to launch any boat with any aquatic species clinging to the exterior, including native weeds.

The inspections take a few minutes, and clean trailers are marked.

The original 2009 legislation starting the program contained language making participation mandatory, Boatner says. However, it was removed because it was considered in violation of Oregon's constitutional ban on roadblock checks of motorists, Boatner says.

Since then, a state Department of Justice review concluded that very specific mandatory stops, such as for boat inspections, fell within state constitutional guidelines, Boatner says.

Last year, inspectors checked 2,852 boats statewide, with no quagga or zebra mussels detected, Boatner says. Of the 19 boats that were decontaminated, five were pressure washed and 14 had aquatic plants or barnacles removed by hand, he says.

Of Oregon's five inspection teams last year, Patterson and Dodenhoff were the busiest, logging 501 inspections at various southwest Oregon boat ramps and 295 at inspection stations.

"At the boat ramps, you have a captive audience," Dodenhoff says.

Spence says he pulled over to have his boat inspected because he saw the "Boat Inspection Ahead" signs on I-5 and thought it was mandatory.

"Maybe the signs should say, 'Boats Please Exit,' " Spence says.

Commercial hauler Ed Pellham, of Kalama, Wash., stopped for an inspection of the 38-foot salmon-fishing boat "Prosperity" he was hauling from Morro Bay, Calif., to Portland after first weighing in at the Point of Entry.

"It seems like it's mandatory now," Pellham says. "When the weighmaster tells you, 'Go over there,' it's not voluntary."

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