Al Potter created a map noting 41 illegal dumpsites around Highway 397 south of Kennewick.
Forty-one sites filled with tires, construction debris, old electronics and other refuse.
Now, all but four are cleared.
"Other people have made this very same effort (in the past). We are part of this continuing process of staying on top of this illegal dumping. We've got a big chunk out of the way. I believe people are watching for it now," said Potter, who spearheaded the cleanup effort with Mike Robinson.
The friends, from Kennewick, are avid cyclists who began to notice a growing amount of trash during rides.
They became frustrated with the illegal dumping -- an act that can mean costly cleanup fees for landowners -- and brought renewed public attention to the issue late last year through social media and a front-page article in the Herald.
They've been working with Benton County leaders and other area officials on the issue, and have organized cleanups large and small.
More than 50 volunteers gathered one day in March to help remove the junk.
In all, more than 20 tons of trash has been cleared away. Waste Management has taken most of it at no cost, including about 100 tires.
Les Schwab Tire Centers on West Clearwater Avenue and near the Columbia Center mall took in another 330-or-so tires, and Windermere Real Estate/Tri-Cities chipped in for commercial construction debris disposal.
Robinson said he feels good about the progress. "I feel like everybody else who's been involved with this does -- you feel like you're doing something that actually is important and is working," he said.
Illegal dumping is a misdemeanor or gross misdemeanor, depending on the volume, and is punishable by fines and jail time.
If the dumper can't be found, it can fall to landowners to pay the disposal costs.
In the last few months, some alleged dumpers have been nabbed.
Benton County Sheriff's Lt. Chuck Jones said three or four people have been cited for illegal dumping in the area that's been the focus of the community effort.
He also noted 15 people were cited for trespassing one weekend in March after they were found target shooting off Owens Road despite no trespassing signs.
Robinson said he sees the community response to illegal dumping as something that can be replicated elsewhere. The message, he said, is that "we don't have to accept this. That's the word (for other communities): You do not have to accept this."
He also has this message for would-be dumpers: "Eyes are everywhere."