Dirty diapers. Empty beer bottles. Discarded coffee cups.

These are things you’d expect to find in a garbage dump, not on a hiking trail.

So Sara Thein picked up a garbage bag and started a movement.

Thein, 28, of Snohomish, is the founder of Clean Up Washington, an all-volunteer group that organizes events to pick up litter on trails, in parks and green spaces around the state.

The idea, Thein says, is to balance environmental stewardship with hiking, while also promoting Leave No Trace principles, such as disposing of waste properly, respecting wildlife and being considerate of other trail users.

“A common motto I tell volunteers is, ‘No piece of trash is too small,’” she said. “It all adds up.”

Using trash pickers, gloves and heavy-duty bags, Thein’s volunteers have removed garbage from scenic places such as the Lake 22 trail off the Mountain Loop Highway, in Wallace Falls State Park and around Lake Serene. She’s organizing another cleanup hike June 1, coinciding with National Trails Day, at Heather Lake Trail east of Granite Falls.

Litter on trails are more than an eyesore; it can contaminate water sources and harm wildlife that ingest it. Thein says she has found dead small animals inside coffee cups; the critters crawled inside to find food but became stuck and died.

Thein, who was raised by environmentally conscious parents in Chicago, graduated from Purdue University in Indiana and moved here seven years ago. Her day job is flight sciences engineer for Boeing.

She launched the Clean Up Washington group in April as a way to celebrate Earth Week.

“I didn’t start hiking until late 2015, but I kind of noticed then that I had very profound sense of respect and connection with nature,” she said. “I’d always tried to do my little part by picking up trash, but never to the extent of bringing a 13-gallon trash bag with me.”

Thein spent all seven days of Earth Week packing out trash from various trails with the help of her husband, Derek Thein. She also posted updates on Clean Up Washington’s Facebook page, as well as on Instagram and Reddit to encourage others to join the effort.

In seven days, volunteers had filled about 20 13-gallon trash bags. Lowell Riverfront Trail in Everett, which she cleaned up on Earth Day, April 22, was the biggest offender — that’s where she collected so much litter that she filled nine trash bags to the brim.

The garbage was disposed of in trash cans at trailheads, when available. When they weren’t, volunteers were in for long, smelly rides to the dump — especially when the bags were filled with dirty diapers.

They plugged their noses, rolled down the windows and toughed it out.

After Earth Week, Thein kept the momentum going, drawing volunteers to events at Poo Poo Point Trail near Issaquah and Paradise Valley Conservation Area east of Maltby. She hopes to expand the program across Washington and eventually to other states. Already, Thein has inspired others to organize events in Seattle and Enumclaw.

She said a team of eyes working to spot trash on a hiking trail makes a big difference. Litter is often discarded just off the path where hikers assume it can’t be seen. And smaller pieces of trash, such as the corner wrapper from an energy bar, are hard to spot.

“I’ll post a picture on Facebook saying I just packed out 5 pounds of trash, and someone will comment saying they just hiked there and didn’t see any trash,” Thein said. “That’s a common response, but once you start looking for it and knowing what the common items are, you’ll start to notice.”

It’s a fine line, though; Thein says having too many volunteers cleaning up at the same time goes against Leave No Trace ethics, which call for as little user impact to the trail as possible. It’s more effective, she said, to spread out on multiple trails, with just a handful of volunteers hiking each one.

Dog waste bags, chewing gum and glass bottles are the most common items Thein finds on trails. She also picks up orange and banana peels. It takes up to six months for orange peels to decompose and as many as two years for banana peels to decay.

Her efforts haven’t gone unnoticed. Other trail users express their gratitude whenever they see Thein and volunteers packing out loads of garbage.

“‘You’re doing God’s work’ is a phrase we hear a lot,” Thein said. “It keeps you going once your arms and shoulders are sore.”

Evan Thompson: 425-339-3427, ethompson@heraldnet.com. Twitter: @ByEvanThompson.

If you go

Clean Up Washington’s next event is June 1 at Heather Lake Trail, 17 miles east of Granite Falls. Meet at the trailhead at 9 a.m. A Northwest Forest Pass is required. Bring your own gloves and tools to pick up trash. Garbage bags will be provided.

Getting there: Follow the Mountain Loop Highway for about a mile past the Verlot Public Service Center. Turn right on Pilchuck Access Road. The trailhead is 1.3 miles up the road.

Go to www.facebook.com/cleanupwashington for more information and to RSVP.