The annual event drew thousands of volunteers to clean up parks, paths and river banks across the city on Sunday.

2500 people signed up to take part for the 51st year in a row, and for many participants, it’s not just a cleanup, it’s a checkup on the changing city environment.

“This gravel bar is kind of a new thing,” said volunteer John McDermid as he stood on the riverbank. “It wasn't here before the flood five years ago. It seems to act as a comb that picks up a lot of drinking straws, stuff like that.”

Volunteers are looking for anything that doesn’t belong in the natural environment like food packaging and household waste. Once the bags are filled, what's collected is sorted into recycling and trash. Sometimes some pretty strange stuff is found like coconuts, appliances, tires and even Christmas trees with the decorations still on.

Various cleanups take place at different times of the year but Sunday's event has grown into the biggest since being started in 1967. It’s a massive job with more than 200 kilometres in the river pathway network alone, but organizers say it’s well worth it.

“These events we get volunteers coming out cleaning up along the pathways, rivers, making sure our greenspaces are healthy, but it's also great for the wildlife, making sure that all that garbage is out and it won't harm any of them,” said Hadi Fares, City of Calgary Parks.

In addition to taking care of the environment, it’s also a chance for participants to get outside on a nice, sunny day and make a few friends.

“I think it's just a wonderful opportunity to help out around the city. I mean, keeping our green space clean is really important and every bit helps,” said Jason Jing, youth volunteer.

If you couldn’t make it out for the official cleanup, you can still lend a hand. The city also offers free cleanup kits for people who wish to help out at any time of the year. You can find information on that here. If you just want to volunteer on any kind of project, check out the city’s website here.