It wasn’t planned, it wasn’t on the calendar, yet it was important enough to spur people into action.

The April 23 Hawaii News Now report on the litter at Honolulu’s Lili‘uokalani Botanical Garden prompted Sustainable Coastlines Hawaii to organize what they called a "pop-up cleanup" four days later.

And why not?

"We have a group of willing people and a network of followers that probably would rally together to take care of this," said executive director Kahi Pacarro. "We usually focus on beach cleanups, but what happens is all that trash strewn across the banks of the river — less than a mile away from the ocean — washes out to sea."

At the suggestion of one of its members, Sustainable Coastlines Hawaii, a 501(c)(3) nonprofit founded in 2011, put the word out via Facebook and Instagram. Close to 30 people volunteered to help clean the 7.5-acre garden, focusing mostly on the streams in the upper area of the park.

The group has a core of regulars but many first-timers came for this cleanup.

"A lot of them were people we had never met before," said Pacarro. "They were stoked. We were happy."

Volunteers spent April 27, a Sunday, picking up trash from the streams including plastic bags, utensils, water bottles, disposable razors, cigarette butts, plastic-foam ramen bowls, milk cartons, aluminum cans and paper plates. Larger items included mattresses.

Pacarro said volunteers were unable to weigh the trash, but he estimates at least a ton was collected.

Some of the trash appears to have come from nearby homeless encampments after a big rain. Some of the items picked up indicate "a dark aspect to the stream banks," he said, including "people getting ready for the night."

There were numerous condoms, at least one needle and tubes of lubricant.

"Thank goodness some of our crew had strong stomachs," said Pacarro. "They just pulled up their gloves extra tight and picked up the disgustingness."

The pop-up cleanup was organized quickly with the approach of just getting it done. Hashtags on the group’s Facebook included: #stopwhining, #justgetitdone and #dosomething.

But it wasn’t the nonprofit’s first pop-up cleanup. The first one took place in January at China Walls, where volunteers removed lead weights, fishing lines and hooks from the bottom of the ocean. Only experienced divers participated, said Pacarro, on a day when the ocean was flat.

Pacarro says the group will hold pop-up cleanups from time to time, but typically won’t announce them until two days prior, depending on what the project entails.

He says they hope to return to the garden for follow-up cleanups in collaboration with the city.

"It’s so beautiful over there and right in the heart of Honolulu," he said. "It’s this gem with a stream and waterfall running through it."

A city sign on premises says: "Welcome to Lili‘uokalani Botanical Garden. Let us take care of this special gift."

Part of the message the group wants to get out is how litter on the streets eventually ends up in storm drains and eventually the ocean.

For Earth Day in April, the group hosted a Mauka to Makai celebration at Kualoa Ranch, offering hundreds of volunteers the opportunity to work in a loi (taro patch), restore a fishpond, clean beaches and restore native plants at various sites.

The next scheduled beach cleanup is in collaboration with the Kokua Hawai‘i Foundation June 21 at Point Panic in Kakaako. Check-in time is 9:30 a.m.