The owners of the Royal Hawaiian Golf Club must provide bathrooms, parking and trash receptacles for hikers of Maunawili Falls Trail or face losing their permit to operate the 18-hole course, the city said Thursday.

Art Challacombe, acting director of the Department of Planning and Permitting, has ordered HRT Realty LLC to come up with a plan for the improvements by June 1 and complete them by October or risk losing the 20-year-old conditional use permit that allows the Kailua golf course to operate on 420 acres of agriculturally zoned land.

Originally, the golf club only had to provide public access from the Maunawili Estates subdivision to Maunawili Falls. A surge in popularity of the Windward Oahu hiking trail has led to complaints from nearby homeowners about hikers allegedly trespassing on their property, using their lawns as toilets and vandalizing their cars.

“Something has to be done,” Challacombe said. “This problem has festered for 15 or more years. … Unfortunately, HRT has not stepped up to the plate to work with us.”

The city said HRT, which operates the golf course and clubhouse, has the authority to close access to the trail until October while working on the improvements. HRT must notify the city if and when it plans to close the trail and how it intends to close it.

HRT did not respond to a voicemail and email requesting comment.

Challacombe said he anticipates HRT will comply.

The department’s initial review of the permit was a result of community concern.

Challacombe said that because of the increased popularity of the trail, there needs to be changes.

“With all of these problems, the department realized the trail needs resource management,” Challacombe said.

DPP held a public hearing in February, and testimony was overwhelmingly in support of closing the trail, the city said.

Chris Nakamatsu, president of the Maunawili Estates Community Association, said DPP’s ruling is a first step in the right direction.

“The root of the problem is that the current trail has no stewardship. No one monitors use. No one maintains it. There is no security, no parking, no bathrooms, no trash pickup, even as use has escalated to over 1,000 hikers a week,” Nakamatsu said.

Nakamatsu said the trail has been destroyed as a result of the overuse.

“Human waste and filth wash down the mountains to Kawai Nui Marsh,” she said. “The trail itself is badly eroded with many spur trails to nowhere. Hikers come out covered from head to toe in mud with no place to wash off. Hikers often are lost at night wandering around the mountain and needing to be rescued in the dark. Hikers are getting hurt almost every week on this trail — many serious enough to require helicopter rescues all at taxpayer expense.”

Honolulu City Councilman Ikaika Anderson said HRT must bear some responsibility to the community.

“I don’t want to see access closed, but I do want to see the trailhead moved to another location on HRT Realty property,” Anderson said. “HRT bears some maintenance responsibility, and they should allow for parking accommodations and restroom access. Even Porta-Potties are better than what we have now, which is nothing.”

If hikers decide to ignore the closure, they would face charges for trespassing on private property.

Nakamatsu said the Maunawili community is planning to meet with the Honolulu Police Department to discuss what to do if HRT closes the property and hikers trespass.