YOSEMITE NATIONAL PARK, California (AP) ― On busy days, more than 8,000 cars pass through Yosemite Valley in the nation’s third most-visited national park. But, there are only 1,100 parking spaces.

The scarcity of visitor parking in the narrow glacial valley is just one of many challenges facing Yosemite National Park officials say as they launch their third attempt at a master plan to protect its heart, the Merced River.

After striking out twice with the courts, park officials are asking the public to do what $65 million spent over the course of 15 years and four park superintendents have failed to do ― come up with a viable strategy to balance public access against the strict protections that come with the river’s 1987 congressional designation as “Wild and Scenic.”

“The Merced River Plan is a big deal that the public is snoozing through,” said Rick Deutsch, who has written a book about the park. “It could radically alter the facilities, parking and recreation at the park.”

The end result could do the unthinkable in a place that belongs to the people: set limits on the number visitors allowed in the gates, even as some worry whether the park with a hotel with big city prices has enough access as is for those of moderate means.

“In the past the park steered clear of difficult decisions,” said Greg Adair, co-founder of the group Friends of Yosemite Valley, which successfully sued to stop previous plans it deemed inadequate to protect nature. “They left any real capacity decisions to be determined later or never. The court ruled against that approach.”

Yosemite is remarkable among America’s national parks with a combination of stunning beauty, inspiring hikes and easy driving distances from populous metropolitan areas. Despite the park’s 3108 square kilometers of wilderness, 95 percent of the 4 million visitors each year end up in the valley, where senses are overwhelmed by the towering Half Dome and El Capitan granite monoliths, stands of pines and stair-step waterfalls.

It means traffic congestion that can rival a major city, degraded air quality, a lack of parking, and a strain on the centerpiece river that John Muir called the voice of Yosemite.

“We have very limited space on which we can build,” said park spokesman Scott Gediman. “So for us it’s always a question of if we can build.”

It’s not just parking that’s complicating the park’s access problems. El Nino’s fury in 1997 caused the river to breach its banks, obliterating hundreds of lower-cost lodging spaces.

Stressing the park further is recent acknowledgement by officials that the hazards of boulders sloughing off the granite icons along the valley’s edge are a threat to public safety.

Between rock fall risk and floods the park has lost 400 campsites, 500 lodging rooms and 300 employee cabins over the past decade and a half. Many were inside the kilometer wide corridor that the new plan must set aside to allow the river to ebb and flow as nature intended.

The loss of lodging has coincided with increased demands on the revered park. Only the Great Smoky Mountains and the Grand Canyon see more visitors, but over a much larger area.

Recreational demands have become so strained that this year the park instituted a daily lottery for permits to climb Half Dome, where congestion often was so bad that hikers followed heel-to-toe up the steep, slippery grade.

The new plan could force a different way of looking at everything from Yosemite’s restaurants and gift shops to a hike along the river. Those who comment on the plan can assign a value to their favorite pursuits, such as picnicking, rock climbing, rafting and hiking back country trails.

“In past plans the pizza parlors and retail shops were as protected as trail walking or family picnicking,” Adair said. “We think ― and the ruling in the 9th Circuit strongly agreed ― that all recreation is not equal in a protected river corridor ... and those that focus on experiencing nature are deserving of a plan that protects and even enhances.”

Park officials are asking the public to weigh in on everything from picnic area placement and intersection configuration to trail access. They will hold a series of meetings, including one five hours away in San Francisco Nov. 9, a week later in a webcast, and four others in and near the park. The comments will help shape an environmental report due by June 2013.

Almost certainly the end result will be reduced access to the river. Visitors already are funneled to riverbanks along paths instead of cutting through forests. Kayaking and rafting might be limited for the launching impacts on riverbank erosion. Some picnic areas could be closed or made smaller to reduce the trampling of vegetation. High country camp sites could be made fewer.

“We are looking for the public to tell us what they value,” park spokesman Gediman said. “How that will affect park visitors remains to be seen.”