Rendering of proposed parking garage/desk for the National Zoo from the concept submission to the National Capital Planning Commission. (Michelle Spofford/Smithsonian National Zoological Park)

Over the next decade, the number of visitors to the National Zoo could grow by a million to 3.5 million a year. Many of those visitors will take public transportation, zoo officials say, but many more may drive.

If they drive, they will need parking. That’s why, nearly a decade after it was first proposed, Smithsonian officials are dusting off plans to build a six-story parking garage to accommodate more than 1,280 vehicles.

The revised proposal, unveiled last month, would consolidate four of the zoo’s five surface parking lots into a single garage and repurpose those spaces for new animal habitats and stormwater management.

The zoo has just over 880 parking spaces on its Connecticut Avenue campus.

The $50 million project would increase the total number of spaces to just over 1,400.

Rendering of proposed parking garage/desk for the National Zoo from the concept submission to the National Capital Planning Commission. (Michelle Spofford/Smithsonian National Zoological Park)

For an institution devoted to the protection and care of animals, what’s more significant, according to zoo administrator Dennis W. Kelly, is that the project would free up at least two acres of space for new animal habitats.

“We’re taking asphalt dedicated to cars and giving it back to animals,” Kelly said.

Even so, some residents in surrounding neighborhoods are not sure building a parking garage is the answer. They worry about the impact on traffic and don’t think it will solve the problem of people parking on residential streets. The zoo charges $22 for parking, so visitors often opt to park for free in the neighborhood. According to a zoo survey, about one-third of zoo visitors park on neighborhood streets rather than zoo property.

“It seems to me that rather than expanding parking in the zoo, people should be discouraged from driving to the zoo,” said Alan Weinstein, who lives just north of the zoo’s campus.

An analysis by the District Department of Transportation found that the addition of the garage will likely increase congestion at key intersections in and around the zoo. Jim Sebastian, DDOT’s acting associate director, has concerns about traffic but said there are ways to reduce the potential impact. One the department has long favored is extending service of the D.C. Circulator bus, which stops at the Woodley Park Metro station, north to the zoo. Zoo officials have indicated their support of constructing a bus turnaround to accommodate that shift.

Still, other residents wonder whether the millions spent to build the garage might be better used promoting alternatives, such as shuttle buses to and from the two nearby Metro stations.

“I understand the problem because I live it,” said Bob Ward, who lives near the zoo. “But the whole idea of building the parking garage to solve this problem, I think, is misguided.”

Ward also worries that offering garage parking makes it less likely that visitors will patronize local businesses. That concern is shared by three longtime Advisory Neighborhood Commission members, Lee Brian Reba, Gwendolyn Bole and Nancy MacWood, who represent the areas affected by the zoo.

In a letter, they say that while they support the project, they will work with zoo officials to encourage more people to use Metro in hopes that they will patronize the businesses around the zoo.

Additionally, in the years since the garage plan was first proposed, much has changed about the way people move around.

Uber, Lyft and car-sharing services such as Car2Go and Zipcar have enabled people to get where they want to go without owning a vehicle. That, and a future that includes self-driving cars, has some institutions, including airports and cities, rethinking how they deal with parking.

A traffic study done as part of the garage project found that the number of people who drive to the zoo has dropped from roughly 65 percent in 2007 to 53 percent in 2016.

A staff report from the National Capital Planning Commission (NCPC), which reviews projects on federal land, noted the zoo is unique among federal facilities because of its location and because of the audience it serves.

Roughly 61 percent of the groups that visit the zoo include children. Zoo officials said many of the visitors who come to the zoo “are taking day trips to the city and need to park their vehicle to visit the zoo.”

“We are all seeing a fundamental shift in the way we move around,” Kelly said. “At the same time, we serve 5 million people from Manassas and Gaithersburg. We’re a favorite place for families with children. Getting from Gaithersburg and Manassas with strollers and all the equipment that goes with modern-day child-raising — we think we’ll be more accessible if we give [families] an opportunity to come straight to the Smithsonian National Zoo.”

Plans for a parking garage were first approved by the NCPC in 2008 as part of the zoo’s master plan process. Kelly said the idea has been around since the late 1970s. In this new version, zoo officials have requested an additional 144 spaces. Because the National Zoo is a federally funded institution, Congress would have to give final approval before construction could begin.

The parking garage would be located at the rear of the zoo along North Road and Beach Drive.

It would be built on top of the zoo’s general services building, which houses the commissary where the animals’ food is prepared as well as administrative offices, and extend into the current C parking lot.

The garage would be built through a public-private partnership: The developer would design, build and manage the garage, and the zoo would receive a portion of the parking revenue.

Kelly said that even though a private operator would manage the garage, he does not expect rates to increase significantly. A request for proposals is expected to go out this month.

Construction on the project could begin as early as next year and could be completed in 2020.