For months San Diego has debated the Chargers’ future and lately has focused on a 15-acre downtown site for a new stadium.

But a challenge 10 times bigger lies eight miles north: The future of Qualcomm Stadium and its 166-acre site.

Ever since the stadium opened in 1967, urban planners, politicians, Mission Valley residents and developers have eyed the site as an opportunity waiting to happen — to turn a centrally located, underutilized plot of city-owned land into something more than just an 18,500-space parking lot and occasionally used stadium.

In the last 50 years, the valley has seen untold numbers of condos, apartments, shops, offices, hotels and restaurants fill up the 10-mile-long valley. New plans are afoot to redevelop the Riverwalk golf course, Mission Valley mall, auto dealerships, low-rise garden office parks and obsolete motel properties.

Now a plan is in the works to tackle the biggest underdeveloped site of all.

A citizens initiative gathering signatures for a November election would authorize the sale of the Qualcomm site to San Diego State University, UC San Diego , the San Diego Community College District or some combination. They would be required in return to convert it into an educational complex, sports and recreation complex and an “urban rivers scientific interpretative center.”

The initiative also includes a means to build a new Chargers’ stadium and expand the convention center east of Petco Park downtown, ideas that have stalled for years.

“One thing that’s been happening over the past many years is that nothing has changed,” said former City Councilwoman Donna Frye, a key supporter of the initiative. “We’re still in the same place we were 15 years ago. At least with this proposal it lays out some ideas and opportunities to address all this.”

The opportunity in Mission Valley could be game changing in many ways.

▪ An asphalt no-man’s land could become a vibrant urban center filled with thousands of students, park goers and fans going to a new Aztec stadium that doubles as a major league soccer venue.

▪ A proposed 50-acre park could fill a long-felt need to meet recreational needs for Mission Valley’s 22,000 residents and restore a portion of the San Diego River.

▪ The car-oriented nature of Mission Valley, dating back to the 1950s, could be undone with the reconfiguration of the streets, roadways, mass transit and biking and walking paths, as modeled at a replanned Qualcomm site.

Said architect and urban planner Frank Wolden: “Why is it that Mission Valley is one-tenth the density of downtown and the traffic is worse? It’s because you have to drive across the street to go from store to restaurant.”

The future of the “Q” property comes at the same time the Mission Valley Planning Group is revising its 1985 community plan. City planner Nancy Graham said the review of the valley’s current conditions is done and meetings are scheduled for April and June to consider alternatives for the future. Public workshops would happen this summer with environmental analysis, community review and City Council action later. The Qualcomm redevelopment would be folded into the final plan.

The San Diego River Park Foundation also is at work independently to imagine how the park will fit into the larger river park planned to stretch from the beach to the mountains.

“It’s that big a deal,” said Executive Director Rob Hutsel.

The foundation has asked landscape architect Glen Schmidt to come up with various scenarios that Schmidt said might include a lake, restored Murphy Canyon Creek, revitalized wildlife wetlands, ballfields and pathways.

Clearly, the biggest piece of the stadium redevelopment idea involves higher education:

▪ San Diego State would get a new Aztec stadium and space to grow. The campus currently occupies only 277 acres, just 111 more than at Qualcomm Stadium, for its 30,000-student population.

▪ UC San Diego, with a student population of 33,735, would get a new field research unit. The campus occupies more than 1,100 acres.

▪ Students would get new housing that might be attractive enough to lure them away from the jury-rigged “minidorms” that property owners have created in College Area single-family homes.

Proponents, particularly former state Sen. Steve Peace, D-San Diego, see it as solving several problems at once — namely relieving SDSU’s land shortage; advancing San Diego’s big ambitions as a science and environmental leadership powerhouse via the new research center; and taking off the city’s hands an obsolete stadium and the maintenance headaches that come with it.

“This is something that has its payoff long after you and I are dead and long gone,” Peace said in an interview.

Neither campus has endorsed the concept, but both SDSU President Elliot Hirshman and UC San Diego Chancellor Pradeep Khosla have been briefed and reportedly are interested.

The higher education focus grabbed the attention of retiring Sen. Marty Block, D-San Diego, who taught at SDSU for 26 years and whose district includes both Mission Valley and the campus. He mentioned the idea at a subcommittee hearing he chaired Thursday on educational capital needs in the fiscal 2017 state budget.

“I wouldn’t foreclose looking at additional ideas,” Block said. “But I think studies have shown that the best economic driver for that area is not housing or shops but an educational center, particularly with a biotech science center.”

But what exactly is the plan for what Block is calling Aztec Riverfront Park?

JMI Realty, the company headed by former Padres owner and SDSU/UCSD benefactor John Moores, spent about $200,000 last year to test various concepts for the property with and without an NFL stadium. Peace, an adviser to Moores, has been sharing the concept publicly and privately over the last few months.

“The work that has been done to date on Mission Valley is conceptual,” Peace said. “Its purpose is to understand the capacity of the site. Actual plans for use would be developed over a period of years while the Chargers continue to play in Qualcomm Stadium.”

As developed by the architectural firm Carrier Johnson + Culture, the non-NFL “education and science campus” could have these components:

▪ Student housing: 3,500 apartments housing perhaps 14,000 students. SDSU currently houses 4,500 students on campus, UCSD, about 13,000.

▪ Faculty housing: 400 apartments averaging 1,000 square feet each.

▪ Academic offices and noninstructional space: 630,000 square feet that could house research facilities and such things as KPBS and the SDSU Foundation.

▪ Commercial offices: 200,000 square feet in two buildings.

▪ Retail space: 50,000 square feet serving student and faculty residents and daytime workers.

▪ Hotel: 200 rooms.

▪ Stadium: 35,000 to 40,000 seats for college football and major league soccer, campus commencements, concerts and other public events, located at the northeast corner of the site. Qualcomm Stadium would be demolished and replaced by the green space called “The Commons” and “The Bowl” amphitheater -- gathering places for concerts and informal recreation.

▪ Park space: A 28.8-acre river park and 10.2 acres of open space, somewhat smaller than the citizens initiative calls for and 65 acres desired by the San Diego River Park Foundation.

▪ Parking: 9,000 spaces in two big garages and 5,760 spaces in surface lots and below or alongside the residential and hotel buildings. That is much less than normally required, because student parking would be provided for only one space for every other apartment. In other words, seven of the eight students in two four-bedroom units would have to rely on car pooling, public transit, bikes and their own feet to get around.

Architect Gordon Carrier carried the analysis one step further and imagined an alternative approach to demolishing the Q new Aztec stadium. He said it’s possible to tuck a small stadium into the existing facility and enclose enough of the perimeter space to create as much as 800,000 square feet for faculty and administrative offices, research labs and classrooms. SDSU counts 3.9 million square feet of academic and administrative space on campus.

The cost of either stadium concept has not been calculated but Carrier said it’s likely half of what an $800 million NFL stadium would have cost. An adaptive reuse option would not only prove more environmentally responsible but also preserve one of San Diego’s most recognized landmarks.

"We'll listen to any idea that comes to us, but obviously a critical step in deciding the fate of the Mission Valley site will be knowing what's going to happen with the Chargers," said Craig Gustafson, spokesman for Mayor Kevin Faulconer .

Developers Dennis Cruzan and Steve Black analyzed the site for JMI Realty from a feasibility standpoint and said it might take five years to secure approval and 10 years to complete.

“We believe the university kicks off more of that development than a (NFL) stadium does in our view,” Cruzan added.

Cruzan and Black did not calculate an overall cost estimate but they discounted the predevelopment land value, to only $50 million given the cost of offsite improvements, entitlement processing and other “soft” costs that a developer or university consortium would have to cover.

Nathan Moeder at the London Group Realty Advisors consulting firm and other experts indicate JIM's redevelopment could cost about $2.4 billion, based on average costs applied to the various elements in the plan.

Other developers and urban experts have raised questions about the JMI approach.

David Malmuth, a partner in the I.D.E.A. District in downtown’s East Village, said he wishes the Chargers would remain in Mission Valley and leave its preferred downtown site for high-tech companies and university-related research facilities. He and his business partner Pete Garcia led a workshop Saturday on that alternate vision at the Newschool of Architecture and Design.

“Simply putting an expansion of SDSU or the UCSD campus in Mission Valley doesn’t accomplish the much larger goal of a cluster to drive high-wage jobs,” he said, because it would not be located in a vibrant urban center that millennials and start-ups crave.

Development consultant Gary London said the JMI plan misses the opportunity to create a much denser urban node with more housing and commercial development that otherwise will scatter to other parts of the county. Plans he previously released called for nearly 6,000 housing units and 2.8 million square feet of offices and related retail alongside a new NFL stadium.

“What could be created on the Qualcomm site would be a new class of master-planned community with a commercial campus, which would include high-rise office and intensive residential, commercial and other uses,” he said.

Just because Mission Valley has had little or no new office development doesn’t mean that big national developer wouldn’t seize the opportunity here, he said, and outside firms have told him as much, he added.

Marco Sessa, development vice president at Sudberry Properties, oversees the 266-acre, 4,780-home Civita master plan community now under construction off Friars Road. He said the educational theme might work at Qualcomm but it would have to be attractive enough for students to live there.

“At the end of the day you are competing with other places that are out there for students,” he said.

He also said the development will have to pay its fair share in public improvements, pencil out financially and secure public support.

“Today most sophisticated real estate development companies understand that they need support and getting that support comes with public benefits,” he said.

Jeff Marston, a former state Assembly member and former SDSU alumni president, organized a panel discussion last month on campus featuring Peace, Cruzan and Black and said their plan was well received.

“If you want to go to the Gaslamp Quarter, you jump on the trolley and there you go,” he said. “It’s as accessible, if not more so, for students to live in Mission Valley than if they were living on campus. I think it would be really cool. Obviously, it has to be planned correctly.”