Mayor Rahm Emanuel’s $30 million plan to merge the Jackson Park and South Shore golf courses into a single, championship-caliber course will require costly shoreline improvements and the closing of Marquette Drive, a chief proponent said Monday.

Brian Hogan, co-founder of the Chicago Parks Golf Alliance, said golf course architects from the firm owned by Tiger Woods have determined that the project won’t work unless the road is closed between Cornell and Lake Shore Drive.

“Marquette Drive bisects right through two large portions of Jackson Park and cuts it into two very narrow strips. Closing that road would connect more green space for the availability of golf holes. We don’t think we could build the character of open course that Tiger Woods Design is looking to do the way Marquette limits the direction of play,” Hogan said Monday.

“If we have the ability of routing golf holes both from north to south and east to west in that portion, it will also open what we hope to be expanded youth programs and a short-course learning area. It adds to the green space we’re able to work with.”

Hogan said he does not believe the proposal to close Marquette Drive will be nearly as controversial as former President Barack Obama’s plan to close Cornell Drive between 60th and 67th Streets to add as much as 5 acres of new park land for his presidential library.

Thousands of motorists use Cornell Drive every day to connect from South Lake Shore Drive to Stony Island Avenue and the Chicago Skyway.

“Cornell has a greater impact as a commuting road whereas Marquette Road bisects straight through the park, so it creates much more green space. It doesn’t quite have the impact upon daily commutes that Cornell does,” Hogan said.

“We’re hoping to mitigate the amount of crossings between golf carts and golfers and maintenance equipment and cars for safety issues throughout the whole community,” he said. “We’re excited that President Obama called upon improving the dynamic of all activities in Jackson Park. This gives the Tiger Woods design team a tremendous opportunity to design a golf course in a complementary fashion.”

The Chicago Sun-Times reported in early March that the golf course merger that gained momentum when Obama chose Jackson Park for his presidential library had hit a fundraising snag, derailing Park District Supt. Mike Kelly’s plan to begin construction this spring.

At the time, private donors were waiting to see results of design and engineering studies before writing checks for the project.

They wanted to know “what the holes were going to look like and how they would interact with an underpass or any other street or public space.”

They also needed to know whether the condition of the shoreline would make it possible to follow through on a potentially “spectacular” plan to build holes adjacent to the lake or whether potentially costly shoreline improvements will be needed.

On Monday, Hogan disclosed that shoreline conditions uncovered by civil engineers from SmithGroupJJR working in conjunction with golf course architects from Tiger Woods’ firm are worse than anticipated and more costly to repair.

“The study has revealed significant shoreline erosion, danger to current conditions at multiple points of the South Shore Cultural Center — not just at the golf course but throughout and near the intersection of 67th and South Shore Drive,” Hogan said.

“There are steel pilings sticking up in the beach, crumbling steel walls, unsightly elements from the golf course as well as the trail and beach areas of the Cultural Center. These sorts of things don’t exist on the North Side. The golf course is often flooded around the second hole, and it’s not just rain water. That wave action splashes over. That’s not a sustainable state for the golf course.”

Although private donations are expected to cover 80 percent of the golf course project, public money will be used to make shoreline improvements and build new underpasses — at 67th Street and South Shore Drive and at Jeffery Boulevard and 66th Street — needed to make the new golf course work.

The 67th Street underpass alone could cost Chicago taxpayers at least $11 million.

On Monday, Hogan was asked whether he was concerned that the cost of those public improvements would make the golf course project a non-starter at a time when there are more important demands for the shrinking pot of public money.

“We believe these are improvements that are going to happen regardless of the golf course project to remedy significant erosion to the southern lakefront and the street-level crossing at 67th and South Shore Drive that’s very dangerous to pedestrians,” he said.

“We are looking forward to learning the full details and recommendations of the engineering study. But we remain confident in Chicago Parks Golf Alliance ability to fundraise private charitable donations. We’re also confident that, through raising this money, it will enable the Park District to maintain rates near current levels for longtime players.”

Kelly could not be reached for comment. He has promised not to “put a shovel in the ground” until he has community support and at least $5 million in private contributions.