In the wake of a debate that seemed to pit developers against preservationists, the city of Des Moines is preparing amendments to an ordinance that governs the designation of historic landmarks.

If approved by the City Council, changes would apply in cases where property owners object to the designation.

The debate was triggered late last year when historic preservationists sought landmark status for the former Riverfront YMCA at 101 Locust St., a site overlooking the Des Moines River that has long been considered the prime development spot in the city, if not the state.

Hubbell Realty Co. is considered the leading contender to buy and develop the property, minus the 58-year-old Riverfront Y, which is scheduled to be demolished this summer, with the cost fronted by Polk County.

If that sale should fall through, Des Moines Redevelopment Co., the nonprofit organization of local businesses and business leaders that was formed to purchase and hold property for future development, has a $4.5 million option to buy the site.

Not long after the 1.86-acre site, which is owned by the YMCA of Greater Des Moines, went on the market in September 2013, historic preservationist Jack Porter and others launched a campaign to have it declared a historic landmark, a designation that would have complicated redevelopment efforts.

The YMCA opposed the designation.

So did the Des Moines City Council, which turned down the application in November 2014. The council also asked city staff to revisit the historic landmark ordinance, with some council members saying a single resident should not be able to launch a time-consuming and expensive process.

The city’s Landmark Review Board, Plan and Zoning Commission and City Council will consider the request, with public hearings before the Plan and Zoning Commission and City Council, which has final say on the issue.

According to a staff report today to the city’s Urban Design Review Board, a nomination submitted over the objection of the property owner would require signatures from 50 people eligible to vote in city elections. In addition, a supermajority of the City Council (six members of the seven-member council) would be required to overcome the written objection of a property owner.

Both the Mayor’s Task Force on Historic Preservation and Demolition and the Historic Preservation Commission support the 50-person petition amendment and both oppose requiring more than a simple majority vote of the council to override a landowner’s objection, according to the staff report.

The Urban Design Review Board voted today to support the petition but not the supermajority vote. The Landmark Review Board is made up of members of the Urban Design Review Board and Historic Preservation Commission.

The Plan and Zoning Commission will consider the changes at either its July or its August meeting.

Porter, a former Des Moines councilman, said today that he too supports the petition, remarking that he could have gathered 5,000 signatures of people supporting landmark status for the Riverfront Y, which, he has argued, is notable for its architectural style and brick murals. Read more about efforts to replicate the murals.

He said his efforts had created “dust and caused heartburn” for developers but contained the message that “protecting landmarks is important.”

The amendment calling for a supermajority vote creates “an almost impossible threshold,” he said.