The Arden Hills City Council has rejected Ramsey County’s request for a mediator to hash out development differences at Rice Creek Commons, the largest shovel-ready tract of land in the county.

At their meeting Monday, City Council members accused county leaders of being evasive and not disclosing precisely what they want to build on the former Twin Cities Army Ammunition Plant (TCAAP) property, including the number of homes the county hopes to put on the 427-acre site.

“It is impossible for the city or the public to evaluate the traffic, environmental and service delivery impacts of ‘more,’ ” according to a letter drafted by city officials and sent to the County Board.

County officials responded Tuesday, saying that they had arrived at “a critical time for the project” because the market currently favors development and funding deadlines are fast approaching.

“With the rejection by Arden Hills of our proposal for professional mediation, we are currently evaluating our options for moving this project forward,” said Kari Collins, the county’s economic development director, in a statement.

Arden Hills leaders indicated they’re not interested in abandoning the preliminary master plan approved by both the city and county in 2016 that calls for 1,460 housing units and a mix of office, commercial and retail space.

“There is an agreement that has been in place for two years,” City Council Member Fran Holmes said Monday. “I don’t know what we would be mediating. We’ve already said 1,460 units. Period. Done.”

But Collins said that mediation was part of the 2012 joint agreement reached between the county and city to oversee redevelopment of the site.

“We have tried working through the Joint Development Authority for nearly a year without real progress or results,” she said. “The first step in solving a problem is to recognize it.”

City and county officials have been sparring over the TCAAP site for years. The county bought the land from the federal government in 2013 and cleaned it up. But development needs city approval since the property is in Arden Hills.

Last fall, Ramsey County Administrator Ryan O’Connor sent a terse letter to Arden Hills indicating the county wanted more housing than laid out in that plan.

There are also disputes about how much money the city will contribute, O’Connor said. The county, which has spent more than $40 million on the project, asked the city to agree to mediation earlier this month.

“Density and affordable housing are core issues in building a sustainable community at Rice Creek Commons,” he said in the letter. “But Arden Hills does not appear open to negotiating these issues further.”

At Monday’s work session and meeting, all five members of the Arden Hills City Council took turns criticizing the county’s negotiating tactics and what they said were unclear demands. Council Member Brenda Holden said the county has not been negotiating in good faith.

“They never want to come to the table unless they can shove it down the city’s throat,” Holden said at the work session.

City leaders said they felt that county officials were portraying the city as unwelcoming and inflexible. Council members pointed out that Rice Creek Commons will double the size of the city, which now has about 10,000 residents, and that they want to control risks if the economy worsens and the development stalls after they spend millions on infrastructure.