A longstanding dispute between Ford Motor Co. and Ramsey County is scheduled to move forward in Minnesota Tax Court in December.

The seven-member county board met Tuesday in a closed-door executive session to consider legal options in the case, which relates to the automaker’s property tax assessments from 2006 to 2010.

The company, which shuttered its 80-year-old Twin Cities Assembly Plant in Highland Park in December 2011, has sought to lower the property’s assessed value and tax payments, in part because of unknown amounts of contamination on the site.

Ford has argued in negotiations with the county that the site, which spans 122 acres above the Mississippi River bluffs, has no market value once cleanup costs are deducted, and that the company should be reimbursed for its tax payments, plus interest.

That amount would total $10.6 million in repayments to the automaker. “Ford’s valuation for all five years is zero,” said Ramsey County Assessor Stephen Baker.

Ford also argued that the property should be assessed as if the site were industrial land, rather than its highest and best use, which would include commercial land with a higher assessable value. The company is current on its tax payments.

The Minnesota Tax Court is scheduled to begin trial on Dec. 9, following legal motions on Dec. 2 pertaining to the admissibility of witnesses and consultant’s findings.

Baker said the county assessed the market value of the Ford land at $46.1 million in 2006 and $33.1 million in 2010, the last year included in the suit. Ford has since filed lawsuits in Ramsey County District Court pertaining to tax years 2011 and 2012, though those are not scheduled to be heard by the tax court in December.

Ramsey County won a partial victory in the case five months ago. Owners of contaminated properties can reduce their tax burden by identifying cleanup costs. In June, however, the Minnesota Tax Court found that the Ford site had no “contamination value” under the law because Ford had not completed an environmental investigation and response action plan.

The Ford campus was placed on the state’s Superfund list of contaminated properties in 1992 but later removed after areas with underground storage tanks were cleaned up.

Ford is now demolishing buildings on the 67 acres that make up the core-building area. The automaker is working with St. Paul and is expected to begin marketing the site to developers in 2015.

Frederick Melo can be reached at 651-228-2172. Follow him at twitter.com/FrederickMelo.