On Tuesday night, Charleston City Council will consider requiring the city to compensate property owners when certain zoning changes hurt property values. With Mayor Joseph P. Riley Jr. and the Preservation Society of Charleston already aligning against the proposed ordinance, it could make for one of this year’s livelier debates about zoning.

The ordinance deals specifically with downzoning, in which the city places more stringent limits on how a property can be used. It also requires the city to notify homeowners about proposed zoning changes 30 days in advance and to make an assessment of how much any proposed downzoning would affect property value. Owners would be paid the difference in property value after rezoning takes place.

The part of the ordinance that has some critics up in arms reads: “Not less than 180 days after the date of adoption of a government-initiated downzoning, the City shall: (1) repeal the government-initiated downzoning; or (2) pay just compensation to the owners(s) of real property or an interest in real property that is subject to the government-initiated downzoning.” This section includes exceptions to the compensation requirement if the downzoning is required by federal law, if it is “necessary for the protection of public health and safety,” if it prohibits a public nuisance, or if it was adopted prior to the ordinance’s ratification.

In a letter to council, Mayor Riley said the potential financial expense to the city “cannot be overstated.”

“Most rezonings affect value, at least to some degree,” Riley writes. “This bill would require the City to pay for any negative effects on value, whether the rezoning is directed to uses allowed on the property, or the percentage of a lot that can be utilized, or the height of structures on the property or its landscaping requirements, or whether it requires protection due to its architectural integrity.”

City Councilman Aubry Alexander, who proposed the ordinance to council, says he started looking into the city’s zoning ordinance after a meeting this summer when council was asked to rezone hundreds of properties in Cannonborough-Elliotborough from General Business to a new, more restrictive Neighborhood Business classification. After intense debate, the decisions to create the new zoning category and rezone the properties were deferred for a public hearing, which will also be held at Tuesday night’s council meeting.

In the process of debating the new measures, Alexander says he learned that some of the property owners had never been notified about the potential changes that would affect their properties, and he decided the city’s zoning codes needed revisiting. “The bottom line is we need a process that’s fair, a process that defines how downzoning can occur, and also integral to it is compensation,” Alexander says.

Asked if he had any way of estimating how much the ordinance would cost the city per year, Alexander replied, “The more you use it, the more it costs you. The less you use it, the less it costs you.”

In a letter supporting Mayor Riley’s position against the ordinance, the Preservation Society of Charleston wrote that the ordinance would hobble city planning efforts:

If the proposed ordinance were to pass, the City would be bankrupted if it sought to make changes to current regulations … The City would be unable to protect its residents and business owners from changing conditions that might otherwise lead to inappropriate intensification of commercial uses, overscaled new construction, inappropriate development density, destructive alterations to historic properties, and any other future negative impacts that we can’t possibly predict today.

Alexander says he hasn’t gauged the other councilmembers’ opinions on the ordinance, but he does anticipate “a large crowd from the neighborhood coming there to give their opinion to council.” He says he ultimately sees the downzoning ordinance as a matter of morals. “You have to look at your values — I mean personal values, not monetary values,” he says. “Is it right to take something from somebody else without compensating? If the Preservation Society can say yes it is, God bless them.”

The proposed ordinance will have its first reading Tuesday night, and City Council will allow public comments. The meeting is scheduled to begin at 5 p.m. at City Hall.