The powers of a Historic Preservation Commission to keep tabs on significant older properties are fleshed out in the city’s proposed historic preservation ordinance.

The contents are going to a public hearing at tonight’s Common Council meeting. The Council likely will vote to enact the law at its Sept. 17 business meeting.

A group of volunteers led by city resident Bob Hagen has been at work for more than a year writing the law. Hagen said its aim is not necessary to restore the grand old but to protect what’s left of it after decades of creeping change.

“We’re not trying to freeze things like we’re in the 1800s, we’re trying to not destroy what’s there. That’s the whole idea,” Hagen said.

The law creates a preservation commission that would identify properties — individually or in neighborhoods/districts — worthy of structural and aesthetic protection. Once properties were formally designated, their owners would not be allowed to make any exterior changes without the commission’s approval.

Interior changes and uses would not be subject to the commission’s OK, Hagen said.

The law is aimed at protecting the outer features only of properties found to have some historic, aesthetic, architectural or archaeological significance to the city, state, region or nation.

“Significant” sites could be those where a particular architectural, construction, or composition style is seen or the property is the work of a noted master builder, engineer, designer, architect or landscape architect; a significant event occurred or the property is linked with notable people; the property exemplifies heritage; or its design is innovative.

Currently, there are more than 20 properties in the city listed with the National Register of Historic Places, including the Historic Post Office, the Clinton/Gooding streets industrial district and miscellaneous stone houses. Without a local preservation law, Hagen said, there is nothing stopping owners from changing, covering or deleting their historic features.

The law puts the preservation commission in charge of recommending landmarks and the parameters of historic districts. Final decisions are up to the Common Council.

To decide which properties and neighborhoods deserve protection, the city would hire an architecture specialist to survey properties constructed before a certain year. The preservation committee picked 1940 as its cutoff, while the State Office of Historic Preservation recommended 1960.

About 5,100 properties in the city were built before 1940. The architecture specialist would pick particular properties for inspection of structural “intactness” and historic status, Hagen said. Landmark and district listings would be derived from that closer look.

Surveying half of the 5,100 properties would cost about $50,000. The city has asked the state for a grant to cover 60 percent of the tab.

Once properties are designated, the preservation commission would take charge of approving changes on them. When owners want to alter exterior features, the commission would have a say in the proposed dimensions, elevations, color, materials, lettering and/or lighting.

The law would not compel property owners to undertake restoration, but it would demand enough upkeep to prevent architectural features being lost. Allowing deterioration of exterior walls, roofs, chimneys, foundations, stucco and mortar on listed properties, or failing to waterproof their base features, would be considered a crime.

“We’re not in the business of telling people what to do with their property, but if you have historic property you have an obligation to preserve it,” Hagen said. “The law gives property owners confidence that if they invest in it, the value will be retained or enhanced because the neighborhood is protected.”

Formal historic preservation will help boost property values, stabilize neighborhoods and build cachet for the city as a heritage tourism destination, Mayor Michael Tucker said. He acknowledged some owners probably will dislike having to submit to an extra layer of authority when they want to work on their property, but said, “overall, it’s going to protect our city. It’s for the general good.” The city wants to be a “certified local government” under state and federal preservation laws, so that it can qualify for state preservation grants and the commission can nominate properties for the National Register. Enacting the law and appointing a commission are the required first steps; obtaining certified status could take until 2010, Hagen said.

Property owners who restore landmarks can qualify for federal income tax credits and apply for grants from preservation interests. The state Legislature OK’d a state income tax credit for historic preservation but it hasn’t been signed by Gov. David Paterson yet.

Hagen said the city could adopt state-authorized legislation giving temporary assesssment exemptions on the value of historic-structure improvements; in the case of residential projects, the break would be in addition to a general home improvers’ assessment exemption.

The public hearing on the proposed law will be held immediately after the opening of the 6 p.m. Council meeting. Three other public hearings will follow, on a proposed business sign law, proposed amendment to the sewer rents schedule and proposed local hiring policy for municipal contractors.

Contact reporter Joyce Miles at 439-9222, ext. 6245.