We cannot speak authoritatively about whether any toxic substances lurk beneath developer Patrick Conley’s property on Allens Avenue in Providence, but it seems a wise move for the city to limit public activities at the site.

The city’s Zoning Board of Appeals recently canceled a scheduled carnival, and spurned Mr. Conley’s proposal for an outdoor tiki bar to serve passengers of the Providence-Newport ferry, a boat service that departs from his pier.

Myrth York, chairwoman of the panel, said Mr. Conley never made clear that his property — built on top of the heavily polluted site of a former gas-manufacturing plant and petroleum-storage depot — was safe for the public, including young children. Mr. Conley, calling the ruling “mean-spirited,” insisted that the contaminated land was covered with sufficient clean soil and gravel.

One thing seems clear: The property, in the middle of a working industrial port, is absurdly ill-suited for Mr. Conley’s proposed uses. A carnival for children along a busy street on an environmentally questionable lot in the midst of a heavily industrialized port makes little sense, when there are many safer sites throughout the city and state. It makes even less sense, at least considering the big picture, to use that valuable port land for a parking lot, something Mr. Conley has won permission to do.

The dispute is yet more evidence that the state needs to better preserve its working waterfronts to protect high-paying jobs and generate economic activity. Instead of letting developers try to turn the Port of Providence into yet another playground with marinas, festivals and hotels, the state should make sure Rhode Island preserves its ports for industrial activities that take place there. Such ports, with high-paying jobs, are important economic engines for the entire state, and they cannot be moved anywhere else.