A new report says that a dangerous chemical detected in groundwater near a Superfund site in New Jersey could pose a threat to a nearby reservoir that provides drinking water to as many as 3.5 million people.

The report by the Jacobs engineering firm for the Wanaque Reservoir operators recommends treating the contaminated water at the Ringwood Mines site, once used by Ford Motor Co. and now polluted with paint sludge and industrial waste.

The Record reports that the probable cancer-causing chemical, 1,4-dioxane, is the main concern. The chemical hasn't been found in the reservoir but high levels have been found in groundwater and brooks that feed into the reservoir.

The report also says the reservoir isn't outfitted to remove the chemical.

Federal environmental officials are reviewing the report.