Tap water in some Denver homes contains elevated lead. Now Denver Water, CDPHE and others are fighting about what to do.

Six years after Denver Water detected elevated lead in tap water at some homes, state health officials have ordered the injection of a chemical into water supplies to slow lead-pipe corrosion — but utility officials are resisting.

The chemical, orthophosphate, would harm humans and hurt the South Platte River basin, worsening algae blooms and increasing the cost of cleaning wastewater, Denver Water contends. Utility officials propose solving the problem with a different chemical to lower the acidity of drinking water, combined with accelerated replacement of old lead plumbing.

This disagreement has escalated into a legal fight, with Denver’s Metro Wastewater Reclamation District, Aurora and the Greenway Foundation battling the Colorado Department of Public Health and Environment in state court — possibly delaying action to deal with the problem.