NASHVILLE, Tenn. (AP) - A new report by an environmental group says the Tennessee Valley Authority has polluted groundwater supplies at all its coal-fired power plants nearly five years after a massive coal ash spill at its Kingston power plant. The report by the Washington-based Environmental Integrity Project says TVA could be doing more to protect drinking water supplies from harmful substances. The ash is a byproduct of burning coal at power plants, and the EPA is currently considering whether to classify it as a hazardous material. The group's report was based on data from TVA monitoring wells, the Tennessean reports (http://tnne.ws/1hSNs6m). It identifies toxic pollutants including arsenic, boron and sulfate. TVA said in a statement it was moving aggressively to prevent future damage to water supplies from coal ash.