State officials are moving ahead with plans to monitor groundwater contamination around coal ash pits used by Progress Energy and Duke Energy to store waste from coal-burning power plants.

The N.C. Division of Water Quality has asked the state's electric utilities to propose locations for installing wells to monitor groundwater near the pits. The ash pits contain metals such as lead, mercury and arsenic that are left over after coal is burned in power plants.

Risks posed by ash pits were largely ignored until a massive spill took place two years ago at a pit in Tennessee, where a dam gave way, releasing tons of the toxic sludge.

Since then federal regulators have increased oversight and North Carolina officials have taken steps to begin monitoring ash pit safety. The state Division of Water Quality plans to monitor groundwater for potential contamination.

The U.S. Environmental Protection Agency last year reviewed 43 ash pits around the country. Five Progress pits in Chatham County received "poor" ratings as did one near Asheville. The EPA urged the company to analyze the sites for structural stability and to make other fixes.