Shares of Duke Energy Corp. fell 1.0% in afternoon trade Monday, after the electricity generator said based on current estimates and closure timeframes excavation, excavation of its coal ash basins in North Carolina will add $4 billion to $5 billion to the current estimate of $5.6 billion for the Carolinas. "We are making strong progress to permanently close every ash basin in North Carolina in ways that fully protect people and the environment, while keeping costs down as much as possible for our customers," Duke Energy said in a statement. The statement comes after the North Carolina Department of Environmental Quality (NCDEQ) determined that excavation of six sites--Allen, Belews, Creek, Cliffside/Rogers, Marshall, Mayo and Roxboro facilities--"is the only closure option that meets the requirement of Coal Ash Management Act to best protect public health." Separately, Duke subsidiary Piedmont Natural Gas filed a request with the North Carolina Utilities Commission to raise its base rates by about 9%, in an effort to recover costs related to system growth, pipeline integrity, infrastructure investments and safety and security upgrades. Duke's stock has gained 3.3% year to date, while the SPDR Utilities Select Sector ETF has rallied 9.0% and the S&P 500 has climbed 14.3%.