APOLLO BEACH — Tampa Electric Co. is taking a big step away from coal. The Tampa-based utility is spending $853 million to convert its coal-fired Unit 1 at its Big Bend Power Station to natural gas and retire coal-fired Unit 2 in 2021.Five workers died in June 2017 after performing a known-to-be-dangerous maintenance procedure on Unit 2. The incident resulted in a $126,749 fine from federal regulators and a "willful" designation for safety violations found following an investigation. Tampa Electric is currently appealing the designation. According to Tampa Electric spokesperson Cherie Jacobs, the June incident was not the primary reason for closing Unit 2."Safety is our first priority, and it influences everything we do," Jacobs said. "But it is not the driving force behind this project. This decision was in the works for more than a year, and this decision was made because it is in the best interest of customers."Tampa Electric CEO Nancy Tower cited a plan to rely less on coal shortly after she took the helm at the utility at the beginning of the year. The changes at Big Bend dovetail with that strategy."Coupled with our significant increase in solar power, these changes will make Tampa Electric substantially cleaner and greener than it is today," Tower said in a release Thursday. "This investment in cleaner generation will also provide significant savings to customers through lower expenses for fuel and maintenance of the existing units."Revamping the Apollo Beach facility will take place by 2023. Tampa Electric did not provide an estimate for how much customers’ monthly bills would increase if the project is approved by state regulators, but that uptick wouldn’t happen until after the project is finished. After the revamp, Big Bend will still have two units that operate on coal with natural gas as their secondary source of power, Jacobs said.The natural gas unit will be able to produce 1,090 megawatts. Read the investigation: Hellfire from above> The switch will change the company’s energy mix. About 75 percent of the energy Tampa Electric produces will be from natural gas at the completion of the project, 12 percent coal, 7 percent solar and 6 percent from "other sources."As of 2017, 67 percent of the utility’s energy comes from natural gas, 24 percent from coal and 9 percent from other sources including solar.Tampa Electric’s move away from coal is typical of what other utilities around the country are doing, said Susan Glickman, Florida director of the Southern Alliance for Clean Energy. "As the cost of solar drops dramatically, the economic opportunity with solar is increasing, and power generated with fossil fuels is becoming more and more uncompetitive," she said. "Plus you have the environmental impact of coal-fired plants which put out the biggest source of mercury pollution and is responsible for vast amounts of greenhouse gas pollution."Getting coal out of the mix is a good step in the right direction, Glickman said. "From an environmental perspective, any time we can move away from coal, it’s a very good thing."MORE: Go here for more Business News Contact this reporter at [email protected] or (727) 892-2249. Follow @malenacarollo.