Southern Co. is about seven months behind schedule, mostly because of the federal approval process for the reactor, according to company executives and filings. Southern Co. also faced delays in getting an important license allowing it to start building the guts of the plant.Another, less exotic problem at Vogtle: At one point, workers built metal bars straight rather than curved, as regulators had directed, so Southern Co. had to rip them out and replace them. Crews in South Carolina, watching the progress at Vogtle, have halted the construction of those bars. Plant Vogtle's designers and builders â¿¿ Westinghouse Electric Co. and The Shaw Group Inc. â¿¿ want Southern Co. to pay an additional $400 million for the licensing delays, according to a May report filed with the U.S. Securities and Exchange Commission. Southern Co. subsidiary Georgia Power, which owns nearly half the new plant, denies responsibility for those costs and is negotiating on behalf of all the owners. Financial information divulged by three companies who own 98 percent of the project show $838 million in potential charges. It is unclear how much this could cost the utility's 2.4 million customers. Southern Co. earlier estimated typical residential customers would see a $10 increase in their monthly bills when both reactors are producing power in 2018. Utility regulators ultimately set the rates. Similar issues have played out in central South Carolina, where SCANA Corp. and Santee Cooper won permission to build two reactors at Plant Summer, about 25 miles north of Columbia. SCANA agreed to pay $138 million in March to settle claims over licensing delays raised by the companies designing and building the reactor. Santee Cooper will pay nearly $113 million as its share of those costs, company officials said. In May, SCANA asked utility regulators to raise its base spending on the project by $283 million, which includes the settlement related to licensing delays and extra costs for cyber security and staffing. However, the company said it will stay within its existing budget because it expects other expenses to be lower.