By JEFF AMYJACKSON, Miss. (AP) â¿¿ Ed Day said his main job as president of Mississippi Power Co. was to successfully complete the company's Kemper County power plant. Now, more than $1 billion in cost overruns at the coal-fired plant have claimed his job, and parent Southern Co. has sent in a top executive to try to salvage the mess. Day abruptly resigned Monday as president of Mississippi Power. His replacement, effective immediately, is Ed Holland. Until Monday, Holland had been the Atlanta-based parent company's top lawyer. He also led an internal inquiry into the April announcement that Kemper was an additional $540 million over budget. Along the way, Holland found that Day failed to respond to requests from a Mississippi Public Service Commission lawyer about when company executives knew about a previous $376 million overrun that was announced in May 2012. Holland told commission lawyer Shawn Shurden last week that Day had failed to respond. "In a subsequent management meeting, Ed Day directed or definitely inferred that the documents should not be given to the commission, and these documents were never given to the commission," said Northern District Commissioner Brandon Presley, a Democrat who has opposed the plant. Holland denies Day tried to defy regulators. "There was no intentional withholding of information," Holland said. He said executives decided to communicate the information in a meeting, but failed to follow through. "We made a mistake of not delivering in a timely fashion," he said. Holland said Day wasn't forced to resign, but said "the pressures" of Kemper and Mississippi Power's other operations probably motivated the decision. Holland said Mississippi Power's vice president of generation, Tommy Anderson, also resigned recently and was not fired. Mississippi Power, with 186,000 customers in 23 counties from Meridian to the Gulf Coast, often seems an afterthought for massive Southern Co. But now there's a chance that the woes of the company's smallest outpost will damage the utility's relationships with regulators elsewhere.