The Metropolitan Sewer District has approved its forth consecutive 6.5 percent rate increase, adding $2.31 to customers' average monthly bill.MSD is under a federal mandate to comply with the Environmental Protection Agency and the Clean Water Act and is responsible for nearly $850 million of repairs and upgrades to its sewage system.Spokesman Steve Tedder said the consent decree plan devised by MSD in 2008 calls for rate increases over the next several years.“There is a schedule through 2025 for rate increases. For the 2014 budget it is scheduled to be 6 percent and going down from there to five-and-a-half in future years," he said.MSD has remained on budget so far, but future rate increases will depend on future budgets, said Tedder.“For us to remain on budget and on schedule for all the improvements that are required is a very good thing," he said.Last week, MSD president Greg Heitzman said many large cities east of the Mississippi are under a federal consent decree and that Louisville's, by comparison, is managable.The recent decision to begin consolidating MSD and the quasi-governmental Louisville Water Company could help the agency’s finances, but Tedder couldn’t say whether it would directly result in lower rates or smaller increases.