Two officials at Louisville’s Metropolitan Sewer District have resigned. Chief Engineer Mark Johnson’s last day will be next Friday after three years with the agency. Board member Charles Weiter has also resigned, though his term wasn’t scheduled to end until June 30.Allegations of ethical misconduct have dogged the agency recently, though an MSD spokesman said Johnson’s resignation wasn’t related. Weiter resigned because family members are pursuing contracting work with MSD and he wanted to avoid the appearance of a conflict of interest.State auditor Crit Luallen is conducting an audit of the MSD’s management and ethics policies, and plans to release the report by the end of the year.