DETROIT — The U.S. Environmental Protection Agency will investigate Michigan’s environment department to determine whether it racially discriminated against a lower-income, majority-Black neighborhood in approving an emissions permit for a new Jeep plant in Detroit. The EPA is acting after five residents whose properties now back up to the Mack Assembly Plant on the city’s east side filed a civil rights complaint in November against the Michigan Department of Environment, Great Lakes and Energy. It failed to do its diligence, the Beniteau Street residents argued, by not conducting a cumulative…