Complex sentence: Since at least 2010 Bridgeton Sanitary Landfill in a suburb of St Louis, MO, has been burning as a subsurface smoldering fire; it had to be served a violation notice in July 2012 before remediating.
Split into simpler sentences: Since at least 2010, Bridgeton Sanitary Landfill, in a suburb of St Louis, Missouri, has been burning as a subsurface smoldering fire. The landfill was served a violation notice in July 2012 before remediating.