Complex sentence: The City of Baltimore operated its Patapsco Waste Water Treatment Plant on the former Martin Wagner site until the late 1990s, when the plant was closed and a nearby residential community was relocated due to environmental concerns.
Split into simpler sentences: The City of Baltimore operated its Patapsco Waste Water Treatment Plant on the former Martin Wagner site until the late 1990s. The plant was closed and a nearby residential community was relocated due to environmental concerns.