Paul Monroe, an engineer who oversees construction at the Juniper Ridge Landfill in Old Town and Alton, Maine, shows a model for collecting leachate in the proposed expansion area. Leachate is a mix of wastewater and harmful substances from the landfill. Photo by Lori Valigra of the Bangor Daily News.This story appears as part of a collaboration between The Maine Monitor and Maine Focus, the investigative team of the Bangor Daily News, a partner…