Removing lines in page theme

Been digging extensively to try and find a solution but have been unsuccessful. I have a theme that originally was using three frames (left and right sidebars plus center content). It was all too squished so I have only a left side bar for now and the content lays out a little better.

Problem is that there is a thin gray line that still shows up where the old right sidebar was and I can’t figure out how to get rid of it. Site: theprojectsolution.org.

Any help for a little nonprofit is appreciated!