Somerville has been hit or miss for me for several years. Sometimes I'm killin em, sometimes I'm lucky to get a bite.
This time of year for bank fishing, I'd try off the end of Welch Creek Park. It starts near the dam, but there is a peninsula that sticks way out into the lake that is the main park, and the very end of that peninsula is a low hill that is sometimes an island. Off the end of that hill, out in the lake, two old creek channels meet. White and hybrid bass school there, and sometimes catfish, too.
Best bait for there is to get a seine or cast net and catch shad and minnows out of the lake, and use those on a minnow hook with a sliding weight or bell weight about 24 inches above. Fish off the bottom, cast out as far as you can.