just to remind you to check out bonecp (http://jolbox.com/) as an alternative to c3p0.
In my leiningen projects I exlcude the org.slf4j/slf4j-api dependency to include a more recent version like this:
:dependencies [ [com.jolbox/bonecp "0.7.1.RELEASE"
This configration lets me direct all logging that's done by the libs (bonecp, h2 database, etc...) I use as well as org.clojure/tools.logging to logback. For legacy libs you can use the slf4j bridges like "jcl-over-slf4j".