WELD 2.3.0.CR2 has the same issue:
Sep 09, 2015 10:02:21 AM org.apache.catalina.loader.WebappClassLoaderBase checkThreadLocalMapForLeaks
SEVERE: The web application [horizon] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@11666e2]) and a value of type [org.jboss.weld.context.AbstractManagedContext.ManagedState] (value [org.jboss.weld.context.AbstractManagedContext$ManagedState@332e92]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.