cannot undeploy archiva webapp

I'd like to undeploy without restarting Tomcat (as I don't have admin acces to the server). When I undelploy archiva webapp using tomcat manager, the webapp/archiva directory is not removed and WEB-INF/lib still contains:

jpox-1.1.1.jar
plexus-container-default-1.0-alpha-10.jar
plexus-security-authorization-rbac-store-jdo-1.0-alpha-6-20061013.204855-1.jar
plexus-security-keys-jdo-1.0-alpha-6-20061013.204855-1.jar
plexus-security-user-management-provider-jdo-1.0-alpha-6-20061013.204855-1.jar
webwork-2.2.4.jar
xwork-1.2.1.jar

I cannot remove those jars (files locked)

Maybe some background thread is not stopped at application undeploy ?