You are probably interested in an alternative:
xcompmgr
see http://wiki.archlinux.org/index.php/Xcompmgr
And you will then be interested in editing your xmonad.hs and importing items such as
import XMonad.Hooks.*
here is some documentation describing some hooks
http://hackage.haskell.org/packages/archive/xmonad-contrib/0.8.1/doc/html/doc-index.html
xcompizmgr is demo software and since xmonad doesn't refresh, you will experience instability (probably in the form of certain hooks will seem to function but break after a while). But if you are really bent on putting compiz in with xmonad it is the only solution I know of.