In message , at 22:00:18 on
Wed, 12 Oct 2011, Charles Ellson remarked:

The "taxiway" runway is an alternative to the normal one when the
latter is closed for some reason.

So not alternate runways but primary and secondary.

Yes, the use alternates between the two. They are never *both* in use
(as runways) at the same time, which is what being a "single runway
airport" means.
--
Roland Perry