The funding for all of the Phoenix Zoo's upcoming improvements has been slowly trickling in, thus this orangutan enclosure might not have an overhaul until at least 2011.
This is another of those exhibits that would be improved no end by just adding a soft substrate and some more exhibit 'furniture'. Space-wise, it's not too bad, though it's a shame about the green shade netting, which never looks particularly good (aesthetically it's worse than concrete to my eyes - just always looks tatty).
I'm not sure just exactly what there plans are now, but for the longest time the reason there was no substrate is due to concerns over the orangutans contracting valley fever, which is ever present in Arizona dirt.