Most of those, (63%) have full or at least partial plans in place to resolve the issues, but 21% of the responses were unclear.
Mae gan y rhan fwyaf (63%) o'r rhain gynlluniau llawn neu, o leiaf, gynlluniau rhannol ar waith er mwyn datrys y problemau ond roedd 21% o'r ymatebion yn aneglur.