Ar 8 Hydref 2012 cyhoeddodd Swyddfa Archwilio Cymru (SAC) adroddiad er budd y cyhoedd mewn perthynas â’i harchwiliad o Fwrdd Draenio Mewnol Gwastadeddau Cil-y-coed a Gwynllŵg (CWLIDB), corff cyhoeddus annibynnol sy’n gyfrifol am faterion draenio Gwastadeddau Cil-y-coed a Gwynllŵg. Roedd adroddiad SAC yn cynnwys nifer o faterion sydd ynghlwm â rheoli a llywodraethu CWLIDB, ac yn ystod yr archwiliad nododd SAC nifer o fethiannau gweithredol.
On 8 October 2012 the Wales Audit Office (WAO) published a report in the public interest in relation to their audit of Caldicot and Wentlooge Levels Internal Drainage Board (CWLIDB); an autonomous public body responsible for drainage matters on the Caldicot and Wentlooge Levels.  The WAO report encompassed a range of matters associated with the management and governance of CWLIDB, and in the course of their audit the WAO identified a series of operational failings.