Royal Assent for the Cardiff Bay Barrage Act was granted in November 1993.  Construction of the Barrage commenced in May 1994.  It was completed in November 1999, at a cost of £120 million, when a saline impoundment was created.  Freshwater impoundment commenced in the Spring of 2001. 

The main operational section of the Barrage, which includes the locks, sluices and fishpass, was constructed in the dry, in a sand cofferdam.  The sand used was dredged from the Bristol Channel, and was then re-used for completing the embankment. 

Stone used at the Barrage embankment came from local welsh quarries.  All the heavy materials were delivered via the north end of the construction site, which necessitated construction of a large temporary opening bridge.  Steel reinforcement came from the steel mill in Cardiff.

The concrete caissons for the outer harbour breakwaters were constructed in the dry dock at Cardiff and floated into position.

The following materials were used for the Barrage construction: