1. Caisson, located approx. 400m off Breaksea Point. The caisson provides part of the cooling water process for Aberthaw Power Station, West Aberthaw.

L. Osborne, RCAHMW, 5th Oct. 2011.

2. The caisson was constructed in onshore in 1958 before being floated and towed into position. In December of that year, the construction was completed by the delivery of 256kg payload skips of ready-mixed concreate via helicopter. The 19.8m-tall caisson, which has an external diameter of 29m, was then connected with the power station via a 731.5m long access tunnel through fissured rock.

(Sources: `Aberthaw Power Station, engineering-timelines.com (entry funded by Institute of Civil Engineers); see also P. M. Fraenkel and R. L. Triggs, `Special Features of the Civil Engineering Works at Aberthaw Power Station?, Proceedings of The Institution of Civil Engineers, 23: 1 (Sep. 1962), 63?92.; Information and feedback received from member of the public)
A.N. Coward, RCAHMW, 21.01.2019