 The Somerset coal field was opening up, and was to be served by a Somerset Coal Canal feeding into the wider canal system by means of the Kennet and Avon, whose owners would greatly benefit from the development.However, the Somerset Coal Canal suffered from serious water supply problems at Combe Hay; and the Kennet and Avon Company suggested Weldon's innovation as the solution.Three caisson locks were proposed, each to be long and deep and containing a closed wooden box which could take the boat.