The parliamentary bill was hotly contested, and the House of Lords asked Trinity House to produce a report on the three rivers. This favoured the scheme, and in May 1699 the act of Parliament was granted. It named 18 undertakers, nine from the Corporation of Leeds, and nine "gentlemen of Wakefield", who would oversee the improvements to the River Aire (from the River Ouse at Airmyn via Castleford to Leeds) and the River Calder (from Castleford to Wakefield). The act gave them powers which included the creation of weirs bypassed by short "cuts" equipped with locks, the creation of a towpath, and the right to buy and demolish mills and weirs. John Hadley was engaged as the engineer immediately, and by 1704 the original work was completed, including 12 locks on the Aire between Haddesley and Leeds and 4 on the Calder. The locks were long by wide with depths over the sills.