Section 55 sets out transitional arrangements for the Act to apply to controlled reservoirs already under construction or alteration when the Act is commenced. Part 3 and sections 67 to 69 (related enforcement powers of the Department) apply except that the reservoir manager must notify the Department of the relevant works, appoint a construction engineer, and notify the Department of that appointment all within 28 days of the commencement of section 43. Subsection (3) enables the Department to extend the periods for notifying the Department of the relevant works and the commissioning of a construction engineer.