The Council when in its judgment it is deemed expedient and necessary, shall construct, maintain and operate a system for the control and disposition of surface waters within the boundaries of the County. For such purpose the Council is given all of the power and authority, including the right to condemn, and the right and authority to negotiate with any public agency and to make contracts with such agencies, including the government of the United States or any bureau or department thereof, provided that a petition requesting such a system is presented to the Council signed by the owners of at least twenty percent (20%) of the assessed valuation of the real property located in the area affected.