1. The board of supervisors shall, in the resolution herein provided for, levy and provide for the collection of a pumping tax, in the form of a royalty on the mineral concentrates produced from the lands affected by such plan for reclamation, not exceeding, however, two percent of the gross sale value of such mineral concentrates, and a tax or charge for the crushing and cleaning of ores and minerals by or through the concentrating plant or plants operated or to be operated by the district, such milling tax or charge shall be fixed by the board of supervisors at a stated rate per ton of such ores and minerals so crushed and cleaned and, when added to the proceeds of the aforesaid pumping tax, shall be sufficient to produce the sum or sums required to pay interest on the bonded indebtedness of the district at any time outstanding, to pay maturing bonds of the district according to the terms and tenor thereof, to pay the operating expenses of the district and to provide an adequate reserve fund for maintenance, depreciation and contingencies.

2. All funds received by the district for and on account of the tax levies or charges herein provided for shall be deposited by the treasurer of the district in some solvent bank or trust company and shall at all times be secured by such collateral or otherwise as the board of supervisors may direct, and shall be used for no other purpose than as hereinbefore and hereinafter authorized.

3. All taxes or charges herein provided for shall constitute a first and a paramount lien on the ores, minerals and concentrates mined and produced from the lands affected by such plan for reclamation, and the board of supervisors of any such district may hold possession of the ores, minerals and concentrates so produced or crushed and cleaned by or through the concentrating plant or plants operated by the district until the taxes and charges herein provided for shall have been paid, or such board may sell such ores, minerals and concentrates on the open market and, after deducting the amount of such taxes or charges, remit the remainder to the person or persons entitled thereto.

4. To secure the continuous operation of mines within the district, to secure the continuous operation of such concentrating plant or plants to the capacity thereof and to secure the prompt payment of all taxes and charges herein provided for, such board of supervisors is authorized to enter into a contract or contracts with any owner or owners of lands, affected by such plan for reclamation, their lessees or any other persons interested therein; such contract or contracts to contain such provision or provisions, as the board of supervisors may find necessary or advisable to effectuate the purposes of sections 242.700 to 242.750, and to carry out the powers herein conferred on such board of supervisors.