The district may from time to time incur a bonded indebtedness as provided in this chapter to pay the cost of acquiring, constructing or completing the whole or any portion of any transit facilities, or for acquiring any works, lands, structures, rights, equipment, or other property necessary or convenient to carry out the objects, purposes, or powers of the district. The total amount of bonds issued and outstanding shall not exceed twenty percent (20%) of the assessed value of the taxable property of the district as shown by the last equalized assessment roll of the County of Marin.