In the discretion and at the option of the board such bonds may be secured by a trust indenture by and between the district and a corporate trustee, which may be a trust company or bank having powers of a trust company within or without the State of West Virginia, but no such trust indenture shall convey, mortgage or create any lien upon the public service properties or any part thereof. The resolution authorizing the bonds and fixing the details thereof may provide that such trust indenture may contain such provisions for protecting and enforcing the rights and remedies of bondholders as may be reasonable and proper, not in violation of law, including covenants setting forth the duties of the district and the members of its board and officers in relation to the construction or acquisition of public service properties and the improvement, extension, operation, repair, maintenance and insurance thereof, and the custody, safeguarding and application of all moneys, and may provide that all or any part of the construction work shall be contracted for, constructed and paid for, under the supervision and approval of consulting engineers employed or designated by the board and satisfactory to the original bond purchasers, their successors, assignees or nominees, who may be given the right to require the security given by contractors and by any depository of the proceeds of bonds or revenues of the public service properties or other money pertaining thereto be satisfactory to such purchasers, their successors, assignees or nominees. Such indenture may set forth the rights and remedies of the bondholders and such trustee.