No buildings or additions may be erected, and no bonds may be issued or the proceeds used for the payment of the cost of any projects under section 55-08-08, except for specified projects designated and authorized by legislative act, or the board if permitted by the legislative assembly. No such project may be erected at a cost exceeding the amount fixed by the legislative assembly or by the board if provided by the legislative assembly as the maximum to be expended for the project. The proceeds of all bonds credited to the state park fund must be used solely for the purpose or purposes for which the bonds are authorized. The board may make and execute all instruments which may be deemed necessary or advisable to provide for the completion of any project or for the sale of the bonds or for interim financing deemed necessary or advisable pending the sale of the bonds and pledging the proceeds of the bonds. The director of the office of management and budget shall issue warrants upon the state treasury against the fund for such amounts as is due upon audited itemized estimates and claims that bear the approval of the officials designated by the board for that purpose. The state park fund and revenue bond fund may be deposited by the state treasurer with the Bank of North Dakota or in a bank that is a duly designated depository for state funds, or may be invested under direction of the board in securities that are direct obligations of the United States of America, except to the extent that the investment is prohibited or restricted by any covenant made with or for the benefit of bondholders.