Section 69. The commission may replace or rebuild any bridge over the Charles river within the metropolitan parks district whenever funds for the purpose shall become available by gift under the provisions of this section; provided, that no such bridge shall be replaced or rebuilt unless the consent of the city council and of the selectmen of any town in which any part of the bridge is situated shall first be obtained. Any such bridge may be replaced or rebuilt without a draw for the passage of vessels, and may be of no greater height above the water than, in the judgment of the commission, the architectural appearance of the bridge would require, except that every such bridge over the Charles river basin shall be so constructed as to leave a clear height of at least twelve feet above the ordinary level of the water in the basin over the main ship channel, and the piers and other obstructions to the flow of the river shall be constructed in such form and in such places as the secretary of war of the United States shall approve. When the work of replacing or rebuilding any such bridge is completed, the bridge shall be maintained and policed under and in accordance with the laws governing such maintenance and policing at the time when the work was begun. The state treasurer may receive, hold, manage and invest any funds given or bequeathed to him in trust by any person, upon such terms, conditions and limitations as the donor may impose, for the purpose of enabling the commission to carry out the provisions of this section, and the commission, whenever it shall deem that the public interests so require, may expend, under authority of this section and of any other provision relating to the acquirement and maintenance of reservations or boulevards by the commission, any such funds in accordance with the terms, conditions or limitations aforesaid. Any owner or lessee of property abutting on the Charles river above any drawless bridge built under the authority of this section and under authority of the act of congress entitled ''An Act to authorize the construction of drawless bridges across a certain portion of the Charles river in the State of Massachusetts'', approved February twenty-seven, nineteen hundred and eleven, shall be entitled to adequate compensation for damages, if any, caused to said property or leasehold interests therein, by reason of the interference with access by water to said property due to the construction of any such drawless bridge, in accordance with provisos contained in said act of congress. Upon petition of any such owner or lessee entitled to such damages, filed in the supreme judicial court within one year after any such bridge without a draw is opened for public travel, said court shall appoint three commissioners to hear the parties in interest, and to assess the damages to said property; and the decision of said commissioners as to the amount of said damages and as to questions of fact involved shall be final.