SEC. 2. The board of public improvements shall at all times, beginning with the selection of the site out of the three sites above referred to, until the close of said world's fair or exposition, and until the complete restoration of said site as hereinafter provided, have the power to provide such regulations, conditions, and requirements as it may deem necessary to protect the interests of the city with respect to the construction of all sewers, drains, and conduits of any kind, and the laying of water pipes or fixtures; and the plans and specifications for the construction of the foregoing work shall be subject to the approval of the board of public improvements, and no such work of any kind shall be done without such approval by the board. All such sewers, drains, conduits, pipes, and fixtures shall become and be the property of the city. SEC. 3. Within six months after the close of said fair or exposition, the corporation or association aforesaid shall clear the park, or in the event of the selection of Forest Park, the part thereof above described, of all tramways and railway tracks, rubbish and debris, and of all buildings, sheds, pavilions, towers, and other structures of every kind, and shall within twelve months after the close of such fair or exposition, fully restore the park selected as a site, or in the case of Forest Park, that portion thereof above-described, by doing all necessary grading, the restoration and repair, or the formation of all walks and roads, the planting of trees, the placing of sod and the planting of shrubs and plants, all in accordance with plans to be approved by the board of public improvements, and all to be done subject to the inspection of the park commissioner, and to his entire satisfaction and approval.