65 ILCS 5/11-45-13

When the commissioners determine to commence the construction of a band-shell, or performing arts structure, or to proceed as herein otherwise authorized, they may adopt the plans therefor and provide estimates of the costs thereof, and shall advertise for bids for the completion of the program and shall let the contract or contracts for the same to the lowest and best responsible bidder or bidders, and may require from such bidders such security for the performance of the bids as the commissioners may determine.