Our association sets some aside each year in a capital account, as we know we are going to have some expensive repair needs in upcoming years. Since you say your issue is a bridge, you might also look into the impact on lake water quality downstream. That might open up some funding through 23 MRSA 3106, or grant money from a lake association. Several years ago, our road got a grant through the Lakes Environmental Association because they said two of our culverts were in danger of washing out and impacting an at-risk lake. With their help we were able to put in bigger culverts that are capable of handling torrential rains such as used to overwhelm the old culverts. Also, you might want to look into the options for replacing the bridge. Compare prices and availability of a concrete arch, or of replacing the bridge structure with the frame from a railroad car.