For those outside of the area and unfamiliar with where the park is located, there was a LOT of massive heavy construction that went into reshaping the stretch of land to make it viable for the park as planned. 2 miles of a major 4-lane road was entirely closed for two (or has it been three?) years. They basically recreated the bank of the river over those miles also.
While I'm not sure all of that planning was necessary, I can see how the civil engineering drove the costs to those figures.
While I'm not sure all of that planning was necessary, I can see how the civil engineering drove the costs to those figures.