Top Down construction techniques allow for construction over environmentally-sensitive areas.
Top down or deck level construction is a construction method that eliminates the need for heavy equipment on the ground by building outward from the start point and traveling equipment across the completed structure instead of along the ground. This minimizes the damage to the environmentally sensitive marshlands. As much work as possible is done from the bridge literally reducing the footprint of building the bridge. This is particularly useful in areas of heightened environmental sensitivity and in areas where building from a barge or other structure would be difficult or not be possible.