A stormwater filtration system includes a dry well structure including a top having an access opening, a bottom and a sidewall extending between the top and the bottom to define an internal volume of the dry well structure. A deck assembly partitions the dry well structure into an upper region and a lower region. The deck assembly includes a plurality of deck members sized to be delivered through the access opening of the dry well structure and configured to be assembled within the internal volume to form the deck assembly.