In the event that wetlands or other undevelopable areas exist in the location of a required buffer, and such areas do not provide an effective buffer in their natural state, plantings and/or berms and/or fencing, etc., sufficient to meet the intent of the buffer, as determined by the joint Land Use Board, shall be required to be provided outside of such undevelopable areas. The foregoing shall not be construed to require that such additional plantings, etc., have a minimum depth of 20 feet. The nature and extent of the buffer in such case shall be determined by the Joint Land Use Board based upon field conditions.