In a mooring area with a density of greater than one boat per acre, the department shall conduct a pollution assessment to support the classification of that portion of the growing area in accordance with the NSSP Model Ordinance. The department may amend the density requirement in this section if the mean water depth in an enclosed bay is less than 12 feet or under certain hydrographic conditions where dilution calculations show the area cannot meet 14 fecal coliform/100 ml at the sanitary line.