Estimation of stormwater pollutant loads using land use based models has been widely used for establishing regulations and management practices. This approach requires land use information to assign the imperviousness or runoff coefficients (RC) and event mean concentrations (EMCs) for the pollutants of interest. This simplistic approach is useful to estimate the total mass emissions. However, different research groups have used various parameters based upon similar data sources, and there are very few validations using actual field data. This study compares the assumptions, methodologies and results of several, independent modelling efforts, and functions as a quality and sensitivity study of the methodologies. The similarity or differences of the various model results serve as a qualitative indicator of the state of art for this type of stormwater modelling.