The Importance of Assessing Pollutant Loads from Land Development Projects and the Design of Effective Storm Water Treatment Systems

Impacts on water quality due to land development projects are widely known. The adverse impacts of pollutants associated with non-point source are becoming more pronounced in many areas of the country. These types of pollutants can easily affect water quality in streams and lakes. This paper will discuss the use of, the benefits and potential drawbacks of certain models, such as SLAMM (Source Loading and Management Model) and the P8 model (Program for Predicting Polluting Particle Passage through Pits, Puddles and Ponds) along with the Simple Method. By the use of the Simple Method, it will be shown how the calculation of pollutant loads can be determined both on an annual basis and for the 90 percent storm (1" of rain). In particular, it will be demonstrated how the loads determined for the 90 percent storm will provide a reasonable assessment of impacts that can readily be understood by local land use agencies. The next step in this process is the proper design of storm water treatment systems. In order for the treatment systems to be effective at the removal of non-point source pollutants, the design parameters must provide certain benchmarks. The various aspects of treatment systems, such as hydrologic capacity, flow paths and vegetative systems will be discussed along with the importance of each component. It will be shown how pollutant removal efficiencies for various treatment systems can be applied to the calculated loads to demonstrate the effectiveness of the storm water treatment system to remove the pollutants. The myriad benefits of the creation of a treatment train versus a stand alone system will also be discussed. In conclusion, the many environmental benefits of this approach to maintaining the health streams and lakes will be provided.