**4. Conclusions**

The CSM for the NBSA has met its objectives of supporting a comprehensive understanding of the physical, chemical and biological processes influencing the fate and transport of contaminants of potential concern from sources to exposure media (water, sediment, and biota). The CSM provides an updated description of the conditions and processes in the NBSA based on the data generated from recent RI investigations and secondary data.

The NBSA's complex hydrodynamics and sediment dynamics can pose challenges to accurately quantify freshwater and sediment loadings, circulation patterns, and transport of sediments and contaminants. To quantify current, historical, and future fate and transport of contaminants in this system in support of the RI/FS, it is necessary to develop a numerical model. The processes and variables described in the CSM can guide the development and application of the numerical model.

The major aspects of the hydrodynamic and sediment transport processes within the NBSA system are summarized below:

