The purpose of the model documentation is to provide a detailed description of the modeling and risk analysis procedures used in CR-ERNS/PAM to assist OSCs and other Superfund decision-makers in interpreting the system results. PAM is a screening-level model; to properly interpret PAM's outputs, the user must understand the limitations and uncertainties in the equations and data used to generate these results. Chapter 2 presents the system's fate and transport models and describes the assumptions associated with these equations. Chapter 3 describes PAM's auxiliary data bases and provides the source(s) of each parameter and the methods by which values were selected. Chapter 4 explains the methods and exposure assumptions used to estimate exposures to hazardous substances and to evaluate the risks and hazards associated with these exposures. Chapter 5 presents examples of reports generated by PAM and explains the meaning of the 'flags' assigned to hazardous substances, media, and facilities. Appendix A contains versions of the fate and transport equations used for radionuclides. Appendix B contains copies of PAM's reports.