This report presents the general methodology of calculating the atmospheric dispersion coefficients (x/Q') to be used in the safety basis documents for the tank farm facilities. Values of x/Q' given in this report were generated using the GXQ code Version 4.OF, which reproduces the statistical treatment of the Hanford Site joint frequency meteorology specified in US. Nuclear Regulatory Commission (NRC) Guide 1.145, Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants. GXQ is documented in WHC-SD-GN-SWD-30002, GXQ 4.0 Program Users' Guide, and a listing of the code is shown in Appendix A. Alternate calculations used to verify the GXQ results are contained in the appendices. The alternate calculations are included to demonstrate compliance with Nuclear Quality Assurance (NQA)-1 requirements for software use. Calculation of the basic dispersion parameters used at the tank farms is discussed in Section 2.2 with results given in Section 2.2.6. Specific assumptions and input used to generate the x/Q's at the tank farms are discussed. The logarithmic interpolation procedure used to generate x/Q's used for long-duration (greater than 2 hr) releases is described in detail. A sample input file and a set of run files are listed in Appendix B. Modifications to the basic dispersion coefficients to account for plume depletion, momentum/thermal plume rise, and large source effects are discussed in Section 2.3 with examples calculated. Corresponding sample m files are listed in Appendix C. The GXQ results were verified using a set of alternate calculations documented in Chapter 3.0. Special GXQ run files used in the independent verification are listed in Appendices D, E, and F. Chapters 4.0 and 5.0 present detailed discussions of the procedures used to estimate radiological and toxicological exposures using the dispersion coefficients developed in Chapters 2.0 and 3.0. Additional x/Q' values that were requested to support the documented safety analysis (DSA) are included as Appendices G, H, I, J, K, and L. Future requests for x/Q's will be documented as additional appendices to this report.