As part of a broader ERS assessment of the costs of manure management, a regional modeling framework was developed to evaluate the effect of Federal guidelines for farmland application of manure on the costs of hauling and spreading manure. This report presents technical details of the regional modeling system, applied to the Chesapeake Bay watershed. The report includes an overview of the model's scope and structure, data sources, and modeling assumptions. Results from an initial application of the modeling system are featured in the ERS publication Manure Management for Water Quality: Costs to Animal Feeding Operations of Applying Manure Nutrients to Land (AER-824, June 2003).