The Surface Water Treatment Rule (SWTR) and the proposed Disinfectant/Disinfection By-Products (D/DBP) Rule, Information Collection Rule (ICR), and Enhanced Surface Water Treatment Rule (ESWTR) are intended to monitor and control disinfection byproducts and pathogenic organisms in potable water. A result of these regulations has been an increased interest in using membrane processes for treatment of surface waters. Nanofiltration (NF) has been proven as an effective DBP precursor removal technology for treating groundwaters but has not been used extensively in treatment of surface waters due to the propensity to foul. Pretreatment processes to reduce NF fouling, when treating surface waters, are necessary before NF can be considered a reliable treatment technology. However, capacity of raw water and pretreated waters to foul NF systems is primarily determined through pilot testing. Correlation of a fouling index to NF fouling would be of great benefit to utilities interested in rapid and inexpensive assessment of the viability of NF for surface water treatment. The objective of this study is to provide clearer understanding of the Silt Density Index (SDI) and Modified Fouling Index (MFI) as a means of predicting NF fouling rates, when treating a highly organic raw water and raw water pretreated using alum coagulation (AC), granular activated carbon (GAC), and microfiltration (MF) processes. This study is part of a larger project funded by the United States Environmental Protection Agency on the use of NF for ground and surface water treatment.