This study provides a decision-support framework and a design methodology for preliminary evaluation of field application of in-situ activated carbon (AC) amendment to sediment to control the (bio)availability of hydrophobic organic contaminants. The decision-making framework comprises four sequential steps: screening assessment, input parameter determination, model prediction, and evaluation for process optimization. The framework allows the application of state-of-the-art experimental and modeling techniques to assess the effectiveness of the treatment under different field conditions and is designed for application as a part of a feasibility study. Through a stepwise process it is possible to assess the effectiveness of in-situ AC amendment with a proper consideration of different site conditions and application scenarios possible in the field. The methodology incorporates the effect of various parameters on performance including: site-specific kinetic coefficients, varied AC dose and particle size, sediment and AC sorption parameters, and pore-water velocity. The modeling framework allows comparison of design alternatives for treatment optimization and estimation of long-term effectiveness over a period of 10-20 years under slow mass transfer in the field.