New York State requires all decisions to be made by an approving authority considered under the State Environmental Quality Review Act (SEQRA). SEQRA requires one to study the changes that will occur from the Chappaqua Hamlet today to what it will be under the new form-based code. Changes in the environmental significance such as building height, visual impacts, traffic circulation, parking, stormwater, drinking water, etc. have been examined to understand the effect of the code changes and balance the environmental impacts with social and economic factors.

The proposed form-based code is designed to encourage flexibility in development and to revitalize the hamlet, therefore new development is expected to occur due to the adoption of the new code. The level of development allowed under the new form-based code is anticipated to result in changes in land use and improvements to the aesthetic character and walkability of the hamlet. From further review and analysis of SEQRA, the New Castle Town Board declared that changing the zoning legislation is a Type I Action that may result in one or more significant environmental and therefore (Type I designation, alone, does not require an EIS) required preparation of a Generic Environmental Impact Statement (GEIS).