T.F. Green Airport Improvement Program - FEIS Chapters - PVD

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) Evaluationfloodplain may have occurred downstream of the Project Area to the crossing of Warwick Avenue, but this has notbeen quantified. Historical floodplain filling has likely impacted water quality maintenance and groundwaterrecharge functions.Under Alternative B4 approximately 2.3 acres of floodplain would be altered, and under Alternative B2approximately 0.5 acres. With appropriate mitigation, as described in Chapter 6, Mitigation, the PreferredAlternative (Alternative B4) would not result in increased depth, duration, or lateral extent of flooding beyondthe Airport property and therefore would not have adverse cumulative effects on the ability of the floodplain tomoderate floods.5.14.7 Comparison of Alternatives B2 and B4This section provides a comparison of impacts to floodplains under Alternatives B2 and B4.5.14.7.1 Significant ImpactsAlternatives B2 and B4 would encroach on the estimated 100-year FEMA floodplain which may be classified asa “significant encroachment” based on FAA Order 1050.1E section 9.2f(3) since either alternative would causeadverse impacts on natural and beneficial floodplain values. Without mitigation, Alternatives B2 and B4 wouldconstitute a “significant encroachment” since they would cause adverse impacts on natural and beneficialfloodplain values, however, mitigation would be provided to replace lost floodplain values. Floodplain impactsof Alternative B2, though of a smaller total area and volume than impacts of Alternative B4, would primarilyoccur between Airport Road and Lakeshore Drive, adjacent to residential areas. Floodplain impacts ofAlternative B4 would primarily occur south of Runway 34 in an area surrounded by an extensive undevelopedwetland and meadow area. Impacts on the east and west of Runway 34 end are similar between Alternatives B2and B4 (Figure 5-46). Due to the proximity to residential areas, the potential for adverse impacts to humansafety, health and welfare, a stated goal of Executive Order 11988, is greater for Alternative B2 than forAlternative B4. The floodplain impacts are not avoidable at the Runway 34 End, as it is situated in floodplain;however, minimization efforts were undertaken.5.14.7.2 Other ImpactsBased on the FIRM floodplain elevation, Alternative B2 would result in a smaller area of estimated floodplainloss than Alternative B4. The floodplain area and volume filled by Alternative B2 would be less thanAlternative B4. The natural and beneficial floodplain values lost by floodplain fill associated withAlternatives B2 and B4 include the natural moderation of floods and water quality maintenance. Alternative B2would directly impact a segment of Buckeye Brook in the federal floodplain potentially impacting fish passage.Alternative B4 would not impact this natural and beneficial floodplain value.5.14.8 Avoidance and MinimizationMitigation of floodplain impacts consists of three sequential steps: avoidance through the examination ofpotential project alternatives, minimization through the incorporation of special design measures that reduceunavoidable impacts; and finally floodplain mitigation (see Chapter 6, Mitigation) to offset unavoidable impacts.Chapter 5 - Environmental Consequences 5-249 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc