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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) EvaluationTable 5-126Alternatives B2 and B4: Summary of Impacts to Estimated FloodplainsProgram Element and Associated ActionRunway 23 End and AMF Access Road relocationRunway 34 End and Taxiway C relocationFloodplain AreaArea(acres)Alternative B2StorageVolume(cubic yards)Area(acres)0.02.3Alternative B4StorageVolume(cubic yards)0726A0.4218B0.1 1 0C 0.0 15 0.0 0Total 0.5 233 2.3 7261 Alternative B2 impacts associated with Floodplain Area B are related to navigational aids. Area and volume impacts are considered negligible.Alternative B2 would impact the estimated floodplain in two locations: Floodplain associated with the AMFAccess Road and at the Runway 23 glide slope critical area near the Runway 23 End (Area A) and floodplain onthe east side of the Runway 34 End (Area C).Airport efficiency enhancements at the Runway 23 End would require approximately 218 cubic yards of fill tobe placed below the FEMA 100-year flood elevation in approximately 0.4 acres of floodplain in Area A(Figure 5-46).The impacts to Floodplain Area C would result from Airport safety enhancements. On the east side of Runway 34the Perimeter Road would be constructed below the elevation of the end-fire antenna to avoid interference withaircraft navigation. In order to relocate the Perimeter Road, fill slopes would be extended below the floodplainelevation. An estimated fill volume of 15 cubic yards would be placed below the FIRM floodplain elevation at thislocation, impacting a negligible acreage of floodplain (Figure 5-46 and Table 5-126).Indirect ImpactsFilling 0.4 acres of floodplain with 218 cubic yards of fill to construct the Runway 23 glide slope critical area andrelocate the AMF Access Road would displace existing flood storage in Wetland A5. This displacement, alongwith the addition of 30 linear feet of pipe could cause the culvert at Lakeshore Drive to overtop more frequently,resulting in temporary closures of Lakeshore Drive.Significant Impacts: Alternative B2 would not create a high probability of loss of human life or likely havesubstantial, encroachment-associated costs or damage, including interrupting aircraft service or loss of a vitaltransportation facility. However, Alternative B2 would have a significant impact since it would impact 0.5 acresof floodplain which, if unmitigated, would affect the natural moderation of floods, fish passage, groundwaterrecharge, and water quality maintenance.5.14.4.3 Alternative B4Alternative B4 would not impact floodplains at the Runway 23 End because the Runway-5-23 extension to atotal 8,700 feet would occur only to the south, outside of existing floodplains. Impacts associated with safetyChapter 5 - Environmental Consequences 5-247 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc