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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) Evaluationenhancements (Runway 34 RSA enhancements) are described in this section, shown in Figure 5-46, andsummarized in Table 5-126.Direct ImpactsSafety enhancements for Alternative B4 would require approximately 726 cubic yards of fill to be placed belowthe FIRM elevation of 14 feet NAVD 1988. This would alter approximately 2.3 acres of floodplain south ofRunway 34 (Area B).Indirect ImpactsThe 2.3 acres of floodplain fill associated with Alternative B4 that would occur within the FEMA floodplaincould potentially cause impacts indirectly at outside of the project area if not mitigated. However, the analysispresented in Appendix L, Floodplains, shows the impacts are limited to within the Project area. Therefore thereare no indirect impacts associated with this alternative.Significant Impacts: Alternative B4 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 B4 would have a significant impact on floodplains since it wouldimpact a total of 2.3 acres of floodplain, which could affect the natural moderation of floods, groundwaterrecharge, and water quality maintenance if unmitigated.5.14.5 Short-term Construction ImpactsThere are no temporary construction impacts to floodplains associated with Alternative B2 or B4.5.14.6 Cumulative ImpactsThe FIRM depicts a portion of the existing Runway 16-34 as being within the 100-year floodplain. 431 Based on theexisting topography at the Airport, this segment of runway is at approximate elevation 30 feet above NAVD1988, which is 14 to 15 feet above the 100-year flood elevation of 14 feet NAVD 1988. Because this runway wasconstructed prior to December 31, 1974, RIAC may file a Letter of Map Amendment requesting FEMA to revisethe Special Flood Hazard Zone depicted in the FIRM based on existing ground elevations. The Effective Date ofthe FIRM Community Panel Nos. 44003C 0113G, 4400131G, 4400129G, and 4400127G is December 3, 2010.According to FEMA, structures built on or before December 31, 1974, or before the effective date of the initialFIRM of the community (1973), whichever is later, are considered pre-FIRM. Since Runway 16-34 was extendedto 6,081 feet in 1967, the fill placed in floodplain to construct it would be considered pre-FIRM. After thePreferred Alternative enhancements have been designed, a Letter of Map Revision Based on Fill would be filedto revise the limits of the Special Flood Hazard Zone based on the ground elevations that would exist after theAirport enhancements have been constructed.Figure 5-47 depicts extensive areas west of the Runway 34 End where the former Truk-Away landfill and otheroperations may have filled larger areas of floodplain. These and other activities are estimated to have filled up to80 acres of floodplain along Buckeye Brook and Warwick Pond. Other minor encroachments into the Buckeye Brook431 Flood Insurance Rate Map City of Warwick, Rhode Island, Community Panel Number 445409 0006 E Map, Revised June 16, 1992.Chapter 5 - Environmental Consequences 5-248 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc