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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) Evaluation5.14.8.1 AvoidanceThroughout the project design, the RIAC and FAA worked to identify alternatives that would avoid impacts tofloodplain. During this process several alternatives were designed and assessed to determine if they werepracticable.Runway 34Impacts to the floodplain south of Runway 34 could be avoided if all the enhancements were shifted northtowards the Runway 16 End where no floodplains are present. The Runway 34 RSA enhancements proposedunder Alternative B2 are not practicable because this action would require the taking of Airport Plaza resulting inunacceptable socioeconomic impacts associated with the loss of jobs and taxable infrastructure. Alternative B4shifts Runway 16-34 nearly 100 feet north away from floodplain at the Runway 34 End. This was determined to bethe greatest distance the runway could be shifted north without the need to demolish Airport Plaza.Earlier designs for the Runway 34 End included a hold apron for aircraft awaiting clearance or conducting apreflight checklist in preparation for takeoff. This feature was eliminated to avoid floodplain impact. Impactwas further avoided by routing the Perimeter Road between the runway end and the EMAS installed withinthe RSA.Runway 23Under Alternative B2, the floodplain at the Runway 23 End would be impacted in order to relocate the AMFaccess road to an area that would not conflict with the ROFA and to construct the level glide slope critical areaused as a navigational aid for planes landing at Runway 23. Alternative B4 avoids any impacts to the estimatedfloodplain and state-regulated floodplains at the Runway 23 End by shifting Runway 5-23 to the south only.5.14.8.2 MinimizationThroughout the project design, the RIAC and FAA worked to identify alternatives that would achieve theproject while minimizing impacts to floodplain. During this process several alternatives were designed andassessed to determine if they were practicable.Runway 34As previously reported in the DEIS, EMAS has been used at both ends of Runway 16-34 to shorten the length ofRSA that needs to be filled from 1000 linear feet from the runway end to 600 linear feet. Since an alternativewithout EMAS was not designed, it is difficult to assess the benefit, but most of the additional RSA would havebeen within floodplain. After completion of the DEIS, impacts to floodplain east of Runway 34 (Area C) wereminimized by re-examining the location of the Perimeter Road on the east side of Runway 34 along with thedesign requirements for the end-fire glide slope; a critical part of the system that allows aircraft to makeinstrument landings on the runway. Runway 34 is equipped with an end-fire antenna. The imaging type glideslope, which is used at the other three runways at the Airport, has specific site requirements reflected in theprevious glide slope area grading design for Runway 34. The end-fire system is a non-image system, and isdesigned for use in areas where conformance to the imaging type glide slope criteria is impractical. Due to theuse of an end-fire system at Runway 34, the side slopes along the runway can be steepened beginning at theedge of the RSA. This in turn allowed the Perimeter Road to be shifted closer to the side of Runway 34. ThisChapter 5 - Environmental Consequences 5-250 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc