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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) EvaluationOne final minimization measure incorporated in the Runway 34 design presented in the FEIS involvedsteepening the side slopes adjacent to wetlands from the previous 4:1 gradient to the presently proposed 3:1slopes. This resulted in a further reduction of approximately 0.9 acres of wetland impact. These minimizationmeasures have been incorporated into the design of Alternatives B2 and B4.Runway 23Extending Runway 23 in Alternative B2 would result in direct impact to Wetland A5, the relocation ofapproximately 112 linear feet of Lower Buckeye Brook and placement of 30 linear feet of Lower Buckeye Brookin an extended culvert at Lakeshore Drive. Impacts to this wetland resource cannot be further minimizedbecause of the required configuration of the runway glide slope area, and the requirement to keep the PerimeterRoad and AMF access road out of the ROFA.Alternative B2 would minimize disturbance to Wetland A5 by routing the AMF Access Road over the fill section ofan existing Airport security road. Alternative alignments were considered for access to the AMF, including filling thenorth end of Wetland A5 and crossing Buckeye Brook on a structure midway between Lakeshore Drive and existingAirport Road. The selected option minimizes impact to wetlands by following the alignment of an existing gravelroad constructed in fill along the northeastern perimeter of the Airport. This existing gravel road is used by AirportOperations to inspect Airport property including the perimeter security fence. Alternative B4 avoids all wetlandimpacts at the Runway 23 End; therefore, minimization measures would not be necessary for this alternative.Fully Relocated Airport RoadThe Fully Relocated Airport Road cross section designed for Alternative B2 has been reduced to 64 feet(four 12-foot travel lanes, two 2-foot shoulders, and two 6-foot sidewalks) to minimize impacts to wetlands. Theuse of a bridge structure was considered to further minimize impacts, but relief between adjacent uplands andthe forested swamp is typically less than six feet. The depth of a bridge structure would not provide adequateclearance over the wetland to avoid impact to the wetland area spanned to justify the additional cost.Alternative B4 does not include Fully Relocated Airport Road. The roadway fill section could be confined byretaining walls with guard rails to minimize impact to the wetland.5.11 Water QualityThis section considers potential impacts to water quality from Alternatives B2 and B4 as compared to theNo-Action Alternative. It includes a discussion of the direct impacts, indirect impacts, the potential temporaryconstruction impacts, and the cumulative impacts that would occur to local water resources in the foreseeablefuture, and the potential mitigation measures that may be considered to reduce the magnitude of any significantimpacts to water quality.5.11.1 Regulatory ContextSeveral federal, state, and local statutes and ordinances protect water quality, including the CWA. The EPArequires a National Pollutant Discharge Elimination System (NPDES) permit for discharges of stormwater tosurface waters of the U.S. (40 CFR Parts 122,123 and 124). In Rhode Island, the NPDES authorized underChapter 5 - Environmental Consequences 5-208 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc