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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) EvaluationIndirect ImpactsAlternative B2 would increase the amount of parking areas and roadways within the Greenwich Bay watershedby 17.8 acres. All new roadway and parking areas would include mitigation measures designed to meet statestormwater requirements and would not adversely affect water quality. Alternative B2 would therefore notresult in adverse indirect impacts to the coastal watershed.Significant Impacts: Alternative B2 would not result in significant impacts to water quality. Increases inimpervious surfaces are mitigated for Alternative B2 through the design of a stormwater management systemdeveloped in compliance with regulatory standards.5.11.4.3 Alternative B4This section describes the direct and indirect impacts that would occur under Alternative B4. Table 5-116 shows thechanges in impervious area within the affected drainage areas. This analysis has been revised since the DEIS andnow assumes that the existing roadways will not be removed within the acquisition areas with the exception ofroadways that are to be relocated, such as Airport Road, or are physically impacted by the Improvement Program.Compared to the No-Action Alternative, Alternative B4 would increase the total impervious area by 70.2 acres, ofwhich the majority is split among the Buckeye Brook North drainage area (21.9 acres caused by the new taxiways,and Integrated Cargo areas), the Buckeye Brook South drainage area (34.9 acres caused by the new Runway 16-34RSA enhancements, the new taxiways, and the south service area) and the Tuscatucket Brook watershed (14.6 acrescaused by the Runway 5-23 extension). These would be partially offset by decreases due to removing commercial andresidential parking lots required for construction. Alternative B4 would include stormwater controls that willmanage discharges to Warwick Pond, Buckeye Brook North, Buckeye Brook South, and Tuscatucket Brook andwould limit peak flows and erosion at the outfalls and in the downstream reaches of these brooks. In addition,Callahan Brook would have reduced overall peak flow due to the decreased impervious area in the watershed.Table 5-116 Impervious Surfaces by Drainage Area (Alternative B4)Impervious Area (acres) 1 Alternative B4 Change in Impervious Area (acres) 2Drainage Area No-Action Alt. B4Required forConstruction 3Voluntary LandAcquisition Areas 4 TotalBuckeye Brook North 237.0 258.9 +21.9 0 +21.9Warwick Pond 11.7 12.9 +1.2 0 +1.2Buckeye Brook South 161.6 196.5 +34.9 0 +34.9Mill Cove (cumulative) 5 410.3 468.3 +58.0 0 +58.0Tuscatucket Brook 35.0 49.6 +15.0 (0.4) +14.6Callahan Brook 24.3 21.9 +1.1 (3.5) (2.4)Brush Neck Cove (cumulative) 6 59.3 71.5 +16.1 (3.9) +12.2Total 469.6 539.8 +74.1 (3.9) +70.2Source: VHB, Inc.1 Portions of the watersheds that fall within the maximum combined footprint of the Alternatives (including both on and off Airport areas). 2 Includes existing pavement, proposed pavement, and impervious surfaces from land acquisitions. Existing roadways were assumed to remain impervious.3 Construction elements include EMAS, parking, roadways, taxiways, and RSA and RPZ clearing, depending on drainage area.4 Associated with the Completed and Current Part 150 VLAP.5 The Mill Cove drainage area consists of the combined Buckeye Brook North, Warwick Pond, and Buckeye Brook South drainage areas evaluated in this analysis.6 The Brush Neck Cove drainage area consists of the combined Tuscatucket Brook and Callahan Brook drainage areas evaluated in this analysis.Chapter 5 - Environmental Consequences 5-217 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc