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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) Evaluationsurfaces, such as taxiways and runways, from the closed drainage system would further decrease pollutantloading.Alternative B4 includes small local increases in impervious surfaces within specific drainage areas that wouldrequire additional treatment. For example, Alternative B4 includes a small increase (1.0 acres in the BuckeyeBrook South drainage area, 1.5 acres in the Callahan Brook drainage area) in roadway area discharging toBuckeye Brook south of Warwick Pond and Callahan Brook, although there is no net increase within anydrainage area. Additionally, Alternatives B2 and B4 include small local increases in pollutant loading,corresponding to the increases in impervious surfaces within the drainage area that would require additionaltreatment. For example, Alternative B2 and B4 include an increase (5.2 and 13.5 percent in the Warwick Ponddrainage area respectively) in the pollutant loading from the area draining to Warwick Pond. Overall, thepollutant loading would be greater for Alternative B2.In the absence of mitigation, any local increases in roadway area could increase pollutant loads entering thereceiving waters from a specific outfall. Alternatives B2 and B4 would include BMPs for any new roadways andparking areas to meet Rhode Island water quality regulations and TSS removal requirements. As a result ofthese BMPs and the net decrease in roadway area, neither Alternative B2 nor B4 would cause downstreamwater quality impacts from roadway runoff.Alternatives B2 and B4 would have similar construction period impacts, including potential contact withgroundwater near the former Truk-Away Landfill site. Rhode Island requirements for handling contaminatedmaterials and preventing environmental impacts from erosion would be followed.Overall, Alternative B2 would have greater water quality impacts than Alternative B4 due to a substantial increase inroadway and parking areas. Alternative B2 requires greater overall new impervious area and would have a newstormwater discharge to Spring Green Pond from the Fully Relocated Airport Road. Alternatives B2 and B4 wouldreduce roadway and parking areas within the Tuscatucket Brook watershed and the Brush Neck Cove watershed asa whole, thereby reducing pollutant loading. This analysis shows that, with mitigation, Alternatives B2 and B4 wouldmeet state stormwater standards and other stormwater BMPs would avoid or mitigate any water quality problems.Table 5-119Measure of ImpactComparison of Impervious Surface ChangesTotal Impervious Surface Area (acres)No-ActionAlternativeAlternativeB2AlternativeB4Change in Area (acres) 1AlternativeB2AlternativeB4Impervious Area in Mill Cove Drainage Area410.3478.1468.3+67.8+58.0Impervious Area in Brush Neck Cove Drainage Area59.371.371.5+12.0+12.2Total Impervious Area469.6549.4539.8+79.8+70.2Roadway and Parking Area in Mill Cove Drainage Area 2Roadway and Parking Area in Brush Neck Cove Drainage Area 2Total Roadway and Parking Area 2 158.140.1198.2178.737.3216.0159.139.1198.2Source: VHB, Inc.1 All changes in this table are relative to the No-Action Alternative. Totals rounded.2 Roadway and parking area is a subset of the impervious area and is included in the overall impervious area measurements.+20.6(2.8)+17.8+1.0(1.0)0.0Chapter 5 - Environmental Consequences 5-223 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc