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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) Evaluationnew measures would further reduce the amount of unrecovered deicing fluid entering the stormwater system.The improved glycol collection and diversion system and new glycol treatment facility that RIAC intends toimplement under a revised SWPPP to meet the terms of the RIPDES permit will further reduce the discharge ofglycol-impacted stormwater during the deicing season.In the foreseeable future, operations would decline at the Airport before increasing again beginning at a modestrate in 2012 due to the recent national economic recession. By 2025, aircraft operations at T.F. Green Airport areforecast to be similar to the 2004 activity level.Operations would increase over the No-Action Alternative for Alternatives B2 and B4 by 8.0 percent in 2020 and8.3 percent in 2025. The deicing and fueling operations associated with the flights would take place within theMill Cove drainage area, affecting the same urbanized water bodies that already receive runoff from the City ofWarwick and from the Airport. If BMPs were not implemented, the increases in operations could impact waterquality in tributaries to Mill Cove. Impacts will be avoided by the glycol blending system and implementationof the new deicing management system and by implementing stormwater BMPs such as detention- andinfiltration-based systems to prevent hydrologic impacts.With the implementation of BMPs, Alternatives B2 and B4 are not expected to have an adverse effect on thehydrology or water quality of the Brush Neck Cove and Mill Cove watersheds or the larger watersheds(Upper Narragansett Bay and Greenwich Bay). The changes in the amount of impervious surface would be lessthan 17 percent, and increases in peak discharge would be mitigated by compliance with stormwaterregulations. Any potential effects on water quality would be negligible.5.11.7 Comparison of Alternatives B2 and B4This section presents a comparison of impacts associated with Alternatives B2 and B4.5.11.7.1 Significant ImpactsAlternatives B2 and B4 would not result in significant water quality impacts since they would be designed incompliance with all applicable state and federal regulatory standards, including the 2010 RIDEM StormwaterDesign and Installation Standards Manual, to mitigate the significant impacts to water quality and ensure thereceiving waters are not impacted from new discharges. While Alternatives B2 and B4 both would increaseimpervious surfaces and the amount of glycol used for deicing departing aircraft, the proper design of a newstormwater management system and construction of the new deicer management system would ensure that bothAlternatives would meet state stormwater standards.5.11.7.2 Other ImpactsAlternative B2 would result in a net increase in roadway and parking area (impervious surfaces), with a17.8-acre net increase (Table 5-119), and Alternative B4 would result in no net change in roadway and parkingarea (impervious surfaces). The majority of the increases in impervious surfaces for both Alternatives are theresult of new runway, taxiway, and building impervious areas. Alternative B2 and B4 would also result in a1.0 and 0.9 percent net increase in pollutant loading respectively (Table 5-120), corresponding to the changes inimpervious surfaces. Alternatives B2 and B4 require mitigation measures designed to meet state stormwaterrequirements and would not adversely affect water quality. Additional measures to separate imperviousChapter 5 - Environmental Consequences 5-222 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc