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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) Evaluation5.11.6 Cumulative ImpactsOver the last several decades, the City of Warwick has become more urbanized and the Airport has expanded insize. The lack of long-term historical water quality data makes it difficult to quantify the exact impact ofurbanization, but the qualitative changes to surface water bodies are clearly visible on the historical photographs.Since 1939, large areas of farmland in the City of Warwick have been replaced by residential development,including many new roads and buildings. This urbanization included a municipal stormwater system, whichconveys runoff from the streets into the local surface waters with little or no treatment. Replacing vegetatedareas with streets and urban structures has reduced groundwater recharge, increased peak flows during storms,and increased the potential for surface water contamination and stream erosion.Buckeye Brook receives the stormwater from hundreds of acres of residential development and approximately80 percent of the Airport (refer to Figure 5-43). It is highly likely that the impaired water quality in Buckeye Brook,Warwick Pond, and Mill Cove (part of the Upper Narragansett Bay watershed) is due in part to this urbanization.In addition to general impairment due to urbanized runoff, Buckeye Brook receives discharges from the Airport(combined flow from Outfalls 005A through 008A). The Airport has continuously improved the collection ofglycol-impacted stormwater, thereby reducing the Airport’s impacts on local water bodies. Additionalimprovements set forth in the No-Action Alternative will continue to reduce the amount of glycol-impactedstormwater during the deicing season. Under the No-Action Alternative, some benefits to water quality areanticipated regardless of whether or not the Improvement Program is implemented. Development unrelated to theAirport is expected in the Study Area, which is assumed to be constructed in accordance with RIPDESrequirements and would not affect water quality.Tuscatucket Brook and Callahan Brook, which discharge to Brush Neck Cove (part of the Greenwich Baywatershed), are surrounded by urban development and major roads such as Main Avenue andWest Shore Road. These water bodies are impaired due to elevated bacteria levels due to past changes andpresent uses within the watershed. Brush Neck Cove is considered a valuable and sensitive water body and iscurrently impaired due to pathogens, excess nutrients, and low dissolved oxygen. It receives runoff from only20 percent of the Airport (via Tuscatucket Brook) and receives the rest of its flow from the urbanized residentialareas surrounding the Airport. The secondary deicing area near the Runway 5 End discharges to Brush NeckCove via Tuscatucket Brook, which may impact Tuscatucket Brook. However, the deicing area is rarely usedand involves far less glycol than the primary deicing locations.In the No-Action Alternative, development unrelated to the Airport occurs in the Study Area, such as InterLink,constructed west of Post Road (completed in December 2010). The former Fain Farm property north of existingAirport Road is the intended site of a new retail development. In addition to these projects, minor improvementsare proposed for existing Airport Road. These are assumed to be constructed in accordance with RIPDESrequirements and would not affect water quality.The Airport has a variety of recovery measures in place to reduce the amount of deicing fluid that enters thestormwater system. RIAC has constructed a blending facility to reduce the amount of glycol used at the Airport,and made improvements to glycol collection, control, and recovery systems. These measures include the captureof glycol using catch basin inserts, vacuum trucks, and glycol-recovery vehicles with scrubbers. These measureshave reduced the magnitude of the Airport’s impacts on local water bodies in recent years, and implementingChapter 5 - Environmental Consequences 5-221 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc