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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) EvaluationTable 6-7Alternative B4: Summary of Potential Noise BarriersBarrier Project Road NeighborhoodLength(feet)(feet) Cost 1 Loss (dB)Range ofHeightInsertionNumber ofProtectedDwelling UnitsCEI($$/unit) 2CEI ($$/dBA(IL)/unit) 31 Main Ave Greenwood 114 12 $27,300 13 1 $27,300 $2,1502 Main Ave Greenwood 106 12 $25,480 6 1 $25,480 $4,5503 Main Ave Greenwood 278 12 $66,660 14 2 $33,330 $2,4334 Main Ave Greenwood 1,398 12 $335,520 5 to 15 15 $22,368 $2,1725 Main Ave Greenwood 468 12 $112,420 8 to 10 7 $16,060 $1,7276 Main Ave Greenwood 230 12 $55,280 10 to 15 2 $27,640 $2,229Note: See Figure 6-1 for location of the proposed noise barriers.Source: HMMH, 2011.1 Estimated barrier costs based on a unit cost of $20/square-feet.2 The cost-effectiveness index (CEI) was calculated two different ways, both of which are according to RIDOT policy. In the second column from the right, the CEI was computed in units of cost per protected dwelling unit ($/unit). Per RIDOT, a barrier is cost effective if the CEI, calculated in this manner, is less than or equalto $25,000/unit.3 The cost-effectiveness index (CEI) was calculated two different ways, both of which are according to RIDOT policy. In the rightmost column, the CEI wascomputed in units of cost per decibel of weighted insertion loss per protected dwelling unit ($/dBA(IL)/unit). Per RIDOT, a barrier is cost effective if the CEI,calculated in this manner, is less than or equal to $2,500.00/dbA(IL)/unit.Although both noise barriers (or “sound walls”) and berms both can provide effective noise mitigation, use ofberms often is limited by available right-of-way. Typically, berms are graded with a maximum vertical-tohorizontalslope of 1:2. That is, for each one foot of height, each side of the berm requires two feet of horizontalright of way. Therefore, a 12-foot high berm typically would require a minimum 48-foot footprint along its entirelength. The berm would look like a small hill along the roadway. In the majority of the Project Area, the use ofberms, rather than noise barriers, would require the acquisition of additional property or easements. Thewestern portion of Barrier 4 (Figure 6-1) that is on RIAC property is one area where a berm could be reasonablyconstructed. This area is already owned by RIAC and a wide footprint would not be a constraint. Furtherevaluation of the feasibility of constructing berms as an alternative to noise barriers will occur during laterstages of project design for the Preferred Alternative. Wherever possible the noise barriers or berms would beattractively landscaped and would be designed to not be an obstruction to air traffic.6.2.4.5 Install Quiet Pavement on Relocated Airport Road and Main AvenueAs part of constructing Partially Relocated Airport Road and Realigned Main Avenue for Alternative B4, RIACproposes to install open-graded asphaltic concrete (OGAC) pavement, or other quieter pavement, subject toRIDOT approval. Quieter pavement is a relative term for any pavement that produces less noise than another fromthe action of vehicle tires rolling over it. Quieter pavements are not limited to either asphalt or concrete, but ratherincorporate known practices, such as fine-tuning texture and/or porosity, to make either quieter. These measureshave the potential to reduce traffic noise levels by one to two decibels for nearby receptors, when compared toconventional pavement. These benefits tend to be greatest when traffic is mostly cars, speeds are greater than30 mph, and traffic is free flowing. In other cases, the roadside noise reduction from a quieter pavement can beChapter 6 – Mitigation 6-15 July 2011\\Mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH06_Mitigation_JUL_2011.doc