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Paul M. Kohler Noise Abatement Program Manager
DULLES CONNECTOR ROADSOUND WALL PROJECT
John C. Muse District Environmental Manager
Welcome
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• Introductions• Project Purpose and Guidelines• Results of the Study• Project Schedule• Fundamentals of Traffic Noise
Project Purpose
Per Chapter 874 Virginia Acts of Assembly 2010 “Pursuant to the provisions of the Memorandum of Agreement between the Commonwealth of Virginia Department of Transportation and the Metropolitan Washington Airports Authority, in conjunction with the construction of rail mass transit in the right of way of the Dulles Access/Toll Road Connector (DATRC), sound walls shall be constructed along residential properties from the beginning of the DATRC to Interstate Route 66 with funding from the Commonwealth Transportation Fund."
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Project Guidelines
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• Construct concrete sound walls along both sides of the highway within existing right-of-way
• Replace all existing wood walls• Identify noise receptors at nearest ground level area
of frequent human use• Compute loudest hour noise levels for rail & traffic
for existing and future year conditions• Reduce future noise levels below 67 decibels (dBA)*• Evaluate sound wall heights for most effective
mitigation of future noise level increases *Federal Highway Administration, 23 CFR Part 772 Table 1 – Noise Abatement Criteria for Activity Category B (July revision)
Noise Analysis Results
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• Over 600 locations within 500 ft modeled for loudest hour in Existing (2010) and Future (2032) Year Conditions
• 268 adjoining residential properties reported• Reflected traffic noise included in modeling• Computed noise levels along the corridor
vary due to attenuating features (e.g. berms)• 53 residential properties were predicted to
have future noise levels of 66 dBA or more
Noise Analysis Results
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Computed Noise LevelsExisting Conditions(w/ wood structure) 47 – 68 dBA
Design Year (2032)(w/out wood structure) 51 – 69 dBA
Computed with Proposed Noise BarriersDesign Year (2032) 48 – 65 dBA
Noise Reduction Up to 12 dBAAll future noise reduced below 67 dBA
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Summary of Proposed Sound Walls
Barrier ID Description Height Range (ft) Length (ft) Surface
Area (ft2)
EB-1Eastbound
(Route 123 to Idylwood Rd.)
13 7,726 100,441
WB-1Westbound
(Route 123 to Idylwood Rd.)
9 to 13 7,681 99,830
EB-2**Eastbound
(Idylwood Rd. to I-66)
13 2,408 31,307
WB-2Westbound
(Idylwood Rd. to I-66)
13 to 14 3,026 39,923
Totals 9 to 14 20,841 271,501
Project Schedule
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• Two Construction Phases
– Phase I – Ground mounted noise barriers– Phase II – Independent structure mounted
noise barriers
• Both Phases administered concurrently
Project Schedule
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• Public Hearing: September 2012
• Advertisement: December 2012
• Begin Construction: Spring 2013
• Substantial completion: December 2014
• Complete construction: Spring 2015
Comments1) Court Reporter
2) Comments Sheeta. Submit at tonight’s meetingb. Mail to VDOT
c. Email to VDOT: [email protected](please reference “Dulles Connector Sound Walls” in the subject line
Your comments would be appreciated bySeptember 23, 2012
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FUNDAMENTALS OF TRAFFIC NOISE
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WHAT IS NOISE?
• Noise is unwanted sound.• It is perceived differently by every person.• Can be irritating to one person may be
tolerant to another.• Sound is transmitted by pressure variations in
the air from its source.• Most sound sources are characterized as a
point or lines sources.• Noise barriers do not eliminate noise
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POINT vs. LINE SOURCE
• A point source occurs when a sound source is stationary (e.g. a horn).
• Sound radiates equally in all directions.• Noise levels for a point source decreases by 6
decibels per doubling of distance.
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POINT vs. LINE SOURCE
• A line source when many source are moving in a line (e.g. traffic noise).
• Noise levels for a line source decreases by 3 decibels per doubling of distance.– Example: If you experience 60 decibels at 50 feet then
you would experience 57 decibels at 100 feet.
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• Noise is measured in decibels on a logarithmic scale. This scale does not work the same way as most other familiar scales.
THE DECIBEL
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THE DECIBEL
≠ 279 dB
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• An increase in 10 decibels is considered as twice as loud to the average listener.
THE DECIBEL
Physical Noise vs. Perceived NoiseActual Sound Level
ChangePerceived Sound Level
Change+20 dBA Four times as loud
+10 dBA Twice as loud
+5 dBA Readily perceptible
+3 dBA Barely perceptible
0 dBA Reference level
-3 dBA Barely perceptible-5 dBA Readily perceptible
-10 dBA Half as loud
-20 dBA One quarter as loud
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• Doubling of the sound source causes noise levels to increase by 3 decibels.
THE DECIBEL
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THE DECIBEL
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THE DECIBEL
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THE DECIBEL
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THE DECIBEL
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• Traffic Noise Model 2.5 (TNM)• TNM used to predict and assess noise
levels in future (design) year. • TNM went through an extensive
validation effort to ensure its accuracy.• April 14, 2004 FHWA mandated the use
of TNM.
THE NOISE MODEL
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• Noise Model Inputs– Noise Sensitive
Receptors– Proposed design
alternative– Traffic (volume, speed,
composition)– Propagation Features
(Cut/Fill Lines, Building Rows, Ground Zones, etc.)
– Existing or Proposed Barriers
THE NOISE MODEL
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• Noise Model Results– Noise levels (existing,
design year, mitigated)– Barrier design
information
THE NOISE MODEL
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MITIGATION
• Where do we place the sound wall?– Between the source and the receiver.
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MITIGATION• Is there an optimal location?
– Yes but it depends on the terrain, existing utilities, and structures (bridges, signs and culverts) which is balanced among these variables.
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MITIGATION
• How high should we design the wall?– That depends on where noise impacts occur.– Was the line of sight broken?
Comments1) Court Reporter
2) Comments Sheeta. Submit at tonight’s meetingb. Mail to VDOT
c. Email to VDOT: [email protected](please reference “Dulles Connector Sound Walls” in the subject line
Your comments would be appreciated bySeptember 23, 2012
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Thank you for attending tonight’s
Public Hearing!
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DULLES CONNECTOR ROADSOUND WALL PROJECT
