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Analysis and Abatement Guidance

Appendix B: Highway Traffic Noise Reporting

Noise Analysis Documentation

The final product of a highway traffic noise study should be a clear, concise written discussion of the study. This report gives the reader a detailed description of all the elements of the analysis done for the study including information on noise fundamentals and regulatory requirements. Additionally, the environmental document for Type I projects, i.e., Categorical Exclusion (CE), Environmental Assessment/Finding of No Significant Impact (EA/FONSI), Environmental Impact Statement (EIS), should contain a brief summary of the important points found in the highway traffic noise study report. The project development records should fully document the highway traffic noise analysis level-of-effort, strategies considered, adjacent resident's views on the desirability and acceptability of abatement, and a final decision on the feasibility and reasonableness of abatement.

Section 772.11(a) is the major requirement to prepare a highway traffic noise analyses on all Type I projects. However, these requirements include evaluation of noise reduction benefits, abatement cost, and SEE effects. This evaluation requires a balancing by the highway agency of benefits and disbenefits. Section 772.13 covers noise reduction benefits and abatement cost. The public involvement process strongly influences balancing noise abatement and the SEE effects of the mitigation. The people who live next to the highway project can best evaluate if the abatement benefits will outweigh the SEE effects. The highway agencies should not do this evaluation without public involvement.

It is also important to remember that noise abatement consideration should be an inherent project consideration incorporated and considered in the total project development decision. A noise analysis is required for all Type I and Type II projects regardless of their classification (i.e. controlled access, uncontrolled-access roads).

A simplified example of noise analysis documentation follows. A complete noise analysis should clearly describe each alternative under study and detail the adjacent land uses. Accurately labeled aerial photography and aerial photography with project alternative overlays also help readers visualize the project and gain a better understanding of the context and intensity of the proposed project. The noise analysis should include the following information. Examples of some of the sections follow. The order or format is not required, but the following provides a representation of the information needed in a highway traffic noise study.

NoiseAnalysis Contents
Section 1 Include Discussion Of:
1.Executive SummaryConcise project description, noise impacts, abatement considerations, commitments
2.Project History and Background InformationProject planning, detailed project description, purpose and need, ancillary improvements, characteristics of noise
3.Existing ConditionsLand uses, traffic conditions, roadway information
4.Existing Noise EnvironmentNSAs, sensitive receptors, measurement procedures and equipment, measured noise levels, modeled existing noise levels, FHWA NAC activity areas, basis for determining worst-case existing noise conditions
5.Analysis MethodologyFHWA and State noise policies, analysis procedure/model /version, validation/calibration process and results, model inputs, analysis years
6.Future Noise EnvironmentNo-Build and Build noise levels and comparisons, increase over existing levels
7.Traffic Noise ImpactsComparison with FHWA and State noise policies, identification of impacted and non-impacted receptors
8.Consideration of AbatementNAC, abatement options considered and examples, feasible/reasonable determinations, findings and recommendations, acoustical profiles
9.Construction NoisePhases, levels, impacts, abatement considerations
10.Public InvolvementCommunity meetings/input, survey/voting results, abatement commitments, effects of public input
11.Coordination with Local OfficialsRelated contacts, input, and information provided
12.Noise Report AppendicesThis section includes field data sheets, traffic data, FHWA TNM data files, feasible/reasonable worksheets, calibration certificates, etc. Some highway agencies may require submission of some or all of this information digitally to reduce the size of the report.

1NHI Noise Course Lesson 11 Noise Study Documentation

Existing Noise Environment Documentation Example

Figure # is a plan map of the study area and shows the location of the noise measurement sites. The microphone was located 5 feet above the ground. Measurement Site Nos. l, 2, and 4 are along the existing Airport Drive and near the apartment buildings closest to the project roadway. The selected sites are representative of receptors in the project study area and document existing noise levels and traffic conditions at the residential area where the potential for noise impacts due to the project exists. Sites 3 and 5 are located in residential areas near the location of the proposed extension of Airport Drive. This area has the lowest existing noise levels in the project corridor. Sites 6 and 7 are near the other roadways in the study area that carry substantial traffic and connect to the proposed project.

The existing noise measurements occurred during midday hours on June 12 and 13, 1988. The temperature varied around 22 degrees C, and winds were light and variable, having little effect on sound propagation over moderate distances.

Field staff collected noise measurements with an ABC Model 123 portable integrating sound level meter set to collect the A-weighted Leq at a slow response time. During the measurement, field staff noted ambient noise sources and counted local traffic. The duration of each measurement period was between 20 and 35 minutes.

Future Noise Environment Documentation Example

The noise analysis includes prediction of 2025 noise levels at each receiver for each of the seven alternatives under consideration using the FHWA TNM. This model uses the number and type of vehicles on the planned roadway, their speeds, and the physical characteristics of the road, e.g., curves, hills, depressed, elevated, etc. Preliminary alignment and roadway elevation characteristics were available for use in this noise analysis. The models included existing natural or man made barriers, but did not assume inclusion of any noise abatement measures. The model uses traffic volumes obtained from the Metropolitan Council Regional Traffic Assignment Model. The noise predictions made in this report are highway related noise predictions for the traffic conditions during the design year. For this analysis, the peak hour volumes and corresponding speeds for trucks and automobiles result in the noisiest conditions. During all other periods, the noise levels will be less than indicated in this report.

Traffic Noise Impact Documentation Example

The traffic noise analysis for the proposed actions predicts greatest noise impacts to occur at residential sites near the proposed loop location. Table No. 7 shows the result of this analysis. The average increase at the selected sites is +12 dB(A). The largest increases (up to +25 dB(A)) occur at rural residences close to the proposed highway.

For the preferred Alternate 3, 52 single family residences, 12 multiple family residences and 2 places of worship approach or exceed the noise abatement criteria. Fifty-two single family residences, 28 multiple family residences, 2 businesses, and 2 places of worship will experience a substantial increase in existing noise levels.

Consideration of Abatement Documentation Example

The most likely method available to reduce noise levels and alleviate noise impacts from Airport Drive is incorporation of noise abatement measures into the highway design. Since the alignment and grade of Airport Drive are established, noise barriers beside the roadway are the most acceptable means of noise abatement.

... The first proposed barrier location is along Airport Drive at the East Avenue Fair Oaks apartment complex. The proposed barrier is located 12 feet from the edge of Airport Drive, is about 1,770 feet long, and runs from a point about 150 feet north of the edge of Niners Road at the Airport Drive intersection to about 70 feet north of the northernmost apartment building. A barrier 10 feet above grade level provides 9 11 dB reduction in the noise levels at the nearest building, first floor elevation (5 feet above ground). This reduces the predicted exterior Leq noise levels near these buildings from 73 74 dB to 62 65 dB and achieves the 7 d(BA) reasonableness design goal.

...The cost of noise barriers depends directly on the material used to build it. Depending upon material selection, barrier costs including installation may be as little as $15 per lineal foot or as great as $75 per lineal foot. A wooden barriers erected along Airport Drive at the apartments would cost approximately $85,000. The cost of the barrier for the three homes is approximately $35,000.

Table 9: Example of Abatement Information for an environmental document
EXISTING AND FUTURE EXTERIOR NOISE LEVELS (Leq in dB(A))
Noise Receiver NumberLand Use Activity CategoryNumbers by Activity1 Average Distance to Roadway (Ft)Noise Abatement CriteriaMeasured Existing Noise LevelFuture Noise Levels by Project Alternative (Without and With Abatement)2
No-
Build
234
1B3 MF30067556366/5868/6068/60
2B7 SF17067585870/6072/6173/65
3C2 B26072545567/6069/6070/63
4B11 SF, 7 MF10067566273/6575/6575/69
5B16 MF15067525262/5966/6167/64
6B14 SF17067525475/6677/6977/71
7B12 SF, 1 MF20067535666/6269/6769/66
8B2 PW18067535469/6173/6273/69
9C3 B15072626769/-69/-70/-
10B7 SF, 1 MF23067576169/6669/6470/64
1 SF-Single Family Residence, B-Business
MF-Multiple Family Residence, PW-Place of Worship
2 66/58: 66 without abatement/58 with abatement

Reporting Decibel Levels

Highway agencies may consider reporting noise levels to the whole decibel by either rounding or truncating measured or modeled noise levels. Reporting noise levels to the tenth of a decibel may imply a false sense of accuracy and precision. Use caution in presenting material as this approach may result in presenting contradictory information to the public since the TNM reports noise levels to the tenth of a decibel. If a highway agency implements reporting of noise levels to the whole decibel, the highway agency should develop custom output tables from TNM for inclusion in noise analysis reports that round or truncate the results per the highway agency's noise policy.

Construction Noise Documentation

It is difficult to predict levels of construction noise at a particular receiver or group of receivers. Heavy machinery, the major source of noise in construction, is constantly moving in unpredictable patterns. Daily construction normally occurs during daylight hours when people tolerate occasional loud noises. The duration for individual receivers should be short; therefore, there are no anticipated disruptions of normal activities. However, the project plans and specifications include provisions requiring the contractor to make every reasonable effort to minimize construction noise through abatement measures such as work-hour controls and maintenance of muffler systems.

For additional information on construction noise, please refer to the FHWA Construction Noise Handbook (FHWA-HEP-06-015) and the Roadway Construction Noise Model (RCNM). Both are located at http://www.fhwa.dot.gov/environment/noise/construction_noise.

Coordination with Local Officials

This section documents the coordination process with local officials. The highway agency provides the specific information given to local officials to satisfy 23 CFR 772.17, notably, the best estimate of future noise levels on undeveloped land adjacent to the project within their jurisdiction and noise compatible planning strategies.

Updated: 01/26/2012
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