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Last Updated: Friday, October 5, 2012 10:51 AM

Chapter 12 - Noise

WHAT DOES THE TOPIC INCLUDE?

This chapter provides an overview of Caltrans noise policies and procedures as they relate to transportation project planning and delivery. Information is provided to give the reader a basic understanding of the need to consider noise impacts, evaluate potential abatement measures and documentation requirements.

DECISION TREE - PRELIMINARY NOISE ABATEMENT (23 CFR 772)

Graphic of Noise Decision Tree

LAWS, REGULATIONS AND GUIDANCE

- See also SER Volume 1, Chapter 1 - Federal Requirements , Chapter 2 - State Requirements , and Chapter 38 - NEPA Assignment.

Federal Laws and Regulations

State Laws and Regulations

Guidance

Policy Memos

FURTHER REFERENCE

The following documents are available from the FHWA Highway Traffic Noise Website This link exits the SER website.

THE FEDERAL NOISE ANALYSIS

For a federal or federal-aid project, the noise technical report and the noise section of the environmental document must reflect the following basic analytical steps for all alternatives:

  • Is the project a Type 1 project?
  • If the project is a Type 1 project, would the project result in a noise impact that requires consideration of abatement?
  • If the project would result in a noise impact that would require consideration of abatement, noise abatement must be considered.
  • Is the proposed noise abatement reasonable and feasible?

Type 1 Projects

A Type 1 project as defined in 23 CFR 772, is a federal or federal-aid project for:

  • Construction of highway on new location; or
  • Physical alteration of vertical or horizontal alignment of existing highway; or
  • Additional through-traffic lanes.

For projects with noise studies completed after July 13, 2011, Type 1 project will be defined as a federal or federal aid project for:

  1. The construction of a highway on a new location or
  2. The physical alteration of an existing highway where there is
    either:
    1. Substantial horizontal alteration. A project that halves the
      distance between the traffic noise source and the closest
      receptor between the existing condition to the future build
      condition, or
    2. Substantial vertical alteration. A project that removes shielding
      thereby exposing the line-of-sight between the receptor and the
      traffic noise source. This is done by altering either the vertical
      alignment of the highway or the topography between the
      highway traffic noise source and the receptor; or
  3. The addition of a through-traffic lane(s). This includes the addition
    of a through-traffic lane that functions as a high-occupancy vehicle
    (HOV) lane, high-occupancy toll (HOT) lane, bus lane, or truck
    climbing lane; or
  4. The addition of an auxiliary lane, except for when the auxiliary
    lane is a turn lane; or
  5. The addition or relocation of interchange lanes or ramps added to a
    quadrant to complete an existing partial interchange; or
  6. Restriping existing pavement for the purpose of adding a through traffic
    lane or an auxiliary lane; or
  7. The addition of a new or substantial alteration of a weigh station,
    rest stop, ride-share lot, or toll plaza.

Caltrans extends the Type 1 definition in 23 CFR 772 to State highway projects without federal funding.

For local agency federal-aid transportation projects "off" the State Highway System (SHS) (Local Assistance projects) the determination as to whether or not a project is a Type 1 Project, and the decision to prepare a Noise Study, is made during completion of the Preliminary Environmental Study (PES) form. Instructions for determining Type 1 Projects are provided in the Local Assistance Procedures Manual, Chapter 6, Exhibit B, #1.

When Does a Project Result in a Noise Impact that Requires Consideration of Abatement

After the determination is made that the project is a Type 1 project, the next step in the analysis is to determine whether the project would result in a noise impact that requires consideration of noise abatement. To determine whether the project would result in a noise impact that requires consideration of abatement, several steps must be taken:

1. Identify Noise-Sensitive Land Uses - Identify existing land use activities which may be affected by noise from the highway. Examples of sensitive land uses include residences, schools, and hospitals. When identifying sensitive land uses, undeveloped lands for which development is planned, designed and programmed must also be included.

2. Determine Existing Noise Levels at Sensitive Receptors - Existing noise levels are determined at the worst hourly traffic noise hour. The Technical Noise Supplement (TeNS) provides information of how to conduct noise measurements. Also, the Caltrans Division of Environmental Analysis web page for noise issues provides online training on measurements and instrumentation (click on the “Training” link).

3. Model Future Noise Levels with the Project - Currently, the TNM 2.5 ProgramThis link exits the SER website. is the modeling software of choice to predict noise levels within a project. Prediction is based on inputs such as projected traffic volume (average daily traffic), traffic mix (percentage of truck traffic), topography and distance of the project from the receptors. Caltrans has agreed to require all new project noise studies, beginning after January 15, 2005, to use TNM version 2.5 or later for acoustic modeling of traffic noise. The exception to this requirement is for a reevaluation noise study of a project that was originally modeled using Sound 32 or Sound 2000.

4. Determine if Noise Impacts are Identified - A noise impact occurs when: 1) there is a substantial noise increase or/and; 2) the future traffic noise level with the project approaches or exceeds the noise abatement criteria (NAC).

Noise Abatement Considerations

If traffic noise impacts are predicted, noise abatement measures must be evaluated and considered. Preliminary noise abatement design includes considerations such as barrier heights, lengths, and location (see TeNS Section N-6000 for additional details). Noise abatement is only considered where frequent human use occurs and a lowered noise level would be of benefit.

Determining Whether the Proposed Abatement is Reasonable and Feasible

Noise abatement will be included as part of the project only if constructing the abatement is reasonable and feasible. To determine whether a noise abatement measure is reasonable, conduct a cost-benefit analysis taking the following criteria into account: absolute noise level, build versus existing noise, environmental impacts of abatement, public and local agencies input, newly constructed development versus development pre-dating 1978 and the total noise abatement allowance versus the project cost. Additional information on “reasonableness” can be found in the CaTNAP, Section 3 (for noise studies to be completed after July 13, 2011, see Noise Abatement subsection starting on page 14 of the Traffic Noise Analysis Protocol May 2011.) PDF icon The preliminary decision of providing noise abatement for exteriors of residential areas in activity Category B is made from the reasonable allowance per benefited residence. CaTNAP, Section 3 describes the process of how to determine the reasonable allowance per benefited residence (for noise studies to be completed after July 13, 2011, see Noise Abatement subsection starting on page 14 of the Traffic Noise Analysis Protocol May 2011.) PDF icon For noise studies that will completed after July 13, 2011, as part of the reasonableness analysis a determination will be needed regarding whether or not the proposed abatement meets the design goal of achieving a 7 dBA reduction in the future noise level at one or more benefited receptors.

Feasibility of noise abatement is basically an engineering concern. A minimum 5 dBA reduction in the future noise level must be achieved in order for an abatement measure to be considered feasible. Other considerations include topography, access requirements, other noise sources and safety considerations.

 

NOISE ANALYSIS FOR "STATE ONLY" PROJECTS

Noise analysis for state-only (no federal involvement) projects centers on whether the project or the proposed noise abatement would result in significant adverse environmental effects. Whether an increase in future noise level would result in a significant adverse effect for purposes of CEQA is determined based on the setting and magnitude of the noise increase, by comparing the existing noise level to the predicted noise level with project. For additional information, see Section 7 of the Traffic Noise Analysis Protocol May 2011.

Proposed noise abatement may also have the potential to result in significant adverse environmental effects if the abatement negatively affects other environmental resources, such as designated scenic highways, historic sites or endangered species. Whether the impact to another resource would result in a significant adverse effect is determined based on the setting and magnitude of the impact.

If the proposed project or the proposed noise abatement would result in a significant environmental effect, then an overall mitigation plan must be developed and reported in the Noise Study Report to be included in the environmental document. Note if a soundwall is included as "mitigation" for a potentially significant impact under CEQA, it must be built or the environmental document revised and potentially recirculated if the decision is made not to build the soundwall.

INTERAGENCY COORDINATION

There is no “resource” agency for Highway Traffic Noise. It is the responsibility of Caltrans (under NEPA Assignment) though the approval of environmental documents to ensure compliance with the provisions of 23 CFR 772. For "state-only" projects, Caltrans is responsible for the environmental document. For further guidance, see SER Volume 1, Chapter 38, NEPA Assignment.

State Right of Way (ROW) property is not subject to local government ordinances. However, all possible effort should be made to comply with the local ordinances.

Local noise ordinances can be found by accessing the local government’s web page. Local government web sites can be accessed here.This link exits the SER website.

A listing of all local governments that have noise ordinances is available at: http://ceres.ca.gov/planning/bol/1998/noise.html.This link exits the SER website.

REPORTING

Determining The Need For A Separate Technical Report: Traffic Noise Screening (for use only for projects using the 2006 Noise Protocol)

The screening procedure is intended to determine whether a detailed analysis is necessary. If a project passes the screening procedure, further analysis is normally not necessary and the results are documented in a brief technical memorandum. In instances when a project is considered controversial or when the net effects of changes in topography and shielding are not obvious, a detailed analysis is warranted even if the screening procedure may indicate otherwise. The complete procedure is covered in 2009 TENS – Chapter 4 page 4-1.

Noise Study Report/Noise Abatement Decision Report (NADR):

If the project fails the traffic noise screening process, then the results of a detailed traffic noise analysis is documented in the Noise Study Report. CaTNAP, Section 3 and TeNS Chapter 7, page N-105, describes in detail the process of developing a noise study report (for noise studies completed after July 13, 2011, see Section 5 of the Traffic Noise Analysis Protocol May 2011.) The Template - Noise Abatement Decision Report (NADR) is a report that documents the abatement considerations.

Preparer Qualifications

There are no required qualifications for the preparer of the noise study report. However, the preparer needs to be very knowledgeable of the laws and regulations pertaining to the noise issues.

Content and Recommended Format

The TeNS, section 7000 describes the proper format of the noise study reports. A good noise report contains all the necessary information for the reviewer to perform a review of the report with minimum need for further clarification and consultations. A good noise study report contains:

  • Detailed discussion of: land uses, existing and future measurements, proposed abatement, reasonable and feasibility analysis
  • Visual aids: Vicinity maps, area of potential effect (APE), layout that clearly indicate the location of impacted receptors relative to the project, proposed location of barriers, topographic information, etc.
  • Technical Information: meteorological information at the time of noise measurement, instrumentation used, inclusion in the appendices of any references mentioned in the report, modeling input and output files, projected traffic volume data
  • Evaluation of construction noise impacts

For Departmental projects, there are no formalized processing requirements for the noise study. However, the draft noise study report should be reviewed by the environmental generalist (project coordinator), the project manager and the project engineer at minimum. Following internal review of the draft noise study report, the noise study may be finalized. For further guidance, see SER Volume 1, Chapter 38, NEPA Assignment.

Local Agency Projects - Noise Study Reports prepared in support of local agency federal-aid transportation projects "off" the State Highway System (Locals Assistance projects) shall be processed through the District Local Assistance Engineer (DLAE). The report shall be reviewed by the district local assistance environmental generalist and/or a district local assistance engineer (if available). The District local assistance environmental staff review the noise study report to ensure that:

  • it complies with the requirements of all applicable federal laws, regulations, policy and guidance
  • the report format and content are consistent with the SER
  • the report summary and conclusions are consistent with the information included in the environmental document

Following Caltrans internal review of the Noise Study Report, the study may be finalized. For further guidance, see SER Volume 1, Chapter 38, NEPA Assignment.

Information for Environmental Documentation

The appropriate environmental document (e.g., draft environmental impact statement, environmental assessment) serves as the vehicle to circulate the preliminary noise abatement (NEPA/23 CFR 772) and CEQA mitigation decisions to the public for review and comment. More information on the process of reporting the preliminary noise abatement and mitigation decision can be found in the CaTNAP, Section 5 (for noise studies completed after July 13, 2011, see Section 5 of the Traffic Noise Analysis Protocol May 2011.).

CONSTRUCTION IMPACTS

Construction noise is only substantial in exceptional cases, such as pile driving and crack and seal pavement rehabilitation operations. The CaTNAP, Section 3 discusses construction noise (for noise studies completed after July 13, 2011, see Section 3 of the Traffic Noise Analysis Protocol May 2011.).

TIMING THE STUDIES WITH THE ENVIRONMENTAL PROCESS

The preliminary noise abatement decision (NEPA process) along with the preliminary noise mitigation decision (CEQA process) are incorporated into the environmental documentation. The draft environmental document is publicly circulated and substantive comments are addressed in the final environmental document. An illustration of this process and detailed description of the process are available in the CaTNAP, Figure 2 (for noise studies completed after July 13, 2011, see Figure 2 of theTraffic Noise Analysis Protocol May 2011.).

INFORMATION NEEDED FOR PROJECT DELIVERY

Regional Transportation Plan

This information should be documented in the environmental impact report prepared for the Regional Transportation Plan (RTP) and serve as a building block in subsequent decision making.

An RTP requires the preparation of a CEQA environmental document, normally a program or master EIR. Caltrans encourages the Metropolitan Planning Organizations/ Regional Transportation Planning Agencies (MPO/RTPA) to include the following information, as appropriate, in the environmental document for the plan:

  • Project conceptual design (highway on new alignment; substantially change vertical or horizontal alignment of existing highway; or increase number of through lanes; realignment, etc.)
  • Land uses (with reference to Noise Abatement Criteria categories)
  • Locations of potentially sensitive receptors within subarea or corridor under study (such as hospitals, schools, churches, libraries, auditoriums, public meeting rooms, motels, hotels, residences, recreational facilities and lands on which serenity and quiet are of extraordinary importance and which serve an important public need)
  • Existence of local noise ordinances covering the corridor or subarea

Project Initiation Document

Project Study Reports (and equivalents) should contain an “inventory of environmental resources, identification of potential environmental issues and anticipating environmental processing type. Potential mitigation requirements and associated costs would also be identified.”

For projects off the SHS (Local Assistance projects), complete the Preliminary Environmental Study (PES) form.

For projects on the SHS, the following information concerning noise is to be documented in the Preliminary Environmental Analysis Report and included in the PID:

  • Potential noise receivers (receptors) within or adjacent to the project
  • Potential noise impacts
  • Possible need for noise abatement measures
  • Monitoring need

Draft Project Report and Noise Abatement Decision Report (NADR)

The information contained in the Noise Study Report and NADR should be presented in the draft environmental document. Include the proposed configuration of any noise abatement measures along with the assessment of any impacts under the NEPA process and under the CEQA process.

Project Report

In addition to the information provided in the draft environmental document, also provide the following information in the final environmental document:

  • Noise attenuation features recommended for the preferred alternative
  • Cost estimates for abatement and mitigation measures

ACTIVITIES THAT MAY OCCUR DURING PROJECT DESIGN

Project re-analysis may be necessary if:

  • Significant change in design or scope
  • More than three years between milestones for an environmental impact statement
  • Undeveloped land becomes Planned, Designed and Programmed (PDP) after the noise analysis but before the project Date of Public Knowledge. (see CaTNAP, Section 3; for noise studies completed after July 13, 2011, see Section 3 of the Traffic Noise Analysis Protocol May 2011).
  • A PDP undeveloped land becomes developed after the project Date of Public Knowledge (disclose the impact but abatement not considered).

ACTIVITIES THAT MAY OCCUR DURING CONSTRUCTION

During the construction the project engineer may need to take action to resolve issue arise from:

  • Design specifications - may be not implementable on the construction site, therefore design modifications may be necessary.
  • Construction noise - refer to Noise Study Report for abatement considerations.
  • Construction induced noise - see the Transportation- and Construction-Induced Vibration Manual located on the Caltrans Noise and Vibration Publications website.

NOISE CONSIDERATIONS DURING MAINTENANCEANDOWNER-OPERATORACTIVITIES.

There are no known maintenance and owner-operator activities that need noise considerations.

OTHER ITEMS RELATED TO NOISE

Activity Categories And Noise Abatement Criteria

Federal Highway Administration and Caltrans have defined traffic noise impacts as those impacts which occur when the predicted traffic noise level approach or exceed the noise abatement criteria or when the predicted traffic noise levels substantially exceed the existing noise levels. CaTNAP, Section 3 describes the activity categories and the noise abatement criteria. For noise studies completed after July 13, 2011, the revisions to 23 CFR 772 did include modifications to the activity categories, see Section 3 of the Traffic Noise Analysis Protocol May 2011.

Substantial Noise Increase

Caltrans defines substantial noise increase when the predicted noise levels with the project exceed existing noise levels by 12 dBA, Leq(h).

Unusual and Extraordinary Abatement

Unusual and extraordinary abatement, such as noise insulation of residential units is considered for cases where the private residential dwelling units is predicted to be exposed to severe traffic noise impacts and normal abatement measures are physically not feasible or are economically unreasonable. Severe traffic noise impacts can be demonstrated, if the after-project exterior noise levels will reach a noise levels of 75 dBA, Leq(h), or more, or if the project will cause a noise level increase of 30 dBA or more over predicted noise levels if no project was constructed. CaTNAP, Section 3 discusses the various noise abatement methods considered for these extreme case.

For noise studies completed after July 13, 2011, the categories have changed by eliminating an interior requirement for residences. There is no longer a severe impact (75 dB) category and so no longer "extraordinary abatement". There is an interior requirement for public buildings of 52 dB under which the outside noise will be used to predict insertion loss of building facade.

(Last content update: 10/5/12: mcc, MCS)