7.0 MITIGATION OF CONSTRUCTION NOISE
7.1 Introduction
This chapter provides more examples of typical mitigation techniques and options. Information provided is not to be considered all-inclusive, nor is it intended to limit the ingenuity or resourcefulness of designers, contractors, and inspectors, or create a strategy uniquely suited to the characteristics of a specific project.
| Design Options |
|---|
| Design and Project Layout |
| Sequence of Operations |
| Alternative Construction Methods |
| Contract Specifications/Special Provisions |
| Operational Constraints |
| Time Periods and Duration |
| Specified Equipment |
| Noise-Related Incentives/Disincentives |
| Training Programs for Contractor |
| Mitigation at the Source |
| Stationary Equipment |
| Mobile Equipment |
| Selection of Equipment |
| Inspection/Maintenance Programs |
| Equipment Operation Training |
| Mitigation Along the Path |
| Natural Shielding |
| Temporary Shielding |
| Permanent Shielding |
| Mitigation at the Receiver |
| Building Envelope Improvements |
| Masking |
| Relocation of Residents |
| Public Involvement and Project Coordination |
| Critical components of the overall mitigation strategy. Should be considered during all phases of a project. |
Table 7.1 Overview of mitigation options.
The level of detail in a contract required to address construction noise mitigation is dependant on the complexity of the project, the amount and type of work required, and the sensitivity of the area beyond the project boundary. Therefore, not all projects require the same amount of detail. Such detail could range anywhere from the inclusion of a standard specification requiring the contractor to be governed by local noise ordinances, to realigning the highway, providing for abatement structures, and/or relocation of residents.
The effective control of highway construction noise can be achieved in much the same manner as the control of operational traffic by considering the following techniques:
- Alternative design options;
- Mitigation at the source;
- Mitigation along the path; and
- Mitigation at the receiver.
Another effective technique is the inclusion of operational conditions via contract specifications and special provisions.
Public Involvement and project coordination are also essential components of the overall mitigation strategy worthy of consideration during all phases of a project. For a more detailed discussion of this topic, refer to Chapter 8.
Most of the options presented in this chapter can be employed independently or in combination, depending on the scope of the project and the resultant effects that are desired. While reductions in noise levels will vary with the method employed, consideration of all practical and feasible options is essential during all stages of the project development from planning through design and construction to final evaluation.
7.2 Design Options
Noise impacts can occur on any project involving the construction of a highway facility. While the magnitude of the impact construction noise may have on a community may not be known early in the project development stages, measures can be implemented during the design phase that can help to reduce the anticipated noise impacts at sensitive receptors. However, design changes and modification to project layout are not always practical or feasible. Also, the magnitude of the noise reduction attained from some of these techniques is usually difficult to determine prior to and possibly even during construction.
7.2.1 Design Phases
In addressing construction noise mitigation during the design phases of a project, abatement opportunities can be considered for a variety of areas and features including those listed below:
- Storage Areas: During the planning and design stages of a project, storage areas may be able to be designated in locations removed from sensitive receptors. Where this is not possible, the storage of waste materials, earth, and other supplies may be able to be positioned in a manner that will function as a noise barrier.
Figure 7.1 Storage area in highway right-of-way (Photo #177)
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Figure 7.4 Designated haul routes (Photo #560) |
- Detours: Increased noise generated by temporarily rerouting traffic during construction is considered as part of construction noise. It is essential to consider efforts to reduce the impact from such changes during the design phases of the project.
Figure 7.5. Shifting of traffic to accommodate construction. (Photo #1261)
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Figure 7.6 Existing retaining wall acting as noise barrier during construction (Photo #543) |
7.2.2 Sequence of Operation
The sequencing and scheduling of construction operations is equally important in addressing and mitigating construction-related noise:
- Concurrent Operations: It may be possible to schedule several noisy operations concurrently to take advantage of the fact that the combined noise levels produced may not be significantly greater than the level produced if the operations were performed separately.
Figure 7.7 Early construction of noise barriers (Photo #447)
- Early Construction of Noise Barriers: Ultimately, noise barriers that are to be constructed as part of the project for traffic noise abatement can possibly be installed during the initial stages of construction to reduce the noise impacts of the construction.
7.2.3 Alternative Construction Methods
Alternatives to standard construction techniques may also be available and determined to be more practical and/or cost-effective in dealing with construction noise impacts and perceptions. Examples associated with several operations are discussed below.
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Figure 7.8 Alternative to pile driving (Photo #509) |
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Figure 7.9 Diesel compressor with baffled housing (Photo #69) |
7.3 Contract Specifications and Special Provisions
Contract specifications and special provisions are typically produced during the design stages of project development and may be included in the project plans and contract documents. Ideally, use of these documents is considered in conjunction with other control methods to achieve an overall construction noise strategy. Examples of such specificationsref023, ref028, ref103, and ref053 are referenced in this Handbook.
7.3.1 Construction Noise Criteria Limits
When establishing suitable noise criteria limits for specifications and special provisions, they can be characterized as either being "relative" or "absolute" or a combination of both. These can be defined even further by dividing the set limits into specific time periods during the day, such as daytime, evening, and nighttime. Experience has shown that the "absolute" criteria combined with the "relative" criteria levels appears to be more realistic and tends to be self-adjusting to varying conditions, particularly when defined for the various periods of the day. An example of one such set of construction noise criteria is shown in Table 7.2.
Table 7.2 Example of Absolute and Relative Construction Noise Criteria Limits.
| Lot-Line Construction Noise Criteria Limits A-weighted in dB, RMS slow | ||||||
|---|---|---|---|---|---|---|
| Noise Receptor Locations and Land-Uses | Daytime (7 AM - 6 PM) | Evening (6 PM - 10 PM) | Nighttime (10 PM - 7 AM) | |||
| L10 | Lmax | L10 | Lmax | L10 | Lmax | |
| Noise-Sensitive Locations: (Residences, Institutions, Hotels, etc.) | 75 or Baseline + 5 (whichever is louder) | 85 90 (impact) | Baseline + 5 | 85 | Baseline + 5 > (if Baseline <70) >Baseline + 3 (if Baseline 70) | 80 |
| Commercial Areas: (Businesses, Offices, Stores, etc.) | 80 or Baseline + 5 | None | None | None | None | None |
| Industrial Areas: (Factories, Plants, etc.) | 85 or Baseline + 5 | None | None | None | None | None |
Notes: L10 noise compliance readings are averaged over 20 minute intervals. Lmax noise compliance readings can occur instantaneously. Baseline noise conditions must be measured and established prior to construction work, commencing in accordance with the noise specification, which requires baseline noise readings over three 24-hour periods at each receptor lot-line location.
Source: Adapted from Central Artery/Tunnel Noise Specification and Table 2 in Appendix A.
As shown in Table 7.2, the noise specification's lot-line criterion is primarily a relative criterion in which construction noise levels, in general, can not exceed baseline (preconstruction) L10 noise levels by more than 5 dB at identified noise sensitive receptor locations. Lmax noise limits also apply at the lot lines and are intended to address loud impact-type noise events. In the above criteria, the following three types of receptor land uses have been suggested:
- Noise Sensitive Areas consisting of sites with nighttime land use such as residences, hotels, and hospitals;
- Commercial Areas containing land uses such as businesses and office buildings; and
- Industrial Areas containing factories and large plants.
The lot-line criteria limits are more stringent for residential receptors than for commercial or industrial receptors in lieu of the more sensitive nature of residential land uses. In addition, there are different criteria limits depending on various times of day, with the most restrictive noise limits applied to the more sensitive nighttime period.
As shown in Table 7.3, contract specifications can also contain an absolute noise criterion which can be applied to generic classes of heavy equipment to limit their noise emissions. Equipment-specific A-weighted Lmax noise limits, in dBA, evaluated at a reference distance of 50 feet, are defined in the noise specification. Thus, contract specifications could contain two types of noise criteria limits (relative lot-line limits and absolute equipment emissions limits), defining compliance requirements for the contractor. Consequently, if measured or anticipated construction noise levels exceed the allowable noise criteria limits, noise mitigation measures may be warranted during similar work activities.
Table 7.3 Example of Possible Construction Equipment Noise Emission Criteria Limits.
| Equipment Description | Lmax Noise Limit at 50 ft, dB, slow |
Equipment Description | Lmax Noise Limit at 50 ft, dB, slow |
|---|---|---|---|
| All other equipment > 5 HP | 85 | Gradall | 85 |
| Auger Drill Rig | 85 | Grader | 85 |
| Backhoe | 80 | Horizontal Boring Hydraulic Jack | 80 |
| Bar Bender | 80 | Hydra Break Ram | 90 |
| Blasting | 94 | Impact Pile Driver (diesel or drop) | 95 |
| Boring Jack Power Unit | 80 | Insitu Soil Sampling Rig | 84 |
| Chain Saw | 85 | Jackhammer | 85 |
| Clam Shovel | 93 | Mounted Impact Hammer (hoe ram) | 90 |
| Compactor (ground) | 80 | Paver | 85 |
| Compressor (air) | 80 | Pickup Truck | 55 |
| Concrete Batch Plant | 83 | Pneumatic Tools | 85 |
| Concrete Mixer Truck | 85 | Pumps | 77 |
| Concrete Pump | 82 | Rock Drill | 85 |
| Concrete Saw | 90 | Scraper | 85 |
| Crane (mobile or stationary) | 85 | Slurry Plant | 78 |
| Dozer | 85 | Slurry Trenching Machine | 82 |
| Dump Truck | 84 | Soil Mix Drill Rig | 80 |
| Excavator | 85 | Tractor | 84 |
| Flat Bed Truck | 84 | Vacuum Street Sweeper | 80 |
| Front End Loader | 80 | Vibratory Concrete Mixer | 80 |
| Generator (25 KVA or less) | 70 | Vibratory Pile Driver | 95 |
| Generator (more than 25 KVA) | 82 | Welder | 73 |
Source: Adapted from Central Artery/Tunnel Noise Specification
7.3.2 Time Periods and Duration
Time constraints and use of equipment regulations can be effective in reducing the impacts caused during sensitive time periods. In addition, operating noisy equipment only when necessary and switching off such equipment when not in use can minimize noise impacts.
Figure 7.10 Nighttime bridge construction (Photo #661)
Figure 7.11 Nighttime demolition operation (Photo #1049)
7.3.3 Specified Equipment
Another effective noise mitigation technique involves use of the quietest practical type of equipment. To avoid confusion and misinterpretations, such types should be specified in the contract specifications and special provisions.
7.3.4 Noise Related Incentives/Disincentives
Another technique worthy of consideration involves the inclusion of incentives and/or disincentives in the contract specifications to encourage contractors to participate in the mitigation program and to make the contractors more accountable for impacts.
7.3.5 Training Programs for Contractors
It may be appropriate to require contractors to participate in training programs related to project-specific noise requirements, specifications, and/or equipment operations. Such training may be provided by agency or project management personnel, outside consultants, and/or equipment manufacturers or suppliers. For example, project personnel (or consultants assigned to the project) may train the contractor in the measurement of construction-related noise levels that may be required to meet the contract specifications.
The contractor may also receive onsite training related to noise-specific issues and noise-critical areas and sites adjacent to the project. Equipment manufacturers and/or suppliers may be available to provide training to the contractor on the proper use of the noise abatement features of specific pieces of construction equipment. Any training requirements that are envisioned to be required would typically be described or referenced within the contract's specifications and special provisions.
