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Construction Noise Handbook

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.

Table 7.1 Overview of mitigation options.

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.

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:

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:

A storage area for equipment and other goods needed for the construction project can be placed far from sensitive receptors or in land uses not affected by noise, such as highway right-of-way.

Figure 7.1 Storage area in highway right-of-way (Photo #177)

A storage area with a few supplies and construction equipment are shielded partially by a stock pile of excess fill.

Figure 7.2 Partial shielding of storage area in residential area (Photo #247)

A storage area for supplies and equipment (as noted by the crane) in a residential location that is placed far from residences and near the highway right-of-way. A temporary wooden barrier can also be seen partially shielding the storage area.

Figure 7.3 Storage area in remote location (Photo #1257)

  • Haul Roads: Haul roads can be designated in locations where the noise impacts caused by truck traffic will be reduced.

An orange sign with directional arrow posted on existing sign pole designating a street as a haul route for trucks on the Woodrow Wilson Bridge project in metro DC area.

Figure 7.4 Designated haul routes (Photo #560)

A street next to a roadway is blocked off as a construction site, thus causing congestion on the adjacent roadway. A dump truck, hoe ram, and front end loaders are on site.

Figure 7.5. Shifting of traffic to accommodate construction. (Photo #1261)

  • Existing Barriers: As early as possible in the design development process, natural and artificial barriers such as ground elevation changes, existing buildings, noise walls, and other structures can be considered for use as a noise shield during certain operations.

A construction site in the highway right-of-way uses an existing retaining wall to act as a noise barrier for a stationary grout injection activity. An historic cemetery and residences are in the background.

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:

An aerial photo of a highway construction site that has been graded. Since noise barriers were part of the highway project, they were built first to shield nearby residences from the majority of construction activities.

Figure 7.7 Early construction of noise barriers (Photo #447)

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.

  • Pile Driving: Pile driving may produce noise levels in excess of acceptable limits, even when feasible noise reduction methods are used. Various dampening and shielding methods discussed later can attain some reduction. However, such methods rarely reduce the noise level to an acceptable level for the sensitive receptors close to the site. As an alternative to driving piles, it is possible to use vibration or hydraulic insertion techniques. Drilled or augured holes for cast-in-place piles are another alternative that may produce noise levels significantly lower than the traditional driving method.

Instead of pile driving (an extremely noisy activity), alternative construction methods can be utilized. An auger is used to drill a hole for a cast-in-place pile.

Figure 7.8 Alternative to pile driving (Photo #509)

  • Compressors: While most compressors are powered by diesel or gasoline engines, many are contained or have baffles to help abate noise levels. Electric compressors are significantly quieter than diesel or gasoline engine powered compressors.

A diesel compressor with baffled housing is used for a project where nearby residences are present. An electric compressor is significantly quieter than a diesel or gasoline compressor.

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:

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.

A crane is placing a span of bridge onto two abutments on a nighttime bridge project.

Figure 7.10 Nighttime bridge construction (Photo #661)

A nighttime demolition of an existing concrete bridge span has a loader, bulldozer, and several water sprayers to minimize dust.

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.

7.4 Mitigation at the Source

Source control is, in general, the most effective form of noise mitigation and involves controlling a noise source before it is able to emit potentially offensive noise levels. Construction noise (exclusive of blasting) is typically generated by two source types:

Noise levels from both types of noise sources are dependent on equipment characteristics and their operation.

7.4.1 Equipment - All Types

The following discussions relate to both stationary and mobile construction equipment:

Several construction workers use a vibratory soil compacter on a roadway project. In comparison, the picture on the right is of the same roadway project with one construction worker using a typical soil compacter, which is much larger in Several construction workers use a typical soil compacter on a roadway project. In comparison, the picture on the left is of the same roadway project with several construction workers using a vibratory soil compacter, which is much smaller in size.

Figure 7.12 In some instances, using a less noisy piece of equipment (right) may be possible, as opposed to using more conventional and sometimes noisier equipment (left) to perform the same operation (Photos #505 & #506)

A stationary piece of recycling equipment uses a muffler system to reduce or eliminate noise. Mufflers can be used on the air intake and exhaust systems of stationary and mobile equipment.

Figure 7.13 Muffler system on recycling equipment (Photo #1287)

A stationary piece of equipment that is unshielded and not baffled. Shielding on stationary equipment can be quite effective for noise reduction.

Figure 7.14 Unshielded, non-baffled equipment (Photo #74)

A compressor on a trailer is contained within a shell that shields the compressor noise.

Figure 7.15 Shielded compressor (Photo #18)

A 20 foot high, round dampener surrounds a pile driving hammer to minimize noise from the impact of the hammer on the pile.

  • Dampeners: Equipment modifications, such as dampening of metal surfaces, is effective in reducing noise due to vibration. Another possibility is the redesign of a particular piece of equipment to achieve quieter noise levels.

A 20 foot high, round dampener surrounds an underwater pile driving hammer to minimize noise from the impact of the hammer on the pile.

Figure 7.16 Examples of pile driver shielding and dampening (Photos #1277, #1281 & #1308)

A 20 foot high, square dampener surrounds a pile driving hammer to minimize noise from the impact of the hammer on the pile.

  • Bubble Curtains: Where piles are driven or drilled through water, bubble curtain technology may be employed. Bubble curtain techniques introduce specifically sized air bubbles into the water surrounding the pile in a controlled manner, thus dampening the shock waves and helping to minimize the effects on aquatic life. Air may be released in a variety of ways, including through a ring, as shown in Figure 7.18 below.

A construction worker stands near an underwater pile driving hammer with an operating bubble curtain surrounding the pile and hammer. The bubbles are visible at a few feet higher than the water surface at the top of the curtain.

Figure 7.17 Bubble curtain (Photo #57)

See References 030, 036, 046, 054, 060, 061, and 102 for information related to aquatic effects.

A bubble curtain air release ring. This is a ring of round pipe that has specifically sized holes that release compressor provided air.

Figure 7.18 Bubble curtain air release ring (Photo #51)

A bubble curtain operates around an underwater pile that is part of a multiple pile structure. The air bubbles are visible at the water surface.

Figure 7.19 Bubble curtain (Photo #52)

  • Enclosures: Enclosures for stationary work may be constructed of wood or any other suitable material and typically surround the specific operation area and equipment. The walls could be lined with sound absorptive material to prevent an increase of sound levels within the structure. They should be designed for ease of erection and dismantling.

Low cost straw bales are stacked like blocks in a four-sided enclosure. One corner is open so a worker may access the equipment. The access site can be blocked when worker is completed with task.

Figure 7.20 Straw bail enclosure for stationary equipment (Photo #58)

Blasting mats constructed with black tires can be seen intermingled amongst a pile of large rocks post blast.

Figure 7.21 Blasting mats constructed with black tires (in foreground of photo) (Photo #261)

A blasting mat made of black tires is being placed into position with a excavator.

Figure 7.22 Blasting mats being placed into position (Photo #1341)

A large, bulky, dirty, and rusty paver still functions well, but may emit louder noise than a newer piece of equivalent equipment.

Figure 7.23 Older equipment may be as efficient as new, but may not meet noise emission requirements (Photo #809)

Paving equipment that is small, efficient, and in good working condition is likely quieter than older equivalent equipment.

Figure 7.24 Newer paving equipment (Photo #813)

A new, efficiently designed wheel loader appears to be clean and well maintained. Regular service of equipment is an essential to quietest operation possible. Equipment suppliers may also be valuable source of training related to proper use of equipment.

Figure 7.25 Regular service of equipment is an essential component to quietest operation possible. Equipment suppliers may also be valuable sources of training related to proper use of equipment. (Photo #827)

7.4.2 Stationary Equipment

Whenever possible, positioning stationary noise sources such as generators and compressors as far away as possible from noise sensitive areas should be considered. Temporary barriers can be employed and/or enclosures can be built around noisy equipment. These techniques can significantly reduce noise levels and, in many cases, are relatively inexpensive. These barriers can typically be constructed on the work site from common construction building material (plywood, block, stacks, or spoils). Enclosures are often constructed from commercial panels lined with sound absorbing material to achieve the maximum possible shielding effect.

To be effective, the length of a barrier should be greater than its height, the noise source should not be visible, and any barrier should be located as close as possible to either the noise source or the receiver. In addition, providing increased distance between a noise source and a noise receiver can also be considered a form of abatement.

Stationary equipment is enclosed on all six sides with a temporary barrier of plywood found on the construction site.

Figure 7.26 Temporary shielding of stationary equipment (Photo #1340)

A construction worker at his workstation is shielded by a seven foot tall U-shaped barrier of plastic or vinyl material that can be easily relocated.

Figure 7.27 Temporary barrier around stationary activity (Photo #1339)

7.4.3 Mobile Equipment

Many construction operations are mobile and tend to progress along the length of a project at varying rates. Noise levels at the receiver tend to vary considerably, not only as the speed and power of the equipment varies, but also as the equipment is constantly changing in terms of its distance from the receivers and its relative location. To address this, all the equipment noise mitigation techniques listed in Section 7.4.1 are worthy of consideration with the exception of the enclosures. Enclosing mobile equipment is usually not possible, unless the operation is slow moving and the enclosures can be easily moved.

7.5 Mitigation along the Path

In some situations, such as in urban areas or on isolated sections of a project, it may be beneficial and necessary to construct barriers adjacent to the work area or at the right-of-way. These can take the form of natural shielding, temporary shielding, and/or permanent shielding.

7.5.1 Existing Features

Utilizing existing shielding such as berms, existing noise barriers, or structures for relatively static equipment such as pumps, generators, compressors, air ventilation, batch plants, and storage areas may be appropriate.

An existing noise barrier in between residences and highway widening construction is left in place until replacement barrier is constructed along highway right-of-way

Figure 7.28 Existing noise barrier left in place until replacement noise barrier is constructed (Photo #483)

An equipment and storage yard, noted by a compressor and steel pipes, are located near an adjacent retaining wall and underneath an existing bridge span.

Figure 7.29 Equipment and storage area shielded by existing structures (Photo #558)

7.5.2 Temporary Abatement

Advantage may also be taken of the screening effect of any nearby object such as parapet walls, buildings, trailers, or temporary site offices.

An existing structure, 4 stories tall, and plywood on chain link fence shield a construction site – one baffled, shielded compressor is visible.

An existing structure, 4 stories tall, and plywood on chain link fence along with a gate and absorptive mat combination shield a construction site.

Stationary equipment within the enclosed site is shielded with an absorptive mat.

Several construction workers and stationary and mobile equipment can be seen working within the enclosed site.

Figure 7.30 Use of existing structure and temporary plywood on chain link fence plus absorptive mats to shield recycling equipment (Photos #690, #390, #395 & #679)

A temporary barrier combination of a panel of plastic material mounted on a portable jersey barrier block a construction site from an adjacent roadway in an urban area.

Figure 7.31 Temporary barrier of plastic material (Photo #194)

Other temporary abatement techniques include the use of temporary and/or movable shielding for both specific and nonspecific operations. Some mobile shielding is capable of being moved intact or being repeatedly erected and dismantled to shield a moving operation. An example of such a barrier utilizes noise curtains in conjunction with trailers to create an easily movable, temporary noise barrier system.

Six tractor trailers used for storage are aligned as a barrier to shield adjacent residences and businesses from a construction site. Vinyl sheeting extends from the back and bottom of the trailers to completely shield the line-of-sight to the residences.

A close-up of the vinyl sheeting extending from the back and bottom of the tractor trailers which fills in the gaps left between and underneath the trailers to completely block the line-of-sight from the construction site to the receivers.

Figure 7.32 Storage trailers modified to act as temporary noise barrier (Photos #1030 & #1029)

7.5.3 Early Construction of Permanent Noise Barriers

As mentioned in Section 7.2.2, shielding of certain construction activities may be accomplished by specifying that the construction of permanent noise barriers be implemented as early as possible during the project's construction phase. Obviously, some noise-producing activities will likely be required before such barriers can be constructed. In addition, the actual erection of the noise barriers is a noise generating activity.

An aerial photo of a new highway on new location construction site where a noise berm/wall combination has been built before the initial grading activity

Figure 7.33 Early construction of permanent noise barriers (Photo #472)

7.6 Mitigation at the Receiver

Mitigation at a receiver can vary in its complexity, ranging anywhere from relocating residents for a day to insulation of a building. Even after mitigation measures have been applied, the outcome may still be unpredictable with no guarantees that the implemented methods achieve expected results. Therefore, mitigation at the receiver should only be considered as a last alternative. However, there are cases where creative techniques have been successfully implemented.

7.6.1 Building Envelope Improvements

Building envelope mitigation to reduce construction noise can include techniques such as sealing existing building elements, providing new sealed windows and doors, adding building insulation, etc. Such techniques, while effective, may also require modification of the building's heating, ventilation, and air conditioning system. Prior to proposing such treatments, thorough consideration of the costs and implications of such modifications is suggested.

An urban school with window treatments and air ventilation system shown near elevated expressway prior to demolition and construction of depressed highway.

Several air ventilation units are located on the roof of the urban school (as seen from the roof).

Several air ventilation units are located on the roof of the urban school (as seen from the highway).

Figure 7.34 Installation of a complete air handling system and window treatments at urban school solely to abate construction noise due to future conversion of arterial to depressed expressway (Photos #1300, #1303 & #1304)

The following discussion of window treatments is based on information provided in Reference 009. The reader is directed to this reference document for more information.

Acoustical window treatments to improve the noise reduction qualities of residential window openings represents a proven successful means to implement receptor noise control. In general, window openings are the weak link in a structure's external façade, allowing noise infiltration into the building. When properly specified and installed, window treatments can provide for a significantly quieter interior noise environment, particularly in multi-story buildings with upper floors that may not benefit from typical noise barriers. In general, window treatments are most cost-effective when a relatively few or widely scattered number of receptors require noise mitigation. Window treatments have the added attraction of reducing noise from all noise sources, such as traffic noise, aircraft noise, and general community noise, in addition to reducing construction noise.

Several forms of acoustical window treatments are available. Each has its pros and cons:

The recommended type of window treatment for a given receptor should be evaluated on an individual basis. If the existing windows and frames are in decent physical condition and if the window frame depth will allow the necessary air space (~ 3 inches), then the most cost-effective treatment may involve insertion of interior storm sashes. If, however, an existing window or frame is in disrepair, then a full replacement acoustic window may be more appropriate.

Timing and logistic issues that may challenge any window treatment program could include:

In light of these issues, a project should consider evaluating any window treatment options based on some eligibility criterion that evaluates the need and justifies window treatments on a case-by-case basis.

It is recommended that any type of noise abatement treatment applied to a building be verified as to its proper installation and performance. Providing funding for such treatments directly to a property owner without such a performance and verification program is not recommended and, in fact, would be against federal regulations.

7.6.2 Noise Masking

Noise masking is a technique that is still in the developmental stage but may have potential in isolated cases. Masking considerations could include techniques such as constructing water falls or other cascading water designs, employment of noise cancellation technologies, changing "background" noise levels, etc. Such techniques require a consideration of the type of noise generator (stationary, mobile, etc.), the source's noise frequency content, variability of the noise source in terms of its magnitude and duration, and the noise environment of the receptor being protected.

Experimental sound system of two speakers and amplifiers mounted on a light pole is used to mask nighttime construction noise for a nearby apartment community. Close-up of experimental sound system mounted on the light pole at right angles in direction of nearby residences. Speakers and amplifiers consist of elbows of wide plastic pipe where the top is enclosed to weather and the side is open to permit transmission of sound from speaker.

Figure 7.35 Experimental sound system used to mask nighttime construction noise in the community (Photos #42 & #38)

7.6.3 Relocation of Residents

In certain instances it may be appropriate, and possibly more cost-effective, to temporarily relocate a resident or residents from the construction area. By temporarily eliminating the noise receptor, noisy construction activities may be able to be undertaken unimpeded and completed in far less time than would be required under a noise-restrictive procedure. Such a technique was employed when several spans of a damaged interstate highway structure required demolition in close proximity to a row of residences. The residents were relocated to a hotel for a weekend while the damaged bridge structure was completely demolished. Another project which included relocation of residents as a mitigation measure is discussed in Reference 103.

7.7 Selection of Mitigation Measures

After the potential impacts resulting from the construction activities have been established, the next step in the process is the selection of appropriate control measures to be implemented on the project. This can typically be accomplished by identifying all feasible measures that could be used, selecting the most suitable techniques, and assembling them into a final mitigation strategy.

7.7.1 Identification of Feasible and Reasonable Measures

This stage involves identification of control strategies that could be implemented to bring about the desired reductions in noise impacts. Some of the factors that influence this identification process are:

Based on these and other factors, various noise mitigation strategies can be examined to determine what measures are best suited for implementation on a specific project. Factors influencing this selection include:

7.7.2 Selection of Mitigation Strategies

This stage involves the selection of a reasonable control strategy from the methods examined in the identification stage. The measure or measures chosen should be weighed as to their benefits compared to their adverse effects. This weighting should take into consideration:

7.8 Monitoring Noise Levels During Construction

Regardless of the types of noise abatement strategies and techniques employed on any particular project, successes or failures are ultimately determined by resultant effects on noise levels at sensitive sites and the adherence of the resultant noise levels to the stated construction noise level criteria.

Evaluation of such success or failure is typically addressed by a program, the requirements of which are usually detailed in the contract specifications and special provisions. An adequate program requires:

On those projects where construction noise impacts require a significant level of physical and operational mitigation, the ability to successfully monitor construction noise is closely tied to the commitment to meet the requirements detailed in the contract specifications and special provisions.

To be able to successfully enforce any project's construction noise requirements, it is essential that the project's specifications and special provisions embody the following:

7.9 Examples of Construction Noise Regulations

While 23 CFR 772 requires the evaluation of construction noise and the consideration of mitigation for identified construction noise impacts, it does not include specifications or specific language related to construction noise mitigation techniques, criteria, or restrictions. Such detail is included in various State and local documents, some of which are included as References 001, 009, 053, 077 and 103 and/or referred to in Table 10.1 of this Handbook.

Updated: 07/05/2011
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