Report from the Construction Breakout Group1
Every construction project has tradeoffs among duration, noise levels, and cost, noted Erich Thalheimer, who delivered the report for the breakout group on construction noise, and these tradeoffs can evolve over the course of the project. At some points, noise may be the biggest problem, while at others, traffic management or pedestrian enjoyment may be the biggest concern. Maintaining both flexibility and good practice is essential.
The breakout group broke its discussion of the issues into three broad categories: source controls, path controls, and receiver controls.2
Source controls prevent noise from occurring in the first place. They include:
- Time constraints—prohibition of work during sensitive hours for humans or wildlife (e.g., dawn, dusk, nighttime)
- Scheduling—performance of noisy work during less sensitive time periods
- Equipment restrictions—restrictions on the type of equipment that can be used
- Specialty products—special purpose pads, liners, and enclosures that reduce noise
- Noise emission limits—specification of equipment noise limits
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1 The Construction Breakout Group members were Cynthia Lee, Proctor Reid, Randy Stanley, Erich Thalheimer, and Jock Whitworth.
2 In this context a “receiver” or “receptor” is a human being within hearing distance.
- Substitute methods—use of quieter methods or equipment when possible
- Exhaust mufflers—installation of quality mufflers on equipment
- Lubrication and maintenance—regular care to support quieter equipment
- Reduced power operation—use of equipment of only the necessary size and power
- Limited equipment onsite—onsite presence of only necessary equipment
- Noise compliance monitoring—presence of an onsite technician to monitor compliance
- Quieter backup alarms—manually adjustable, ambient--sensitive, or broadband alarms, or no alarm if an observer directs the vehicle’s rearward motion
As an example of a source control, Thalheimer described new kinds of backup alarms that are more easily masked by background sources, can be about 20 decibels quieter than standard alarms, and are still readily audible behind the vehicle, as required by OSHA. OSHA also allows the use of vehicles without backup alarms if an observer directs the rearward motion of the vehicle. This is also an example of a tradeoff between introducing more risk to the contractor and public in exchange for minimizing noise.
The Park Service purchases and uses dozers, loaders, backhoes, generators, graders, dump trucks, jackhammers, rock drills, compressors, pumps, and rollers, and noise control measures are available for all. For example, anything with a diesel engine can have a muffler in good condition and a housing door that is closed. Jackhammers can use quieter bits or exhaust mufflers, and electric jackhammers are quieter than pneumatic, which are quieter than gas powered.
Path controls interrupt a noise between its source and a receiver. They include:
- Noise barriers—permanent or portable wooden, metal, plastic, earthen, or concrete barriers
- Noise curtains—flexible vinyl curtains hung from supports or draped on equipment
- Enclosures—encasing or enclosure of localized and stationary noise sources
- Increased distance—location of noisy activities farther from receivers or offsite
As an example of a path control, Thalheimer mentioned vinyl noise curtains (available from several manufacturers) that are about one-quarter inch thick and typically have an absorptive side that is placed toward the source of the noise. The curtains can be tucked, hung, and wired together as needed. The absorptive side also reduces reverberant buildup. Noise insulation can even be put around individual pieces of equipment such as jackhammers so long as the device can still be used safely and without damage to the equipment.
Receiver controls limit the amount of noise received or prepare people for what they will hear. They include:
- Window soundproofing—installation of double- or triple-pane windows or storm windows
- Air conditioners—window units or a central system
- Receptor noise limits—establishment of cumulative noise limits at receptor locations
- Stakeholder meetings—open dialogue to involve the affected stakeholders and share information
- Noise complaint process—capacity to log and respond to noise complaints
- Temporary relocation to hotels—for use only in extreme, otherwise unmitigatable cases
As an example of a receiver control, Thalheimer noted that informing stakeholders of work requirements and schedules can increase their tolerance of noise. Information can be provided on a website, in print, in person, or through social media (e.g., Twitter, text messages), with contact information for complaints. With respect to air conditioners, the associated closed windows and presence of background noise may reduce the level of unwanted sounds, but the conditioners themselves increase the outdoor ambient noise level.
DEVELOPING AND IMPLEMENTING CONSTRUCTION NOISE PROGRAMS
Construction noise programs need to include both proactive avoidance of noise and the reactive ability to control noise if it becomes problematic. Proactive measures include “buy quiet” programs using product and vendor guidance sheets or lists of acceptable equipment along with soundscape management plans and contractor noise control plans. Reactive measures include use of a noise control plan to observe and inspect the work, enforce limits, and hold contractors accountable.
A comprehensive noise specification provides control over the amount of noise generated. It can include definitions, time and equipment restrictions, source emission limits, receptor limits, a noise control plan, penalties, and incentives.
A noise mitigation or control plan incorporates soundscape goals in the bid process. To accommodate the NPS soundscape plan, the contractor proposes equipment locations, times, and durations, including worst-case scenarios. The contractor also predicts noise levels, identifies impacts, and commits to mitigation. The noise control plan then becomes enforceable in the field.
Once noise specifications are in place, enforcement can hold a contractor accountable. This requires compliance measurements and mechanisms for complaint investigations. Thalheimer emphasized that whoever interacts with a contractor has to be authorized to do so. A training program and guidance manual for park managers could demonstrate generic noise specification and compliance measures.
Expectations have to be realistic, Thalheimer said. Construction projects are not going to be inaudible, and interests inevitably conflict. The use of the best available controls and techniques can manage, mitigate, and minimize noise, but flexibility will be needed once a project begins. For instance, park managers may need the flexibility to approve construction that exceeds a source limitation without exceeding a receptor limitation. Good public outreach can prepare park visitors for noises that are unavoidable.
