The Environmental Engineering Section comprises the Air Quality, Hazardous Materials, Traffic Noise, and NOA/E Sections. The National Environmental Policy Act (NEPA), required on NDOT projects with federal funding, needs input from each of these disciplines.

In addition, each section responds to public inquiries, maintains compliance with regulations, and protects the public interests.

The team may be reached here during regular office hours of 8 a.m.-5 p.m. Monday through Friday.

Hazardous Materials

The Hazardous Materials Section is committed to the protection and preservation of our state’s unique environment as well as support of NDOT internal operations and the numerous transportation projects throughout the state.
 
The Hazardous Materials team conducts and routinely assists:

• NDOT staff at station and District levels to identify, manage, and appropriately dispose of generated or unidentified waste streams.
• Station inspections to ensure compliance with city, state, and federal environmental laws.
• Phase 1 and Phase 2 environmental site assessments.
• Project managers in making informed transportation project decisions relating to property acquisition and potential inherited environmental liability.
• Asbestos containing material inspections and surveys.
• Underground storage tank removals and closure.
• With mitigation and remedial options and costs considerations when adverse environmentally impacted sites are realized.
• In the oversight and management of statewide operational permits as regulatory mandated.
• Coordination and working with regulatory agencies as needed.
• Project impacts for Environmental Impact Statements and Environmental Assessments, as required by the NEPA process.

Robert Piekarz, Supervisor II
Hazardous Materials 

Staff II Associate Engineer, Vacant

Natural Occurring Asbestos & Erionite (NOA/E)

Transportation projects and activities may encounter NOA/E. The NOA/E section assesses the existence and effect of NOA/E on material usage and management and identifies potential worker safety concerns.

Austin Smith, Staff II
Associate Engineer

Air Quality & Traffic Noise Analysis

Transportation conformity regulations require project sponsors to evaluate the potential air quality effects that may result from construction and operation of a proposed transportation project. The primary function of the Air Quality section is to prepare or review NEPA documentation for NDOT construction projects.

NDOT traffic noise engineers analyze proposed highway projects for traffic noise impacts. The traffic noise engineers also respond to traffic noise complaints from residents that live near Nevada Highways. NDOT follows the Federal Highway Administration’s noise standard as outlined in the Code of Federal Regulations 23 CFR 772, “Procedures for Abatement of Highway Noise."

Revised 2022 “Traffic and Construction Noise Abatement Policy"- updated Oct. 20, 2022

Previous "Traffic and Construction Noise Abatement Policy"- effective before Oct. 20, 2022

Jessica Goza-Tyner, Staff II
Associate Engineer

Traffic Noise FAQs

Below are some frequently-asked questions we hear from Nevada residents.

QUESTION: How is noise measured?

ANSWER: Noise, usually defined as unwanted sound, is measured in terms of decibels. A decibel is a unit of measurement that quantifies the sound pressure differences in the air that we perceive as sound on a scale that starts at zero decibels, which is the threshold of human hearing. For highway traffic noise studies, noise levels are quantified in terms of the equivalent sound level, or Leq. The Leq is essentially the average noise level over period of time, usually one hour.

This scale is logarithmic, not linear. An example of this would be to add sounds together, say of two vehicles. Each vehicle is 60 decibels (dBA). The answer to the equation 60 dBA + 60 dBA = 63 dBA. Doubling the traffic volume or reducing the distance between the sound source (vehicles) and the receiver (home) will increase the sound level by 3 dBA. Conversely, reducing the traffic by half or doubling the distance between the sound source and receiver will decrease the sound by 3 dBA. 

Q: How are noise level changes perceived?

A: Studies have shown that changes in noise levels of 3 decibels or less are not normally detectable by the average human ear. An increase of 5 decibels is readily noticeable and a 10-decibel increase is usually perceived to be twice as loud as before. Studies have also determined that traffic noise is not usually an issue for residences that are at least 500 feet away from the offending roadway. 

Q: How do changes in traffic or roadway geometry affect noise levels?

A: Due to the nature of the decibel scale, doubling of traffic will only result in a 3 dBA increase in noise levels, which typically isn’t a perceivable noise increase. Similarly, cutting traffic in half would only reduce noise by 3 dBA. If a highway is moved twice as close to existing homes as it is now (i.e., from 200 to 100 feet), the noise levels will increase by 3 decibels. Conversely, if a highway is moved double the distance from existing homes, the noise levels will decrease by 3 decibels. Noise level increases from highway projects usually are because of a combination of increased traffic and changes in roadway alignment.

Q: What constitutes a traffic noise impact?

A: A noise sensitive receiver (defined as homes, parks, schools, businesses, etc.) is considered impacted by noise if either future noise levels (generally, a 20-year outward projection) approach or exceed the NDOT Noise Abatement Criteria or if there is a substantial increase in future noise levels above and beyond existing noise levels from a proposed NDOT project as described above. These are the noise levels experienced at the commonly used, exterior portions of a property on the lowest or ground level for each home or individual unit. For residences, schools, and parks, impact is defined when the Leq is 66 decibels or higher, and for noise-sensitive businesses, the impact Leq value is 71 decibels. A substantial increase impact occurs when there is a projected 12-decibel increase over existing noise levels. Impacts such as these require mitigation consideration and analysis, which may result in the construction of noise barriers if they are determined to be feasible and reasonable.

Q: Is a noise analysis required when the speed limit of a highway is changed?

A: No. Under the current regulations, a speed limit increase does not qualify as a project in which a noise analysis is required. NDOT does not have legal enforcement authority on the highways and cannot enforce lower speeds. Enforcement of the traffic laws is the responsibility of local law enforcement agencies.

Q: Does NDOT analyze noise levels on existing highways?

A: In the absence of a major highway project as described above, NDOT does not regularly perform noise studies or mitigate noise for existing highways.

Q: What types of noise barriers are constructed?

A: Noise barriers are commonly constructed as walls, earthen berms, or a combination of the two. Walls are most common and are usually constructed out of dense materials, such as concrete or masonry block. Earth berms are a natural alternative to walls but require much more land to construct. Walls can be constructed on top of berms in order to raise the overall height of the barrier.

Q: How do noise barriers work?

A: Noise barriers reduce noise by blocking the direct travel of sound waves from a source (such as vehicles on a highway) to adjacent homes or businesses, forcing the waves over the top or around the barrier. The barrier must be high enough and long enough to block the view (line of sight) of the highway, which allows a noise barrier to provide a perceivable noise reduction. Noise barriers do very little good for homes on a hillside overlooking a road or for buildings that rise above a barrier. Openings or gaps in barriers for driveway connections or street intersections reduce barrier effectiveness. Noise barriers are most effective for the first one or two rows of homes at distances up to 200 to 300 feet from the barrier. As noise levels decrease with distance, there is a point away from the highway at which noise barriers are no longer effective. It is important to note that barriers are NOT designed to eliminate or block all noise.

Q: How much do soundwalls cost?

A: A rough estimate of soundwall costs is $2 million per mile. This includes cost of material for wall, foundation, and labor. It does not include utility relocation, or right-of-way.

Typical Noise Levels

How Noise Affects Communities

QUESTION: How are noise reflections from buildings and barrier walls considered?

ANSWER: Highway traffic noise levels are not substantially increased by construction of a noise barrier or the presence of a building on the opposite side of a highway from sensitive properties. This is because the theoretical maximum noise increase from a source is limited to 3 decibels, which corresponds to a doubling of the source. In practice, not all of the sound energy is reflected back to the receiver. Some of the sound is diffracted over the barrier, some is reflected to points other than the affected property, some is scattered and/or absorbed by ground coverings and other terrain, and some is blocked by the presence of other vehicles on the highway. The overall noise increase is usually limited to 1-2 decibels at most. In general, this is not a perceptible increase, but the character of the noise may seem to change, which is what is usually noticed.

In the case of parallel barriers, however, studies have shown that if two walls are constructed very close together, there is a potential for multiple reflections that may perceptibly increase noise levels. Generally, this is not normally a problem for barriers greater than 200 feet apart or where the width-to-height ratio is more than 10:1, meaning that barriers 10 feet high should be at least 100 feet apart).

Q: Are noise barriers built to protect locations on the upper floors of homes?

A: Noise barriers may, under certain geographic conditions, be able to be designed to protect upper levels of multi-family structures, where each unit is a separate residence. For single-family homes, the primary consideration is the outdoor, ground-floor areas of human activity. Barriers built for the second floor would have to be tall enough to provide a substantial noise reduction for those areas, which, in most cases, would require very high walls that are not be feasible or reasonable.

Q: Will planting vegetation help reduce noise levels?

A: Planting vegetation is not an effective way to reduce noise levels. It is not feasible to plant enough vegetation along a highway to achieve noise reduction, although planting trees or shrubs can provide aesthetic benefit and visual screening from the roadway.

Q: What is the effect of pavement type on noise levels?

A: Research regarding pavement influence on noise levels has been an ongoing process. In general, the use of certain types of asphalt pavements or the texturing of concrete pavement can result in an initial noise reduction for properties that are 200 to 300 feet from the highway. Over a long period of time, however, it is not known if noise reduction continues to be realized. As a result, pavement type in and of itself isn’t considered an alternative to conventional noise mitigation measures. NDOT's policy for pavement type selection is made based on a lifecycle cost analysis, which does not consider noise as a primary factor.

Noise Policies and Standards

QUESTION: When is a noise analysis required?

ANSWER: A noise analysis is required for a federally funded proposed NDOT project when that project consists of the following: A new highway built in a new location; interchange modifications; or an existing highway that is significantly altered by substantially changing the horizontal or vertical characteristics of the road, such as the number of through traffic lanes being increased. Minor projects like roadway resurfacings (without adding new lanes) do not require a noise analysis. Additionally, a noise analysis is required if there is an addition of a new, or a substantial alteration, of an existing roadway, weigh station, rest stop, or ride-share lot.

Q: How was the establishment of the noise levels in the Noise Abatement Criteria determined?

A: NDOT's selection of the noise abatement criteria levels were based on guidance from the U.S. Federal Highway Administration (FHWA) and is consistent with the criteria used by all state DOTs. FHWA used numerous approaches in establishing the noise abatement criteria were considered, such as hearing impairment, annoyance, sleep interference, and speech communication interference.

The main challenge in establishing the criteria was to balance desirable noise levels with those that are achievable. As a result, speech impairment was applied as the condition that best met that balance. What this means in practical terms is that if the noise would be too loud to speak in normal voices while sitting outside (across a 24-hour average), then it might need to be addressed. Simply hearing noise doesn’t mean mitigation is necessary.

Q: What does NDOT consider "feasible and reasonable"?

A: A noise barrier must be both feasible and reasonable if it is to be constructed as part of a highway project. Feasibility and reasonableness are determined by criteria that are quantifiable. As a result, noise mitigation is not automatically provided where noise impacts have been identified. A barrier is feasible if it can be constructed without major engineering or safety issues and provides a minimum 5 dBA noise reduction to at least half of the roadway adjacent (front row) receivers. Reasonableness regards whether the barrier can be designed to achieve a noise reduction design goal of 8 decibels, whether the barrier can be constructed in a cost-efficient manner, and the opinion of the community. All three criteria must be met for a barrier to be considered reasonable in order to be built.

Q: Does the community get to vote on a wall?

A: Not initially. NDOT’s policy is that all sound walls that are feasible and reasonable will be constructed. If a resident does not want a wall built in their neighborhood, he or she will need to trigger the voting process during the NEPA public involvement process. Only those who are adjacent property owners who will be affected by a proposed sound wall can vote against its installation. More information on this can be found under the reasonableness section of the State of Nevada Department of Transportation Traffic and Construction Noise Analysis and Abatement Policy.

Q: What is a "substantial noise reduction"?

A: A noise barrier must provide a readily perceptible decrease in noise levels to adjacent receivers to be feasible. This is defined as a noise decrease of at least 5 decibels to at least half of the first, or front row, of receivers. A “benefitted receiver” is one which receives at least a 3 dBA reduction at any location behind the wall. As noise level changes of 3 decibels or less are not generally perceivable, it is not fiscally prudent to construct a noise barrier that gives only a 1 or 2 decibel benefit to adjacent properties.

Q: Does NDOT allow participation of third-party funding?

A: No.

Q: Can anything be done about "Jake Brake" use?

A: NDOT has not restricted the use of these devices for safety reasons. However, NDOT has assisted local jurisdictions with this issue by installing "Engine Brake Mufflers Required" signs along select highways. To inquire about installation of such a sign, please first contact your local city or county government to see if they have an ordinance. If not, email info@dot.nv.gov or call 775-888-7000.

Nevada Revised Statute NRS 484D.285 states:

1. The driver of a vehicle which is equipped with a device for braking that uses the compression of the engine of the vehicle shall not use the device at any time unless:

(a) The device is equipped with an operational muffler; or

(b) The driver reasonably believes that an emergency requires the use of the device to protect the physical safety of a person or others from an immediate threat of physical injury or to protect against an immediate threat of damage to property.

2. A person who violates the provisions of this section is guilty of a misdemeanor.

(Added to NRS by 2003, 403) (Substituted in revision for NRS 484.6055)

The enforcement of this law is the responsibility of the local authorities.