Clean Air  

Asphalt Plants

BREDL Comments on Tar Heel Paving Draft Permit

March 12, 2001

Dr. Ernest Fuller
Division of Air Quality, Raleigh Regional Office
3800 Barrett Drive
Raleigh, NC 27609

Re: Tar Heel Paving, DRAFT Permit No. 08977R00

Dear Dr. Fuller:

I write to comment on the draft permit for Tar Heel Paving in Henderson County. Based our analysis and research done by experts in asphalt plant air pollution, we recommend denial of this permit. Further, we recommend that a statewide epidemiological study be undertaken by the DAQ so that we may better determine the health effects of human exposure to asphalt fumes. Also, we recommend that DAQ develop and implement noise pollution control measures for all asphalt plants.

Based on our experience working with residents living near asphalt plants, we must conclude that the skin rashes, difficulty breathing, asthma, hypertension, and cancer clusters associated with living near these plants constitute a public health problem of unknown magnitude. It is hard to believe that all these problems are due solely to careless plant operators who lack concern for their neighbors. Rather, it is the responsibility of the state agencies charged with protecting public health to take action to reduce known sources of death and disease.

General Comments

Asphalt cement additives, higher operating temperatures at small plants, and use of recycled asphalt paving cause increases in toxic emissions. These variables are not accounted for in the EPA emissions data which is used to permit asphalt plants. Further, the state persists in utilizing inappropriate smokestack models to predict ambient fugitive emission levels.

The asphalt paving industry has dozens of diluents and modifiers which are used to alter asphalt properties. These additives include plastic/rubber, rejuvenating oils, anti-stripping agents, extenders and anti-oxidants. . These additives change the volatility of the hot mix asphalt product. These substances are added in significant amounts: from one to several percent by weight of the asphalt. It is important to note that the recommended amount of additive exceeds the typical volatiles content. According to experts, these additives alter the vapor pressure of the asphalt by increasing the volatility of some of the lighter components which otherwise might not have volatilized in the temperature range of 275 to 375 degrees-F. EPA estimates of volatiles content are based on asphalt cement without additives and may bear little relation to the emissions from asphalt paving practices in North Carolina.

Another factor which increases asphalt fume emissions is operating temperature. Emissions increase exponentially with temperature. State highway departments specify minimum and a maximum temperature for HMA when delivered to the job site where the pavement is being installed, typically 275 to 325 degrees-F. Obviously, the actual temperature of the asphalt loaded into a truck is higher. Such restrictions do not apply to HMA for non-state supervised jobs. Further, private contractors will demand a higher temperature at load-out since a smaller mass of HMA will cool faster in smaller trucks

When a plant switches from one hot mix formula to another emissions may increase. For example, a plant using recycled asphalt pavement (RAP) has a higher operating temperature to provide extra heat to evaporate water associated with RAP, since RAP is stored in the open. Switching to a formula without RAP, the plant load-out will emit a higher level of organics because of overheating. Examples of this exist in the data collected by the EPA at Plant C, a drum mix plant, where emissions increased by a factor of 2 to 3 over a 40 minute period. Episodes of high emissions caused by variations such as high temperatures are missed by the total reliance on averages of data collected under ideal test conditions. The table below shows the effect of different volatile contents and operating temperatures on emissions.

Load Out Emissions (a) EPA (c) CITIZENS (d)
Total Particulate Matter 104 515
Organic Particulate Matter 68 478
Total Organic Compounds (Method 25A) 832 5,836
Carbon Monoxide 270 1,893

Silo filling emissions (b)    
Total Particulate Matter 117 423
Organic Particulate Matter 51 356
Total Organic Compounds (Method 25A) 2,437 17,100
Carbon Monoxide 236 1,656

a) Load-out emissions for both batch and drum plants - See AP-42, Table 11.1-14

(b) Load-out emissions for plants with silo storage- mainly, but not exclusively, drum plants. See AP-42, Table 11.1-14

(c) EPA estimates for drum plant in lb/200,000 tons of HMA. Volatility of 0.5%, 325 degrees-F

(d) Citizen estimates for drum plant in lb/200,000 tons of HMA. Volatility of 1.0%, 375 degrees-F

The report (Attachment A) issued by citizens groups after the issuance of EPA’s fugitive emissions test results states:

It can be seen that the emissions calculated by using EPA-derived equations, particularly emissions of noxious organic compounds, increase by over 600% under conditions of higher operating temperature and volatility contents. Both the EPA and the Citizen numbers would increased by another 20 to 30% to compensate for the low bias introduced by the “background correction” and “Method 204", discussed later in this report. Finally, it should be noted that although the numbers in Table 1 are shown on an annual basis to help compare them to Table 1 in the Executive Summary of the Emission Assessment Report, the citizens are aware that actual annual emissions will be lower since a plant will not always operate with an asphalt with a high volatiles content at high temperatures. On the other hand, the table clearly shows the type of variation in emissions that is likely to occur under such conditions with its acute effects on nearby residents.

Minority Report on Emissions from Asphalt Plants, January 29, 2001, page 8

Based on reports from residents in communities with operating asphalt plants, we believe that periods of high emissions are frequent. Further, the public health impacts of these emissions are more significant since asphalt plants in unzoned communities are located closer to residential areas and small operators, such as John Pace Enterprises, are more likely to demand hotter asphalt. These emissions data are even more significant in light of the already high levels of PM-10, carbon monoxide, and benzene emissions indicated by the DAQ’s analysis of Tar Heel Paving.

Finally, the DAQ’s use of computerized screening models for toxic, ground level (fugitive) emissions remains troublesome because such dispersion models do not apply within the atmospheric boundary layer, a distance of 30 feet from the ground where frictional effects predominate (see Attachment B, Affidavit of Dr. R. Nadkarni). This means that the use of such models for fugitive emissions will predict more dispersion and lower pollutant levels than will actually occur. North Carolina’s acceptable ambient limits for toxics are designed to protect human health, but the use of the dispersion model in this case predicts the wrong ambient level. Other air dispersion studies, based on average factors from EPA’s AP-42, show that ambient air quality standards are often exceeded for arsenic, cadmium and other heavy metals and for organic chemicals such as benzene and formaldehyde. With almost 2,000 dangerous chemicals in asphalt fume, it is important that the decision to build an asphalt plant in a populated valley prone to inversions not be based on a model which was developed solely for smokestack emissions, not boundary layer fugitive emissions. Because of the DAQ’s persistent and inappropriate use of screen models for fugitive emissions, we have little confidence in the draft permit’s ability to protect public health at this site.

Specific Comments

1) The permit will not control odorous emissions

Under Specific Conditions and Limitations, the draft permit states,

As required by 15A NCAC 2D .0522 “Control and Prohibition of Odorous Emissions,” the Permittee shall not cause, allow, or permit any source to be operated without employing suitable measures for the control of nuisance odors.

State law prohibits operation of a plant without suitable measures to control odorous emissions. The stated purpose of 2D .0522 is “to provide for the control and prohibition of odorous emissions.” [2D .0522 (a)]. It states further that, “This regulation shall apply to all operations that produce odorous emissions.” [2D .0522 (b)] (emphases added). Also, the DAQ Permit Review states that, “No facility shall emit odorous emissions without suitable control measures.” However, no specific measures for the control of odor are listed. As written, this draft permit fails to stipulate measures for the control of odor. Further, the Division has no objective means to determine if the plant is in compliance with permit requirements and the law. As a practical matter, the DAQ inspector who might respond to a plant neighbor’s complaint about odor would have no means of enforcing this regulation. This is an omission which must be corrected before any air permit is issued.

2) Air pollution is underestimated

The draft permit lists regulated emission sources ES-1 aggregate dryer; ES-2, ES-3, and ES-4 three 100-ton storage silos; and ES-5, ES-6, and ES-7 gravity-drop truck-loadouts. An attachment to the permit also lists Activities Exempted from Permitting Under 15A NCAC 2Q .0102. The officially exempted sources include: 1) a No.2 fuel oil fired asphalt tank heater ES-8, and 2) two 30,000 gallon fuel oil storage tanks ES-9 and ES-10. The attachment acknowledges that the asphalt tank heater and the storage tanks are sources of toxic air pollutants and Title V criteria pollutants. Omitted from the permit exemption list are: 1) mobile sources of diesel exhaust, 2) material handling and road dust, and 3) fugitive emissions from loaded trucks prior to departure to the job site. A recent EPA report lists all the above sources with corresponding emissions of criteria pollutants and hazardous air pollutants. I have attached Table 2 from the December 2000 EPA Hot Mix Asphalt Plants Emission Assessment Report to these remarks. The DAQ’s omission of so many known air pollution sources from the permit should be corrected. The true total of toxic air emissions should be included in the determination of whether the plant meets the required acceptable ambient limits.

3) Air Inversions and Pollution Trapping

Topography in area of Henderson County near the proposed asphalt plant site ranges from about 2060 to 2600 feet amsl (Attachment C). An aerial photograph taken over Henderson County (Attachment D) reveals a surface inversion at about 150 feet above the ground. High altitude cloud cover was present on that day and is shown in the photo. Cloud cover reduces sunlight and heating of the surface which is the major way for such inversions to be broken. Such conditions could cause this inversion could persist into the evening hours, and into the next day. This is, perhaps, the worst case scenario for air pollution in the valley along Muddy Creek. The inversion traps the air from above, and hills and mountains (Attachment E) trap it laterally. These conditions are akin to an automobile with the engine running in a room with the doors and windows closed. No screening model used by North Carolina is conservative enough to account for these circumstances.

4) Noise Pollution is an Uncontrolled Threat to Public Health

The problem with noise is that it negatively affects human health and well-being. Problems related to noise include hearing loss, stress, high blood pressure, sleep loss, distraction and lost productivity, and a general reduction in the quality of life. While I can find no applicable state statute or rule which applies to asphalt plant noise, the close proximity to residential areas in which the Tar Heel Paving plant would operate requires an assessment of noise impact on plant neighbors. The relevant example here would be the Rhodes Brothers Paving plant in Macon County which began operation in May 1999.

Since the plant commenced operation, residents have reported effects associated with excess noise including hypertension and anxiety. In a letter to Macon County on December 22, 1999 (Attachment F), State Health Director Dennis McBride states, “OEE is concerned that chronic exposure to noise, a stressor, emanating from the Rhodes Brothers Asphalt Plant may have a negative impact on the health of the Cullasaja community over a long-term period.”

If the Division of Air Quality proposes to issue a permit for a plant which would create noise levels high enough to damage public health, it must take steps to ensure that the residents are protected. It would be an inadequate response to pass this off because noise is not a chemical compound. According to NC Occupational and Environmental Epidemiology Branch, the Rhodes Brothers plant created noise levels of 66-70 dBA. Dr. McBride stated that this exceeds the levels specified by some local ordinances and the EPA.

The Commonwealth of Massachusetts Division of Air Quality Control Policy states:

“A source of sound will be considered to be violating the Department's noise regulation (310 CMR 7.10) if the source: Increases the broadband sound level by more than 10 dB(A) above ambient, or Produces a “pure tone” condition - when any octave band center frequency sound pressure level exceeds the two adjacent center frequency sound pressure levels by 3 decibels or more. These criteria are measured both at the property line and at the nearest inhabited residence. Ambient is defined as the background A-weighted sound level that is exceeded 90% of the time measured during equipment operating hours. The ambient may also be established by other means with the consent of the Department.

North Carolina does not expect local governments to adopt toxic air pollution rules; neither should the state expect them to control noise pollution from industrial plants permitted by the Division of Air Quality.

Thank you for considering these remarks.

Respectfully submitted,

Louis Zeller