August 18, 2014


The Environmental and Science Advisory Board held a joint informational meeting with the City of Fort Collins Air Quality Advisory Board.  The attendees include ESAB and Air Quality Advisory Board members, County Commissioners Gaiter and Johnson, City Councilman Cunniff, support staff from both jurisdictions, and members of the public.  The meeting was held at the City office building at 215 N Mason Street. 


The purpose of the meeting was to review the draft Colorado air emissions permit for the Martin Marietta Materials asphalt plant located at 1800 North Taft Hill Road.  The City and County jointly retained the consulting firm of Air Resource Specialist, Inc. to perform a technical review of the draft emissions permit.  Howard Gebhart, the manager of the Environmental Compliance Section at ARS, presented the draft of his written report titled 2014 Martin Marietta Materials Technical Report Review of Draft Air Quality Permit 13LR2446. 


Mr. Gebhart used a power point presentation to outline the major points in the report. The Summary & Conclusions from the report are copied here:



The major findings of the ARS technical review are summarized below.


·  The emissions data used for the MMM permit are generally supported by AP-42 and

other appropriate data. However, the CO emissions used by APCD are higher than the

corresponding AP-42 data. APCD claims that historical emissions data do not support the

lower emissions reported by AP-42; however, this claim has not been substantiated by

APCD. Because Fort Collins is a designated maintenance area, CO emissions are

required to meet RACT and the AP-42 data suggest that lower emissions are in fact

achievable and would represent RACT. APCD should require lower CO emissions based

on AP-42 or better document why the selected CO emissions level is in fact RACT.


 The MMM draft permit used the AP-42 toluene emissions factor for drum mix asphalt

plants fired on #2 fuel oil. The AP-42 factors for natural gas drum mix asphalt plants

were used to calculate HAP emissions for other pollutants. This appears to be an

oversight by APCD and should be corrected. Also, two other HAPs listed in the AP-42

data (AP-42, Table 11.1-10) where emissions are comparable to the HAPs calculated by

APCD. These HAPs are hexane (0.00092 lb/ton) and xylene (0.00020 lb/ton). It is

unknown why these HAPs were not considered by APCD given that the emissions are

comparable to other HAPs where emissions were tabulated. APCD’s permit analysis

should be amended to address hexane and xylene emissions in addition to the other



 In assessing the asphalt plant, the APCD appears to have considered only those emissions

directly related to the asphalt plant. However, MMM owns and operates other air

emission sources in the immediate vicinity of the asphalt plant, including an aggregate

materials mining and processing operation on the west side of Taft Hill Road. MMM’s

other aggregate processing activities are located on “contiguous or adjacent properties”

and should therefore be considered in the assessment of the overall facility emissions. It

is unlikely that the added emissions from adjoining MMM operations will alter the

minor/major source classification of the asphalt plant, but a complete and accurate

analysis by APCD requires that these emissions also be considered when determining the

total emissions of the “source”.


 The AERSCREEN modeling for MMM’s CO emissions has been conducted following

standard regulatory practices and principles. This modeling also employed several

significant conservative assumptions. Although the modeling showed that MMM’s

emissions comply with the NAAQS by a small margin, the conservatisms inherent in the

modeling study means that MMM’s operations will comply with the NAAQS, with a

substantial safety margin.



 ARS used APCD’s AERMOD modeling results to make an assessment of potential HAP

impacts on public health and the environment. The HAP modeling results from MMM

were compared to “safe” concentration levels determined using USEPA’s Risk-Based

Screening Approach. ARS’ modeling assessment determined that HAP emissions from

MMM’s asphalt plant operations would not cause ambient concentrations above the

“safe” concentration levels.


 Recommendations have been provided for consideration by the ESAB and AQAB on

formal comments on the draft MMM air quality permit. This includes making any

voluntary pollution control practices adopted by MMM enforceable requirements under

the permit. These recommendations are intended to make the final permit more protective

of public health and the environment (the recommendations are contained in Section 4.0 – Technical Comments on the Draft Permit). 


Following Mr. Gebhart’s presentation, members from the two advisory boards asked questions about the report and its conclusions.  Topics included selection of the AERSCREEN vs the AERMOD air dispersion model, the use of “conservative assumptions” in the model to ensure that it does not under-predict the impacts to the community, the recommendation to include other Martin Marietta emissions associated with the mining operation, the prioritization of the recommendations, the source and update dates for the U.S. EPA hazardous chemical risk data, the use of Carbon monoxide background data from the downtown CSU monitoring site, the recommendation to include some hazardous air pollutants in the required stack testing, the importance of upset conditions for air emission rates, the availability of representative background air quality information for hazardous air pollutants, the control of fugitive particulate emissions, and the differences that would entail if the asphalt plant was considered a major source under air quality rules. 


The meeting adjourned at 7:30 PM.  The ESAB will meet again on Tuesday, August 26 at 6:00 PM to discuss their review of the draft emissions permit and the ARS technical review and recommendations.  The goal at that meeting will be to authorize comments to send to the County Commissioners.  The County Commissioners would plan to consider the ESAB comments at their September 2 Administrative Matters meeting.  The deadline for submitting comments to the Colorado Department of Public Health and Environment is Wednesday, September 3.