INNOVATIVE DISPERSION MODELING PRACTICES TO ACHIEVE A REASONABLE LEVEL OF CONSERVATISM IN AERMOD MODELING DEMONSTRATIONS CASE STUDY TO EVALUATE EMVAP, AMR2, AND BACKGROUND CONCENTRATIONS
Presentation delivered at the Board meeting for the Upper Midwest section of the Air and Waste Management Association meeting on September 16, 2014.
Innovative dispersion modeling techniques are presented including ARM2, EMVAP and the 50th percentile background concentration. Case study involves peaking engines that are used 250 hour per year. These intermittent sources are required to undergo a modeling evaluation in many states. Current modeling techniques grossly overestimate the emissions from these sporadic sources.
INNOVATIVE DISPERSION MODELING PRACTICES TO ACHIEVE A REASONABLE LEVEL OF CON...Sergio A. Guerra
Presentation delivered at the Annual Air and Waste Management Association conference in Long beach, California on June 26, 2014.
Innovative dispersion modeling techniques are presented including ARM2, EMVAP and the 50th percentile background concentration. Case study involves peaking engines that are used 250 hour per year. These intermittent sources are required to undergo a modeling evaluation in many states. Current modeling techniques grossly overestimate the emissions from these sporadic sources.
NOVEL DATA ANALYSIS TECHNIQUE USED TO EVALUATE NOX AND CO2 CONTINUOUS EMISSIO...Sergio A. Guerra
The current study presents a new data analysis technique developed while evaluating continuous emission data collected from a trash compactor. The evaluation involved tailpipe sampling with a portable emission monitoring system (PEMS) from a diesel fueled 525-horsepower trash
compactor. The sampling campaign took place by running the compactor with regular no. 2 diesel, B20 and ULSD fuels. The purpose was to determine the possible emission reductions in nitrous oxides (NOx) and carbon dioxide (CO2) from the use of B20 and ULSD in an off-road
vehicle. The results from the NOx analysis are discussed.
The initial data analysis identified two important issues. The first concern related to a bias in the calculated F values due to the very large number of samples (N). The large N influenced the probability values and indicated a false statistical significance for all factors tested. Additionally,
the data observations were found to be highly autocorrelated. Thus, a time interval data reduction
technique was used to address these two statistical limitations to the robustness of the statistical
analyses. The result in each case was a subset of quasi-independent observations sampled at an interval of 800 seconds. The autocorrelation and false statistical significance issues were promptly resolved by using this technique. Since the issues of false statistical significance and autocorrelation are inherent in continuous data, the positive results obtained from the use of this technique can be far-reaching. This technique allowed for a valid use of the general linear model (GLM) with engine speed as the covariate factor to test day, fuel type and compactor factors. This technique is most relevant given the advancements in data collection capabilities that
require data handling techniques to satisfy the statistical assumptions necessary for valid analyses to ensue.
Pairing aermod concentrations with the 50th percentile monitored valueSergio A. Guerra
Presentation delivered to the Background Concentrations Workgroup for Air Dispersion Modeling organized by the Minnesota Pollution Control Agency. delivered on May 29, 2014. Three topics covered include 1) Screening monitoring data, 2) AERMOD’s time-space mismatch, and
3) Proposed 50th % Bkg Method
Presentation includes information related to gently sloping terrain, AERMINUTE, and EPA formula height.
Presented at the 27th Annual Conference on the Environment on November 13, 2012.
AIR DISPERSION MODELING HIGHLIGHTS FROM 2012 ACESergio A. Guerra
Presentation includes some highlights from the dispersion modeling papers presented at the Annual AWMA conference in San Antonio, TX. Topics covered include: EMVAP, distance limitations of AERMOD, and two case studies comparing predicted and monitoring data,
Presented at the A&WMA UMS Board Meeting on August 21, 2012.
Use of Probabilistic Statistical Techniques in AERMOD Modeling EvaluationsSergio A. Guerra
The advent of the short term National Ambient Air Quality Standards (NAAQS) prompted modelers to reassess the common practices in dispersion modeling analyses. The probabilistic nature of the new short term standards also opens the door to alternative modeling techniques that are based on probability. One of these is the Monte Carlo technique that can be used to account for emission variability in permit modeling.
Currently, it is assumed that a given emission unit is in operation at its maximum capacity every hour of the year. This assumption may be appropriate for facilities that operate at full capacity most of the time. However, in most cases, emission units operate at variable loads that produce variable emissions. Thus, assuming constant maximum emissions is overly conservative for facilities such as power plants that are not in operation all the time and which exhibit high concentrations during very short periods of time.
Another element of conservatism in NAAQS demonstrations relates to combining predicted concentrations from the AMS/EPA Regulatory Model (AERMOD) with observed (monitored) background concentrations. Normally, some of the highest monitored observations are added to the AERMOD results yielding a very conservative combined concentration.
A case study is presented to evaluate the use of alternative probabilistic methods to complement the shortcomings of current dispersion modeling practices. This case study includes the use of the Monte Carlo technique and the use of a reasonable background concentration to combine with the AERMOD predicted concentrations. The use of these methods is in harmony with the probabilistic nature of the NAAQS and can help demonstrate compliance through dispersion modeling analyses, while still being protective of the NAAQS.
INNOVATIVE DISPERSION MODELING PRACTICES TO ACHIEVE A REASONABLE LEVEL OF CON...Sergio A. Guerra
Presentation delivered at the Annual Air and Waste Management Association conference in Long beach, California on June 26, 2014.
Innovative dispersion modeling techniques are presented including ARM2, EMVAP and the 50th percentile background concentration. Case study involves peaking engines that are used 250 hour per year. These intermittent sources are required to undergo a modeling evaluation in many states. Current modeling techniques grossly overestimate the emissions from these sporadic sources.
NOVEL DATA ANALYSIS TECHNIQUE USED TO EVALUATE NOX AND CO2 CONTINUOUS EMISSIO...Sergio A. Guerra
The current study presents a new data analysis technique developed while evaluating continuous emission data collected from a trash compactor. The evaluation involved tailpipe sampling with a portable emission monitoring system (PEMS) from a diesel fueled 525-horsepower trash
compactor. The sampling campaign took place by running the compactor with regular no. 2 diesel, B20 and ULSD fuels. The purpose was to determine the possible emission reductions in nitrous oxides (NOx) and carbon dioxide (CO2) from the use of B20 and ULSD in an off-road
vehicle. The results from the NOx analysis are discussed.
The initial data analysis identified two important issues. The first concern related to a bias in the calculated F values due to the very large number of samples (N). The large N influenced the probability values and indicated a false statistical significance for all factors tested. Additionally,
the data observations were found to be highly autocorrelated. Thus, a time interval data reduction
technique was used to address these two statistical limitations to the robustness of the statistical
analyses. The result in each case was a subset of quasi-independent observations sampled at an interval of 800 seconds. The autocorrelation and false statistical significance issues were promptly resolved by using this technique. Since the issues of false statistical significance and autocorrelation are inherent in continuous data, the positive results obtained from the use of this technique can be far-reaching. This technique allowed for a valid use of the general linear model (GLM) with engine speed as the covariate factor to test day, fuel type and compactor factors. This technique is most relevant given the advancements in data collection capabilities that
require data handling techniques to satisfy the statistical assumptions necessary for valid analyses to ensue.
Pairing aermod concentrations with the 50th percentile monitored valueSergio A. Guerra
Presentation delivered to the Background Concentrations Workgroup for Air Dispersion Modeling organized by the Minnesota Pollution Control Agency. delivered on May 29, 2014. Three topics covered include 1) Screening monitoring data, 2) AERMOD’s time-space mismatch, and
3) Proposed 50th % Bkg Method
Presentation includes information related to gently sloping terrain, AERMINUTE, and EPA formula height.
Presented at the 27th Annual Conference on the Environment on November 13, 2012.
AIR DISPERSION MODELING HIGHLIGHTS FROM 2012 ACESergio A. Guerra
Presentation includes some highlights from the dispersion modeling papers presented at the Annual AWMA conference in San Antonio, TX. Topics covered include: EMVAP, distance limitations of AERMOD, and two case studies comparing predicted and monitoring data,
Presented at the A&WMA UMS Board Meeting on August 21, 2012.
Use of Probabilistic Statistical Techniques in AERMOD Modeling EvaluationsSergio A. Guerra
The advent of the short term National Ambient Air Quality Standards (NAAQS) prompted modelers to reassess the common practices in dispersion modeling analyses. The probabilistic nature of the new short term standards also opens the door to alternative modeling techniques that are based on probability. One of these is the Monte Carlo technique that can be used to account for emission variability in permit modeling.
Currently, it is assumed that a given emission unit is in operation at its maximum capacity every hour of the year. This assumption may be appropriate for facilities that operate at full capacity most of the time. However, in most cases, emission units operate at variable loads that produce variable emissions. Thus, assuming constant maximum emissions is overly conservative for facilities such as power plants that are not in operation all the time and which exhibit high concentrations during very short periods of time.
Another element of conservatism in NAAQS demonstrations relates to combining predicted concentrations from the AMS/EPA Regulatory Model (AERMOD) with observed (monitored) background concentrations. Normally, some of the highest monitored observations are added to the AERMOD results yielding a very conservative combined concentration.
A case study is presented to evaluate the use of alternative probabilistic methods to complement the shortcomings of current dispersion modeling practices. This case study includes the use of the Monte Carlo technique and the use of a reasonable background concentration to combine with the AERMOD predicted concentrations. The use of these methods is in harmony with the probabilistic nature of the NAAQS and can help demonstrate compliance through dispersion modeling analyses, while still being protective of the NAAQS.
Background Concentrations and the Need for a New System to Update AERMODSergio A. Guerra
Presentation delivered at the EPA 11th Conference on Air Quality Modeling at RTP, NC.
Topics covered include background concentrations and the need for a new system to update AERMOD. An evaluation of what is being proposed in the draft guidance related to background concentrations and an alternative approach to determine background concentrations for dispersion modeling evaluations is presented. A review of the lessons learned from Appendix W and a proposed new method to incorporate science into the model.
Using Physical Modeling to Evaluate Re-entrainment of Stack EmissionsSergio A. Guerra
Fume re-entry is an important concern for many types of facilities such as hospitals and laboratories that emit pathogens and toxic chemicals that may impact public health by being re-entrained into the building though nearby air intakes. Numerical methods can be used to evaluate dispersion of pollutants from stacks at sensitive receptors. However, numerical methods have limitations and simplifications that can significantly affect its predictions. An alternate way of analyzing stack re-entrainment is with physical modeling in a wind tunnel. In such a study, a scale model that accounts for buildings, topography, and vegetation is used with planned and alternate stack designs to determine the toxic emission impacts on air intakes and other sensitive locations. In a wind tunnel study different stack designs and possible mitigation options can be evaluated. This method is superior to numerical methods (e.g., dispersion models) because it accounts for the immediate structures, topography, and vegetation that is often ignored or oversimplified in numerical methods.
This presentation will show a hypothetical case study evaluating a site with toxic air emissions using AERMOD and physical modeling.
PRIME2_consequence_analysis_and _model_evaluationSergio A. Guerra
The Plume Rise Model Enhancements (PRIME) building downwash algorithms1 (Schulman et al. 2000) in AERMOD2 are being updated to address some of the most critical limitations in the current theory. These enhancements will incorporate the latest advancements related to building downwash effects. The technical aspects of these enhancements are discussed in more detail in a companion paper titled “PRIME2: Development and Evaluation of Improved Building Downwash Algorithms for Solid and Streamlined Structures (MO13)”. The updates to the PRIME code include new equations to account for building wake effects that decay rapidly back to ambient levels above the top of the building; reduced wake effects for streamlined structures; and reduced wake effects for high approach roughness. A consequence analysis comparing the current AERMOD/PRIME model versus the new AERMOD/PRIME2 model was performed. Additionally, a field data evaluation was conducted with the Bowline Point database. The results from these analyses are discussed below.
Advanced Modeling Techniques for Permit Modeling - Turning challenges into o...Sergio A. Guerra
Advance modeling techniques can be used in AERMOD to refine the inputs that are entered in the model to get more accurate results. This presentation covers:
-AERMOD’s Temporal Mismatch Limitation
-Building Downwash Limitations in BPIP/PRIME
-Advanced Modeling Techniques to Overcome these Limitations
Solutions include:
Equivalent Building Dimensions (EBD)
Emission Variability Processor (EMVAP)
Updated ambient ratio method (ARM2)
Pairing AERMOD values with the 50th % background concentrations in cumulative analyses.
Using Physical Modeling to Refine Downwash Inputs to AERMODSergio A. Guerra
Achieving compliance in dispersion modeling can be quite challenging because of the tight National Ambient Air Quality Standards (NAAQS). In addition, AERMOD’s limitations can, in many cases, produce higher than normal concentrations due to the inherent assumptions and simplifications in its formulation. In the case of downwash, the theory used to estimate these effects was developed for a limited set of building types. However, these formulations are commonly used indiscriminately for all types of buildings. This presentation will cover how the basics of wind tunnel modeling can overcome some of these limitations and be used to mitigate downwash induced overpredictions to achieve compliance.
dispersion modeling requirements are more common in air permitting projects and in many cases become the bottleneck in permitting. Unlike any other consulting firm, CPP promotes cutting edge techniques which can alleviate excessive conservatism in permit modeling to a reasonable level that still protects public health. At CPP we start with the standard modeling techniques and apply the following advanced analysis tools, as needed, to optimize your permitting strategy:
• Analysis of BPIP output to verify if AERMOD is overpredicting,
• Screening tool to assess the benefit of refining the BPIP building dimensions inputs,
• Use of Equivalent Building Dimension (EBD) studies to correct building wake effects in AERMOD,
• Evaluation of background concentrations to determine a reasonable value to combine with predicted concentrations,
• Use of the Monte Carlo approach (i.e., EMVAP) to address sources with variable emissions,
• Use of the adjusted friction velocity (u-star) option in AERMET to address AERMOD’s overestimation during low wind stable hours,
• Site analysis to determine whether stacks taller than formula GEP stack heights are justified,
• Site specific wind tunnel modeling to determine GEP stack heights and Equivalent Building Dimensions,
• Site-specific wind erosion inputs, and
• Area and volume source enhancements.
EVALUATION OF SO2 AND NOX OFFSET RATIOS TO ACCOUNT FOR SECONDARY PM2.5 FORMATIONSergio A. Guerra
On January 4, 2012, the EPA committed to engage in rulemaking to evaluate updates to the Guideline on Air Quality Models (AppendixWof 40 CFR 51) and, as appropriate, incorporate new analytical techniques or models for secondary PM2.5. As a result, the National Association of Clean Air Agencies (NACAA) developed a screening method involving offset ratios to account for
secondary PM2.5 formation. This method can be used to evaluate total (direct and indirect) PM2.5 impacts for permitting purposes. Therefore, the evaluation of this method is important to determine its viability for widespread use.
The Plume Rise Model Enhancements (PRIME) formulation in AERMOD has been updated based new equations developed from wind tunnel measurements taken downwind of various solid and streamlined structures. These new equations, along with other building downwash improvements have been included as alpha options in the upcoming new version of AERMOD. The PRIME2 options include: • PRIME2UTurb which enables enhanced calculations of turbulence and wind speed • PRIME2Ueff which defines the height used to compute effective parameters Ueff, Sweff, Sveff and Tgeff at plume height and at 30 m • Streamline defines the set of constants for modeling all structures as streamlined. If omitted, rectangular building constants are used. The ORD Options include: • PRIMEUeff which controls the heights for which the wind speed is calculated for the main plume concentrations. • Average between plume height and receptor height recommended in ORD version • Default is current method in AERMOD, stack height wind speed. • PRIMETurb which adjusts the vertical turbulence intensity, wiz0 from 0.6 to 0.7. • PRIMECav modifies the cavity calculations These improvements aim to address important theoretical issues that significantly affect the accuracy of predicted concentrations subject to downwash effects. This research effort was funded in part by the American Petroleum Institute, the Electric Power Research Institute, the Corn Refiners Association and the American Forest & Paper Association. As part of it, the PRIME2 subcommittee under the A&WMA APM committee was formed to: (1) establish a mechanism to review, approve and implement new science into the model for this and future improvements; and (2) provide a technical review forum to improve the PRIME building downwash algorithms. Collaboration and cooperation from the EPA Office of Research and Development (ORD) has been on-going during the research project resulting in new alpha options aimed at solving known issues with the treatment of building downwash effects in AERMOD. The intent is that these experimental options will be tested by the user community to create enough justification to make these beta (approved on a case-by-case basis) and eventually default options in AERMOD. A preliminary evaluation for the following four cases will be presented: • Arconic- Davenport, IA (formerly Alcoa) • Mirant Potomac River Generating Station- Alexandria, VA • Basic American Foods- Blackfoot, ID • Oakley Generating Station- Oakley, CA The evaluation includes comparing 1-hr, 24-hr and annual averages along with Q-Q plots and isopleths. A discussion related to the results obtained will also be presented.
Highlights from the 2016 Guideline on Air Quality Models ConferenceSergio A. Guerra
The revision of the Guideline on AQ Models (Appendix W) will prompt many changes in the way dispersion modeling is conducted for regulatory purposes. Some of the changes to the Guideline include enhancements and bug fixes to the AERMOD modeling system, new screening techniques to address ozone and secondary PM2.5, delisting CALPUFF as the preferred long-range transport model, and updates on the use of meteorological input data. These changes will have a significant impact on the regulated community. In anticipation of these updates, the Air & Waste Management Association will hold its 6th Specialty Conference: “Guideline on Air Quality Models: The New Path” to provide a technical forum to discuss the Guideline. This talk covered the main highlights from this conference including the presentations from EPA on the status and future direction of the Guideline. Learn how these changes may impact dispersion modeling evaluations for short and long range transport.
Important theoretical issues that significantly affect the accuracy of predicted concentrations subject to downwash effects have been identified in AERMOD/PRIME. These issues have prompted a number of industry groups to fund new research aiming at overcoming these shortcomings. The Plume Rise Model Enhancements (PRIME) building downwash algorithms1 (Schulman et al. 2000) in AERMOD2 are being updated to address some of the most critical limitations in the current theory. These enhancements will incorporate the latest advancements related to building downwash effects. The technical aspects of these enhancements are discussed in more detail in a recent publication "PRIME2: Development and Evaluation of Improved Building Downwash Algorithms for Solid and Streamlined Structures". The updates to the PRIME code include new equations to account for building wake effects that decay rapidly back to ambient levels above the top of the building; reduced wake effects for streamlined structures; and reduced wake effects for high approach roughness. A comparison with field data was conducted with the Bowline Point, Alaska North Slope, Millstone Nuclear Power Station, and the Duane Arnold Energy Center databases. A new experimental BPIP-PRM version is also discussed.
Evaluation of the Theoretical Problems with Building Downwash Using A New Met...Sergio A. Guerra
While the current EBD method is the best available option to determine correct building dimensions in the model, a different method was suggested by EPA in the 2011 Memo: Model Clearinghouse Review of EBD for AERMOD. Attachment B to the 2011 Memo includes an assessment of the Alcoa Davenport Works EBD Study. In this evaluation EPA compared wind tunnel observations with AERMOD derived concentrations. However, this evaluation has important shortcomings. First, to carry out this comparison between wind tunnel and AERMOD concentrations, it is necessary to collect velocity profiles that include longitudinal and vertical turbulent intensity measurements upwind of the stack. These data were not available for the EPA evaluation of the Alcoa Davenport Works EBD Study. Second, the wind tunnel model operating conditions were converted to full scale conditions by using exact similarity. However, exact similarity is not used to specify model operating conditions since only momentum ratios are matched but not buoyancy ones. Whereas EPA did not provide important details on how this study was performed, this paper outlines how to properly carry out this new method where AERMOD is used to determine equivalent building dimensions. The viability of this new method was also evaluated and discussed.
New Guideline on Air Quality Models and the Electric Utility IndustrySergio A. Guerra
The revision of the Guideline on AQ Models (Appendix W) will prompt many changes in the way dispersion modeling is conducted for regulatory purposes. Some of the changes to the Guideline include enhancements and bug fixes to the AERMOD modeling system, new screening techniques to address ozone and secondary PM2.5, delisting CALPUFF as the preferred long-range transport model, and updates on the use of meteorological input data. These changes will have a significant impact on the regulated community. This presentation will cover the main highlights from this guidance and how the electric utility industry will be impacted. In addition, the latest information provided by EPA during the 2016 Regional, State, and Local Modelers' Workshop will also be presented.
Complying with EPA's Guidance for SO2 DesignationsSergio A. Guerra
EPA is under a Court order to complete the remaining SO2 designations for the rest of the country in three additional rounds. On March 20, 2015 the EPA released an updated guidance for 1-hr SO2 area designations. The two options included are compliance through dispersion modeling or ambient monitoring. Of these two options, dispersion modeling is the fastest and most cost effective one to characterize SO2 air quality. However, this compliance demonstration can be challenging given that AERMOD tends to produce overly conservative concentration estimates. Source characterization techniques and probabilistic techniques may be used to achieve compliance with the 1-hour NAAQS. Three advanced methods discussed: 1) Equivalent Building Dimensions (EBD); 2) Emission Variability Processor (EMVAP); 3) 50th Percentile Background Concentrations.
EFFECTS OF MET DATA PROCESSING IN AERMOD CONCENTRATIONSSergio A. Guerra
The current study evaluates the effect that different parameters used to process meteorological data have on AERMOD concentrations. Specifically, this study evaluates the effect from the use of AERMET processed with; 1-minute wind data collected by the Automated Surface Observing System (ASOS) and pre-processed using AERMINUTE, refined National Climatic Data Center (NCDC) station location and anemometer height, surface moisture, and urban/rural options. In this evaluation, one year of meteorological data was processed with nine different sets of input parameters and then used in AERMOD to run a short, medium and tall stack scenario for 1-hour, 24-hour and annual averaging periods. Downwash and terrain effects were not considered in this study. The results indicate that the three stack scenarios are sensitive to the location used for the meteorological station. Anemometer height changes had a small effect on concentrations for all scenarios except for the tall stack scenario which produced a modest increase in concentrations for the annual averaging period. Surface moisture was not found to have a strong effect on the scenarios evaluated. The use of AERMINUTE data resulted in significantly higher concentrations for the 1-hour (85%), 24-hour (81%), and annual (88%) averaging periods. The ice free group station option in AERMINUTE was also evaluated. When using AERMINUTE without specifying that the station is part of the ice free wind group stations, the concentrations obtained for tall stack scenario were lower for the 1-hour (64%), 24-hour (68%), and annual (78%) averaging periods. Finally, when it comes to the urban/rural evaluation, the greatest effect is observed in the medium stack scenario where concentrations double for the 1-hour scenario when using the rural option. However, in the tall stack scenario, significantly lower concentrations were obtained by using the urban parameter for the three averaging periods evaluated.
Presented at the 10th Conference of Air Quality Modeling
EPA‐Research Triangle Park, NC Campus on March 15, 2012; at the AWMA UMS Dispersion Modeling Workshop on May 15, 2012 and at the Annual AWMA Conference on June 20, 2012.
Pairing aermod concentrations with the 50th percentile monitored valueSergio A. Guerra
Presentation delivered to the Background Concentrations Workgroup for Air Dispersion Modeling organized by the Minnesota Pollution Control Agency. delivered on March 25, 2014. Three topics covered include 1) Screening monitoring data, 2) AERMOD’s time-space mismatch, and
3) Proposed 50th % Bkg Method
Using Physical Modeling to Refine Downwash Inputs to AERMOD at a Food Process...Sergio A. Guerra
Demonstrating compliance with air quality standards using dispersion modeling is increasingly difficulty because of significant tightening National Ambient Air Quality Standards (NAAQS) that has occurred in the last decade. Compliance with these standards is usually demonstrated using AERMOD, EPA’s standard model for assessing air quality impacts from industrial sources. However, AERMOD often produces higher predictions of air quality impacts due to the inherent conservative (high) assumptions and simplifications in its formulation. A specific situation involves the calculations used to assess the impacts of air flow downwash around buildings. Although the theory used to estimate these effects was developed for a limited set of building types, these formulae are applied indiscriminately to all types of buildings in a conservative fashion, often leading to significant overpredictions of downwash effects.
This presentation covers the basics of wind tunnel modeling and how it can be used to correct downwash induced overpredictions to achieve compliance. The presentation will also describe the setup and execution of wind tunnel modeling at a food processing facility to develop improved downwash parameters and increase the accuracy of dispersion modeling results.
Effects of Wind Direction on VOC Concentrations in Southeast KansasSergio A. Guerra
Twenty-four-hour whole-air samples were collected in evacuated stainless steel canisters and analyzed for volatile organic compounds (VOC) at selected sites in southeast Kansas from March 1999 to October 2000. The purpose was to assess the influence on air quality of four industrial facilities that burn hazardous waste located in the communities of Coffeyville, Chanute, Independence and Fredonia. Fifteen of the VOC analytes were found at concentrations above the detection limit and above levels observed in the blanks. Data were analyzed to investigate whether sampling site and date had a significant effect on VOC concentration. Results indicate that site and/or date were significant factors for many of the VOCs. To further investigate the temporal factor, sampling days were divided into four classifications based on wind direction: predominantly north winds, predominantly south winds, calm/variable winds and
other winds. Results from statistical analyses show that wind direction was a significant factor for benzene, toluene, o-xylene, naphthalene, and carbon tetrachloride. Data from upwind and downwind samples were analyzed for the four cities of interest in the study area, to investigate the effect of the four targeted sources on VOC concentrations. Results from Fredonia showed higher concentrations of toluene, ethyl benzene, styrene, methyl chloride, and trichloroethylene in the upwind samples, although none of the results were statistically significant. Chanute also showed higher concentrations of the same compounds and m,p-xylene in the upwind samples; results were significant at the 0.05 level for toluene, ethylbenzene, and xylene. These results indicate that sources other than those targeted in the sampling network may be contributing to
the VOC levels. Results from Independence showed higher concentrations of ethylebenzene and styrene in the downwind samples; results were statistically significant. These results indicate that the source targeted in the sampling network may be contributing to the VOC levels at those sampling sites.
Probabilistic & Source Characterization Techniques in AERMOD ComplianceSergio A. Guerra
The short term NAAQS are more stringent and traditional techniques are not suitable anymore. The probabilistic nature of these standards also opens the door to modeling techniques based on probability. Source characterization studies can also be used to refine AERMOD’s inputs to be more accurate and achieve reductions of more than half. This presentation will cover these compliance methods.
Currently, it is assumed that a given emission unit is in operation at its maximum capacity every hour of the year. However, assuming constant maximum emissions is overly conservative for facilities such as power plants that are not in operation all the time at full load. A better approach is the use of the Monte Carlo technique to account for emission variability. Another conservative assumption in NAAQS modeling relates to combining predicted concentrations from AERMOD with maximum or design concentrations from the monitor. A more reasonable approach is to combine the 50th percentile background concentration with AERMOD values.
The inputs to AERMOD can be obtained by more accurate source characterization studies. Such is the case of building dimensions commonly calculated with BPIP. These dimensions tend to overstate the wake effects and produce significantly higher concentrations especially for lattice structures, elongated buildings, and streamlined structures. An Equivalent Building Dimensions (EBD) study can be used to inform AERMOD with more accurate downwash characteristics.
Background Concentrations and the Need for a New System to Update AERMODSergio A. Guerra
Presentation delivered at the EPA 11th Conference on Air Quality Modeling at RTP, NC.
Topics covered include background concentrations and the need for a new system to update AERMOD. An evaluation of what is being proposed in the draft guidance related to background concentrations and an alternative approach to determine background concentrations for dispersion modeling evaluations is presented. A review of the lessons learned from Appendix W and a proposed new method to incorporate science into the model.
Using Physical Modeling to Evaluate Re-entrainment of Stack EmissionsSergio A. Guerra
Fume re-entry is an important concern for many types of facilities such as hospitals and laboratories that emit pathogens and toxic chemicals that may impact public health by being re-entrained into the building though nearby air intakes. Numerical methods can be used to evaluate dispersion of pollutants from stacks at sensitive receptors. However, numerical methods have limitations and simplifications that can significantly affect its predictions. An alternate way of analyzing stack re-entrainment is with physical modeling in a wind tunnel. In such a study, a scale model that accounts for buildings, topography, and vegetation is used with planned and alternate stack designs to determine the toxic emission impacts on air intakes and other sensitive locations. In a wind tunnel study different stack designs and possible mitigation options can be evaluated. This method is superior to numerical methods (e.g., dispersion models) because it accounts for the immediate structures, topography, and vegetation that is often ignored or oversimplified in numerical methods.
This presentation will show a hypothetical case study evaluating a site with toxic air emissions using AERMOD and physical modeling.
PRIME2_consequence_analysis_and _model_evaluationSergio A. Guerra
The Plume Rise Model Enhancements (PRIME) building downwash algorithms1 (Schulman et al. 2000) in AERMOD2 are being updated to address some of the most critical limitations in the current theory. These enhancements will incorporate the latest advancements related to building downwash effects. The technical aspects of these enhancements are discussed in more detail in a companion paper titled “PRIME2: Development and Evaluation of Improved Building Downwash Algorithms for Solid and Streamlined Structures (MO13)”. The updates to the PRIME code include new equations to account for building wake effects that decay rapidly back to ambient levels above the top of the building; reduced wake effects for streamlined structures; and reduced wake effects for high approach roughness. A consequence analysis comparing the current AERMOD/PRIME model versus the new AERMOD/PRIME2 model was performed. Additionally, a field data evaluation was conducted with the Bowline Point database. The results from these analyses are discussed below.
Advanced Modeling Techniques for Permit Modeling - Turning challenges into o...Sergio A. Guerra
Advance modeling techniques can be used in AERMOD to refine the inputs that are entered in the model to get more accurate results. This presentation covers:
-AERMOD’s Temporal Mismatch Limitation
-Building Downwash Limitations in BPIP/PRIME
-Advanced Modeling Techniques to Overcome these Limitations
Solutions include:
Equivalent Building Dimensions (EBD)
Emission Variability Processor (EMVAP)
Updated ambient ratio method (ARM2)
Pairing AERMOD values with the 50th % background concentrations in cumulative analyses.
Using Physical Modeling to Refine Downwash Inputs to AERMODSergio A. Guerra
Achieving compliance in dispersion modeling can be quite challenging because of the tight National Ambient Air Quality Standards (NAAQS). In addition, AERMOD’s limitations can, in many cases, produce higher than normal concentrations due to the inherent assumptions and simplifications in its formulation. In the case of downwash, the theory used to estimate these effects was developed for a limited set of building types. However, these formulations are commonly used indiscriminately for all types of buildings. This presentation will cover how the basics of wind tunnel modeling can overcome some of these limitations and be used to mitigate downwash induced overpredictions to achieve compliance.
dispersion modeling requirements are more common in air permitting projects and in many cases become the bottleneck in permitting. Unlike any other consulting firm, CPP promotes cutting edge techniques which can alleviate excessive conservatism in permit modeling to a reasonable level that still protects public health. At CPP we start with the standard modeling techniques and apply the following advanced analysis tools, as needed, to optimize your permitting strategy:
• Analysis of BPIP output to verify if AERMOD is overpredicting,
• Screening tool to assess the benefit of refining the BPIP building dimensions inputs,
• Use of Equivalent Building Dimension (EBD) studies to correct building wake effects in AERMOD,
• Evaluation of background concentrations to determine a reasonable value to combine with predicted concentrations,
• Use of the Monte Carlo approach (i.e., EMVAP) to address sources with variable emissions,
• Use of the adjusted friction velocity (u-star) option in AERMET to address AERMOD’s overestimation during low wind stable hours,
• Site analysis to determine whether stacks taller than formula GEP stack heights are justified,
• Site specific wind tunnel modeling to determine GEP stack heights and Equivalent Building Dimensions,
• Site-specific wind erosion inputs, and
• Area and volume source enhancements.
EVALUATION OF SO2 AND NOX OFFSET RATIOS TO ACCOUNT FOR SECONDARY PM2.5 FORMATIONSergio A. Guerra
On January 4, 2012, the EPA committed to engage in rulemaking to evaluate updates to the Guideline on Air Quality Models (AppendixWof 40 CFR 51) and, as appropriate, incorporate new analytical techniques or models for secondary PM2.5. As a result, the National Association of Clean Air Agencies (NACAA) developed a screening method involving offset ratios to account for
secondary PM2.5 formation. This method can be used to evaluate total (direct and indirect) PM2.5 impacts for permitting purposes. Therefore, the evaluation of this method is important to determine its viability for widespread use.
The Plume Rise Model Enhancements (PRIME) formulation in AERMOD has been updated based new equations developed from wind tunnel measurements taken downwind of various solid and streamlined structures. These new equations, along with other building downwash improvements have been included as alpha options in the upcoming new version of AERMOD. The PRIME2 options include: • PRIME2UTurb which enables enhanced calculations of turbulence and wind speed • PRIME2Ueff which defines the height used to compute effective parameters Ueff, Sweff, Sveff and Tgeff at plume height and at 30 m • Streamline defines the set of constants for modeling all structures as streamlined. If omitted, rectangular building constants are used. The ORD Options include: • PRIMEUeff which controls the heights for which the wind speed is calculated for the main plume concentrations. • Average between plume height and receptor height recommended in ORD version • Default is current method in AERMOD, stack height wind speed. • PRIMETurb which adjusts the vertical turbulence intensity, wiz0 from 0.6 to 0.7. • PRIMECav modifies the cavity calculations These improvements aim to address important theoretical issues that significantly affect the accuracy of predicted concentrations subject to downwash effects. This research effort was funded in part by the American Petroleum Institute, the Electric Power Research Institute, the Corn Refiners Association and the American Forest & Paper Association. As part of it, the PRIME2 subcommittee under the A&WMA APM committee was formed to: (1) establish a mechanism to review, approve and implement new science into the model for this and future improvements; and (2) provide a technical review forum to improve the PRIME building downwash algorithms. Collaboration and cooperation from the EPA Office of Research and Development (ORD) has been on-going during the research project resulting in new alpha options aimed at solving known issues with the treatment of building downwash effects in AERMOD. The intent is that these experimental options will be tested by the user community to create enough justification to make these beta (approved on a case-by-case basis) and eventually default options in AERMOD. A preliminary evaluation for the following four cases will be presented: • Arconic- Davenport, IA (formerly Alcoa) • Mirant Potomac River Generating Station- Alexandria, VA • Basic American Foods- Blackfoot, ID • Oakley Generating Station- Oakley, CA The evaluation includes comparing 1-hr, 24-hr and annual averages along with Q-Q plots and isopleths. A discussion related to the results obtained will also be presented.
Highlights from the 2016 Guideline on Air Quality Models ConferenceSergio A. Guerra
The revision of the Guideline on AQ Models (Appendix W) will prompt many changes in the way dispersion modeling is conducted for regulatory purposes. Some of the changes to the Guideline include enhancements and bug fixes to the AERMOD modeling system, new screening techniques to address ozone and secondary PM2.5, delisting CALPUFF as the preferred long-range transport model, and updates on the use of meteorological input data. These changes will have a significant impact on the regulated community. In anticipation of these updates, the Air & Waste Management Association will hold its 6th Specialty Conference: “Guideline on Air Quality Models: The New Path” to provide a technical forum to discuss the Guideline. This talk covered the main highlights from this conference including the presentations from EPA on the status and future direction of the Guideline. Learn how these changes may impact dispersion modeling evaluations for short and long range transport.
Important theoretical issues that significantly affect the accuracy of predicted concentrations subject to downwash effects have been identified in AERMOD/PRIME. These issues have prompted a number of industry groups to fund new research aiming at overcoming these shortcomings. The Plume Rise Model Enhancements (PRIME) building downwash algorithms1 (Schulman et al. 2000) in AERMOD2 are being updated to address some of the most critical limitations in the current theory. These enhancements will incorporate the latest advancements related to building downwash effects. The technical aspects of these enhancements are discussed in more detail in a recent publication "PRIME2: Development and Evaluation of Improved Building Downwash Algorithms for Solid and Streamlined Structures". The updates to the PRIME code include new equations to account for building wake effects that decay rapidly back to ambient levels above the top of the building; reduced wake effects for streamlined structures; and reduced wake effects for high approach roughness. A comparison with field data was conducted with the Bowline Point, Alaska North Slope, Millstone Nuclear Power Station, and the Duane Arnold Energy Center databases. A new experimental BPIP-PRM version is also discussed.
Evaluation of the Theoretical Problems with Building Downwash Using A New Met...Sergio A. Guerra
While the current EBD method is the best available option to determine correct building dimensions in the model, a different method was suggested by EPA in the 2011 Memo: Model Clearinghouse Review of EBD for AERMOD. Attachment B to the 2011 Memo includes an assessment of the Alcoa Davenport Works EBD Study. In this evaluation EPA compared wind tunnel observations with AERMOD derived concentrations. However, this evaluation has important shortcomings. First, to carry out this comparison between wind tunnel and AERMOD concentrations, it is necessary to collect velocity profiles that include longitudinal and vertical turbulent intensity measurements upwind of the stack. These data were not available for the EPA evaluation of the Alcoa Davenport Works EBD Study. Second, the wind tunnel model operating conditions were converted to full scale conditions by using exact similarity. However, exact similarity is not used to specify model operating conditions since only momentum ratios are matched but not buoyancy ones. Whereas EPA did not provide important details on how this study was performed, this paper outlines how to properly carry out this new method where AERMOD is used to determine equivalent building dimensions. The viability of this new method was also evaluated and discussed.
New Guideline on Air Quality Models and the Electric Utility IndustrySergio A. Guerra
The revision of the Guideline on AQ Models (Appendix W) will prompt many changes in the way dispersion modeling is conducted for regulatory purposes. Some of the changes to the Guideline include enhancements and bug fixes to the AERMOD modeling system, new screening techniques to address ozone and secondary PM2.5, delisting CALPUFF as the preferred long-range transport model, and updates on the use of meteorological input data. These changes will have a significant impact on the regulated community. This presentation will cover the main highlights from this guidance and how the electric utility industry will be impacted. In addition, the latest information provided by EPA during the 2016 Regional, State, and Local Modelers' Workshop will also be presented.
Complying with EPA's Guidance for SO2 DesignationsSergio A. Guerra
EPA is under a Court order to complete the remaining SO2 designations for the rest of the country in three additional rounds. On March 20, 2015 the EPA released an updated guidance for 1-hr SO2 area designations. The two options included are compliance through dispersion modeling or ambient monitoring. Of these two options, dispersion modeling is the fastest and most cost effective one to characterize SO2 air quality. However, this compliance demonstration can be challenging given that AERMOD tends to produce overly conservative concentration estimates. Source characterization techniques and probabilistic techniques may be used to achieve compliance with the 1-hour NAAQS. Three advanced methods discussed: 1) Equivalent Building Dimensions (EBD); 2) Emission Variability Processor (EMVAP); 3) 50th Percentile Background Concentrations.
EFFECTS OF MET DATA PROCESSING IN AERMOD CONCENTRATIONSSergio A. Guerra
The current study evaluates the effect that different parameters used to process meteorological data have on AERMOD concentrations. Specifically, this study evaluates the effect from the use of AERMET processed with; 1-minute wind data collected by the Automated Surface Observing System (ASOS) and pre-processed using AERMINUTE, refined National Climatic Data Center (NCDC) station location and anemometer height, surface moisture, and urban/rural options. In this evaluation, one year of meteorological data was processed with nine different sets of input parameters and then used in AERMOD to run a short, medium and tall stack scenario for 1-hour, 24-hour and annual averaging periods. Downwash and terrain effects were not considered in this study. The results indicate that the three stack scenarios are sensitive to the location used for the meteorological station. Anemometer height changes had a small effect on concentrations for all scenarios except for the tall stack scenario which produced a modest increase in concentrations for the annual averaging period. Surface moisture was not found to have a strong effect on the scenarios evaluated. The use of AERMINUTE data resulted in significantly higher concentrations for the 1-hour (85%), 24-hour (81%), and annual (88%) averaging periods. The ice free group station option in AERMINUTE was also evaluated. When using AERMINUTE without specifying that the station is part of the ice free wind group stations, the concentrations obtained for tall stack scenario were lower for the 1-hour (64%), 24-hour (68%), and annual (78%) averaging periods. Finally, when it comes to the urban/rural evaluation, the greatest effect is observed in the medium stack scenario where concentrations double for the 1-hour scenario when using the rural option. However, in the tall stack scenario, significantly lower concentrations were obtained by using the urban parameter for the three averaging periods evaluated.
Presented at the 10th Conference of Air Quality Modeling
EPA‐Research Triangle Park, NC Campus on March 15, 2012; at the AWMA UMS Dispersion Modeling Workshop on May 15, 2012 and at the Annual AWMA Conference on June 20, 2012.
Pairing aermod concentrations with the 50th percentile monitored valueSergio A. Guerra
Presentation delivered to the Background Concentrations Workgroup for Air Dispersion Modeling organized by the Minnesota Pollution Control Agency. delivered on March 25, 2014. Three topics covered include 1) Screening monitoring data, 2) AERMOD’s time-space mismatch, and
3) Proposed 50th % Bkg Method
Using Physical Modeling to Refine Downwash Inputs to AERMOD at a Food Process...Sergio A. Guerra
Demonstrating compliance with air quality standards using dispersion modeling is increasingly difficulty because of significant tightening National Ambient Air Quality Standards (NAAQS) that has occurred in the last decade. Compliance with these standards is usually demonstrated using AERMOD, EPA’s standard model for assessing air quality impacts from industrial sources. However, AERMOD often produces higher predictions of air quality impacts due to the inherent conservative (high) assumptions and simplifications in its formulation. A specific situation involves the calculations used to assess the impacts of air flow downwash around buildings. Although the theory used to estimate these effects was developed for a limited set of building types, these formulae are applied indiscriminately to all types of buildings in a conservative fashion, often leading to significant overpredictions of downwash effects.
This presentation covers the basics of wind tunnel modeling and how it can be used to correct downwash induced overpredictions to achieve compliance. The presentation will also describe the setup and execution of wind tunnel modeling at a food processing facility to develop improved downwash parameters and increase the accuracy of dispersion modeling results.
Effects of Wind Direction on VOC Concentrations in Southeast KansasSergio A. Guerra
Twenty-four-hour whole-air samples were collected in evacuated stainless steel canisters and analyzed for volatile organic compounds (VOC) at selected sites in southeast Kansas from March 1999 to October 2000. The purpose was to assess the influence on air quality of four industrial facilities that burn hazardous waste located in the communities of Coffeyville, Chanute, Independence and Fredonia. Fifteen of the VOC analytes were found at concentrations above the detection limit and above levels observed in the blanks. Data were analyzed to investigate whether sampling site and date had a significant effect on VOC concentration. Results indicate that site and/or date were significant factors for many of the VOCs. To further investigate the temporal factor, sampling days were divided into four classifications based on wind direction: predominantly north winds, predominantly south winds, calm/variable winds and
other winds. Results from statistical analyses show that wind direction was a significant factor for benzene, toluene, o-xylene, naphthalene, and carbon tetrachloride. Data from upwind and downwind samples were analyzed for the four cities of interest in the study area, to investigate the effect of the four targeted sources on VOC concentrations. Results from Fredonia showed higher concentrations of toluene, ethyl benzene, styrene, methyl chloride, and trichloroethylene in the upwind samples, although none of the results were statistically significant. Chanute also showed higher concentrations of the same compounds and m,p-xylene in the upwind samples; results were significant at the 0.05 level for toluene, ethylbenzene, and xylene. These results indicate that sources other than those targeted in the sampling network may be contributing to
the VOC levels. Results from Independence showed higher concentrations of ethylebenzene and styrene in the downwind samples; results were statistically significant. These results indicate that the source targeted in the sampling network may be contributing to the VOC levels at those sampling sites.
Probabilistic & Source Characterization Techniques in AERMOD ComplianceSergio A. Guerra
The short term NAAQS are more stringent and traditional techniques are not suitable anymore. The probabilistic nature of these standards also opens the door to modeling techniques based on probability. Source characterization studies can also be used to refine AERMOD’s inputs to be more accurate and achieve reductions of more than half. This presentation will cover these compliance methods.
Currently, it is assumed that a given emission unit is in operation at its maximum capacity every hour of the year. However, assuming constant maximum emissions is overly conservative for facilities such as power plants that are not in operation all the time at full load. A better approach is the use of the Monte Carlo technique to account for emission variability. Another conservative assumption in NAAQS modeling relates to combining predicted concentrations from AERMOD with maximum or design concentrations from the monitor. A more reasonable approach is to combine the 50th percentile background concentration with AERMOD values.
The inputs to AERMOD can be obtained by more accurate source characterization studies. Such is the case of building dimensions commonly calculated with BPIP. These dimensions tend to overstate the wake effects and produce significantly higher concentrations especially for lattice structures, elongated buildings, and streamlined structures. An Equivalent Building Dimensions (EBD) study can be used to inform AERMOD with more accurate downwash characteristics.
La Municipalidad de Asunción a través de la Dirección de Emergencias y Desastres Municipal (COMUEDA), se encuentra abocada a la asistencia de las familias en situación de riesgo, a raíz de la crecida del Rio Paraguay, que a la fecha a alcanzado una altura de 4.66 mts, la Dirección del Comueda está trabajando en forma continua para dar respuesta inmediata a las necesidades de las familias afectadas.Total de familias asistidas en situación de RIESGO: 1.276.
Class Slides / 29.09.2014 from DOM E-5064 Digital Strategies for Museums & Cultural Heritage Course at Aalto University Autumn 2014: http://mlab.taik.fi/digitalmuseum/
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Similar to INNOVATIVE DISPERSION MODELING PRACTICES TO ACHIEVE A REASONABLE LEVEL OF CONSERVATISM IN AERMOD MODELING DEMONSTRATIONS CASE STUDY TO EVALUATE EMVAP, AMR2, AND BACKGROUND CONCENTRATIONS
ALTERNATE METHOD TO COMBINE MONITORED AND PREDICTED CONCENTRATIONS IN DISPERS...Sergio A. Guerra
The advent of the short term NAAQS has prompted us to reassess the level of conservatism commonly used in dispersion modeling analyses. An area of conservatism in NAAQS demonstrations relates to the combining of predicted (modeled) concentrations from AERMOD with observed (monitored) concentrations. Normally, some of the highest monitored observations are combined with AERMOD results yielding a very conservative total concentration. For example, in the case of the 1-hour NO2 NAAQS, the chances of the 98th percentile monitored concentration occurring at the same time as the meteorology to generate the 98th percentile ambient concentration is extremely low. Therefore, assuming that both of these happen at the same time is overly conservative.
This presentation includes justification for the use of a reasonable background concentration to combine with the AERMOD predicted concentration. The use of this method, if accepted by regulatory agencies, can help facilities demonstrate compliance in dispersion modeling analyses by assuming a more reasonable background concentration while, at the same time being protective of the NAAQS.
AERMOD Tiering Approach Case Study for 1-Hour NO2BREEZE Software
This study reviews 1-hour NO2 concentrations predicted by AERMOD for a hypothetical source at four locations throughout the United States with hourly varying background ozone concentrations.
Air pollution is a global environmental challenge that has continued to receive worldwide attention despite the recent decline in concentration of atmospheric pollutants following stringent environmental protection regulations. The major source of this pollution remains fossil fuels; hence the urgent need for cleaner energy sources. This study presents a review of the models applied in monitoring ambient air quality. The primary aim of air pollution modeling is to identify and quantitatively characterize pollutant emission at its source and subsequent dispersion through the atmosphere, subject to meteorological conditions, physical and chemical transformations. The common models and model assumptions for modeling air pollution and quality were critically reviewed and analyzed in this work for application in both forecasting and estimation of air pollutants on the basis of considered causes and in air quality assessment and air pollution control.
Flare radiation-mitigation-analysis-of-onshore-oil-gas-production-refining-fa...Anchal Soni
The main objective of this paper is to calculate the sterile area around an existing vertical flare of length 112 meters, located in an onshore facility and evaluate whether the current design is acceptable during a General Power Failure (GPF) scenario. The sterile area will be calculated at an elevation of 2m, which represents the typical head height for personnel.
On farm comparison of two liquid dairy manure application methodsLPE Learning Center
Similar to INNOVATIVE DISPERSION MODELING PRACTICES TO ACHIEVE A REASONABLE LEVEL OF CONSERVATISM IN AERMOD MODELING DEMONSTRATIONS CASE STUDY TO EVALUATE EMVAP, AMR2, AND BACKGROUND CONCENTRATIONS (20)
A renewed interest and scrutiny of downwash shortcomings has fueled a parallel, yet complementary effort, led by industry and EPA. Industrial groups funded the update to the Plume Rise Model Enhancements (PRIME) formulation in AERMOD based on new equations derived from wind tunnel measurements. Concurrently, EPA’s Office of Research and Development (ORD) conducted research that led to new enhancements to the downwash formulation.2 The new PRIME equations (PRIME2), along with EPA-ORD’s building downwash improvements, have been included as alpha options in an upcoming new EPA version of AERMOD.
As part of the renewed interest in building downwash, the PRIME2 subcommittee under the A&WMA APM committee was formed to: (1) establish a mechanism to review, approve and implement new science into the model for this and future improvements; and (2) provide a technical review forum to improve the PRIME building downwash algorithms. Collaboration and cooperation from EPA’s ORD and OAQPS have been on-going during this research project. These efforts included a downwash summit at EPA’s RTP facilities on February 16, 2018 where representatives of the PRIME2 committee and research funders met with EPA’s ORD and OAQPS staff to discuss the newly developed building downwash improvements. During that meeting it was decided that these enhancements would be included as new alpha options in AERMOD. The intent is that these experimental options will be tested by the user community to create enough justification to transition them to a beta status (approved on a case-by-case basis) and eventually to default options in AERMOD. An evaluation of some of these new downwash options is presented.
Solution to AERMOD/PRIME PM10 Overpredictions for Extremely Short, Long and W...Sergio A. Guerra
The current formulation in AERMOD/PRIME is prone to downwash overestimations as documented by Petersen et al. Some of these overpredictions can be minimized by conducting a wind tunnel study to refine the building inputs used in AERMOD/PRIME for critical stacks and wind directions. Most of the wind tunnel studies conducted to date involve taller building structures of at least 20 meters in height. However, a recent wind tunnel study was conducted for the Basic American Foods, Blackfoot, Idaho facility, which has extremely short buildings (7 to 12 meters in height) with very long and wide footprints and many exhaust stacks which are less than 25 meters above ground
The wind tunnel study confirmed that AERMOD was vastly overstating downwash effects for certain critical wind directions. In some cases, AERMOD-predicted concentrations were almost four times higher without the wind tunnel refinements. This study indicates that the previously identified tendency of AERMOD to overpredict downwash using the traditional BPIP-derived building inputs also applies to sites with shorter buildings. Because shorter buildings with shorter stacks are common in many sources subject to the minor New Source Review program (such as most food and beverage and manufacturing facilities), AERMOD’s overpredictions may be causing significantly higher predicted concentrations for many industrial sources.
This paper describes the wind tunnel study performed for this site, presents the benefits obtained from these building input refinements, and reviews comments received on the project from regulatory agencies.
PRIME2: Consequence Analysis and Model EvaluationSergio A. Guerra
This presentation will cover a preliminary consequence analysis and field evaluation related to the updates to the Plume Rise Model Enhancements updates (PRIME2). Additional research needs uncovered through this research project will also be discussed.
Use of Wind Tunnel Refinements in the Dispersion Modeling Analysis of the Ala...Sergio A. Guerra
The proposed Alaska LNG GTP project includes the construction of a natural gas treatment plant on the Alaska North Slope. The Gas Treatment Plant (GTP) is proposed to be located on the west coast of Prudhoe Bay and would treat natural gas produced on the North Slope.
Initial dispersion modeling of the Alaska LNG Gas Treatment Plant (GTP) found results inconsistent with local and regional measurements when evaluating compliance with the 1-hour NO2 National Ambient Air Quality Standard (NAAQS) due in part to two adjacent nearby sources. These existing sources include the Central Gas Facility (CGF) and Central Compression Plant (CCP) located immediately east of the GTP. The prevailing winds at the site are east-northeast and west-southwest which align with the arrangement of the facilities.
The building downwash inputs generated by the Building Profile Input Program for PRIME (BPIPPRM) were evaluated for the CGF and CCP facilities. This analysis confirmed that the building dimension inputs for numerous wind directions were outside of the tested theory used to develop the building downwash algorithms in AERMOD. Previous studies2,8,11,12,13 suggest that AERMOD predictions are biased to overstate downwash effects for certain building input ratios.
Wind tunnel determined equivalent building dimensions (EBD) were conducted for the most critical stacks and wind directions to refine AERMOD-derived predicted concentrations. The current paper covers the EBD method used to refine the building inputs for the CGF and CCP facilities. The regulatory process and benefits from this physical modeling method is also discussed.
Evaluating AERMOD and Wind Tunnel Derived Equivalent Building DimensionsSergio A. Guerra
While the current EBD method is the best available option to determine correct building dimensions in the model, a different method was suggested by EPA in the 2011 Memo: Model Clearinghouse Review of EBD for AERMOD.9 Attachment B to the 2011 Memo includes an assessment of the Alcoa Davenport Works EBD Study. In this evaluation EPA compared wind tunnel observations with AERMOD derived concentrations. However, this evaluation has important shortcomings. First, to carry out this comparison between wind tunnel and AERMOD concentrations, it is necessary to collect velocity profiles that include longitudinal and vertical turbulent intensity measurements upwind of the stack. These data were not available for the EPA evaluation of the Alcoa Davenport Works EBD Study. Second, the wind tunnel model operating conditions were converted to full scale conditions by using exact similarity. However, exact similarity is not used to specify model operating conditions since only momentum ratios are matched but not buoyancy ones. Whereas EPA did not provide important details on how this study was performed, this paper outlines how to properly carry out this new method where AERMOD is used to determine equivalent building dimensions. The viability of this new method was also evaluated and discussed.
Evaluation of AERMOD and Wind Tunnel Derived Equivalent Building DimensionsSergio A. Guerra
While the current EBD method is the best available option to determine correct building dimensions in the model, a different method was suggested by EPA in the 2011 Memo: Model Clearinghouse Review of EBD for AERMOD. Attachment B to the 2011 Memo includes an assessment of the Alcoa Davenport Works EBD Study. In this evaluation EPA compared wind tunnel observations with AERMOD derived concentrations. However, this evaluation has important shortcomings. First, to carry out this comparison between wind tunnel and AERMOD concentrations, it is necessary to collect velocity profiles that include longitudinal and vertical turbulent intensity measurements upwind of the stack. These data were not available for the EPA evaluation of the Alcoa Davenport Works EBD Study. Second, the wind tunnel model operating conditions were converted to full scale conditions by using exact similarity. However, exact similarity is not used to specify model operating conditions since only momentum ratios are matched but not buoyancy ones. Whereas EPA did not provide important details on how this study was performed, this paper outlines how to properly carry out this new method where AERMOD is used to determine equivalent building dimensions. The viability of this new method was also evaluated and discussed.
Overview and update of the PRIME2 Advisory Committee from the Atmospheric Modeling and Meteorology (APM) Technical Committee of the Air and Waste Management Association (A&WMA). Presentation delivered at the 2016 EPA RSL Modelers’ Workshop in New Orleans, LA. Update relates to downwash improvements being done to the current Plume Rise Enhancements Model (PRIME) in AERMOD.
Diesel backup generators are commonly installed in hospitals, data centers, universities, hotels, and other businesses for use in the event of power disruptions. These engines have quick response times that provide an unmatched reliable source of emergency backup power. Facilities that have these backup engines can also benefit from enrolling in demand response (DR) programs that offer economic incentives to participants who volunteer the use of their backup generators to supply electricity to the grid during certain periods of high electricity demand. In recent years, there has been an increase in the number of backup engines that have enrolled in DR programs in exchange for economic incentives. DR programs provide grid reliability, especially during periods of high electricity demand. Therefore, this is a win-win situation for backup engine owners and power utility companies offering these incentives. Generally, a backup generator with a capacity of 500 kilowatt (kW) or more is necessary to participate in DR programs. Participants in these DR programs agree with the local power company to use their backup engines when directed; usually during periods of peak electricity demand or power disruption. However, recent air quality regulations that apply to backup generators can be challenging to meet when participating in a DR program. That is the case because the applicable requirements for backup engine depend on whether the use is strictly for emergency purposes or for DR (considered non-emergency). Purely emergency use engines are subject to work practice standards while non-emergency engines are subject to emission limits that may require emission controls. Additionally, non-emergency engines may be subject to dispersion modeling requirements to show compliance with the national ambient air quality standards (NAAQS). At the moment the dispersion model used in permitting evaluations is extremely conservative and can show compliance issues. In conclusion, DR programs can be a profitable way to get additional cash for owners and operators of backup engines. However, the permitting implications should be considered thoroughly before enrolling in such a program to avoid any unintended adverse consequences.
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Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
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This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
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Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
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Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
INNOVATIVE DISPERSION MODELING PRACTICES TO ACHIEVE A REASONABLE LEVEL OF CONSERVATISM IN AERMOD MODELING DEMONSTRATIONS CASE STUDY TO EVALUATE EMVAP, AMR2, AND BACKGROUND CONCENTRATIONS
1. INNOVATIVE DISPERSION MODELING
PRACTICES TO ACHIEVE A REASONABLE
LEVEL OF CONSERVATISM IN AERMOD
MODELING DEMONSTRATIONS
CASE STUDY TO EVALUATE EMVAP, AMR2, AND BACKGROUND CONCENTRATIONS
Presentation to the Board of the Upper Midwest Section of the Air &
Waste Management Association
September 16, 2014
Sergio A. Guerra - Wenck Associates, Inc.
3. AERMOD Model Accuracy
Appendix W: 9.1.2 Studies of Model Accuracy
a. A number of studies have been conducted to examine model accuracy,
particularly with respect to the reliability of short-term concentrations required
for ambient standard and increment evaluations. The results of these studies
are not surprising. Basically, they confirm what expert atmospheric scientists
have said for some time: (1) Models are more reliable for estimating longer
time-averaged concentrations than for estimating short-term
concentrations at specific locations; and (2) the models are reasonably
reliable in estimating the magnitude of highest concentrations occurring
sometime, somewhere within an area. For example, errors in highest
estimated concentrations of ± 10 to 40 percent are found to be typical, i.e.,
certainly well within the often quoted factor-of-two accuracy that has long been
recognized for these models. However, estimates of concentrations that occur
at a specific time and site, are poorly correlated with actually observed
concentrations and are much less reliable.
• Bowne, N.E. and R.J. Londergan, 1983. Overview, Results, and Conclusions for the EPRI Plume Model Validation and
Development Project: Plains Site. EPRI EA–3074. Electric Power Research Institute, Palo Alto, CA.
• Moore, G.E., T.E. Stoeckenius and D.A. Stewart, 1982. A Survey of Statistical Measures
of Model Performance and Accuracy for Several Air Quality Models. Publication No.
EPA–450/4–83–001. Office of Air Quality Planning & Standards, Research Triangle Park, NC.
3
4. Perfect Model
4
MONITORED CONCENTRATIONS
AERMOD CONCENTRATIONS
5. Monitored vs Modeled Data:
Paired in time and space
AERMOD performance evaluation of three coal-fired electrical generating units in Southwest Indiana
Kali D. Frost
Journal of the Air & Waste Management Association
Vol. 64, Iss. 3, 2014
5
6. SO2 Concentrations Paired in Time & Space
Probability analyses of combining background concentrations with model-predicted concentrations
Douglas R. Murray, Michael B. Newman
Journal of the Air & Waste Management Association
Vol. 64, Iss. 3, 2014
6
7. SO2 Concentrations Paired in Time Only
Probability analyses of combining background concentrations with model-predicted concentrations
Douglas R. Murray, Michael B. Newman
Journal of the Air & Waste Management Association
Vol. 64, Iss. 3, 2014
7
8. 8
Roadmap
• Case study based on 4 reciprocating internal combustion
engines (RICE) used for emergency purposes
• Engines are also part of a peaking shaving agreement
and may be required to operate 250 hour per year
• 3 Modeling techniques are presented
• EMVAP
• ARM2
• The use of the 50th percentile monitored concentration as Bkg
9. 9
EMVAP
• Problem: Currently assume continuous emissions from
proposed project or modification
• In this case study an applicant is requesting to load shave
250 hour per year.
• Current modeling practices prescribe that the engines be
modeled as if in continuous operation(i.e., 8760
hour/year).
• EMVAP assigns emission rates at random over numerous
iterations.
• The resulting distribution from EMVAP yields a more
representative approximation of actual impacts
10. 10
ARM2
• Emission sources emit mostly NOx that is gradually
converted to NO2
• Chemical reactions are based on plume entrapment and
contact time
• Chu and Meyers* identified that higher NOx
concentrations and lower NO2/NOx ambient ratios were
present in the near proximity of the source, and lower NOx
and higher NO2/NOx ratios occurred as distance
increased.
* Chu and Meyers, “Use of Ambient Ratios to Estimate Impact of NOx Sources on Annual NO2 Concentration”,
presented at the 1991 Air and Waste Management Association annual meeting.
11. Podrez, M. “Ambient Ratio Method Version 2 (ARM2) for use with ARMOD 1-hr NO2 Modeling”, 2013.
11
12. Four cases evaluated
Input parameter Case 1 Case 2 Case 3 Case 4
Description of
Dispersion
Modeling
Current
Modeling
Practices
EMVAP
(500 iterations)
ARM2 Method
EMVAP and
ARM2 Method
Maximum peak
shaving hours per
year
250 250 250 250
Hours of operation
assigned in the
model
8760 250 8760 250
NOx to NO2
Conversion
Assumed
100%
conversion
Assumed 100%
conversion
Calculated based
on the ARM2
equation
Calculated based
on the ARM2
equation
12
14. 14
Results of 1-hour NO2 Concentrations
Case 1
(μg/m3)
Case 2
(μg/m3)
Case 3
(μg/m3)
Case 4
(μg/m3)
Case Description
Current
Modeling
Practices
EMVAP
(500 itr.)
ARM2
Method
EMVAP
and
ARM2
Method
H8H 2,455.6 577.8 491.1 157.7
Percent of
1,306% 307% 261% 84%
NAAQS
16. Sitting of Ambient Monitors
According to the Ambient Monitoring Guidelines for Prevention of
Significant Deterioration (PSD):
The existing monitoring data should be representative of three
types of area:
1) The location(s) of maximum concentration increase from
the proposed source or modification;
2) The location(s) of the maximum air pollutant
concentration from existing sources; and
3) The location(s) of the maximum impact area, i.e., where
the maximum pollutant concentration would hypothetically
occur based on the combined effect of existing sources and the
proposed source or modification. (EPA, 1987)
U.S. EPA. (1987). “Ambient Monitoring Guidelines for Prevention of Significant
Deterioration (PSD).”EPA‐450/4‐87‐007, Research Triangle Park, NC.
16
20. 24-hr PM2.5 Santa Fe, NM Airport
Background Concentration and Methods to Establish Background Concentrations in Modeling.
Presented at the Guideline on Air Quality Models: The Path Forward. Raleigh, NC, 2013.
Bruce Nicholson
20
22. Combining 98th percentile Pre and Bkg
(1-hr NO2 and 24-hr PM2.5)
P(Pre ∩ Bkg) = P(Pre) * P(Bkg)
= (1-0.98) * (1-0.98)
= (0.02) * (0.02)
= 0.0004 = 1 / 2,500
Equivalent to one exceedance every 6.8 years!
= 99.96th percentile of the combined
distribution
22
23. Combining 99th percentile Pre and Bkg
(1-hr SO2)
P(Pre ∩ Bkg) = P(Pre) * P(Bkg)
= (1-0.99) * (1-0.99)
= (0.01) * (0.01)
= 0.0001 = 1 / 10,000
Equivalent to one exceedance every 27 years!
= 99.99th percentile of the combined
distribution
23
24. Proposed Approach to Combine Modeled
and Monitored Concentrations
• Combining the 98th (or 99th for 1-hr SO2) % monitored
concentration with the 98th % predicted concentration is
too conservative.
• A more reasonable approach is to use a monitored value
closer to the main distribution (i.e., the median).
Evaluation of the SO2 and NOX offset ratio method to account for secondary PM2.5 formation
Sergio A. Guerra, Shannon R. Olsen, Jared J. Anderson
Journal of the Air & Waste Management Association
Vol. 64, Iss. 3, 2014
24
25. Combining 98th Pre and 50th Bkg
P(Pre ∩ Bkg) = P(Pre) * P(Bkg)
= (1-0.98) * (1-0.50)
= (0.02) * (0.50)
= 0.01 = 1 / 100
= 99th percentile of the combined
distribution
Evaluation of the SO2 and NOX offset ratio method to account for secondary PM2.5 formation
Sergio A. Guerra, Shannon R. Olsen, Jared J. Anderson
Journal of the Air & Waste Management Association
Vol. 64, Iss. 3, 2014
25
26. Combining 99th Pre and 50th Bkg
P(Pre ∩ Bkg) = P(Pre) * P(Bkg)
= (1-0.99) * (1-0.50)
= (0.01) * (0.50)
= 0.005 = 1 / 200
= 99.5th percentile of the combined
distribution
Evaluation of the SO2 and NOX offset ratio method to account for secondary PM2.5 formation
Sergio A. Guerra, Shannon R. Olsen, Jared J. Anderson
Journal of the Air & Waste Management Association
Vol. 64, Iss. 3, 2014
26
28. 24-hr PM2.5 observations at Shakopee
2008-2010
Evaluation of the SO2 and NOX offset ratio method to account for secondary PM2.5 formation
Sergio A. Guerra, Shannon R. Olsen, Jared J. Anderson
Journal of the Air & Waste Management Association
Vol. 64, Iss. 3, 2014
28
29. Background concentrations
1) Bkg 1: Maximum 1-hour NO2 observations from the
Blaine monitor averaged over three years.
2) Bkg 2: Average of the annual 98th percentile daily
maximum 1-hour NO2 concentrations for years 2010-
2012.
3) Bkg 3: 50th percentile concentration from the 2010-
2012 hourly observations.
29
30. 30
Case 4 with three different backgrounds
Case 4 with
Bkg 1
(μg/m3)
Case 4 with
Bkg 2
(μg/m3)
Case 4 with
Bkg 3
(μg/m3)
Max. 98th% 50th %
H8H 157.7 157.7 157.7
Background 106.6 86.6 9.4
Total 264.3 244.2 167.1
Percent of
NAAQS
140.6% 130.0% 88.9%
33. Conclusion
33
• Use of EMVAP and ARM2 can help achieve more
realistic concentrations
• Use of 50th % monitored concentration is statistically
conservative when pairing it with the 98th (or 99th) %
predicted concentration
• 3 Methods are protective of the NAAQS while still
providing a reasonable level of conservatism