Environmental Forensic Investigation of a Large Creosote-Treated Railroad Tie Fire: Integrating Air Monitoring, Meteorological Reconstruction, Soil Chemistry, and Human Health Risk Assessment
Project Overview
Large industrial fires involving creosote-treated wood present complex environmental forensic challenges because they generate a diverse mixture of combustion products that may be transported through the atmosphere, deposited onto surrounding properties, and potentially affect nearby human and ecological receptors. Unlike conventional hazardous waste investigations that evaluate historical releases from a fixed source, major fire events involve rapidly changing combustion conditions, evolving meteorological influences, emergency response activities, and multiple contaminant transport pathways that must be evaluated collectively to accurately reconstruct environmental impacts. Consequently, modern environmental forensic investigations increasingly rely upon multidisciplinary approaches that integrate environmental chemistry, atmospheric science, contaminant fate and transport, exposure assessment, toxicology, engineering analysis, and environmental data interpretation to develop scientifically defensible conclusions.
This case study summarizes an environmental forensic investigation performed following a large outdoor fire involving a substantial stockpile of creosote-treated railroad ties. The incident generated prolonged combustion, dense smoke production, and the potential release of combustion-derived contaminants capable of affecting surrounding residential and commercial properties. Following the fire, environmental consultants, industrial hygienists, laboratories, and regulatory stakeholders initiated multiple investigations to characterize air quality, evaluate soil contamination, assess environmental exposure pathways, and determine whether contaminants generated during the fire had measurably affected surrounding environmental media. The investigation ultimately incorporated air monitoring, meteorological reconstruction, soil analytical chemistry, excavation confirmation sampling, combustion chemistry, and environmental fate and transport analyses to evaluate the environmental consequences of the incident.
Rather than focusing solely on whether contaminants were detected, the investigation sought to answer several broader environmental forensic questions. These included identifying the contaminants most likely to be generated during combustion of creosote-treated wood; reconstructing smoke plume movement using multiple independent meteorological datasets; evaluating whether measured soil concentrations were consistent with atmospheric deposition; comparing analytical results with risk-based regulatory screening levels; and determining whether multiple independent datasets collectively supported a consistent interpretation of contaminant transport and environmental exposure. This multiple-lines-of-evidence framework represents a fundamental principle of environmental forensic investigations because no individual analytical method can independently characterize every aspect of a complex environmental release.
A distinguishing characteristic of this investigation was the integration of several independent scientific disciplines rather than reliance upon a single dataset. Meteorological observations collected from multiple nearby weather stations were used to reconstruct changing wind direction and wind speed throughout the fire, allowing investigators to evaluate likely smoke transport pathways. These meteorological observations were then compared with real-time community air monitoring results, laboratory analyses of soil samples collected throughout the affected area, excavation confirmation sampling, and engineering information regarding the fire itself. Evaluating these independent datasets collectively reduced uncertainty and provided a more scientifically robust reconstruction of contaminant generation, atmospheric transport, deposition, and potential human exposure than could be achieved through environmental sampling alone.
Chemicals of Concern
Combustion of creosote-treated railroad ties produces a chemically complex mixture consisting of volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), combustion gases, particulate matter, and polycyclic aromatic hydrocarbons (PAHs). Because creosote itself is a distillate derived from coal tar containing hundreds of individual organic compounds, combustion produces both residual parent compounds and numerous secondary combustion products. Consequently, evaluation of contaminants generated during railroad tie fires requires consideration of chemical persistence, atmospheric transport, deposition mechanisms, and toxicological significance rather than simply identifying compounds detected during laboratory analyses.
The principal chemicals of concern identified during this investigation were polycyclic aromatic hydrocarbons (PAHs), a large class of semivolatile organic compounds formed during incomplete combustion of carbon-containing materials. Laboratory analyses identified numerous PAHs commonly associated with creosote combustion, including naphthalene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-cd]pyrene, dibenz(a,h)anthracene, and benzo[a]pyrene, among others, using EPA Method 8270E. These compounds span a broad range of molecular weights and exhibit substantially different environmental behavior, influencing their volatility, atmospheric transport, persistence, and environmental mobility.
Particular attention was devoted to benzo[a]pyrene (BaP) because it is one of the most extensively studied carcinogenic PAHs and frequently serves as an indicator compound during human health risk assessments involving combustion-derived contamination. Unlike lower molecular weight PAHs, which tend to volatilize relatively rapidly following release, benzo[a]pyrene strongly adsorbs to soot and fine particulate matter before depositing onto soils and vegetation. Once deposited, it exhibits relatively low volatility and may persist within surficial soils for extended periods depending upon soil characteristics, sunlight exposure, microbial activity, and other environmental conditions. Because of its toxicological importance and environmental persistence, benzo[a]pyrene is commonly evaluated against risk-based regulatory screening levels during environmental investigations.
The investigation also considered airborne combustion gases and particulate emissions generated during active firefighting operations. Real-time air monitoring evaluated total volatile organic compounds (represented by o-cresol and m-cresol response), carbon monoxide, sulfur dioxide, nitrogen dioxide, hydrogen sulfide, oxygen concentrations, and lower explosive limit (LEL) conditions to characterize short-term airborne exposures during emergency response activities. Monitoring data indicated that these measurements primarily served as screening tools for evaluating worker and community safety during active fire suppression rather than long-term environmental contamination. Nevertheless, they provided valuable information for understanding the temporal progression of emissions throughout the incident and constituted an important independent line of evidence supporting the overall environmental forensic reconstruction.
Finally, the investigation evaluated combustion-derived particulate matter as both a regulated air contaminant and an important transport mechanism for semivolatile organic compounds. Higher molecular weight PAHs preferentially adsorb to airborne soot and fine particulates that can remain suspended in the atmosphere before depositing onto nearby soils and other environmental surfaces. Consequently, understanding particulate generation, atmospheric transport, and deposition was essential for interpreting laboratory analytical results, reconstructing contaminant fate and transport, and evaluating potential exposure pathways affecting nearby properties. Collectively, these chemical evaluations established the scientific foundation for subsequent analyses of environmental sampling data, meteorological reconstruction, exposure assessment, and environmental risk characterization.
Methods
The environmental forensic investigation employed a multidisciplinary methodology designed to reconstruct contaminant generation, atmospheric transport, environmental deposition, and potential human exposure following a large outdoor fire involving creosote-treated railroad ties. Rather than relying upon a single analytical technique, the investigation integrated historical document review, engineering evaluation, meteorological reconstruction, environmental chemistry, laboratory analytical data, real-time air monitoring, soil sampling, contaminant fate and transport analysis, exposure assessment, and regulatory risk evaluation. This multiple-lines-of-evidence approach represents a fundamental principle of environmental forensic investigations because independent scientific disciplines collectively provide a more reliable reconstruction of historical environmental events than any individual analytical method alone.
Historical Reconstruction and Incident Evaluation
The investigation began with a detailed review of available technical documentation describing the fire, emergency response activities, environmental investigations, laboratory analytical reports, meteorological observations, and regulatory correspondence. Particular attention was given to reconstructing the chronology of the fire, including ignition, fire duration, suppression activities, smoke generation, and post-fire remediation efforts. Establishing an accurate sequence of events provided the temporal framework necessary to evaluate contaminant generation, atmospheric transport, environmental deposition, and potential exposure pathways. Historical reconstruction also identified the principal source materials involved in the fire and documented the progression of environmental investigations performed following the incident.
Engineering information describing the characteristics of creosote-treated railroad ties, combustion conditions, and fire behavior was incorporated into the evaluation to better understand contaminant generation mechanisms. Particular emphasis was placed on the production of incomplete combustion products under variable oxygen conditions, prolonged smoldering combustion, and the generation of smoke containing particulate-bound semivolatile organic compounds. These engineering considerations established the scientific basis for evaluating expected contaminant emissions and interpreting subsequent environmental sampling results.
Meteorological Reconstruction
Meteorological reconstruction represented one of the principal components of the environmental forensic investigation. Weather observations obtained from multiple nearby meteorological stations were reviewed to characterize temporal changes in wind direction, wind speed, and other atmospheric conditions throughout the duration of the fire. Using multiple independent monitoring stations allowed investigators to evaluate the consistency of meteorological observations while reducing uncertainty associated with reliance upon a single weather source. These data were subsequently compared with documented smoke observations and environmental sampling locations to reconstruct probable plume movement and atmospheric transport pathways. Rather than evaluating meteorological conditions as isolated observations, the investigation examined changes in atmospheric conditions throughout the fire event to determine how evolving wind patterns may have influenced contaminant dispersion and deposition. This temporal evaluation was particularly important because prolonged fires frequently experience changing meteorological conditions that alter smoke transport over time. Integrating meteorological reconstruction with environmental sampling and air monitoring provided an independent scientific basis for evaluating contaminant movement following the fire.
Air Monitoring and Environmental Exposure Evaluation
Real-time community air monitoring data were reviewed to characterize airborne conditions during active fire suppression and emergency response activities. Monitoring included measurements of volatile organic compounds, carbon monoxide, sulfur dioxide, nitrogen dioxide, hydrogen sulfide, oxygen concentrations, and lower explosive limit (LEL) conditions. These measurements were evaluated to characterize short-term airborne exposures, identify periods of elevated emissions, and document changing atmospheric conditions during the incident. Although these monitoring programs primarily served emergency response and public safety functions, they also provided valuable environmental forensic information regarding the timing and intensity of airborne contaminant releases.
Air monitoring results were interpreted together with meteorological observations rather than independently. This integrated approach allowed investigators to evaluate whether observed changes in monitored air contaminants corresponded with documented fire behavior, changing wind conditions, and potential downwind transport. Combining these independent datasets strengthened interpretation of atmospheric dispersion while reducing uncertainty associated with individual monitoring measurements.
Environmental Sampling and Laboratory Analysis
Environmental sampling data formed a central component of the investigation. Soil samples collected throughout the study area were reviewed to evaluate the occurrence, concentration, and spatial distribution of combustion-derived contaminants following the fire. Laboratory analyses were performed using EPA Method 8270E, which is widely recognized for the determination of semivolatile organic compounds (SVOCs), including polycyclic aromatic hydrocarbons commonly associated with creosote combustion. Analytical results were reviewed for a broad suite of PAHs, including both lower molecular weight compounds indicative of fresh combustion emissions and higher molecular weight compounds that exhibit greater environmental persistence. Excavation confirmation sampling and post-remediation soil analyses were also reviewed to evaluate the effectiveness of removal activities and determine whether remaining contaminant concentrations were consistent with applicable regulatory screening criteria. Rather than relying upon isolated sample results, the investigation emphasized spatial patterns, concentration gradients, consistency among multiple sampling events, and comparison with expected atmospheric deposition pathways. This approach provided a more scientifically meaningful evaluation than interpretation of individual analytical measurements alone.
Human Health Risk Assessment
Potential human exposure was evaluated by integrating environmental sampling results, contaminant properties, exposure pathways, and regulatory screening criteria. Particular attention was devoted to carcinogenic polycyclic aromatic hydrocarbons, including benzo[a]pyrene, because these compounds frequently drive risk assessments involving combustion-derived contamination. Measured concentrations were evaluated in the context of applicable regulatory screening levels together with the environmental persistence, mobility, and toxicological characteristics of the detected compounds.
The investigation considered multiple potential exposure pathways, including incidental soil ingestion, dermal contact with contaminated soil, inhalation of resuspended particulate matter, and short-term inhalation of airborne combustion products during the active fire. Because contaminant behavior differs substantially among individual PAHs, volatile organic compounds, and combustion gases, each chemical group was evaluated according to its unique physical, chemical, and toxicological properties. This contaminant-specific evaluation ensured that the exposure assessment remained consistent with accepted principles of environmental chemistry and human health risk assessment.
Multiple-Lines-of-Evidence Evaluation
The defining feature of the investigation was the integration of all available scientific information into a unified environmental forensic framework. Historical reconstruction, meteorological observations, engineering analyses, air monitoring, laboratory analytical chemistry, soil sampling, regulatory guidance, and toxicological information were evaluated collectively rather than independently. Agreement among these multiple lines of evidence increased confidence in the interpretation of contaminant generation, atmospheric transport, environmental deposition, and potential exposure pathways while reducing uncertainty associated with any individual dataset. This multidisciplinary methodology reflects current best practices in environmental forensic investigations and provides a scientifically defensible foundation for environmental consulting, regulatory investigations, environmental litigation, and expert witness testimony.
Results
Integration of Multiple Independent Lines of Evidence
One of the defining strengths of this environmental forensic investigation was the integration of multiple independent scientific disciplines into a single, comprehensive analytical framework. Rather than relying solely on laboratory analytical results or individual air monitoring measurements, the investigation synthesized engineering analyses, historical reconstruction, meteorological observations, environmental sampling, analytical chemistry, toxicological evaluation, regulatory guidance, and exposure assessment. Evaluating these independent datasets collectively allowed investigators to determine whether each line of evidence consistently supported the same interpretation of contaminant generation, atmospheric transport, environmental deposition, and potential exposure pathways. This multiple-lines-of-evidence methodology significantly reduced uncertainty while increasing confidence in the overall scientific conclusions.
Each discipline contributed a unique component to the environmental reconstruction. Historical documentation established the chronology of the fire and emergency response activities. Meteorological data characterized wind patterns responsible for smoke transport. Community air monitoring documented short-term airborne conditions during active combustion. Laboratory analytical chemistry identified combustion-derived contaminants in environmental media, while comparison with regulatory screening criteria provided context for evaluating the environmental significance of measured concentrations. When interpreted together, these independent datasets produced a scientifically consistent reconstruction of contaminant behavior throughout the investigation.
Meteorological Reconstruction and Smoke Plume Transport
Meteorological analyses demonstrated that atmospheric conditions varied throughout the duration of the fire, resulting in changing smoke transport directions over time. Review of multiple nearby weather stations showed that prevailing wind direction and wind speed evolved as the incident progressed, influencing the location of potential atmospheric deposition. By evaluating observations from several independent monitoring stations rather than relying upon a single source, the investigation reduced uncertainty associated with localized weather variability and improved confidence in the reconstructed plume trajectory. Comparison of reconstructed wind patterns with environmental sampling locations indicated that areas positioned downwind during active combustion generally corresponded with locations selected for subsequent environmental investigation. This consistency supported the use of meteorological reconstruction as an independent line of evidence when interpreting laboratory analytical results. Although meteorological conditions changed throughout the event, the overall pattern of smoke transport remained consistent with documented observations recorded during emergency response activities.
Air Monitoring Results
Real-time community air monitoring provided valuable information regarding airborne conditions during active fire suppression. Monitoring programs measured volatile organic compounds, carbon monoxide, sulfur dioxide, nitrogen dioxide, hydrogen sulfide, oxygen concentrations, and lower explosive limit (LEL) conditions throughout emergency response operations. These measurements primarily served to evaluate worker and public safety during the incident; however, they also provided important environmental forensic information regarding the timing and intensity of airborne emissions.
Evaluation of the monitoring records demonstrated that airborne conditions changed throughout the incident as combustion intensity, suppression activities, and meteorological conditions evolved. Rather than interpreting these measurements independently, the investigation compared monitoring data with reconstructed fire chronology and prevailing wind conditions. This integrated evaluation demonstrated that temporal changes in monitored airborne contaminants corresponded closely with documented fire behavior, providing additional support for the reconstructed atmospheric transport pathways.
Soil Analytical Chemistry and Environmental Sampling
Laboratory analyses of soil samples identified multiple polycyclic aromatic hydrocarbons commonly associated with combustion of creosote-treated wood. Analytical results included both lower molecular weight PAHs, which are generally more volatile and less environmentally persistent, and higher molecular weight PAHs, including benzo[a]pyrene and related carcinogenic compounds that preferentially adsorb to soot and fine particulate matter before depositing onto environmental surfaces. Laboratory analyses were performed using EPA Method 8270E, providing a comprehensive evaluation of semivolatile organic compounds present within the sampled soils. Rather than focusing on isolated analytical measurements, the investigation emphasized regional spatial patterns, concentration gradients, and consistency among multiple sampling events. This broader perspective allowed investigators to distinguish localized analytical variability from larger-scale deposition trends. Confirmation sampling performed following excavation activities further demonstrated the importance of evaluating contaminant distributions over time rather than relying upon a single sampling event. Collectively, these analytical data provided an important independent line of evidence supporting interpretation of contaminant transport and environmental deposition.
Regulatory Evaluation and Human Health Context
Measured contaminant concentrations were evaluated in the context of applicable regulatory screening levels and accepted human health risk assessment principles. Particular attention was devoted to benzo[a]pyrene because of its toxicological significance and widespread use as a representative indicator of carcinogenic PAH contamination. Rather than concluding that the mere presence of contaminants indicated unacceptable risk, the investigation compared measured concentrations with established regulatory benchmarks while considering expected exposure pathways, contaminant persistence, and environmental behavior. This approach ensured that analytical results were interpreted within an appropriate regulatory and toxicological framework rather than in isolation.
Evaluation of potential exposure pathways indicated that the environmental significance of combustion-derived contaminants depended not only upon measured concentrations but also upon contaminant persistence, transport mechanisms, receptor locations, and the likelihood of human contact. Integrating laboratory analytical chemistry with exposure assessment and regulatory guidance provided a scientifically balanced interpretation of potential environmental impacts while remaining consistent with accepted environmental risk assessment methodology.
Overall Scientific Findings
The investigation demonstrated that no individual dataset was sufficient to fully characterize the environmental consequences of the fire. Instead, historical reconstruction, meteorological observations, air monitoring, laboratory analytical chemistry, environmental sampling, engineering analyses, toxicological evaluation, and regulatory screening criteria each contributed complementary information regarding contaminant generation, atmospheric transport, deposition, and potential exposure. The consistency observed among these independent lines of evidence substantially strengthened the scientific defensibility of the investigation and illustrates the value of multidisciplinary environmental forensic investigations when evaluating complex industrial fire events.
More broadly, the investigation illustrates how modern environmental consulting extends beyond traditional environmental sampling by integrating atmospheric science, analytical chemistry, contaminant fate and transport, exposure assessment, and environmental data analysis into a comprehensive scientific framework. Such multidisciplinary investigations provide a technically rigorous basis for environmental litigation, regulatory investigations, environmental due diligence, insurance evaluations, and expert witness testimony while maintaining an objective, evidence-based approach consistent with accepted environmental forensic practice.
Conclusions
Large industrial fires involving creosote-treated materials require environmental investigations that extend well beyond conventional environmental sampling. As demonstrated by this investigation, accurately reconstructing the environmental consequences of a prolonged outdoor fire requires integration of engineering analysis, combustion chemistry, atmospheric science, meteorology, environmental chemistry, analytical laboratory testing, contaminant fate and transport, toxicology, exposure assessment, and regulatory risk evaluation. Individually, each discipline provides valuable technical information; collectively, they establish a scientifically robust framework capable of reconstructing complex historical environmental events and evaluating potential environmental impacts with substantially greater confidence than any individual analytical method alone.
One of the principal findings of this investigation was the importance of evaluating both the combustion source and the environmental transport processes that influenced contaminant distribution following the fire. Combustion of creosote-treated railroad ties generated a chemically complex mixture of volatile organic compounds, semivolatile organic compounds, particulate matter, and polycyclic aromatic hydrocarbons (PAHs). Because these compounds differ substantially in volatility, persistence, and environmental mobility, understanding their behavior required evaluation of combustion conditions together with atmospheric transport, particulate deposition, soil chemistry, and environmental degradation processes. Particular attention was devoted to higher molecular weight PAHs, including benzo[a]pyrene, because of their tendency to adsorb to airborne particulate matter, persist within surficial soils, and serve as important indicator compounds during environmental human health risk assessments.
The investigation further demonstrated the scientific value of integrating meteorological reconstruction with real-time air monitoring and environmental sampling. Meteorological observations collected from multiple nearby weather stations provided an independent means of reconstructing smoke plume movement throughout the duration of the fire, while community air monitoring documented changing airborne conditions during active combustion and emergency response activities. Laboratory analyses performed using EPA Method 8270E subsequently characterized the occurrence and spatial distribution of combustion-derived PAHs within environmental media. Agreement among these independent datasets strengthened confidence in the reconstructed transport pathways and provided a scientifically defensible basis for interpreting contaminant deposition and potential exposure pathways. Another important outcome of the investigation was the recognition that environmental sampling should not be interpreted independently of the broader environmental context. Individual analytical measurements provide important information regarding contaminant occurrence; however, meaningful environmental forensic interpretation requires consideration of sampling location, plume transport, contaminant persistence, regulatory benchmarks, background conditions, and potential exposure pathways. By integrating laboratory analytical chemistry with engineering analyses, meteorological reconstruction, and environmental fate and transport principles, the investigation developed a comprehensive scientific understanding of contaminant behavior following the incident rather than relying solely upon isolated analytical measurements.
The investigation also highlighted the importance of applying risk-based environmental evaluation rather than relying exclusively on contaminant detection. Polycyclic aromatic hydrocarbons are commonly detected in urban and industrial environments because they are generated by vehicle emissions, residential wood burning, industrial combustion, and numerous other anthropogenic activities. Accordingly, interpretation of analytical results required comparison with applicable regulatory screening levels together with consideration of contaminant distribution, persistence, expected exposure frequency, and realistic human exposure pathways. This comprehensive approach is fundamental to modern environmental consulting because it provides scientifically balanced evaluations that distinguish contaminant presence from potential environmental or public health significance.
Beyond the specific circumstances of this investigation, the methodology employed illustrates the increasingly interdisciplinary nature of environmental forensic investigations involving large industrial fires and combustion-related contamination. Questions involving contaminant fate and transport, atmospheric dispersion, soil contamination, exposure assessment, environmental chemistry, toxicology, regulatory compliance, and human health risk assessment rarely can be answered through a single technical discipline. Instead, scientifically defensible investigations require integration of engineering, meteorology, analytical chemistry, environmental data analysis, atmospheric science, and toxicology within a transparent analytical framework capable of evaluating multiple competing scientific hypotheses. This multidisciplinary approach provides a strong scientific foundation for environmental litigation, regulatory investigations, insurance claims, environmental due diligence, remediation planning, and expert witness testimony while maintaining objectivity and scientific integrity.
Although every industrial fire presents unique technical challenges, the investigative framework developed during this project is broadly applicable to wood treatment facilities, railroad operations, industrial storage yards, petroleum terminals, manufacturing facilities, municipal landfills, waste management operations, and other sites involving combustion-derived environmental contamination. By integrating historical reconstruction, meteorological analysis, environmental sampling, laboratory analytical chemistry, contaminant fate and transport evaluation, exposure assessment, and multiple independent lines of evidence, environmental forensic investigations can provide technically rigorous, scientifically defensible evaluations that support informed environmental decision-making while maintaining the analytical transparency expected of modern environmental consulting practice.
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist and environmental forensic expert with extensive experience in environmental exposure assessment, toxicology, air quality, environmental fate and transport, risk assessment, and environmental forensics. Through RoseyFields LLC, Dr. Rosenfeld provides scientific consulting, environmental forensic analysis, regulatory support, and expert witness services involving environmental contamination, human exposure, and public health. His technical oversight helped ensure that the methodologies, scientific interpretations, and conclusions presented in this case study are consistent with accepted scientific principles and current best practices.