Environmental Forensic Investigation of Frac Sand Mining Emissions, Fugitive Dust Deposition, Silica Exposure, Blasting Impacts, and Air Dispersion Modeling
Project Overview
RoseyFields conducted an environmental forensic investigation involving historical emissions and community impacts from frac sand mining operations in Wisconsin. The investigation evaluated whether mining, blasting, material handling, stockpiling, conveying, hauling, processing, and transload activities generated fugitive particulate matter, respirable crystalline silica, PM10, PM2.5, diesel particulate matter, NOx, noise, vibration, and dust deposition that affected nearby residential properties. The analysis integrated facility-history review, community complaints, air monitoring data, meteorological evaluation, particulate matter extrapolation, fugitive dust control analysis, and demonstrative AERMOD air dispersion modeling to evaluate whether facility emissions could migrate offsite and interfere with residents’ use and enjoyment of their homes (U.S. EPA, 2017; Wisconsin DNR, 2012).
Frac sand mining is closely tied to hydraulic fracturing because silica sand is used as a proppant to hold fractures open in oil and gas formations. Wisconsin frac sand deposits are valuable because the sand is generally high-purity quartz, rounded, appropriately sized, and strong enough to withstand high-pressure subsurface conditions. However, the excavation, blasting, crushing, screening, stockpiling, drying, truck hauling, rail loading, and reclamation activities associated with frac sand mining can generate large quantities of airborne dust and respirable particles, particularly where fugitive sources are not adequately controlled (Wisconsin DNR, 2012; U.S. EPA, 2023).
The investigation focused on community exposure pathways associated with airborne particulate transport and deposition. Residents near the mine reported dust on their properties, water-quality concerns, excessive noise, nighttime light, vibration, blasting shock waves, damage to homes, destruction of viewshed, and reduced ability to use and enjoy their property. The report also evaluated whether wind and terrain conditions allowed fugitive dust from mining areas, stockpiles, haul roads, and processing operations to reach nearby residences (U.S. EPA, 2017; ASTM International, 2021).
The case required a multidisciplinary environmental forensic approach because the alleged impacts were not limited to one chemical or one environmental medium. The work involved particulate matter monitoring, crystalline silica evaluation, wind-direction analysis, topographic review, fugitive-dust source characterization, deposition assessment, blasting-related nuisance evaluation, and demonstrative plume modeling. This approach allowed RoseyFields to evaluate both the physical mechanism of offsite dust migration and the broader community impacts associated with long-term frac sand mining operations (ASTM International, 2021; U.S. EPA, 2017).
Chemicals and Pollutants of Concern
The principal pollutants of concern were particulate matter, including PM10, PM2.5, PM4, total particulate matter, and respirable crystalline silica. PM10 consists of inhalable coarse particles, while PM2.5 includes fine particles capable of deeper respiratory penetration. Frac sand operations can generate these particles from excavation, blasting, crushing, screening, stockpile erosion, haul-road traffic, truck loading, rail loading, and wind erosion from exposed sand surfaces (U.S. EPA, 2023; Wisconsin DNR, 2012).
Respirable crystalline silica was an especially important chemical hazard because frac sand is primarily quartz, or silicon dioxide. Fine silica particles can be generated when sand is disturbed, crushed, transported, or windblown, and respirable crystalline silica is associated with serious health concerns, including silicosis, chronic obstructive pulmonary disease, kidney disease, and lung cancer. The investigation therefore considered not only visible dust deposition but also the potential inhalation significance of the smaller particle fractions that may not be visible to residents but can still be transported offsite (NIOSH, 2002; IARC, 1997).
Additional pollutants evaluated included diesel particulate matter and nitrogen oxides from truck traffic, non-road equipment, generators, pumps, conveyors, crushers, and blasting-related processes. Diesel exhaust has been classified by IARC as carcinogenic to humans, and NOx emissions can aggravate respiratory disease, contribute to ozone and secondary particulate formation, and reflect the broader air-quality burden associated with intensive industrial mining and hauling activity (IARC, 2012; U.S. EPA, 2023).
The investigation also considered physical nuisance impacts associated with blasting, vibration, shock waves, nighttime noise, lighting, and sediment or sludge releases. These impacts were relevant because nearby residents complained not only about inhalation exposure, but also about rattling buildings, visible dust, water impacts, sediment movement, and disruptions to property use. A separate reported incident involving the release of approximately 10 million gallons of sludge from a frac sand mine settling pond also illustrated the potential for frac sand operations to affect surface water, drainageways, and nearby properties through process-water and sediment management failures (U.S. EPA, 2017; ASTM International, 2021).
Methods
RoseyFields applied a retrospective environmental forensic methodology designed to evaluate whether fugitive particulate emissions from frac sand mining operations could reach nearby residential receptors. The investigation reviewed discovery materials, Wisconsin DNR records, EPA materials, public technical literature, community complaints, air monitoring data, meteorological information, terrain conditions, source operations, and AERMOD input/output files. The purpose was to identify pollutants associated with the facility, evaluate the basis for residents’ complaints, analyze available ambient monitoring data, and demonstrate the mechanism of particulate matter transport from facility sources to plaintiff properties (ASTM International, 2021; U.S. EPA, 2017).
The facility-history review identified major emission-generating activities, including drilling, blasting, stockpiling, conveying, portable processing, raw sand hauling, waste sand hauling, and fugitive emissions from truck traffic. The DS Mine was located on a 240-acre site and operated from 2012 through July 2019, with substantial throughput during its operating period. The report noted that more than 45,000 loads of raw sand were hauled in 2014, representing over 1 million tons, with additional large volumes of raw sand and waste sand transported during later years (Wisconsin DNR, 2012; U.S. EPA, 1995).
The air monitoring evaluation reviewed PM4 crystalline silica and PM4 particulate matter datasets collected by Air Control Techniques between 2012 and 2015. Monitoring involved 24-hour sampling at the DS Mine using modified EPA reference-method samplers for PM4, followed by laboratory analysis for crystalline silica using X-ray diffraction consistent with NIOSH Method 7500. The investigation evaluated the limits of these data, including the inability of 24-hour samples to capture instantaneous dust spikes and the potential lack of representativeness caused by monitor placement in low-elevation areas relative to the mine and nearby residences (NIOSH, 2002; U.S. EPA, 2017).
RoseyFields used PM4 crystalline silica and PM4 particulate matter data to extrapolate likely PM10 and total particulate matter concentrations. The analysis relied on published ratios from studies evaluating PM10, PM4, and PM4 crystalline silica emissions at aggregate and frac sand operations, then used emission inventory data to estimate relationships among particle-size fractions. This approach was necessary because available monitoring did not fully characterize PM10, PM2.5, total PM, and silica across all relevant exposure periods and receptor locations (U.S. EPA, 2023; Richards et al., 2015).
The meteorological and wind analysis evaluated whether prevailing winds and local terrain could transport dust from mining operations toward plaintiff properties. The report noted that the on-site meteorological station was placed at a lower elevation than the quarry area and was affected by wind channeling from surrounding hills. RoseyFields therefore considered the representativeness of local meteorological data and compared it with the Eau Claire meteorological station, which was identified as the nearest station recommended by the DNR for air modeling and showed winds frequently blowing toward plaintiff locations (American Meteorological Society & U.S. EPA, 2019; U.S. EPA, 2017).
The demonstrative air dispersion modeling used AERMOD and BREEZE 3D Analyst to illustrate the physical mechanism by which particulate matter emissions from the mine could reach nearby properties. The model treated the DS Mine as an area source and assigned an arbitrary emission rate for demonstrative purposes, meaning the model was intended to show plume movement and transport direction rather than calculate quantitative exposure concentrations. Representative winter and summer months were animated to evaluate seasonal and operational variability, and the results demonstrated that ground-level particulate plumes could extend in multiple directions and often reach plaintiff properties (U.S. EPA, 2017; American Meteorological Society & U.S. EPA, 2019).
The fugitive dust control evaluation reviewed whether mitigation measures were adequate to prevent particulate matter from becoming airborne. Wisconsin regulations require precautions such as water application, chemical control, covering, securing materials, roadway maintenance, and similar measures to prevent airborne particulate emissions. The investigation evaluated testimony and evidence indicating that water suppression was used primarily on haul roads, not storage piles, and that watering equipment may have been insufficient to reach the upper portions of large stockpiles where wind-driven dust generation occurred (Wisconsin DNR, 2023; U.S. EPA, 1995).
Results
The investigation found that frac sand mining operations generated multiple community impacts consistent with airborne particulate transport, fugitive dust deposition, noise, blasting vibration, lighting disturbance, and reduced residential enjoyment. Residents near the DS Mine complained about airborne pollution, dust deposition, water pollution, excessive noise, nighttime light, vibration, blasting shock waves, landscape destruction, viewshed impairment, and reduced property values. Town residents also raised concerns about truck traffic, dust on properties, shaking houses, cracks in walls and floors, sand in water pipes, increased lead and iron in water, calcium and manganese seepage into wells, and stormwater discharge from the mine into neighboring property and waterways (ASTM International, 2021; U.S. EPA, 2017).
The source-characterization review showed that the mine involved high-throughput operations capable of generating substantial fugitive dust. Operations included drilling and blasting, material handling, stockpiling, conveying, hauling, portable processing equipment, and waste sand storage. These activities are consistent with known particulate matter sources at frac sand operations, especially where haul roads, exposed stockpiles, and material handling areas are not fully controlled (Wisconsin DNR, 2012; U.S. EPA, 1995).
The monitoring analysis showed that available PM4 crystalline silica and PM4 particulate data were useful but incomplete for evaluating actual community exposure. Sampling occurred over 24-hour periods and therefore could not capture short-duration spikes associated with blasting, wind gusts, truck traffic, storage pile emissions, or visible dust episodes. The report also concluded that the monitoring and meteorological stations were located at lower elevations than the quarry and plaintiff properties, limiting their ability to represent exposure conditions at nearby residences located beyond the mine’s topographic features (U.S. EPA, 2017; NIOSH, 2002).
The wind and terrain evaluation supported the conclusion that particulate emissions could migrate toward nearby residences. RoseyFields found that the on-site meteorological station was affected by local wind channeling in a low-elevation mine area, while the Eau Claire meteorological station showed winds frequently blowing toward plaintiffs. The analysis therefore concluded that reliance only on the on-site meteorological station could underestimate or mischaracterize plaintiff exposure conditions (American Meteorological Society & U.S. EPA, 2019; U.S. EPA, 2017).
The demonstrative AERMOD animations showed that particulate matter from the DS Mine could reach the plaintiffs’ property. The model illustrated temporally variable plume behavior, with emissions extending in multiple directions depending on meteorological conditions. This finding supported the physical plausibility of residents’ observations that dust from facility activities traveled offsite and deposited on nearby properties (U.S. EPA, 2017; American Meteorological Society & U.S. EPA, 2019).
The fugitive dust control review supported the conclusion that mitigation measures were insufficient to prevent offsite dust transport. Evidence indicated that water suppression was used at the DS Mine, but primarily on haul roads, and not consistently or adequately on storage piles. Testimony and video evidence showed that storage pile watering systems could be ineffective during windy conditions and were not always activated when visible fugitive dust was being released (Wisconsin DNR, 2023; U.S. EPA, 1995).
The investigation also identified additional non-air impacts relevant to the environmental forensic narrative. The La Crosse Tribune article described a May 2018 event in which approximately 10 million gallons of sludge were released from a settling pond at a Trempealeau County frac sand mine, sending orange water and mud into a tributary of the Trempealeau River and turning the river orange downstream. The reported sludge contained primarily water, silt, clay, and sand, with potential trace polyacrylamide used in sand processing, and residents expressed concern that the material was not simply mud but chemically affected process material (ASTM International, 2021; U.S. EPA, 2017).
Overall, the investigation demonstrated that community concerns were supported by multiple independent lines of evidence: resident complaints, deposition testimony, facility operations, fugitive dust records, PM4 crystalline silica monitoring, extrapolation of PM10 and total PM, wind-direction analysis, topographic review, video and photographic evidence, and AERMOD plume visualization. Together, these evidence streams supported the conclusion that frac sand operations were capable of transporting particulate emissions and associated nuisance impacts beyond the facility boundary and onto nearby residential properties (ASTM International, 2021; U.S. EPA, 2017).
Conclusions
This environmental forensic investigation demonstrated that frac sand mining operations can generate complex community impacts involving fugitive particulate matter, respirable crystalline silica, dust deposition, diesel emissions, NOx, blasting vibration, noise, lighting, and water or sediment releases. The case required a multidisciplinary technical approach because the alleged impacts involved both inhalation exposure and property-use interference. By integrating monitoring data, particle-size extrapolation, wind analysis, source characterization, topographic review, fugitive dust control evaluation, and AERMOD plume visualization, RoseyFields developed a scientifically defensible assessment of particulate matter transport from frac sand operations to nearby receptors (ASTM International, 2021; U.S. EPA, 2017).
A principal conclusion of the investigation was that the available monitoring data likely did not fully capture plaintiff exposure. PM4 crystalline silica was collected over 24-hour sampling intervals, which could miss short-duration emission peaks from blasting, hauling, stockpile erosion, or wind-driven dust events. In addition, the monitoring and meteorological stations were located in lower-elevation areas that did not represent conditions at the quarry top or on the other side of the mine near plaintiff properties. These limitations supported the need for independent wind analysis, terrain evaluation, and demonstrative air modeling (U.S. EPA, 2017; American Meteorological Society & U.S. EPA, 2019).
The investigation also concluded that dust suppression and fugitive dust controls were inadequate to prevent offsite impacts. Although water trucks and sprinklers were used, evidence indicated that water application was focused on haul roads, did not adequately reach large stockpiles, and was not consistently effective during windy conditions. Because fugitive dust from sand piles, haul roads, and material handling can produce visible and respirable particulate emissions, incomplete control measures increased the likelihood of offsite dust deposition and inhalation exposure (Wisconsin DNR, 2023; U.S. EPA, 1995).
This case study highlights the role of environmental forensic science in evaluating frac sand mining impacts, community dust exposure, silica emissions, fugitive particulate transport, and nuisance conditions. RoseyFields’ work integrated environmental chemistry, exposure assessment, air dispersion modeling, particulate monitoring analysis, GIS-based receptor evaluation, regulatory review, and source-to-receptor transport analysis to evaluate whether industrial mining operations affected nearby residential properties. These types of investigations are important for environmental consulting, regulatory review, nuisance litigation, toxic tort support, and expert witness services involving mining, silica, dust deposition, and community air-quality impacts (ASTM International, 2021; U.S. EPA, 2017).
This investigation was conducted under the direction of Dr. Paul Rosenfeld, an environmental scientist and environmental forensic expert with extensive experience in particulate matter modeling, silica exposure assessment, air dispersion modeling, fugitive dust evaluation, contaminant fate and transport, human health risk assessment, and environmental nuisance investigations. Through RoseyFields LLC, Dr. Rosenfeld provides environmental forensic analysis, air quality modeling, exposure reconstruction, particulate matter and silica assessment, regulatory review, remediation support, and expert witness testimony involving industrial emissions, mining operations, fugitive dust, and long-term community exposure.
References
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