Denver Site Research Articles

Climate-driven soil suction variation using a natural-order Fourier series approach

In unsaturated soil practice, the near-ground-surface moisture flow is commonly evaluated using the 1-dimensional (1D) suction diffusion equation. This study presents the application of a Natural-Order Fourier Series (NOFS) approach for representing monthly climate-driven soil suction variations near the ground surface, which is a boundary condition that is generally difficult to adequately model. The NOFS incorporates an algorithmic selection criterion to optimize the order of the Fourier series to improve the capture of the seasonal shifts and extreme climate periods, while maintaining acceptable computation efficiency. The climate-soil suction interaction is expressed using published empirical relationships between monthly rainfall, temperature, and soil index properties. An example and validation study of the proposed NOFS selection approach is presented using measured soil properties and historical weather data at a study site in Denver, Colorado USA. Key findings from performance and stability studies of five locations in the United States associated with differing climate regions are discussed. Limitations and recommendations for implementation are also included. The proposed NOFS approach for capturing climate-driven changes in suction near the ground surface can be efficiently implemented in unsaturated soil numerical analyses that are governed by moisture-dependent mechanical soil behavior and can help improve the computation time, stability, and performance associated with stochastic simulations.

Evaluating Pedestrian Service of the New Super Diverging Diamond Interchange on Three Case Study Sites in Denver, Colorado

Ensuring safe and comfortable conditions for pedestrians necessitates specific strategies at intersections and service interchanges where traffic and pedestrians interact in complex ways with other modes of transportation. This study aims to investigate pedestrian performance at the new Super Diverging Diamond Interchange (Super DDI) using real-world locations (i.e., I-225 and Mississippi Ave, I-25 and 120th Ave, and I-25 and Hampden Ave in Denver, Colorado). Three alternative designs, typical DDI, and two versions of Super DDI were considered to make a reasonable comparison with the existing Conventional Diamond Interchange (CDI). A comprehensive series of simulation models (192 scenarios with 960 runs) were tested using VISSIM and Synchro to analyze pedestrian operation (travel time, number of stops, and waiting time) in various traffic and pedestrian distributions. As one of the primary contributions in this paper, pedestrian safety was evaluated based on a surrogate performance measure called design flag, introduced by the new National Cooperative Highway Research Program (NCHRP-948) guideline. The results indicated that the proposed new Super DDI designs are relatively safe when compared with CDI and DDI. For example, a pedestrian analysis of one of the most popular alternative interchanges, DDI, showed potential for unsafe pedestrian conditions in all aspects.

Rates of Appropriate Treatment and Follow-Up Testing After a Gonorrhea and/or Chlamydia Infection in an Urban Network of Federally Qualified Health Center Systems.

Reinfection and partner transmission are common with Neisseria gonorrhoeae (GC) and Chlamydia trachomatis (CT). We assessed treatment and follow-up laboratory testing for GC and CT and evaluated associations with patient- and system-level factors. The analysis included positive GC and/or CT nucleic acid amplification test results from patients aged 14 to 24 years at a federally qualified health center system site in Denver, CO, from January 2018 to December 2019. Outcomes assessed include treatment within 14 days, HIV/syphilis testing within 6 months, and repeat GC and CT testing within 2 to 6 months. Bivariate and multivariable regression modeling assessed associated factors. Among 27,168 GC/CT nucleic acid amplification tests performed, 1.8% (484) were positive for GC and 7.8% (2125) were positive for CT. Within the assessed time frames, 87% (2275) of patients were treated, 54.1% (1411) had HIV testing, 50.1% (1306) had syphilis testing, and 39.9% (1040) had GC and CT retesting. Older patients were more likely to receive treatment (adjusted odds ratio 1.13; 95% confidence interval, 1.00-1.27; P = 0.05) than younger patients, whereas males were less likely to receive GC and CT retesting (adjusted odds ratio, 0.19; 95% confidence interval, 0.11-0.33; P < 0.001) than females. Patients treated on the day of testing were less likely to receive follow-up laboratory tests than those treated 2 to 14 days after. Although most patients received antibiotic treatment, only about half received HIV/syphilis testing and less than half received GC and CT retesting. It is critical to find innovative strategies to improve treatment and follow-up management of these infections to decrease complications, reduce transmission, and combat the rising rates of sexually transmitted infections.

Conditions Leading to Elevated PM2.5 at Near-Road Monitoring Sites: Case Studies in Denver and Indianapolis.

We examined two near-road monitoring sites where the daily PM2.5 readings were among the highest of any near-road monitoring location in the U.S. during 2014–2016: Denver, Colorado, in February 2014 and Indianapolis, Indiana, in November 2016. At the Denver site, which had the highest measured U.S. near-road 24-hr PM2.5 concentrations in 2014, concentrations exceeded the daily National Ambient Air Quality Standards (NAAQS) on three days during one week in 2014; the Indianapolis site had the second-highest number of daily exceedances of any near-road site in 2016 and the highest 3-year average PM2.5 of any near-road site during 2014–2016. Both sites had hourly pollutant, meteorological, and traffic data available, making them ideal for case studies. For both locations, we compared air pollution observations at the near-road site to observations at other sites in the urban area to calculate the near-road PM2.5 “increment” and evaluated the effects of changes in meteorology and traffic. The Denver near-road site consistently had the highest PM2.5 values in the Denver area, and was typically highest when winds were near-downwind, rather than directly downwind, to the freeway. Complex Denver site conditions (near-road buildings and roadway alignment) likely contributed to higher PM2.5 concentrations. The increment at Indianapolis was also highest under near-downwind, rather than directly downwind, conditions. At both sites, while the near-road site often had higher PM2.5 concentrations than nearby sites, there was no clear correlation between traffic conditions (vehicle speed, fleet mix) and the high PM2.5 concentrations.

Editorial introductions

Editorial introductions

Comparisons of urban and rural PM&amp;lt;sub&amp;gt;10−2.5&amp;lt;/sub&amp;gt; and PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; mass concentrations and semi-volatile fractions in northeastern Colorado

Abstract. Coarse (PM10−2.5) and fine (PM2.5) particulate matter in the atmosphere adversely affect human health and influence climate. While PM2.5 is relatively well studied, less is known about the sources and fate of PM10−2.5. The Colorado Coarse Rural-Urban Sources and Health (CCRUSH) study measured PM10−2.5 and PM2.5 mass concentrations, as well as the fraction of semi-volatile material (SVM) in each size regime (SVM2.5, SVM10−2.5), from 2009 to early 2012 in Denver and comparatively rural Greeley, Colorado. Agricultural operations east of Greeley appear to have contributed to the peak PM10−2.5 concentrations there, but concentrations were generally lower in Greeley than in Denver. Traffic-influenced sites in Denver had PM10−2.5 concentrations that averaged from 14.6 to 19.7 µg m−3 and mean PM10−2.5 ∕ PM10 ratios of 0.56 to 0.70, higher than at residential sites in Denver or Greeley. PM10−2.5 concentrations were more temporally variable than PM2.5 concentrations. Concentrations of the two pollutants were not correlated. Spatial correlations of daily averaged PM10−2.5 concentrations ranged from 0.59 to 0.62 for pairs of sites in Denver and from 0.47 to 0.70 between Denver and Greeley. Compared to PM10−2.5, concentrations of PM2.5 were more correlated across sites within Denver and less correlated between Denver and Greeley. PM10−2.5 concentrations were highest during the summer and early fall, while PM2.5 and SVM2.5 concentrations peaked in winter during periodic multi-day inversions. SVM10−2.5 concentrations were low at all sites. Diurnal peaks in PM10−2.5 and PM2.5 concentrations corresponded to morning and afternoon peaks of traffic activity, and were enhanced by boundary layer dynamics. SVM2.5 concentrations peaked around noon on both weekdays and weekends. PM10−2.5 concentrations at sites located near highways generally increased with wind speeds above about 3 m s−1. Little wind speed dependence was observed for the residential sites in Denver and Greeley. The mass concentration data reported here are being used in ongoing epidemiologic studies for PM in northeastern Colorado.

Relationship between land cover patterns and surface temperature in urban areas

The relationship between land cover patterns and surface temperature was examined using random forest as well as simple linear regression for two urban sites in Denver, Colorado, USA. Among four land cover types of buildings, trees, grass, and roads and parking lots, only trees and roads and parking lots show significant spatial metrics affecting surface temperature using both the methods. For trees, total class area seems the most important factor affecting surface temperature (R2 = 0.47; percentage of increased mean standard error when mean patch area is excluded %IncMSE = 5.35 for Site B in July), followed by aggregation metrics measuring physical connectedness (R2 for patch cohesion index = 0.42) and patch isolation (%IncMSE for mean Euclidean nearest neighbor distance = 6.01 for Site A in July). For roads and parking lots, the existence of dominantly large patches is the most important factor (R2 for range in patch area = 0.40, for largest patch index = 0.40, for Site B in July), followed by total class area (R2 = 0.39 for Site B in July). Despite some limitations, the findings of this study provide useful information for alleviating urban heat stress especially during summer and reducing adverse impacts of urban drought.

Building type classification using spatial and landscape attributes derived from LiDAR remote sensing data

Building information is one of the key elements for a range of urban planning and management practices. In this study, an investigation was performed to classify buildings delineated from light detection and ranging (LiDAR) remote sensing data into three types: single-family houses, multiple-family houses, and non-residential buildings. Four kinds of spatial attributes describing the shape, location, and surrounding environment of buildings were calculated and subsequently employed in the classification. Experiments were performed in suburban and downtown sites in Denver, CO, USA, considering different building components and neighborhood environments. Building type classification results yielded overall accuracy>70% and Kappa>0.5 for both sites, demonstrating the feasibility of obtaining building type information from LiDAR data. The shape attributes, such as width, footprint area, and perimeter, were most useful for identifying building types. Environmental landscape attributes surrounding buildings, such as the number of road and parking lot pixels, also contributed to obtaining building type information. Combining shape and environmental landscape attributes was necessary to obtain accurate and consistent classification results.

Gas/Particle Partitioning of 2-Methyltetrols and Levoglucosan at an Urban Site in Denver

In this study, a medium volume sampler incorporating quartz fiber filters (QFFs) and a polyurethane foam (PUF)/XAD/PUF sandwich (PXP) was used to collect 2-methyltetrols (isoprene tracer) and levoglucosan (biomass burning tracer) in gaseous and particle (PM2.5) phases. The measured gas/particle (G/P) partitioning coefficients (Kp,OMm) of 2-methyltetrols and levoglucosan were calculated and compared to their predicted G/P partitioning coefficients (Kp,OMt) based on an absorptive partitioning theory. The breakthrough experiments showed that gas-phase 2-methyltetrols and levoglucosan could be collected using the PXP or PUF adsorbent alone, with low breakthrough; however, the recoveries of levoglucosan in PXP samples were lower than 70% (average of 51.9–63.3%). The concentration ratios of 2-methyltetrols and levoglucosan in the gas phase to those in the particle phase were often close to or higher than unity in summer, indicating that these polar species are semi-volatile and their G/P partitioning should be considered when applying particle-phase data for source apportionment. The Kp,OMm values of 2-methyltetrols had small variability in summer Denver, which was ascribed to large variations in concentrations of particulate organic matter (5.14 ± 3.29 μg m–3) and small changes in ambient temperature (21.8 ± 4.05 °C). The regression between log Kp,OMm and log Kp,OMt suggested that the absorptive G/P partitioning theory could reasonably predict the measured G/P partitioning of levoglucosan in ambient samples.

Concentrations and source insights for trace elements in fine and coarse particulate matter

The Colorado Coarse Rural–Urban Sources and Health (CCRUSH) study is a multi-year study focused on characterizing the mass, composition and sources of coarse particulate matter (PM10−2.5) in Denver and Greeley, CO. Between the two cities, Denver is expected to have greater influence of industry and motor vehicles as sources of PM10–2.5. Greeley is a smaller city with greater expected influence of agricultural activity. As part of the CCRUSH study, we collected integrated 24-h samples of PM from four sites in Denver and Greeley at six day intervals from February 2010 to March 2011. Dichotomous samplers with Teflon filters were used to obtain samples for gravimetric and elemental analysis. Magnetic Sector Inductively Coupled Plasma-Mass Spectroscopy (SF-ICP-MS) was used to analyze digests of monthly composited filter samples for 49 elements. Thirty-nine elements were retained for statistical analysis after excluding those with low signal-to-noise ratios. The elements Sb, Cd, Zn, Mo, As, B, Cu, Pb, and W had crustal enrichment factors greater than 10 in the PM2.5 and PM10–2.5 size ranges in both Denver and Greeley. Using positive matrix factorization (PMF) with bootstrap uncertainty estimation, we identified five factors influencing the element concentrations: a crustal factor contributing to both PM2.5 and PM10–2.5; a sodium-dominated PM10–2.5 factor likely associated with road salt; a vehicle abrasion factor contributing in both size ranges; a regional sulfur factor contributing mainly to PM2.5 and likely associated with coal combustion; and a local catalyst factor identified with high Ce and La enrichment in PM2.5 at one of the sites in Denver.

Errors in coarse particulate matter mass concentrations and spatiotemporal characteristics when using subtraction estimation methods

In studies of coarse particulate matter (PM10-2.5), mass concentrations are often estimated through the subtraction of PM2.5 from collocated PM10 tapered element oscillating microbalance (TEOM) measurements. Though all field instruments have yet to be updated, the Filter Dynamic Measurement System (FDMS) was introduced to account for the loss of semivolatile material from heated TEOM filters. To assess errors in PM10-2.5 estimation when using the possible combinations of PM10 and PM2.5 TEOM units with and without FDMS, data from three monitoring sites of the Colorado Coarse Rural–Urban Sources and Health (CCRUSH) study were used to simulate four possible subtraction methods for estimating PM10-2.5 mass concentrations. Assuming all mass is accounted for using collocated TEOMs with FDMS, the three other subtraction methods were assessed for biases in absolute mass concentration, temporal variability, spatial correlation, and homogeneity. Results show collocated units without FDMS closely estimate actual PM10-2.5 mass and spatial characteristics due to the very low semivolatile PM10-2.5 concentrations in Colorado. Estimation using either a PM2.5 or PM10 monitor without FDMS introduced absolute biases of 2.4 µg/m3 (25%) to –2.3 µg/m3 (–24%), respectively. Such errors are directly related to the unmeasured semivolatile mass and alter measures of spatiotemporal variability and homogeneity, all of which have implications for the regulatory and epidemiology communities concerned about PM10-2.5. Two monitoring sites operated by the state of Colorado were considered for inclusion in the CCRUSH acute health effects study, but concentrations were biased due to sampling with an FDMS-equipped PM2.5 TEOM and PM10 TEOM not corrected for semivolatile mass loss. A regression-based model was developed for removing the error in these measurements by estimating the semivolatile concentration of PM2.5 from total PM2.5 concentrations. By estimating nonvolatile PM2.5 concentrations from this relationship, PM10-2.5 was calculated as the difference between nonvolatile PM10 and PM2.5 concentrations. Implications: Errors in the estimation of PM10-2.5 concentrations using subtraction methods were shown to be related to the unmeasured semivolatile mass when using certain combinations of TEOM instruments. For the northeastern Colorado region, the absolute bias associated with this error significantly affects mean and 95th percentile values, which would affect assessment of compliance if PM10-2.5 is regulated in the future. Estimating PM10-2.5 mass concentrations using nonvolatile mass concentrations from collocated PM10 and PM2.5 TEOM monitors closely estimates the total PM10-2.5 mass concentrations. A corrective model that removes the described error was developed and applied to data from two sites in Denver. Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association.

Intra-urban spatial variability of PM2.5-bound carbonaceous components

The Denver Aerosol Sources and Health (DASH) study was designed to evaluate associations between PM2.5 species and sources and adverse human health effects. The DASH study generated a five-year (2003–2007) time series of daily speciated PM2.5 concentration measurements from a single, special-purpose monitoring site in Denver, CO. To evaluate the ability of this site to adequately represent the short term temporal variability of PM2.5 concentrations in the five county Denver metropolitan area, a one year supplemental set of PM2.5 samples was collected every sixth day at the original DASH monitoring site and concurrently at three additional sites. Two of the four sites, including the original DASH site, were located in residential areas at least 1.9 km from interstate highways. The other two sites were located within 0.3 km of interstate highways. Concentrations of elemental carbon (EC), organic carbon (OC), and 58 organic molecular markers were measured at each site. To assess spatial variability, site pairs were compared using the Pearson correlation coefficient (r) and coefficient of divergence (COD), a statistic that provides information on the degree of uniformity between monitoring sites. Bi-weekly co-located samples collected from July 2004 to September 2005 were also analyzed and used to estimate the uncertainty associated with sampling and analytical measurement for each species. In general, the two near-highway sites exhibited higher concentrations of EC, OC, polycyclic aromatic hydrocarbons (PAHs), and steranes than did the more residential sites. Lower spatial heterogeneity based on r and COD was inferred for all carbonaceous species after considering their divergence and lack of perfect correlations in co-located samples. Ratio–ratio plots combined with available gasoline- and diesel-powered motor vehicle emissions profiles for the region suggested a greater impact to high molecular weight (HMW) PAHs from diesel-powered vehicles at the near-highway sites and a more uniformly distributed impact to ambient hopanes from gasoline-powered motor vehicles at all four sites.

Characterization and Nonparametric Regression of Rural and Urban Coarse Particulate Matter Mass Concentrations in Northeastern Colorado

The Colorado Coarse Rural Urban Sources and Health study (CCRUSH) is an ongoing study of the relationship between coarse particulate mass concentrations (PM10–2.5, particulate matter with diameter between 2.5 and 10 μm) and selected health effects. For two urban monitoring sites in Denver, CO, and two comparatively rural sites in Greeley, CO, hourly mass concentrations of PM10–2.5 and fine particulate matter (PM2.5, diameter less than 2.5 μm) have been measured by using dichotomous tapered element oscillating microbalances (TEOMs) with Filter Dynamics Measurement Systems (FDMS). This paper presents air quality results from just over a year of PM2.5 and PM10–2.5 measurements. Average PM2.5 concentrations ranged from 7.7 to 9.2 μg m−3 across the four sites with higher concentrations in Denver than Greeley. Average PM10–2.5 concentrations ranged from 9.0 to 15.5 μg m−3 with the highest values at the site in northeast Denver. Temporal variability in PM10–2.5 was higher than that in PM2.5 concentrations at all four sites. The two Greeley sites displayed moderate spatial correlation for PM2.5 and high correlation for PM10–2.5, whereas the two Denver sites showed lower spatial correlation for both PM sizes. PM10–2.5 concentrations in Denver were highest with winds from the direction of the city's urban core. PM10–2.5 concentrations in Greeley were moderately elevated with winds from the southwest to the northwest, coming from Denver and other large Front Range communities. Wind speed regressions for PM10–2.5 at the Denver sites primarily exhibited resuspension effects, while PM10–2.5 concentrations in Greeley showed relatively complex wind speed dependence. Copyright 2012 American Association for Aerosol Research

December 2011 Association News

Abstract:“2011 AAA President's Report to Membership” by Virginia R DominguezWORLD ANTHROPOLOGIES:“Revisiting the World Anthropologies Network Project” by Shiv Visvanathan Setha Low and Gustavo Lins Ribeiro are contributing editors of World Anthropologies, the AN column of the AAA Committee on World Anthropologies“AAA Annual Meeting Site Selection Survey and 2015 Meeting Location” by Jason G Watkins“Response to Denver Site Selection” by Dominic Boyer, Michael Chibnik, Carol MacLennan, Mark Moberg and Ramona PerezKeywords:2011 AAA president report, world anthropologies network, AAA annual meeting location, AAA committee on labor relations

Mother Cabrini and the Anatomy of an Illness

Mother Cabrini and the Anatomy of an Illness

Empirical Assessment of Ground Water–to‐Indoor Air Attenuation Factors for the CDOT‐MTL Denver Site

AbstractThe area surrounding the Colorado Department of Transportation Materials Testing Laboratory in Denver was the subject of intense investigation, involving the collection of thousands of ground water, soil‐gas, and indoor air samples in order to investigate indoor air impacts associated with a subsurface release of chlorinated solvents. The preremediation portion of that data set is analyzed and reduced in this work to ground water–to‐indoor air attenuation factors (αgw= the ratio of the measured indoor air concentration to the soil‐gas concentration predicted to be in equilibrium with the local ground water concentration). The empirical αgw values for this site range from about 10−6 to 10−4 with an overall average of 3 × 10−5 (μg/L indoor air)/(μg/L soil gas). The analysis of this data set highlights the need for a thorough data review and data screening when using large data sets to derive empirical relationships between subsurface concentrations and indoor air. More specifically, it is necessary to identify those parts of the data that contain a strong vapor intrusion pathway signal, which generally will require concentrations well above reported detection levels combined with spatial or temporal correlation of subsurface and indoor concentrations.

The Denver Aerosol Sources and Health (DASH) study: Overview and early findings

Improved understanding of the sources of air pollution that are most harmful could aid in developing more effective measures for protecting human health. The Denver Aerosol Sources and Health (DASH) study was designed to identify the sources of ambient fine particulate matter (PM 2.5) that are most responsible for the adverse health effects of short-term exposure to PM 2.5. Daily 24-h PM 2.5 sampling began in July 2002 at a residential monitoring site in Denver, Colorado, using both Teflon and quartz filter samplers. Sampling is planned to continue through 2008. Chemical speciation is being carried out for mass, inorganic ionic compounds (sulfate, nitrate and ammonium), and carbonaceous components, including elemental carbon, organic carbon, temperature-resolved organic carbon fractions and a large array of organic compounds. In addition, water-soluble metals were measured daily for 12 months in 2003. A receptor-based source apportionment approach utilizing positive matrix factorization (PMF) will be used to identify PM 2.5 source contributions for each 24-h period. Based on a preliminary assessment using synthetic data, the proposed source apportionment should be able to identify many important sources on a daily basis, including secondary ammonium nitrate and ammonium sulfate, diesel vehicle exhaust, road dust, wood combustion and vegetative debris. Meat cooking, gasoline vehicle exhaust and natural gas combustion were more challenging for PMF to accurately identify due to high detection limits for certain organic molecular marker compounds. Measurements of these compounds are being improved and supplemented with additional organic molecular marker compounds. The health study will investigate associations between daily source contributions and an array of health endpoints, including daily mortality and hospitalizations and measures of asthma control in asthmatic children. Findings from the DASH study, in addition to being of interest to policymakers, by identifying harmful PM 2.5 sources may provide insights into mechanisms of PM effect.

Relations between exhaled nitric oxide and measures of disease activity among children with mild-to-moderate asthma

Objective Exhaled nitric oxide (FENO) was evaluated in children with asthma after 4 to 6 years of treatment with budesonide, nedocromil, or albuterol as needed. Study design FENO, spirometry, total eosinophil count, and serum eosinophil cationic protein levels were obtained from 118 children at the Denver site of the Childhood Asthma Management Program upon completion of treatment and after a 2- to 4-month washout. Results Budesonide-treated patients had significantly lower median (1st, 3rd quartile) FENO (21.5 [13.2, 84.4] vs 62.5 [26.2, 115.0] ppb, P <.01) and eosinophil cationic protein levels (17.4 [10.1, 24.3] vs 24.0 [15.4, 33.9] mg/dL, P =.05) compared with placebo, whereas no differences were noted between nedocromil and placebo groups. After washout, FENO levels were similar between the three treatments. FENO levels significantly correlated with degree of bronchial hyperresponsiveness, bronchodilator reversibility, allergen skin prick tests, serum IgE, and total eosinophil count. FENO levels were also higher in patients with nocturnal symptoms and in patients requiring β-agonist use at least once weekly. Conclusions Budesonide therapy was more effective than nedocromil in reducing FENO. Unfortunately, the effects of long-term budesonide were not sustained after its discontinuation. FENO may be a complementary tool to current practice guidelines in assessing asthma control and medication response. (J Pediatr 2003;142:469-75 )

Fathering relationships and their associations with juvenile delinquency

AbstractThis study explores the intergenerational transmission of fathering by addressing the associations between men's relationship with their father, their attachment to their children, self‐assessment of themselves as fathers, and antisocial behavior. Subjects for this study were 87 men who were identified as fathers or father figures by women involved in two Early Head Start sites in Denver, Colorado. They were interviewed about their experiences when their child was between 2 and 3 years of age. The study found men who reported high antisocial behavior during their youth reported low assessment of themselves as fathers whereas men who reported a positive relationship with their fathers reported high assessments of themselves as fathers. ©2002 Michigan Association for Infant Mental Health.

A Portable Local Exhaust Hood System Used to Sample One-Ton Containers Previously Filled with Chemical Warfare Munitions

Abstract The Tennessee Valley Authority (TVA), Muscle Shoals, Alabama, by contract with the Department of the Army, Rocky Mountain Arsenal (RMA), Denver, Colorado, sampled and verified the decontamination level of 2354 empty one-ton containers (TCs) previously used to store chemical warfare munitions. The TCs had previously been chemically and/or thermally decontaminated and were stored at RMA awaiting removal and disposal. The size and weight of the TCs prohibited placing them inside an enclosure during sampling. To enable sampling containers in place, a portable local exhaust hood was devised to protect sampling personnel and to prevent the release of any residual chemical agent vapors to the environment. Agent vapors captured by the hood were scrubbed through a 200-lb bed of activated charcoal before being released to the ambient environment. Engineers and work crews on site in Denver conceived the hood design and tested three prototypes before obtaining a functional unit. Craftspersons in Muscle Shoal...