30 Mar 2022

Terrestrial Fate and Effects of Nanometer-Sized Silver

Abstract: Although engineered nanomaterials are active components in a wide variety of commercial products, there is still limited information related to the effects of these nanomaterials once released into the terrestrial environment. A high number of commercial applications use silver nanoparticles (nAg) due to its anti-microbial activity. This may be of concern for waste management since nAg could be applied to soil (e.g., biosolids) or disposed of in traditional landfills, which could lead to possible leaching into surrounding soil. This report aims to provide additional insight into the fate and effects of nAg in terrestrial systems. The studies in this report examine the leachability of nAg in field soil and compares the soil migration to bulk (i.e., micron-sized) silver; examine the ecotoxicity of nAg to earthworms in four field soils spanning several different soil orders; and examine the behavioral effects of earthworms when exposed to engineered nanoparticles in field soil. These data provide additional insight into engineered nanoparticle fate and effects to terrestrial receptors in field soils, an important distinction from laboratory-generated soils. These data will also assist ecological risk assessors to better determine the acute environmental risks of nAg in terrestrial ecosystems with different soil compositions.

29 Mar 2022

Evaluating Cross-Shore Sediment Grain Size Distribution, Sediment Transport, and Morphological Evolution of a Nearshore Berm at Fort Myers Beach, Florida

Abstract: Navigation channels are periodically dredged to maintain safe depths. Dredged sediment was historically placed in upland management areas or in offshore disposal areas. Florida state law prohibits placement of beach fill sediment that contains more than 10% by weight of silt and clay, which is typically a characteristic of dredged material. An alternative is placement in a nearshore berm. Some potential benefits of nearshore berms include wave energy dissipation, reduced cost of dredging and shore protection, and possible onshore movement of the berm material. This study considers sediment distribution, morphological evolution, sediment transport, and shoreline trends along Fort Myers Beach, Florida, related to the nearshore berm constructed in August 2016. Due to timing of the field study, this report also includes information on the influence of a major hurricane that impacted the area. The overall conclusion of this study is that the dredge-sourced sediment in the berm performed as expected. Within 2 years, the berm adjusted to the shoreface environment, maintained a large part of its original volume, and contributed to protection of the beach and shoreline. The impact of Hurricane Irma included a shift in sediment textures and a large but temporary increase in shoreface sediment volumes.

28 Mar 2022

Evaluation of the Wharton & Northern Railroad

Abstract: The Wharton & Northern Railroad was founded in 1905 and combined a series of existing railroads that carried iron ore from the mines located to the south of Picatinny Arsenal, New Jersey. The section of the line north of Picatinny Arsenal was abandoned by Conrail in 1976. The same year, the section of the line south of the Arsenal reverted to Army control and ceased to be utilized. It is the recommendation of the authors of this report that the Wharton & Northern Railroad right-of-way (ROW) is not eligible for the National Register of Historic Places (NRHP) due to the prior demolition of bridges, trestles, yards, and stations throughout. There are certain archaeological sites associated with the railroad that need to be investigated further for Criterion D, such as the Arsenal, Fac-tory, Navy Depot, and Lake Denmark stations. These archeological sites may be eligible for the NRHP due to their association with the Wharton & Northern, but those determinations were beyond the purview of this report.

28 Mar 2022

2020 Guided Wave Inspection of California Department of Water Resources Tainter Gate Post-Tensioned Trunnion Anchor Rods: Oroville Dam

Abstract: The Engineering and Test Branch within the Division of Operations and Maintenance of the California Department of Water Resources (DWR) and U.S. Army Corps of Engineers (USACE), Sacramento District, tasked the Sensor Integration Branch (SIB) at the Engineer Research and Development Center (ERDC) to perform non-destructive testing (NDT) on the trunnion anchor rods at Oroville Dam through the use of ultrasonic guided waves. This is the third year of this NDT. The results of the testing are presented along with qualitative analysis in determining whether a rod is in-tact or compromised. Analysis is based upon the expected results from other rods at the site, knowledge of rod response at other sites, data gathered from the trunnion rod research test bed at the ERDC, and comparison to the previous year’s effort.

25 Mar 2022

Assessment of the COVID-19 Infection Risk at a Workplace Through Stochastic Microexposure Modeling

Abstract: The COVID-19 pandemic has a significant impact on economy. Decisions regarding the reopening of businesses should account for infection risks. This paper describes a novel model for COVID-19 infection risks and policy evaluations. The model combines the best principles of the agent-based, microexposure, and probabilistic modeling approaches. It takes into account specifics of a workplace, mask efficiency, and daily routines of employees, but does not require specific interagent rules for simulations. Likewise, it does not require knowledge of microscopic disease related parameters. Instead, the risk of infection is aggregated into the probability of infection, which depends on the duration and distance of every contact. The probability of infection at the end of a workday is found using rigorous probabilistic rules. Unlike previous models, this approach requires only a few reference data points for calibration, which are more easily collected via empirical studies. The application of the model is demonstrated for a typical office environment and for a real-world case. The proposed model allows for effective risk assessment and policy evaluation when there are large uncertainties about the disease, making it particularly suitable for COVID-19 risk assessments.

16 Mar 2022

Investigating the Influence of Demographics and Personality Types on Practitioners' Level of Systems Thinking Skills

Abstract: Although the application of systems thinking (ST) has become essential for practitioners when dealing with turbulent and complex environments, there are limited studies available in the current literature that investigate how the ST skills of practitioners vary with regard to demographic factors and personality types (PTs). To address this gap, this article uses a structural equation modeling approach to explore the relationship be-tween practitioners’ ST skills, PT, and a set of demographic factors. The demographic factors included in the study are education level, the field of the highest degree, organizational ownership structure, job experience, and current occupation type. A total of 99 engineering managers, 104 systems engineers (SEs), and 55 practitioners with other occupations participated in this article. Results showed that the education level, the field of the highest degree, PT, organizational ownership structure, and current job experience of practitioners influenced their level of ST skills. Additionally, the current occupation type of practitioners partially affects their level of ST skills. An in-depth analysis was also conducted using multiple group analysis to show how seven ST skills of the practitioners vary across their level of education. Taken together, the findings of the study suggest that PT and a set of demographic factors influence the overall ST skill of the practitioners.

15 Mar 2022

Autonomous GPR Surveys using the Polar Rover Yeti

Abstract: The National Science Foundation operates stations on the ice sheets of Antarctica and Greenland to investigate Earth’s climate history, life in extreme environments, and the evolution of the cosmos. Understandably, logistics costs predominate budgets due to the remote locations and harsh environments involved. Currently, manual ground-penetrating radar (GPR) surveys must preceed vehicle travel across polar ice sheets to detect subsurface crevasses or other voids. This exposes the crew to the risks of undetected hazards. We have developed an autonomous rover, Yeti, specifically to conduct GPR surveys across polar ice sheets. It is a simple four-wheel-drive, battery-powered vehicle that executes autonomous surveys via GPS waypoint following. We describe here three recent Yeti deployments, two in Antarctica and one in Greenland. Our key objective was to demonstrate the operational value of a rover to locate subsurface hazards. Yeti operated reliably at −30 ◦C, and it has good oversnow mobility and adequate GPS accuracy for waypoint-following and hazard georeferencing. It has acquired data on hundreds of crevasse encounters to improve our understanding of heavily crevassed traverse routes and to develop automated crevasse-detection algorithms. Importantly, it helped to locate a previously undetected buried building at the South Pole. Yeti can improve safety by decoupling survey personnel from the consequences of undetected hazards. It also enables higher-quality systematic surveys to improve hazard-detection probabilities, increase assessment confidence, and build datasets to understand the evolution of these regions. Yeti has demonstrated that autonomous vehicles have great potential to improve the safety and efficiency of polar logistics.

14 Mar 2022

The Blowing Snow Hazard Assessment and Risk Prediction Model: A Python Based Downscaling and Risk Prediction for Snow Surface Erodibility and Probability

Abstract: Blowing snow is an extreme terrain hazard causing intermittent severe reductions in ground visibility and snow drifting. These hazards pose significant risk to operations in snow-covered regions. While many ingredients-based forecasting methods can be employed to predict where blowing snow is likely to occur, there are currently no physically based tools to predict blowing snow from a weather forecast. However, there are several different process models that simulate the transport of snow over short distances that can be adapted into a terrain forecasting tool. This report documents a downscaling and blowing-snow prediction tool that leverages existing frameworks for snow erodibility, lateral snow transport, and visibility, and applies these frameworks for terrain prediction. This tool is designed to work with standard numerical weather model output and user-specified geographic models to generate spatially variable forecasts of snow erodibility, blowing snow probability, and deterministic blowing-snow visibility near the ground. Critically, this tool aims to account for the history of the snow surface as it relates to erodibility, which further refines the blowing-snow risk output. Qualitative evaluations of this tool suggest that it can provide more precise forecasts of blowing snow. Critically, this tool can aid in mission planning by downscaling high-resolution gridded weather forecast data using even higher resolution terrain dataset, to make physically based predictions of blowing snow.

11 Mar 2022

Field Guide to Identifying the Upper Extent of Stream Channels

ABSTRACT: The upper extent of a channel is a transition zone from the hillslope to the beginning of the stream channel. Accurately and consistently identifying the upper extent of a channel in the field and locating where hillslope processes transition to stream-channel processes can be a difficult task. Physical characteristics located at the beginning of a channel (i.e., channel head), including geomorphic, sediment, and vegetation indicators, can vary significantly across different landscapes in the United States. Remote tools are useful for examining the upper extent of channels, but these remote tools have limitations for identifying the beginning of channels. Even as the resolution of remote data continues to increase, field observations are necessary to validate the remote data on the ground and to accurately and consistently identify and locate the transition from the hillslope to the stream channel. Use of a combination of remote and field evidence is likely the most successful strategy for identifying channel heads. This report presents a case study that demonstrates how a weight-of-evidence approach can combine field and remote evidence to locate the different parts of the transition and ultimately to identify the channel-head location.

9 Mar 2022

Full-Scale Evaluation of Multi-axial Geogrids in Road Applications

Abstract: The U.S. Army Engineer Research and Development Center (ERDC) constructed a full-scale unsurfaced test section to evaluate the performance of two prototype geogrids, referred to as NX950 and NX750, in road applications. The test section consisted of a 10-in.-thick crushed aggregate surface layer placed over a very weak 2 California Bearing Ratio (CBR) clay subgrade. Simulated truck traffic was applied using one of ERDC’s specially designed load carts outfitted with a single-axle dual wheel truck gear. Rutting performance and instrumentation response data were monitored at multiple traffic intervals. It was found that the prototype geogrids improved rutting performance when compared to the unstabilized test item, and that the test item containing NX950 had the best rutting performance. Further, instrumentation response data indicated that the geogrids reduced measured pressure and deflection near the surface of the subgrade layer. Pressure response data in the aggregate layer suggested that the geogrids redistributed applied pressure higher in the aggregate layer, effectively changing the measured stress profile with an increase in pavement depth.