11 Jul 2024

Environmental DNA (eDNA) Assays for the Detection of Ridgway’s Rail (Rallus obsoletus) in the United States

Abstract: We designed two novel environmental DNA (eDNA) assays for the detection of Ridgway’s Rail (Rallus obsoletus), and successfully validated each assay using eDNA samples collected from the species’ known distribution within the United States. These assays add to the suite of tools available for the monitoring of this rare and secretive marsh bird, and may help to further elucidate its movement patterns as well as identify important migration corridors. Observed sensitivity of the assays indicates exceptional performance, with limits of detection at ≤ 8 copies of the target eDNA fragment per reaction. Our publication adds to the growing body of literature supporting eDNA surveys as viable tools for bird monitoring endeavors.

11 Jul 2024

Sliver Spall Mitigation: Field Investigation, Laboratory Study, and Mixture Proportioning Analysis

Abstract: A combined field and laboratory study was conducted to identify factors contributing to sliver spall of concrete pavements and recommend avenues for prevention. In this study, spall density maps of eight airfields were created, and cores were taken for petrographic analysis. A companion laboratory study evaluated nondestructive testing equipment for identifying concrete prone to sliver spalling. Concrete mix designs with good and poor performance were analyzed for trends in mixture proportioning and aggregate gradation. Spall density mapping indicated sliver spalling was more likely to occur on longitudinal joints and that the distress was not solely a material or mixture design-related issue. The laboratory study concluded that surface resistivity measurements were able to differentiate edge-finishing techniques (normal versus overworked, mortar-rich edge) after seven days of curing. An analysis of particle packing theory and mixture proportioning trends showed there was substantial overlap in the gradations for good and poor performing pavement. Thus, acceptable mixture designs can produce poor quality pavement if not constructed properly. The main contributors to early age sliver spalling of concrete airfield pavement occur during pavement construction.

11 Jul 2024

Composite Material Applications and Research Roadmap for US Army Corps of Engineers Civil Works

Abstract: This report discusses and ranks the remaining research, development, and deployment opportunities for fiber-reinforced polymer composite materials in USACE marine infrastructure applications. Following the successes of at least 10 fiber-reinforced polymer composite pilot projects from 2015 to 2022, Public Law 117-58, the Infrastructure Investment and Jobs Act, allocated funding for a roadmap report that articulates lingering implementation barriers and prioritizes steps to overcome those challenges through laboratory and field experimentation. The objective analysis herein draws from real Operational Condition Assessment data generated in the field. Key opportunities lie in inspection techniques, standardized design approaches for molded components, and improved guidance to ad-dress abrasion, fatigue, and concentrated load cases at the 10-meter scale.

10 Jul 2024

Seasonal Variation in Near-Surface Seasonally Thawed Active Layer and Permafrost Soil Microbial Communities

Abstract: Understanding how soil microbes respond to permafrost thaw is critical to predicting the implications of climate change for soil processes. However, our knowledge of microbial responses to warming is mainly based on laboratory thaw experiments, and field sampling in warmer months when sites are more accessible. In this study, we sampled a depth profile through seasonally thawed active layer and permafrost in the Imnavait Creek Watershed, Alaska, USA over the growing season from summer to late fall. Amplicon sequencing showed that bacterial and fungal communities differed in composition across both sampling depths and sampling months. Surface communities were most variable while those from the deepest samples, which remained frozen throughout our sampling period, showed little to no variation over time. However, community variation was not explained by trace metal concentrations, soil nutrient content, pH, or soil condition (frozen/thawed), except insofar as those measurements were correlated with depth. Our results highlight the importance of collecting samples at multiple times throughout the year to capture temporal variation, and suggest that data from across the annual freeze-thaw cycle might help predict microbial responses to permafrost thaw.

10 Jul 2024

Historic Landscape Inventory for Zachary Taylor National Cemetery, Louisville, Kentucky

Abstract: This project was undertaken to provide the US Department of Veterans Affairs, National Cemetery Administration, with a cultural landscape inventory of Zachary Taylor National Cemetery via funding from the St Louis Mandatory Center of Expertise (MCX) for the Curation and Management of Archaeological Collections (CMAC). The 16-acre cemetery, listed on the National Register of Historic Places in 1983, is found in Louisville, Kentucky, and contains more than 11,400 burials. The US Army Engineer Research and Development Center-Construction Engineering Research Laboratory (ERDC-CERL) was tasked with inventorying and assessing the cultural landscape at Zachary Taylor National Cemetery through the creation of a landscape development context, a description of current conditions, and an analysis of changes to the cultural landscape over time. All landscape features were included in the survey as federal policy on national cemeteries requires that all national cemetery landscape features be considered contributing elements, regardless of age. The historic landscape elements of the cemetery, like the original overarching Beaux-Arts plan and circulation, cannot be restored due to the current number of burials. However, some elements can be reemphasized by historic landscape management planning, such as the restoration of the portions of the allée of pin oak (Quercus palustris) trees.

10 Jul 2024

Historic Landscape Inventory for Mare Island Naval Cemetery, California

Abstract: This project was undertaken to provide the US Department of Veterans Affairs (VA), National Cemetery Administration (NCA), with a cultural land-scape inventory of Mare Island Naval Cemetery. The approximately 2.5-acre cemetery is located in Vallejo, California, and contains more than 900 burials. Mare Island Naval Cemetery is part of the Mare Island Naval Shipyard historic district, which was listed concurrently on the National Register of Historic Places and as a National Historic Landmark in 1975. The NCA tasked the US Army Engineer Research and Development Center-Construction Engineering Research Laboratory (ERDC-CERL) with inventorying and assessing the cultural landscape at Mare Island Naval Cemetery through the creation of a landscape development context, a description of current conditions, and an analysis of changes to the cultural landscape over time. All landscape features were included in the inventory as NCA requested ERDC-CERL to follow federal policy on national cemeteries that requires that all national cemetery landscape features be considered contributing elements, regardless of age.

10 Jul 2024

A Study of Phased-Array Ultrasonic Testing (PAUT) for Detecting, Sizing, and Characterizing Flaws in the Welds of Existing Hydraulic Steel Structures (HSS)

Abstract: Hydraulic steel structures (HSS) are components of navigation, flood control, and hydropower projects that control or regulate the flow of water. Damage accumulates in HSS as they are operated over time, and they must be inspected periodically. This is often accomplished using nondestructive testing (NDT) techniques. If damage is detected, the structure’s fitness for continued service must be evaluated, which requires information on the location and size of discontinuities. This information can be obtained using ultrasonic testing (UT) techniques. However, there is limited information on the reliability of UT techniques with respect to detecting, sizing, and characterizing flaws in HSS. This study addresses this gap. Round-robin experiments were carried out using phased-array ultrasonic testing (PAUT) to scan weld specimens representing a variety of HSS geometries. The results of the round-robin experiments were analyzed to estimate the probability of detection (POD) and to assess the influence of factors potentially affecting POD. Uncertainty in estimates of flaw length and height were described, and partial safety factors were derived for use in fitness-for-service analyses. These results demonstrate the importance of the technician as a factor influencing the reliability of NDT techniques applied to HSS.