29 May 2024

Comparing Ecological Models for Assessing Rio Grande Silvery Minnow Response to Environmental Flows

Abstract: The proliferation of continuous streamflow monitoring and spatial data suitable for hydraulic modeling is increasing opportunities to use hydraulic habitat analysis to inform ecological models. However, species population and streamflow data exhibit high variability, making it challenging to identify hydrologic and hydraulic metrics that effectively correlate with ecological outcomes. Metric selection presents a challenge for informing environmental flow decisions and adaptive management of water infrastructure. This study applies models to characterize environmental flows with in-creasing model complexity, including the use of hydraulic models to estimate suitable habitat areas at a given flow. The results are compared to field-measured fish outcomes over the same period using functional data analysis. The variance in model correlation with ecological outcomes aids in identifying the most effective environmental flow parameters while also indicating potential pitfalls from increasing model complexity. This analysis demonstrates techniques that synthesize environmental flows with available habitat analysis and validates the approach. The case study is based on the Rio Grande silvery minnow (Hybognathus amarus, minnow), an endangered fish species in the Middle Rio Grande. Analysis focused on different methods to quantify spring runoff coinciding with the inundation of floodplain nursery habitat necessary for the minnow’s larval and juvenile life stages.

22 May 2024

Beneficial Use of Dredged Material in the Atlantic Intracoastal Waterway: Approaching the Regulatory Process

Purpose: Following the Chief of Engineer’s January 2023 goal to expand the beneficial use of dredged material (BUDM), the US Army Corps of Engineers (USACE) strives to apply new and creative ways to increase utilization of dredged materials from a historic 30%–40% to 70% by 2030. As USACE Savannah District (SAS) increases BUDM efforts, a critical component of this transition is understanding and navigating the regulatory requirements. This Technical Note outlines the regulatory process for placement of dredged material in Georgia, identifies challenges and institutional barriers, and offers potential solutions to streamlining the overall process. By increasing the ease of navigating the regulatory process, USACE can facilitate an increase in BUDM and Engineering with Nature® (EWN®) projects in Georgia, and potentially other projects employing nature-based solutions (NBS). While regulatory details may vary from state to state, the Georgia example presented here can serves as a road map for the general types of regulatory procedures and potential hurdles found nationwide.

21 May 2024

Lessons in Rearing Mealworms for Plastics Degradation

Purpose: The primary objective of this research is to determine if plastics-degrading gut bacterial communities from a nonoptimal insect host can be successfully transplanted into the gut of the optimal mealworm host for large scale composting. To achieve this goal, foundational questions about basic mealworm husbandry needed to be addressed, including proper housing and feeding regimes, expected plastics degradation rates, and survivability on plastics as a food source. This technical note serves as a mealworm husbandry protocol and a guide for lessons learned in the early stages of experimentation dealing with establishment of plastics-degrading mealworm colonies.

21 May 2024

Engineering With Nature: An Atlas, Volume 3

Abstract: Engineering With Nature: An Atlas, Volume 3 showcases EWN principles and practices “in action” through 58 projects from around the world. These exemplary projects demonstrate what it means to partner with nature to deliver engineering solutions with triple-win benefits. The collection of projects included were developed and constructed by a large number of government, private sector, nongovernmental organizations, and other organizations. Through the use of photographs and narrative descriptions, the EWN Atlas was developed to inspire interested readers and practitioners with the potential to engineer with nature.

17 May 2024

Interlaboratory Study of Polyethylene and Polydimethylsiloxane Polymeric Samplers for Ex Situ Measurement of Freely Dissolved Hydrophobic Organic Compounds in Sediment Porewater

Abstract: We evaluated the precision and accuracy of multilaboratory measurements for determining freely dissolved concentrations (Cfree) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in sediment porewater using polydimethylsiloxane and low-density polyethylene polymeric samplers. Four laboratories exposed performance reference compound (PRC) preloaded polymers to actively mixed and static ex situ sediment for approximately one month or more. For Cfree results, intralaboratory precision was high for single compounds; most PAHs and PCBs variability was low. Variability was higher for most hydrophobic PAHs, PCBs, and naphthalene, which were present at low concentrations and required larger PRC-based corrections. Intra- and interlaboratory variability between methods was low. Cfree polymer equilibrium was achieved in approximately one month during active exposures, suggesting using PRCs may be avoided for ex situ analysis using comparable active exposure; however, such testing may not reflect field conditions. Polymer-derived Cfree concentrations for most PCBs and PAHs averaged within a factor of 2 compared with concentrations in isolated porewater; difference factors of up to 6 were observed for naphthalene and the most hydrophobic PAHs and PCBs. Cfree results were similar for academic and private sector laboratories. The accuracy and precision demonstrated for determinating Cfree using polymer sampling are anticipated to increase regulatory acceptance and confidence.

17 May 2024

Rolling Prairie, Minnesota, Beneficial Use Area: A 100-Year Plan for Multiuse Land Management and Restoration Using Dredged Sediment

Purpose: Inland waterway dredged sediment management is challenged by a lack of capacity in existing dredged material confined disposal facilities (CDFs) and a lack of available land to place sediment near frequently dredged navigation channels. Navigation operation and maintenance (O&M) dredging, material management, and coordination costs are increasing, and alternative long-term solutions are required. In response, the US Army Corps of Engineers (USACE), St. Paul District has addressed the challenge by investigating regional sediment management and beneficial use of dredged material when updating navigation pool–specific dredged material management plans (DMMP). The recently completed Pool 5 DMMP planning identified a 950 acre (384 ha)[1] placement site consisting of several land parcels available from willing sellers that will accommodate a “100-year plan” for dredged material management (USACE 2019). This technical note describes the multiple-use site plan that creates sand prairie and wetland habitat, provides public access to sand stockpiles, and implements agriculture studies with the University of Minnesota to evaluate the benefits of dredged material (i.e., sand) amendments in alluvial cropland soils, which has not been widely investigated. The Rolling Prairie site will demonstrate benefits of “distributed DMMPs” in which thin-layer placement on agricultural land near dredging locations can supplement traditional disposal methods. It also shows the advantage of having a large placement site to achieve multiple objectives.

15 May 2024

Business Continuity Management, Operational Resilience, and Organizational Resilience: Commonalities, Distinctions, and Synthesis

Abstract: The concepts of business continuity management, operational resilience, and organizational resilience each refer to actions that businesses and organizations can take in anticipating and responding to disruptions. However, the existing definitions and usages are difficult to differentiate due to overlapping objectives, implementation processes, and outcomes. This article examines definitions and approaches for these three concepts and suggest a framework to operationalize methods and tools relevant to each. These definitions emphasize three dyads: risk versus resilience; organizational processes versus assets; and normal operating conditions versus crisis conditions. Using these dyads to differentiate the concepts of business continuity management, operational resilience, and organizational resilience can support planners in clarifying objectives and identifying which approach will be most beneficial as businesses or organizations plan for and encounter disruptions. This article evaluates these concepts by examining illustrative examples of disruptions and responses.

14 May 2024

Properties and Mechanisms for PFAS Adsorption to Aqueous Clay and Humic Soil Components

Abstract: The proliferation of poly- and perfluorinated alkyl substances (PFASs) has resulted in global concerns over contamination and bioaccumulation. PFAS compounds tend to remain in the environment indefinitely, and research is needed to elucidate the ultimate fate of these molecules. We have investigated the model humic substance and model clay surfaces as a potential environmental sink for the adsorption and retention of three representative PFAS molecules with varying chain length and head groups. Utilizing molecular dynamics simulation, we quantify the ability of pyrophyllite and the humic substance to favorably adsorb these PFAS molecules from aqueous solution. We have observed that the hydrophobic nature of the pyrophyllite surface makes the material well suited for the sorption of medium- and long-tail PFAS moieties. Similarly, we find a preference for the formation of a monolayer on the surface for long-chain PFAS molecules at high concentration. Furthermore, we discussed trends in the adsorption mechanisms for the fate and transport of these compounds, as well as potential approaches for their environmental remediation.

8 May 2024

Coastal Breeding Bird Phenology on the Dredged-Material Islands of the Baptiste Collette Bayou, US Army Corps of Engineers, New Orleans District, Louisiana

Abstract: Coastal bird populations in North America have experienced significant population declines over the past four decades, and many species have become dependent upon human-made islands and other sediment-based habitats created through dredged material deposition. We monitored the breeding phenology of coastal bird populations utilizing dredged-material islands and open depositional areas in the Baptiste Collette Bayou in coastal Louisiana. Monitoring began in early May, prior to when most coastal species begin nesting, and continued through late August, when most breeding activity has ceased. Semimonthly surveys included area searches by foot and boat. Two deposition areas and one island supported large numbers of foraging, roosting, or breeding birds; surveys on these areas included using spotting scopes to identify species and count nests or young. Six islands and two open deposition areas were monitored. We also collected high-definition and lidar imagery using an uncrewed aerial system (UAS) in June, during peak nesting season. We recorded 77,474 cumulative detections of 68 species. Virtually all colonial nesting birds (terns and skimmers) nested on Gunn Island in 2021. We discuss these results in the context of dredged-material deposition by the US Army Corps of Engineers, New Orleans District, and offer recommendations for management of these areas.

8 May 2024

Management Strategy for Overwintering Cyanobacteria in Sediments Contributing to Harmful Algal Blooms (HABs)

Purpose: Cyanobacteria that cause harmful algal blooms (HABs) can overwinter in sediments as resting cells (akinetes or vegetative colonies) and contribute to seasonal bloom resurgences. However, to date there has been limited focus on management tactics specifically targeting the control of cyanobacterial sources from sediments. Targeting resting cells in sediments for preventative management may provide a viable approach to delay onset and mitigate blooms (Calomeni et al. 2022). However, there are limited resources for this novel strategy. Given the growing global impact of HABs, there is a need to develop management strategies focused on sediments as a potential source and contributor to HABs. Therefore, the objective of this report is to provide a management strategy in terms of approaches, information, and case study examples for managing overwintering cyanobacteria in sediments with the goal of mitigating seasonal HAB occurrences.