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.

26 Jun 2024

Flowering Rush Control in Hydrodynamic Systems: Part 2: Field Demonstrations for Chemical Control of Flowering Rush

Abstract: A series of 10 water-exchange studies were conducted from 2019 to 2021 at two sites, Clover Island and Osprey Point, within the McNary Pool of the Columbia River on the Oregon-Washington border. Six of the studies incorporated a barrier curtain or bubble curtain, whereas the other four studies did not include any device to mitigate water exchange. Once annually, diquat aquatic herbicide was applied concurrently with rhodamine water tracing (RWT) dye at the Osprey Point site (2019–2021) to control flowering rush. An additional plot, Clover Island Reference, served as the nontreated control to the Osprey Point treatment plot. Pre- and posttreatment vegetation surveys were conducted in 2019, 2020, and 2021 to determine flowering rush control, treatment impacts to water quality, and nontarget species response. This study sought to (1) document the use of barrier curtains and bubble curtains as potential methods for reducing water exchange and increasing herbicide concentration exposure times within potential flowering rush treatment areas, (2) evaluate bulk water exchange and selective control of flowering rush under varying reservoir operations, and (3) use the results from these studies to provide guidance for managing submersed flowering rush infestations on the McNary Pool, Columbia River, and similar run-of-the-river impoundments.

18 Jun 2024

Initial Rearing, Release, and Establishment of Biological Control Agent Pseudophilothrips ichini to Control Brazilian Peppertree (Schinus terebinthifolia) in South Texas Ecosystem Restoration Projects

Abstract: Control of the invasive Brazilian peppertree (Schinus terebinthifolia) is a major cost component of US Army Corps of Engineers (USACE) ecosystem restoration (ER) projects in South Texas, specifically the USACE Galveston district (SWG) Resacas at Brownsville, Texas, ER Project. Biological control has been developed as a sustainable tool to lower long-term weed management costs. Although a biological control program for S. terebinthifolia has been in operation in Florida since 2019, no similar program existed in Texas until initiated by the Engineer Research and Development Center (ERDC) in 2020. Since 2021, the biological control agent Pseudophilothrips ichini has been reared at ERDC. This technical report details rearing, release, and establishment efforts from fall 2020 to spring 2023 to provide control of S. terebinthifolia in South Texas USACE ER project locations. Initial observations on impact and potential limitations to biological control in hot climates such as those of South Texas are also discussed.

29 May 2024

Impacts of Invasive Species on Populations of Federally Listed Species on US Army Corps of Engineers Project Lands

Abstract: The US Army Corps of Engineers (USACE) is mandated to meet federal, state, and local environmental laws and organizational regulations pertaining to the protection and conservation of ESA (Endangered Species Act 1973)-listed species and associated critical habitats. USACE is also mandated under Executive Order 13112 to document the presence and status of invasive species on their lands. We examine the status of 50 ESA–listed species prioritized by USACE expenditures for ESA compliance from 2014 to 2018. We review the status of invasive species and assess any evidence from published US Fish and Wildlife Service (USFWS) or National Marine Fisheries Service recovery plans or other government documents that indicate whether invasive species are negatively impacting the status of ESA–listed species on USACE lands. We found that 18 of 50 (36%) USFWS recovery plans for these 50 listed species specifically mention invasive species as a primary factor leading to the species’ decline and listing, or they note the need for management and control of invasive species to meet proposed recovery goals. USACE will need to work collaboratively with other federal and state agencies, universities, and nongovernmental organizations to improve control of invasive species and management and recovery of ESA–listed species.

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.