Repository logo

Contract Report


Recent Submissions

Now showing 1 - 3 of 3
  • Item
    Overview of processes affecting contaminant release from confined disposal facilities
    (U.S. Army Engineer Waterways Experiment Station, 1992-01) Martin, James Lenial, 1947-; McCutcheon, Steve C.; AScI Corporation; Environmental Research Laboratory (Athens, Ga.); Dredging Operations Technical Support Program (U.S.)
    Confined disposal facilities (CDFs) are widely used for the disposal of dredged material from Corps of Engineers maintenance dredging projects along the Atlantic and Gulf coasts and waterways and harbors in the Great Lakes. CDFs are a less common disposal alternative along the Pacific coast and inland river systerns. When contaminated dredged material is placed in a CDF, there is a potential for contaminant mobilization and release from the CDF by a variety of physical, chemical, and biological processes. This report provides an overview of the processes affecting mobilization and release of contaminants from CDFs and the potential applicability of multimedia models for prediction of contaminant release. Processes affecting release from in-water CDFs are emphasized, although many of the processes discussed are applicable to nearshore and upland CDFs. Processes affecting contaminant release are complex, involving a variety of chemicals and operational and design considerations. Many of the important processes are reasonably well known. Laboratory column settling and elutriate techniques have been developed to estimate solids and contaminant concentration in water directly released during hydraulic disposal operations. Predictive techniques for other processes are not as available. Processes affecting contaminant transport and fate have received considerable attention and have been incorporated into a number of models, primarily for surface waters. Relatively few attempts have been made to consolidate these process descriptions into a unified mechanistic modeling approach applicable to CDFs. Although the limited modeling studies on CDFs have proved valuable in estimating losses in some cases, these approaches are largely unvalidated. No database of sufficient detail to evaluate their general applicability to CDFs presently exists. Some combination of mechanistic modeling and laboratory techniques presently available may be sufficient to provide reconnaissance-level evaluations of CDF containment effectiveness. However, additional model and laboratory test development as well as supporting field studies are needed to develop fully predictive tools. Such tools would provide cost-effective methods for evaluating CDF design and operational alternatives.
  • Item
    Dredging Elutriate Test (DRET) development
    (U.S. Army Engineer Waterways Experiment Station, 1995-08) DiGiano, Francis A.; Miller, Cass T. (Cass Timothy); Yoon, Jeyong; University of North Carolina at Chapel Hill. Department of Environmental Sciences and Engineering; Dredging Operations Technical Support Program (U.S.)
    The removal of contaminated sediments from waterways by dredging generates concern about the release of contaminants to the water column. The ability to predict the magnitude of these potential releases during the project planning process will improve decision making in regard to water quality impacts and controls or mitigation measures for the dredging project. This report describes the development of a simple laboratory test, the dredging elutriate test (DRET), to predict the concentration of contaminants in the water column at the point of dredging. The DRET is procedurally similar to the modified elutriate test developed by the Corps of Engineers to predict the contaminant concentrations in effiuent from a confined disposal facility. The test involves mixing sediment and site water, allowing the heavier solid particles to settle, sampling and supernatant, and analyzing for dissolved and particulate bound contaminants. Results of the laboratory test compared well with field data collected while dredging New Bedford Harbor sediment, which was contaminated with polychlorinated biphenyls. Most of the contaminated loading was associated with the suspended particles.
  • Item
    Developing and testing TernCOLONY 1.0: an individual-based model of Least Tern reproduction
    (Engineer Research and Development Center (U.S.), 2013-06) Lott, Casey A.; Koohafkan, Michael C.; Railsback, Steven F. (Steven Floyd), 1957-; Sheppard, Colin; Lang, Railsback, and Associates; American Bird Conservancy; Dredging Operations Technical Support Program (U.S.); Dredging Operations and Environmental Research Program (U.S.)
    The TernCOLONY simulation model is an individual-based model of Least Tern reproduction that was developed to better understand how reservoir operations (and other management activities) affect Least Tern breeding populations on large rivers. This report documents the process of model development, including defining the model’s purpose, its structure, its various submodels, and major inputs. This document supplements the TernCOLONY model description (Lott et al. 2012a), which provides the complete formulation of the model with enough detail to make the model reproducible. This document summarizes the pattern-oriented approach taken in developing the model’s major behavioral traits and submodels (adult tern colony and nest site selection, site abandonment, re-nesting, and various mortality submodels). The report also documents the extensive process of independent verification of the model’s code that was undertaken prior to a whole model sensitivity analysis and parameter calibration (also reported here). The tests reported in this document provide the basis for the final submodels, behavioral traits, and parameter values that are reported in the model description and represented in the model’s code (Lott et al. 2012a). The web version of the model, available at, is introduced. The web version provides the graphical interface through which most users will explore TernCOLONY. Finally, future directions in the implementation of TernCOLONY on different river reaches are summarized to address a variety of different management applications and discuss the potential for adapting the model to other contexts (e.g., other habitats or species).
chat loading...