31 Oct 2023

Proceedings from the Basin Sediment Management for Unique Island Topography Workshop, Mayagüez, Puerto Rico

Abstract: This report summarizes the Basin Sediment Management for Unique Island Topography Workshop hosted in-person and virtually at the University of Puerto Rico Mayagüez (UPRM) Department of Civil Engineering and Surveying, Mayagüez, Puerto Rico on 11 March 2022. The workshop was attended by approximately 80 federal, state, local, and academic organizations participants. It focused on Engineering With Nature® (EWN®), green infrastructure (GI) and low impact development (LID) opportunities for unique tropical island topography and included seven presentations from subject matter experts, a discussion on limitations and problems with prior projects, and two concurrent breakout sessions. Preworkshop activities included a field trip to multiple sites in the Añasco watershed conducted 09 March 2022, which served as a base case for the workshop. The field trip provided participants a unique perspective of the island’s topography and post 2017 Hurricane María issues and impacts. During the breakout sessions, participants identified new project opportunities for EWN®-GI and LID at two selected sites from the field trip. Each group developed alternatives for their chosen site and identified concepts that could turn into great opportunities for the surrounding communities and significantly benefit the state of practice in Puerto Rico’s unique tropical island topography.

23 Oct 2023

Considering Sediment Beneficial Use Options at Lake Michigan Harbors in Wisconsin

Abstract: In 2020 the US Army Corps of Engineers (USACE) reassigned 14 federally maintained harbors in the Wisconsin waters of Lake Michigan to USACE–Chicago District. The administrative change presents opportunities for in-creased beneficial use of sediment at harbors that have not traditionally placed sediment beneficially. This paper summarizes a screening-level analysis of 12 harbors to determine which harbors are likely to have sediment appropriate for beneficial use in the future, either in water or upland. The harbors were qualitatively ranked according to the potential for future successful beneficial use of navigationally dredged sediment. Using this screening, data needs were defined and next steps to aid the development of a regional dredged-material management plan were identified.

18 Oct 2023

Guidelines for How to Approach Thin-Layer Placement Projects

Abstract: Historically, dredged material (DM) has been placed at the nearest available placement site. There has been an increasing trend of beneficial use projects recently, often using innovative methods. Thin-layer placement (TLP) involves one- to two-foot-thick DM placement, compared to traditional, thicker sediment placement applications, to restore coastal wetlands. The main idea of TLP is to promote the natural recolonization or reestablishment of habitat and benthic species. These guidelines present a roadmap of TLP’s evolution and offer easily digestible examples and considerations for TLP applications in wetlands and open-water environments. Offered as a tool to the practitioner, the eight chapters of these guidelines cover the history of TLP, characterization of the project area, setting goals and objectives, project design, construction considerations, monitoring and adaptive management, knowledge gaps, and future research needs. Several case studies are presented as examples of how such applications have been implemented and highlight lessons learned, particularly best-management practices. These guidelines offer consideration of TLP as a critical component in the project development phase, a tool for the sustainable management of DM, and a method that may create, maintain, enhance, or restore ecological function while supporting navigation channel infrastructure and providing flood risk management benefits.

10 Oct 2023

Pilot-Scale Optimization: Research on Algae Flotation Techniques (RAFT)

Abstract: The impacts of harmful algal blooms (HABs) on US national waterways continue to cause significant economic and environmental damage. Researchers at the US Army Engineer Research and Development Center (ERDC) successfully demonstrated the Research on Algae Flotation Techniques (RAFT) project at pilot scale. This study was designed to show that the surface concentrations of algal biomass can be effectively increased with near linear scalability utilizing the natural methods by which some algae entrap air within excreted mucilage for flotation. The surface concentration of cyanobacteria measured as phycocyanin pigment increased by six-fold after RAFT flocculation treatment. Further optimization of chemical delivery systems, mixing, and dissolved air exposure will be required before full scale readiness.

10 Oct 2023

Proceedings from the Soft Substrate Island Design Workshop

Abstract: This report summarizes the activities of the Soft Substrate Design Workshop held virtually on 08 September 2021. The 28 participants from federal, state, local, and academic organizations discussed designing and constructing islands with soft sediments in inland waterways. They were introduced to the US Army Corps of Engineers’ (USACE) Engineering With Nature® (EWN®) initiative and the vision for Tri-County Planning Commission (Peoria, Illinois). An overview of collaborative projects using landscape architecture and EWN principles was provided. The focus of discussion was on two primary waterways, the Upper Mississippi River System, and Illinois River. Participants discussed their experience associated with designing and constructing islands with and on soft sediments prior to breakout sessions to discuss specific design and contracting elements. The groups were brought together to discuss design techniques that could be implemented in the Upper Mississippi River and Illinois River systems.

10 Oct 2023

A Review of Algal Phytoremediation Potential to Sequester Nutrients from Eutrophic Surface Water

Abstract: Harmful algal blooms (HABs) and coastal hypoxic zones are evidence of cultural nutrient enrichment affecting public health and water supplies, aquatic ecosystem health, and economic well-being in the United States. Recognition of the far-reaching impacts of Midwest agriculture has led to establishing nutrient reduction objectives for surface waters feeding the Gulf of Mexico, Lake Erie, and many smaller water bodies. Municipal nutrient enrichment impacts have been addressed by increasing levels of sewage treatment and waste management through the Clean Water Act era, but HABs rebounded in the 1990s because of non-point source nutrient enrichment. HAB control and treatment includes watershed and waterbody treatments to reduce loading and address outbreaks. Systems to remove nutrients from impaired waters are expensive to build and operate. This review of algal production systems summarizes emerging algal water treatment technologies and considers their potential to effectively sequester nutrients and atmospheric carbon from hundreds of eutrophic reservoirs and DoD wastewater treatment facilities while producing useful biomass feedstock using solar energy. Algal water treatment systems including open ponds, photobioreactors, and algal turf scrubbers® can be used to grow biomass for biofuel, wastewater treatment, and commercial products. This review recommends continuing research on surface water nutrient reduction potential with algal turf scrubber productivity pilot studies, preliminary site design, and biomass utilization investigations.

10 Oct 2023

Spatial Screening for Environmental Pool Management Opportunities

Abstract: US Army Corps of Engineers (USACE) reservoir projects significantly alter river ecosystem structure and function. Each project adheres to a defined set of operating rules to achieve primary objectives, which typically include flood risk management, hydropower, or navigation along with ancillary objectives for drinking water/irrigation, recreation, and natural resources management. Environmental flows (E-Flows) planning under the Sustainable Rivers Program has demonstrated new opportunities for environmental pool management (EPM; Theiling et al. 2021a, 2021b) that have no negative impact on other reservoir functions. In some locations, water level drivers can be managed to improve ecological outcomes, like wetlands, waterbirds, reptiles, and water quality, by altering the magnitude, timing, frequency, and duration of pool level changes that affect riparian and shoreline plant communities. Reservoirs with large delta areas may provide particularly important wetland or riparian habitat management along avian migratory pathways or in wildlife conservation regions (Johnson 2002). These large deltas can be identified and characterized using available satellite imagery, which along with water level habitat drivers available in hydrology databases, can be used to identify USACE reservoirs with good potential for EPM. A spatial analysis of USACE reservoirs capable to support EPM can be developed utilizing estimates of water occurrence, transition, and seasonality as well as surface elevation data derived from satellite imagery to assess geomorphology drivers. USACE water management records can be used to assess wetland drivers. Nationwide screening will be broken down into ecoregions to establish the anticipated geographic range of variation for wetland and riparian habitat drivers. Southwestern US reservoirs, for example, will have much different hydrology and fauna than Midwest and Eastern US reservoirs.

5 Oct 2023

Review of Riparian Models for Assessing Ecological Impacts and Benefits

BACKGROUND: Riparian zones are key transitional ecosystems between upland and aquatic zones, and these systems are often degraded due to both land use change and stream processes (e.g., deforestation and water impoundments and/or diversions). These important ecosystems require restoration because of the many benefits they provide ranging from providing habitat for diverse species to promoting water quality. Restoration practitioners, regulators, and researchers require riparian assessment methods and models to efficiently guide mitigation and restoration planning. This technical note (TN) compiles a subset of existing riparian tools and evaluates them relative to model objectives, modeling approach, and input variables. Findings are synthesized into a gap analysis of these models to inform future riparian model development and improve riparian assessment.

5 Oct 2023

Unmanned Aircraft Systems and Tracer Dyes Potential for Monitoring Herbicide Spray Distribution

Purpose: Chemical control of nuisance aquatic vegetation has long been the most widely utilized management tool due to its high level of efficacy, limited environmental impacts, and relatively low cost. However, unprecise application of herbicides can lead to uncontrolled invasive plants and unintended management costs. Therefore, precision herbicide delivery techniques are being developed to improve invasive plant control and minimize impacts to non-target plants. These technological advancements have the potential to enhance aquatic ecosystem protection from invasive species while reducing associated management costs. Despite the benefits of using registered herbicides for aquatic plant control in efforts to restore aquatic habitats, their use is often misunderstood and opposed by public stakeholders. This can lead to significant challenges related to chemical control of nuisance aquatic vegetation. Thus, US Army Corps of Engineers (USACE) Districts seek improved methods to monitor and quantify the distribution (i.e., amount of herbicide retained on plant foliage compared to those deposited into the water column) of herbicides applied in aquatic systems. Monitoring herbicide movement in aquatic systems can be tedious and costly using standard analytical methods. However, since the inert fluorescent tracer dye Rhodamine WT (RWT) closely mimics product movement in the aquatic environment it has been used as a cost-effective surrogate for herbicides tracing.

5 Oct 2023

Rapid Algae Flotation Techniques

Abstract: Some harmful algae produce mucilage or extracellular polymeric substances useful for flotation. This study evaluated natural polysaccharides to determine effects on algal flotation with DAF. Food-grade gums (xanthan gum, guar gum, gum arabic, gellan gum, and diutan gum) were tested with cyanobacteria cultures singly and in combination with commercial flocculants (including Tramfloc 222 and Tramfloc 300). Gum arabic alone had no effect when evaluated at concentrations between 10 mg/L and 5,000 mg/L. However, the combination of gum arabic and Tramfloc 300 yielded higher algal flocculation than Tramfloc 300 alone. The combination of xanthan gum (anionic) and guar gum (cationic) did not perform at the level of the combined xanthan gum and Tramfloc 222 in either flocculation or flotation of algae. Tramfloc 222 and xanthan gum; however, yielded effective flocculation seemingly resistant to changes in interfering factors such as turbulence, pH, and temperature. Furthermore, the combination of xanthan gum and Tramfloc 222 provided the most effective flotation and flocculation independent of pH effects. The results suggest that anionic polysaccharides can be used to increase the efficacy of cationic coagulants such as Tramfloc 222.