Samuel McWilliams, E.I.T.

River Energy Resource Characterization, Guyana — Conducted an evaluation of the energy resource in rivers of Guyana to support local development and energy independence. The team collected river bathymetry, current velocity measurements, river water levels, and discharge estimates over a year-long period. Field measurements supported the implementation of a hydrodynamic model to compute energy potential as a function of river stage. Methodology for the study followed guidelines outlined by the International Electrotechnical Commission. A river energy converter technology company incorporated the results into an estimate of the levelized cost of energy for the planned developments.

Pier 39–45 Hydrodynamics and Sediment Stability Assessment, San Francisco, California — Remedial action at Pier 39–43.5 has been undertaken to address environmental concerns resulting from historical operations of a former manufactured gas plant. The remedial design benefited from the implementation of a coupled hydrodynamic and wave model to determine the range of forces that could impact in situ and placed sediment stability. The Pier 39–43.5 DFlow-FM hydrodynamic model leveraged the San Francisco Bay–Delta Community model and included local resolution refinements to capture the local bathymetry, structures, and shoreline. The SWAN wave model extended from the Pacific Ocean through the central portion of the bay. Models captured tidal currents and wave conditions to compute bed forces with remedial zones. Led a field campaign to measure tidal current velocities, wave conditions, and sediment parameters, which bolstered the model calibration and validation effort, ensuring results captured relevant metocean conditions. Performed an extreme event analysis of local wind fields and determined the 100-year storm conditions used to select cap materials capable of resisting erosive forces. Also compared to results of vessel-induced scour to determine appropriate basis of design parameters.

Remedial Design Stability Analysis, San Francisco Bay, California — Implemented a field and desktop study to evaluate efficacy of remedial alternatives for a submerged, contaminated dock area. Sediment containing chemicals from commercial activities in the early twentieth century was at risk of redistribution from local hydrodynamic and wave forces. Remedial activities including the installation of a protective sediment cap were evaluated by first collecting hydrodynamic and wave measurements and then executing a coupled numerical model to simulate local bed forces. Proposed changes were implemented in the model to determine expected maximum forces to use in cap design. A 1-dimensional erosion model representing the proposed multilayer cap design was used to evaluate stability relative to expected design conditions. Post-installation monitoring indicates remedy is stable 5+ years after completion.

Sediment and Contaminant Fate and Transport Modeling, San Francisco Bay — Supporting San Francisco Estuary Institute’s ongoing evaluation of PCBs in San Francisco Bay through the application and interpretation of sediment fate and transport models. Results from the models allow better understanding of the methods, processes, and conditions by which persistent chemicals distribute from the watersheds through the bay margins and into the bay. The suite of models connects watershed loads, tidal circulation patterns, and sediment processes to determine the fate of PCB-laden sediment and the trajectory of concentration reductions in support of determining total maximum daily loads. Initial efforts, which have been focused on San Leandro Bay, include a combination of modeling, field measurements, and lessons learned that will be leveraged to evaluate the wider San Francisco Bay system.

Berry’s Creek Hydrodynamic and Sediment Transport Modeling, East Rutherford, New Jersey — The Berry’s Creek Study Area (BCSA) is a tidal wetland/marsh adjacent to the Hackensack River.  Historical releases of contaminants into the BCSA have resulted in the need for an RI/FS for the site. The study’s goal is to characterize the fate and transport of sediment-bound contaminants. Responsibilities included calibrating and validating the Environmental Fluid Dynamics Code 2-dimensional numerical hydrodynamic and sediment transport model of Berry’s Creek. The data guide a quantitative description of hydrodynamics and sediment transport in the system, providing contaminant fate and transport input to the risk analysis and remedial selection and design.

Marina Sedimentation Analysis, Vallejo, California — Conducted a study on changes to sedimentation rates and the need for dredging activities because of the proposed reconfiguration of a pleasure-craft marina.  Used numerical and analytical models to produce spatial assessments of deposition potential that were compared with estimates of sedimentation rates from bathymetric surveys to determine optimal placement and configuration of the marina. Results of the study informed the selection of design alternatives for reductions in sediment retention within the marina.

Ferry Terminal Sedimentation Analysis, Vallejo, California — Supported the evaluation of modified ferry pier configurations to reduce sedimentation and the need for dredging activities. The team applied a calibrated and validated numerical model resulting in spatial assessments of deposition potential that were paired with estimates of sedimentation rates from bathymetric surveys. Results of the study informed the engineering design team on expected site response from possible pier reconfigurations and suggested a potential reduction in maintenance dredging frequency.

Marine Energy Effects on the Environment, Sandia National Laboratories, New Mexico — The U.S. Department of Energy’s mission to develop a robust and safe renewable energy infrastructure requires that stakeholders, permitting agencies, and developers understand and mitigate negative effects to the environment. To support that understanding, worked to develop application methods for numerical models that simulate the effect that wave and current energy conversion technologies have on their surrounding environment. This has resulted in the development of the Spatial Environmental Assessment Tool to quantify and compare potential power production and risk to the environment.

Suspended Sediment Plume from Underwater Blast, San Francisco Bay, California — Performed a modeling study after the removal of the eastern span of the Bay Bridge in San Francisco Bay, studying potential threats from suspension of sediments to environmentally sensitive areas. The modeling results yielded a theoretical path and residence time estimate for the sediment plume near the environmentally sensitive areas. Assisted in developing monitoring and mitigation plans to track and reduce the potential for harm within the bay.

Estuarine Larval Transport, Mosquito Lagoon, Florida — Developed assessment techniques utilizing hydrodynamic models to determine optimal locations for submerged artificial oyster reefs. Oyster reefs are a bioindicator of a healthy estuarine ecosystem acting as nurseries, food source, and contaminant sink through their filter feeding processes.

Contaminant Fate and Transport Study, San Francisco Bay, California — Supported the completion of a multifaceted study to collect continuous water quality data around the San Leandro Bay estuary. Seven instrument platforms containing water quality sondes and hydrodynamic current sensors were deployed to measure turbidity, salinity, temperature, dissolved oxygen, chlorophyll, acoustic backscatter, and water column currents. Discrete measurements of channel discharge, total suspended solids, and PCB concentrations were collected over the 4-month deployment. Integrated measurements into an OPTically-based In-situ Characterization System (OPTICS) study to determine sediment and contaminant flux into the bay from each watershed, allowing for a more complete description of contaminant fate than using discrete samples alone. Results will support mitigation and monitoring strategies within the wider San Francisco Bay ecosystem.

Coastal Hydrodynamics and Wave Characterization, Hawaii — Conducted an evaluation of the hydrodynamic and wave conditions along a segment of the Oahu coast. An acoustic Doppler current profiler was deployed to measure water column currents and wave conditions over two seasons. Measurements were compared with nearby publicly available data to evaluate spatial variations. Results supported an evaluation of coastal erosion and potential adaptation solutions to limit retreat into critical infrastructure.

SEDflume Study and Hydrodynamic Data Collection, U.S. Military Base — In support of remedial activities in a tidal estuary, supported a multifaceted study to determine hydrodynamic conditions driven by tidal exchanges and river discharge as well as sediment mobility properties using SEDflume. The SEDflume study produced measurements of erosion rates, particle size distribution, and bed density. Critical shear stresses for erosion were derived from the erosion measurements. The hydrodynamic and SEDflume data can support the implementation of numerical models to evaluate the site’s response to a range of hydrodynamic conditions and potential response and stability of the bedded sediment within the system.

Mid-Barataria Bay Sediment Diversion SEDflume Study, Southeastern Louisiana — Conducted a SEDflume study of native Barataria Bay, Louisiana, sediment to support engineering design of a proposed diversion of the Mississippi River. The increased hydrodynamic forces from diverted discharge are expected to erode material near the mouth of the diversion structure. Led a SEDflume study of bed material extending from the surface to 120 ft below mudline to support numerical models simulating flows and estimating the potential for erosion. Study results supported modeling efforts to predict the potential for scour within the system and support the engineering design process.

Dredge Material Study for Beneficial Reuse, Maryland — Conducted a SEDflume study to compare the erodibility of placed dredge material with dredge material supplemented with recycled glass or sand. Test samples were developed in the laboratory by mixing a slurry consisting of supplemental and dredge material. Three test samples were developed for each mixture and allowed to consolidate for 1, 7, and 28 days to compare erodibility over time. The SEDflume study produced measurements of erodibility relative to depth and highlighted the differences in mobilization potential for each material type. The results will help inform appropriate beneficial reuse dredge material management practices for use in restoration projects.

Instrumentation Monitoring for Newtown Creek Hydrodynamic and Sediment Transport Modeling, New York — Deployed an array of oceanographic sensors to collect real-time data regarding free stream and near-bed currents, water quality parameters, and suspended sediments concentrations. Data collected will be used to evaluate remediation techniques.

SEDflume Sediment Erosion Rate Study, Mozambique — Analyzed samples to support deep-water drilling efforts. Application of pre-determined shear stresses to relatively undisturbed sediment cores allowed for the determination of critical shear stresses for erosion with depth. Sediment properties such as vane shear, bulk density, and particle size distribution, in conjunction with the critical shear stress information help to ascertain potential issues when working with these sediments in their natural environment.