Sediment Transport Studies

South Bay Aqueduct Expansion Sediment Study Client: Zone 7 Water Agency
Dr. Lewandowski performed a study of the sediment conditions in the Bethany Reservoir and the South Bay Aqueduct (SBA), as well as potential changes in sediment conditions that may occur with the proposed Stage 3 pump expansion and Dyer Reservoir on the South Bay Aqueduct. The potential feasibility of other sediment management projects in the South Bay Aqueduct system was also reviewed, including the Dyer Reservoir and Stage 3 pumping operations to minimize sediment resuspension, management of Bethany Headlands sediment loads to reduce incoming sediment, dredging of South Bay Pumping Plant intake area to remove settled sediment and to prevent resuspension, and an underwater berm at South Bay Pumping Plant Forebay channel entrance to block sediment movements into the channel. The study was focused on the assessment of sediment related turbidity and the impact to water quality in the South Bay Aqueduct conveyance system. It was conducted to supplement environmental planning for both conceptual design and desired operating conditions at a new Altamont Water Treatment Plant. The study included analysis of the sediment size distribution along the reservoir floor based on sieve and hydrometer testing of sediment sizes, the review of flocculation testing and settleable solids testing to determine approximate deposition rates under various water salinity conditions, the tracking of turbidity spike movement and attenuation through the reservoir and the South Bay Aqueduct system, and the calculation of critical shear stress in the South Bay Pumping Plant Forebay Channel portion of the Bethany Reservoir.

Technical Review of San Benito and Pajaro River Sediment StudiesClient: RMC Water and Environment
Dr. Lewandowski performed a technical peer review of three sediment studies for the San Benito and Pajaro Rivers prepared by Philip Williams and Associates (PWA). In an assessment of the sediment transport characteristics of the Pajaro River flooding plan, the sediment dynamics of the existing condition and several alternatives were conceptually evaluated using a 2-dimensional coupled hydrodynamic and sediment transport model using MIKE-21C software. The sediment transport impact of the proposed benching concept for floodplain restoration was assessed. The simulation along a double meandering reach was performed for identification of conceptual volumes of erosion and deposition expected along other parts of the river. A second study included a simulation of a portion of the San Benito River to assess potential sediment inputs into the Pajaro River at their confluence. A HEC-6T model was used for simulation of the reach, and total the deposition or erosion characteristics of the reach segments were identified. In a third study, the use of a sediment trap on the Pajaro, constructed as a cutoff between two meanders bends was modeled using HEC-6T. Depositional problems in the main channel after the trap construction proved this sediment control strategy should not be used.

Crystal Springs Reservoir Sedimentation Basin Predesign, San Francisco, CA
Dr. Lewandowski served as project engineer for the Upper Crystal Springs Reservoir sedimentation basin conceptual design. In this project, the Habitat Improvement Plan identified the previous sedimentation basin as future habitat for two endangered species. A new basin was relocated in a grassland area, and designed to collect sediments from the creeks discharging into the existing basin.

San Francisco Bay Bridge Storm Water Sediment Study, Caltrans District 4, CA For Caltrans
Dr. Lewandowski led a review of the types and levels of contaminants measured in sediment size fractions collected in the drain inlets of the San Francisco Bay Bridge. These sediments were assumed to be typical of storm water pollutants in bridge runoff. This study included a literature review of bridge and highway sediment quality information throughout the US and Canada. The study was used to identify the types of runoff controls and the type of storm water treatment necessary for the new span of the bridge.

Assessment of Nonuniform Sediment Size Movement in StreamsClient: US Geologic Survey
Dr. Lewandowski performed flume analyses and settling analyses for the study and development of mathematical models for describing movements of nonuniform sediment sizes in stream beds. One flume analysis measured the movement of a band of sand sediment sizes along a gravel bed at different flow rates. A second flume analysis tracked the movement of gravel-sized, paint-tagged tracer particles along the gravel flume bed. Sand particle penetration of the gravel bed was estimated by experimental procedures and equipment in which settling sand is deposited into a gravel bed condition. Size fractions of all sands and gravels were measured for comparison of sizes. Probabilistic methods were researched for analysis of particle bed penetrations, and assessment of particle passage probabilities was performed.
Dr. Jeff Lewandowski, P.E., C 52503

Advanced Hydro Engineering

3082 Cafeto Drive, Walnut Creek , CA 94598

(925) 639-7053

E-mail Jeff Lewandowski :

Dr. Lewandowski is a registered professional engineer in the State of California, and has 30 years of professional experience in water related systems analysis and modeling, including:

Drinking Water Systems
Wastewater Systems
Storm Drain Systems
Subsurface Drainage

His clients appreciate his strategic and practical solutions, his easy to understand explanations of project results and his attention to maintaining the project schedule and budget.