Hydraulic Analysis for Foothill Road Bridge over the Cuyama River County of Santa Barbara
We have conducted so many hydraulic analyses for bridge replacements that the word “countless” comes to mind. However, out of all these bridges, we’ve decided to feature our work on the proposed Foothill Bridge over the Cuyama River in northeastern Santa Barbara County because it is such an interesting variation on the theme of bridge projects. The current crossing is a dirt road at grade—when the rains come, the road is completely impassable (see photo!). The County has been looking at three possible bridge alternatives to replace the at-grade crossing.
We explored the potential hydraulic impacts of each of the three bridge alternatives by running a HEC-RAS (Hydraulic Engineering Center River Analysis System) model for each alternative. Hydrologic data for the model were obtained from multiple sources including the County, Caltrans and our own field investigation. Basically, the HEC-RAS analysis predicts the impact of different replacement bridge scenarios on water surface elevation and water velocity during 50- and 100-year flood events. Our clients require this information when they are conducting bridge replacements.
In addition to HEC-RAS modeling, we also estimated channel bed degradation (“scour”) by examining channel cross sections available for prior years in biennial Caltrans inspection reports. All of this is routine, except for the fact that this crossing location does not have an existing bridge. In addition, there are flow training works (FTW) upstream and downstream of the bridge and we conducted analyses on how the various bridge alternatives might impact or be impacted by the FTW.
Alameda Siphon No. 4 Project San Francisco Public Utilities Commission
This project was part of the San Francisco Public Utilities Commission’s large Water System Improvements Project (WSIP) and included construction of a seismically reliable fourth siphon across Alameda Creek. The siphon consisted of almost 3,000 feet of new 66-inch diameter pipe.
We are enthusiastic about the services we provided on three different parts of the project. In 2008, as a subconsultant to Black and Veatch, we conducted a hydraulic engineering and analysis using HEC-RAS to evaluate both permanent impacts
of the siphon appurtenances and facilities in the 100-year floodplain and temporary impacts
from materials stored in the floodplain during construction. Our hydraulic study and subsequent engineering report demonstrated that the project would not adversely affect the floodplain.
We also were tasked to lead the outage planning that was required in order to conduct the shutdown of the SFPUC’s Coast Range Tunnel. We developed a 45-day shutdown plan, which included close coordination with the Hetch Hetchy Water and Power Project staff, the development of a detailed shutdown schedule using Primavera software, and obtaining endorsement from Cal-OSHA Division of Mines and Safety for safety protocols and requirements.
Once all the planning and permitting was completed, our staff also provided environmental compliance monitoring and support services (as a subconsultant to CH2M Hill) during project construction. This included conducting field trainings, pre-construction surveys and daily construction monitoring.
Alameda Watershed Habitat Conservation Plan San Francisco Public Utilities Commission
The Alameda Watershed Habitat Conservation Plan (AWHCP) is an exciting project for us. The AWHCP will provide a suite of conservation activities as mitigation for potential impacts to covered activities over the 30-year term of the permit. The program integrates state-of-the-art conservation science and environmental planning and includes adaptive management as an integral plan component.
Our biologists are happy to contribute their expertise to this long-term conservation management plan for the San Francisco Public Utilities Commission’s lands in the Sunol Valley. Our lead biologist on the project has been very involved in the writing and response to comments on the AWHCP and has spent extensive hours researching and developing content for the conservation strategy and the analysis of potential impacts. Ernie Avila provides a number of valuable services, including the development of a comprehensive cost model to estimate the lifecycle cost of AWHCP implementation. Our staff is also working on internal training programs for this and other environmental compliance programs within the SFPUC.
We are proud of all that we have and will continue to contribute to the AWHCP.