Localized flooding along Davis Street, in the vicinity of Business Center Drive in San Leandro, has been occurring during high intensity storm events coupled with high tides. The Alameda County Flood Control and Water Conservation District’s existing Zone 13 Line B primary underground pipe system had insufficient capacity to covey the design storm flow by gravity. A new stormwater pump station was constructed to reduce future potential of flooding in the area.
The project proposed to address the significant localized flooding at low points along Davis Street that occurs during storm events with high tides downstream. WRECO performed a flood routing analysis; determined preferred pumps; produced preliminary plans and profiles to determine feasibility; prepared civil and drainage plans; and coordinated a team of architechs, and structural, mechanical, electrical, and corrosion engineers for the design of the pump station. WRECO supported the client during the bid and pre-construction phases by providing responses to contractor inquiries. During construction, WRECO coordinated the design team’s responses to submittals and Requests for Information. Construction was completed in 2015.
Several pump configurations were modeled, including up to five pumps of various types and sizes, such as centrifugal, axial, and propeller, operating in parallel. WRECO prepared a dynamic wave model of the pump station with the drainage system upstream. The model showed that there is not sufficient storage in the upstream culverts to allow for peak flow attenuation at the pump station, and the available footprint is not sufficient to provide the required storage in the sump. Since the total design head is low but still varies beyond the propeller pump range, a single axial pump was proposed with three propeller pumps in order to adapt to the various conditions. This configuration was optimized for the site constraints and will minimize long-term power consumption.
WRECO analyzed the pump station’s effect downstream; performed the design calculations; and prepared plans, specifications, and estimate for repairs and improvements to the pump station. WRECO coordinated the design of a unique trash rack configuration that can be installed and removed in the limited available space. Ultimately, the construction of this pump station will reduce the risk of flooding upstream.