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Bioswale planned at Fairview and Grand to treat stormwater and calm crosswalks
Summary
The commission reviewed a green‑infrastructure project at Fairview and Grand that will create a bioswale and a pedestrian bulb‑out to shorten crossings, treat runoff with an 18‑inch percolation profile, and connect to existing culverts; staff cautioned heavy utilities and engineered overflows will be required for large storm events.
Staff presented a green‑infrastructure plan for the Fairview and Grand intersection designed to meet Alameda County clean‑water requirements: a bioswale footprint, reduced sidewalk width with a bulb‑out to shorten crossings, and planting of species tolerant of periodic saturation (Carex, salvias, mint, sea lavender). The design calls for a percolation profile (about 18 inches) and a cross‑section that holds stormwater in a lower depression before it percolates.
Public Works (Daniel Gonzales) explained the system will be engineered with overflow connections to existing large culverts and pipes to handle extreme events. "There are high level overflows that exist, and they're engineered into this," he said, and added that the project will connect to larger culverts that historically carried creek flows. Staff warned that underground utilities and unknown substructure make installation complex and that while the bioswale will treat most rain events, very large deluges will bypass the GI and go to the bypass infrastructure.
Commissioners encouraged looking for other opportunities to convert wide street sections to similar green infrastructure where feasible. The item will proceed through design and utility coordination before construction scheduling.
