Line H Crossing Improvements at Fremont Boulevard in Fremont, Alameda County, California, Zone No. 6 Project

The Alameda County Flood Control and Water Conservation District (District) is proposing to improve the conveyance capacity on a segment of the District’s Zone 6, Line H at the Fremont Boulevard crossing in the City of Fremont. Line H is an existing trapezoidal concrete lined channel and has a double 6’ wide by 5.5’ high box culvert under the Fremont Boulevard crossing. The proposed project involves installing an approximately 120-foot long, single 8’ wide by 5’ high reinforced concrete box culvert adjacent to the existing double box culvert. The proposed project would include modifying the existing reinforced concrete wing walls; constructing reinforced concrete headwalls and apron slab; modifying and conforming the transition from the culvert box to the concrete channel; placing and compacting Class 2 aggregate base; and furnishing and placing controlled density fill. Estimated depth of excavation is within 4 to 5 feet below the channel bottom. Excavated backfill will be reused if suitable. Work would also include reconstructing concrete driveways, sidewalk, curb and gutter, and the median island; and removing and replacing existing asphalt concrete and chain-link fences and gates. Utilities will be protected and/or relocated as needed. Erosion control measures, a water pollution control plan, best management practices, traffic control, and trench and excavation shoring protection will be prepared and implemented. The purpose of this project is to increase conveyance capacity within the existing culvert to meet the 100-year design flow.