Line A-1 Underground Bypass Zone No. 12

Project Overview

The Alameda County Flood Control and Water Conservation District (District) owns and maintains an underground storm drain system (Line A-1) along Claremont Avenue upstream of Tanglewood Road in the City of Oakland.  A recent drainage study determined that the existing Line A-1 near Claremont Avenue, lack sufficient capacity to convey the 100-year design storm event (a storm with a 1 percent annual chance of occurrence).

To address this conveyance deficiency and reduce the potential for future flooding in the area, the District proposes to construct a new underground storm drain bypass along Claremont Avenue.  The proposed bypass would begin at Tanglewood Road and reconnect to the existing Line A-1 system downstream at Mystic Street, in Oakland.  The project consists of approximately 4,080 linear feet of 60-inch-diameter underground storm drain along with manholes and junction structures.

Construction of the proposed improvements is planned to occur in multiple phases over an approximately five-year period.

Project Features

• Underground 60” diameter culvert bypass system and associated transition junction structures

Community Outreach

• Residences and business in close proximity to the Project site will be notified via mailed letter, once a construction contract is confirmed for award. For project information and updates, visit Alameda County Public Works Agency’s website: Line A-1 Claremont Ave Underground Bypass-Zone No. 12 | ACPWA
• The Project was presented to the Claremont Elmwood Neighborhood Association, in the City of Berkeley, on June 15, 2026.