Infrastructure Improvements along Estudillo Canal (Zone 2 Line A) in San Leandro, Alameda County

Infrastructure Improvements along Estudillo Canal (Zone 2 Line A) in San Leandro, Alameda County

The proposed project consists of the following modifications to Estudillo Canal (Zone 2 Line A) located approximately one half mile southeast of the San Leandro Marina in the City of San Leandro: 1. Tide Gate Structure Rehabilitation. Improvements to the deteriorating tide gate structure about 465 feet upstream from the Monarch Bay Drive Bridge consisting of: a. Removing existing deteriorating timber vehicular and pedestrian bridge deck and beam supports, and replacing with a new concrete bridge deck (with railings) supported by a new concrete abutment at each end and two new intermediate concrete pier walls; b. Removing existing deteriorating vertical reinforced concrete walls supporting the existing deteriorating circular flap gates, and replacing with a new vertical reinforced concrete wall to support the installation of the 14 new rectangular flap gates on top of existing concrete foundation; c. Removing existing downstream concrete apron and cutoff wall, and replacing with a new 4-foot wide reinforced concrete apron with the addition of constructing a new 4-foot wide reinforced concrete apron on the upstream side, both supported by 20-foot deep steel sheet pile cutoff walls across the channel bottom to prevent scouring and seepage underneath the tide gate structure; d. Constructing reinforced concrete pedestrian staircases (with hand railings), supported by 20-foot deep steel sheet pile cutoff wall, at all four corners of the tide gate structure for maintenance access; and e. Removing existing rock rip rap in the southwesterly corner of the structure to facilitate the construction of the new improvements, and placing rock rip rap on the channel banks and toes adjacent to the new concrete staircases to protect against bank scouring. 2. South Levee Improvements. Modifications to the south levee, located downstream of the Union Pacific Railroad tracks, consisting of: a. Lowering an approximately 300-foot long section of the south levee from an elevation of 13.7 feet to 8.0 feet; b. Installing three 36-inch reinforced concrete pipes under the west end of the lowered levee section to allow overflows from the canal to efficiently drain out of the sediment handling basin; c. Installing a new concrete cutoff wall along the north side within levee prism and an articulated concrete block mat along the south side of the new maintenance access road to prevent bank scouring of the lowered segment; and d. Constructing a 13-foot wide reinforced concrete access road on top of the lowered segment to provide vehicular access for year-round maintenance. 3. Monarch Bay Drive Bridge Abutment Protection Repair. Work on the south concrete abutment of the Monarch Bay Drive Bridge over Estudillo Canal consisting of: a. Reconstructing eroded channel embankment in front of the south concrete bridge abutment with new rock slope protection; b. Removing and disposing existing broken concrete rip rap, and replacing with new keyed in rock rip rap around perimeter of the rock slope protection; c. Installing rock slope protection fabric under rock rip rap to minimize underlying fines from migrating; and d. Restoring the settling roadway behind the south concrete bridge abutment. The purposes of the project are (1) to rehabilitate the tide gate structure and bring it up to current FEMA standards, including safety standards for vehicular traffic loading, and maintenance access; (2) contain 100-year design storm flow within the channel to meet current FEMA standards by allowing high storm water flows in the channel to overflow temporarily into the City of San Leandro’s sediment handling pond during winter storm events; and (3) to extend the life span of the Monarch Bay Drive Bridge for public and maintenance access by providing protection of the abutment against tidal erosion.

San Leandro

Alameda

Citywide

Alameda