The Installation of Two Large Trash Capture Devices on Norbridge Avenue near Nunes Avenue and Walker Court in Castro Valley, Alameda County, California

The Alameda County Public Works Agency (County) proposes to install two large underground trash capture devices on Norbridge Avenue near Nunes Avenue and Walker Court in the unincorporated community of Castro Valley, Alameda County, California. The project is intended to support the County’s efforts to achieve 100% trash load reduction requirement established under its current Municipal Stormwater Permit (MRP3) issued by the San Francisco Regional Water Quality Control Board. The two large underground trash capture devices will be installed on two separate storm drainage systems, both of which discharge to Castro Valley Creek. The project involves the installation of new pre-cast trash capture structures on either side of the existing reinforced concrete box culvert below Norbridge Avenue. Near Nunes Avenue, a cast-in-place reinforced concrete structure would be constructed to divert low-flows and trash from the existing storm drain system into the first trash capture structure. Near Walker Court, the second trash capture structure would be installed in-line with approximately 175 linear feet of new 24” diameter reinforced concrete pipe, replacing the existing 18” diameter pipe to enhance the conveyance capacity of the storm drain system. All proposed improvements and associated excavation will be within the County road right-of way. The approximate excavation footprint are 50 feet long by 14 feet wide for the trash capture structure near Nunes Avenue, 16 feet long by 11 feet wide for the trash capture structure near Walker Court, and 225 feet long by 4 feet wide for the pipe replacement. The maximum excavation depth will be approximately 15 feet.