The Trans Bay Tube
The purpose of this project was to provide an updated functional Cathodic Protection (CP) system for BART’s Trans
Cathodic Protection System Improvements
The work performed inside the Transbay Tube (TBT) included several stages. Demolition began with 15 existing rectifier alarms, transformer panels, associated racks and conduits, one existing corrosometer probe junction box and conduit in the TBT Lower Gallery, and demolition of 12 existing permanent reference cells, four existing permanent electrical resistance corrosometer probes and associated conduit located in TBT Upper Gallery Top Hat. Twelve new permanent reference electrodes located in the TBT Upper Gallery Top Hat were provided, along with four new permanent electrical resistance corrosometer probes and transmitters, and 16 new cathodic protection monitoring panels located in the TBT Lower Gallery sections. Conduits, cable, and related pull boxes were added to complete the permanent reference electrode / corrosometer probe / internal line current installations. Existing Upper and Lower Gallery cable trays shall be utilized to route new cabling. Pin brazing at 24 locations was also provided along with name plates for a total of 16 top hat locations.
Other work inside the Transbay Tube and above the Bay from a Barge involved the replacement of existing anode cable through the TBT Top Hat and anode sleds at 10 locations underwater in the San Francisco Bay with District-Furnished Material (DFM) and Contractor Furnished Materials (CFM). Rock was provided in accordance with Contract Specifications Section 26 42 00, Cathodic Protection, and barge lifts were certified and verified for successful dry dock.
Construction Management Services
Ghirardelli Associates served as the District Representative to administer and monitor the Contract. The team coordinated with outside Agencies and internal BART Departments conducted field inspection and were directly responsible for overall construction project management including construction permits, utilities, and traffic. Contract coordination between other contracts working within the same BART Operating System involved reviewing and responding to Contractor submittals, RFIs, and letters. The team also maintained an efficient filing system, strictly followed the Construction Manager’s QA Audit, maintained schedules and conduct weekly progress meetings, process Change Orders and Change Notices, and prepared Engineering cost estimates.
A Project Delivered on Time
Bay Tube (TBT) in the San Francisco Bay. The TBT is BART’s most critical asset. The CP system prevents corrosion and increases the longevity of the structure. Both projects had their challenges, including demolishing the existing rectifiers and corrosometer required out-of-the-box thinking. Most of the work was inside the Upper Gallery of the TBT, a very limited space area. Replacing the anode sleds and cable required real-time coordination between the crew on the barge and the crew inside the Upper Galley of TBT.
Continuous coordination between various public agencies, different BART Divisions, contractor and designer has been key to a successful execution of this project. Prompt resolution to issues related to existing conditions was critical to keep the project within schedule.
