Summary of magnetic field anomalies associated with the Trans Bay Cable (TBC) and bridges in the San Francisco Estuary.

These are deviations from the earth’s natural background magnetic field. The local magnetic fields (in nanotesla, nT) of the bridges and cable were measured with both surface and deep tows during transects that ran perpendicular to the object of measure. The cable was surveyed at bridge site locations as well as a non-bridge location in San Pablo Bay. Cable data is only presented from transects where the cable anomaly was clearly identifiable. Measurements from the two magnetometers were averaged for this study.