Two current profilers were installed for a 29-day period adjacent to Face C of Pier 400, which is the location of the proposed berth on the western side of Pier 400, and adjacent to Face D (location of Face D illustrated above). The water depths at the gage locations were 21 meters below Mean Lower Low Water (MLLW) and 24 meters below MLLW for Face C and Face D, respectively. The gages were configured to measure currents at 10 levels throughout the water column every half hour. The illustration below illustrates the measured current speeds along the berth face for the entire monitoring study.

The results of the current measurements clearly indicate the currents are created by tide propagation through the harbor area. Because tides are the primary cause of the currents, they are not expected to vary significantly throughout the year beyond those measured since measurements were conducted over the full range of tides during the 29-day monitoring period. The results showed maximum ebb tide mid-depth currents along the berth face of slightly more than 10 cm/sec and maximum mid-depth currents along Face D of Pier 400 of slightly more than 15 cm/sec. The maximum flood tide mid-depth currents along the berth face were near 12 cm/sec and near 45 cm/sec along Face D.

Based on the differences in phasing between current speeds and the tide elevation, there appears to be a clockwise gyre associated with flood tides where the westerly currents along Face D create a “hydrodynamic jet” towards the west of Pier 400 which in turn induces the gyre formation with currents along Face C during flood tide traveling towards the south. This flood tide jet and associated gyre are illustrated in the figure below.A similar counterclockwise gyre appears to form during ebb tide, although not as strong.