PCB mass loads are monitored during the dredging process so that PCB sediments traveling downstream do not exceed pre-established load limits. Load limits were established primarily to limit the mass being transported into the Lower Hudson, beyond the furthest downstream sampling station (located at Waterford) and are defined in the Resuspension Standard.
The Phase 2 cumulative net load criteria of the Tri + PCB mass removed during the dredging season is 2 percent at the first far-field water monitoring station (located at the Stillwater Station) and 1 percent as monitored at the Waterford Station. Tri + is the common term that refers to the heavier fraction of PCBs. If river flows are elevated, the load criteria will adjust to 3 percent at the Stillwater Station and 2 percent at the Waterford Station. The Phase 2 load criteria were adjusted to take into account upstream river flows based on Peer Review Panel recommendations as well as knowledge gained during Phase 1.
Phase 2 Year 3 dredging occurred between April 29 and November 2013. Backfilling continued into December 2013. The net Tri+ PCB mass passing the Waterford Station for the 2013 dredging season was approximately 1.1 percent. This is slightly above the 1 percent project limit due to a high-flow event that occurred in June 2013.
If the PCB load targets are exceeded for multiple consecutive days at any of the stations (non-compliant), evaluations must be performed and actions taken to try to reduce the mass being transported downstream. The standards, particularly the load at the Waterford Station, will be re-evaluated and may need to be adjusted and updated as dredging operations move downstream.