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 Schuylerville [Lock 5]/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 Schuylerville [Lock 5]/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.
The sixth and final season of dredging has been completed. Backfilling of previously dredged areas with clean material will extend into November 2015. The following table (Table 1) indicates that the PCB mass load is in compliance with pre-established load criteria at the Schuylerville (Lock 5)/Stillwater and Waterford monitoring stations.
Schuylerville (Lock 5)/Stillwater Far-Field Station
|Waterford Far-Field Station||In-Compliance|
|Date of Last Data Collected: November 4, 2014. Dredging complete for season.
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.