Closing PresentationClosing Presentation

Peer Review MeetingPeer Review MeetingMay 4May 4‐‐6, 20106, 20101

1. Redistribution of suspended sediments during dredging

2. Post‐remediation risks –Upper  & 2. Post remediation risks  Upper  & Lower RiverR d  t t  hi h  l  d d i  3. Remedy targets high value dredging areas

4. Improvements

While it is important to consider While it is important to consider suspended sediment redeposition, 

only limited redeposition is expected outside of the dredging footprintoutside of the dredging footprint

1 0Sediment Trap Data Downstream of CU‐18

d

0 8

1.0

7/22‐8/18Downstream CU‐18 Boundary

0.6

0.8

mm/d) 10/15‐22/09

0.4osition (m

0.2

Dep

o

0.0

0 200 400 600 800 1000 1200Distance Downstream (ft)

1000

East Rogers

100

East Rogers Island Transect

Backfill Operations

50 ft downstream duringBucket Decant Study100

(mg/

L)

Bucket Decant Study

10

SS C

onc

1

T

5/20/2009 6/17/2009 7/15/2009 8/12/2009 9/9/2009 10/7/2009 11/4/2009 12/2/2009

Sample Date

All available data support conclusion   Sediment trap data below CU‐18

Near‐field TSS data Bucket decant study

Consistent with  Consistent with field team observations

Result:  Limited TSS redistribution beyond dredging y g gfootprint

8.0

FishRand MNR and Dredging Predictions vs. Monitoring Data1998-2009

6 0

7.0

et w

t)

5.0

6.0

(mg/

kg w

e

MNR

Black Bass

B llh d

3.0

4.0

CB

Con

c. Bullhead

Yellow Perch

1.0

2.0

Fish

P

0.0

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

10.0Composite Fish - River Section 2 (RM 184)

kg

Original MNA

Remediation with No Resuspension

No long term impacts to fish at 500 ng/L

PCB

mg/

k pTotal PCB 350 ng/L (sr04)

Total PCB 500 ng/L

1.0

Mea

n Tr

i+ P

M

0.1Risk –Based Targets

2005 2010 2015 2020 2025 2030 2035 2040Year

Thompson Island  = 212 ng/Lp g/

Lock 5 (Schuylerville) = 153 ng/Loc 5 (Sc uy e e) 53 g/

Waterford  = 74 ng/L Waterford    74 ng/L

10.0Lower Hudson Fish Tissue Forecasts - RM 152

10.0Original MNA

Remedy with No Resuspension

600 kg Tri+

No long term impacts Even at twice the proposed 

1.0

B m

g/kg

600 kg Tri

800 kg Tri+

1,200 kg Tri+

standard

n Tr

i+ P

CB

0.1

Mea

n

0.02005 2010 2015 2020 2025 2030

Risk –Based Targets

2005 2010 2015 2020 2025 2030Year

Phase 1 data showed small increases in fish body burdens in downstream regionsbody burdens in downstream regions

Modeling was completed to predict  fish body b d  i  d i  d d i  f      burden increases during dredging for a range of concentrations

Forecasts indicate negligible changes in time to risk‐based targets

ROD selected priority areas for dredgingdredging

“REM 3‐10‐select” effectively uses 30‐90‐90 mg/kg criteria by river sectionriver section

Sequestered inventory will remain in RS 3

4. Improvements Use larger buckets where feasible (> 5 CY) Scow unloadingg Minimize time dredged areas left openNear field monitoring  PCBs & TSS Near‐field monitoring – PCBs & TSS

Monitoring diagnostics Address DoC uncertainty Re‐examine dredging tolerancesg g Practicable improvements found in Field Oversight ReportOversight Report

Resuspension shown to be associated with controllable operational factors

Adjusted load standard more realistic for actual PCB inventory; acceptable risky; p

Provision of alternate public water supply alleviates need for automatic shut‐downsalleviates need for automatic shut downs

Fixing scow availability issue will increase productivity and reduce resuspensionproductivity and reduce resuspension

Increasing scow loads will reduce vessel traffic and dredging time and thus resuspensiondredging time…and thus resuspension

Residuals standard was effective at minimizing residuals and undredged inventoryresiduals and undredged inventory

Address DoC uncertainty for more efficient dredging (fewer passes)( p )

Streamlined residuals standard will result in faster CU closure