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Hudson River Dredging:
Overview and Update
January, 2010
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The Hudson: History
• 1948-1977: PCBs used by GE capacitor
manufacturing plants
GE Hudson Falls Capacitor Plant
• 1973: Removal of Ft Edward Dam - PCBs
spread downstream
• 1976: New York and GE settle enforcement
action for PCB discharges
• 1984: 1st EPA ROD calls for shoreline
capping (60 acres), but no dredging
Dam Location
• 1989-1990: GE implements 1984 Remedy
• 1990 – EPA reassessment begins
• 2/1/2002 : new EPA ROD calls for dredging
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3
WARREN
WASHINGTON
Glens
Falls
Hadley
Hudson Falls
Bakers Falls
Fort Edward
Section 1
Thompson Is. Dam
Fort Miller Dam
Section 2
Northumberland Dam
SARATOGA
Upper
Hudson
River
Schuylerville
Stillwater
Section 3
Mechanicville
RENSSELAER
Waterford
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Cohoes
Green Island
0
Federal Dam 0
Troy
5 mi
10 k
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Project Overview
– 2002: ROD selects dredging remedy
– 2004: EPA completes development of Quality of Life and
Engineering Performance Standards, Siting of Processing Facility
and Community Relations
– 2002-2005: Three EPA/GE agreements to perform work
— Sediment sampling (complete)
— Engineering design of 2-phase project (Phase 1 complete)
— Performance of project (Phase 1 complete). Agreement includes
Phase 2 “opt-in/opt-out” provision for GE. Decision to be made in
second half of 2010. If GE opts out, EPA retains all enforcement
authorities to compel performance of Phase 2.
– 2007-2009: Construction of Sediment Processing Facility
– 2009: Phase 1 dredging commences May 15, continues to
November
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Construction of Processing Facility
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2 miles of road; utilities; 90,000+ cy of fill
Rail yard with 7 miles of new track
1,500 foot long wharf to unload barges; widen canal by 65 feet
2 MGD water treatment plant
Screens and a bank of “hydrocyclones” to remove sand
12 filter presses
300,000 sq yds of liners, 55,000 sq yds paved area
7 acres of storm water basins to handle 100-year flood
5 staging areas for dewatered sediment (2 enclosed -- 19,000 cu yds
each)
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Sediment Processing Facility
•April 2007
Champlain Canal
•November
2008
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Sediment Processing Facility Operations
• Once at the processing facility, the sediment is off-loaded and
debris is removed
• The sediment is then processed and the water is extracted. The
water is treated on-site before being returned to the Champlain
Canal
• The remaining sediment, called “filter cake,” is loaded onto
railcars for transport to a secure, PCB-approved landfill in
Andrews, Texas
– some sediment was directly off loaded, dried and then placed in
railcars
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Phase 1 and 2 Dredge Area
Delineation
• > 50,000 sediment samples taken 2002-2006; sampling data
collected to enable EPA and GE to:
– determine the distribution of PCBs in the sediment
– refine estimates of the amount and location of PCBs in the
sediment
– establish river sediment characteristics (e.g., silt, sand,
gravel)
• 490 acres planned to be dredged – 90 acres during Phase 1,
400 acres during Phase 2
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Phase 1 Dredging
– May-November 2009; operating
24/6
– Up to 12 mechanical clamshell
dredges working at same time
– 27 Hopper Barges/13 Tugs
– Constant monitoring
– Backfill (or cap) after dredging
– Habitat replacement (in 2010)
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Dredging Operations
• Dredging & Debris Removal
• Resuspension controls
–
Rock dike
–
Silt curtain
–
7,000 yds2 steel sheeting
• Backfill, if area meets residual standard
–
165,000cy
–
12” of cover over much of area
–
38,000cy near-shore backfill to match
original bathymetry
–
Add’l. backfill in specified planting areas
• Capping, if area cannot meet residual standard
–
Depends on residual concentrations
–
Consider capping if residuals not removed after 4 passes
–
Requires EPA approval
• Dredging and/or backfilling operations continued 24/6 while Champlain
Canal was open (May – November, 2009)
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Engineering Performance Standards
• Engineering Performance Standards were developed to:
- minimize resuspension of PCBs during dredging
- set limits on PCBs left in sediment, and
- set production rates
• Resuspension standard designed to:
- Protect drinking water intakes downriver of the dredging
operations, and
- Limit the downriver transport of PCBs
• Performance standards now being evaluated through peer review
process
• Standards and design likely to be modified for Phase 2
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Quality of Life Standards
• Air
• Noise
• Light
• Odor
• Navigation
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Dredging Began May 15, 2009
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The First Scoop of Mud
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Shoreline Preparation Pre-Dredging
Tree trimming
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Removal of Logs, Stumps & Debris from Western
Channel of Rogers Island
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Debris is a Major Problem
Debris removal
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Dredging in Ft. Edward, NY
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Residents Watch Dredging in the Ft. Edward
Yacht Basin
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Loading a Mini-Scow
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Large Hopper Scow
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Noise Monitors Along Shore of Rogers Island, Ft.
Edward, NY
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Locks Open May - November
Barge transport through Lock 7
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100+ Acre Processing Facility
Unloading at processing facility
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Installation of Plastic Liners in Rail Cars for
Transport of Contaminated Sediment
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Workers Load Rail Cars with Dried Sediment
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Rail Transport to West Texas
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Assessment & Peer Review
• Assessment of Phase 1 underway. Purpose is to
evaluate engineering & performance standards and
make appropriate changes
• EPA & GE prepared draft reports evaluating Phase 1;
reports exchanged and released to public in midJanuary; final reports released March 8
– Reports draw some significantly different
conclusions from same facts
• Peer Review started mid-February, continues to
June
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EPA Report Findings: Overview
– Phase 1 Plan:
• Minimum removal was to be 200,000 CY
• Target was 265,000 CY removed from 90 acres
– Phase 1 Achieved:
• 283,000 CY removed from 48 acres
• >1.5 times more PCB mass removed than estimated in ROD
– About the same mass as estimated in design, but from fewer acres
• 31 acres backfilled; 17 acres capped
– Significantly less capping expected in Phase 2
– East Rogers Island area is atypical of rest of River – about 11.5 acres
capped
-- About half of the remaining capped areas were buried under several
feet of clean backfill thus addressing habitat concerns
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283,000
Cubic Yards
265,000
Cubic Yards
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Phase 1 Target = 18 CUs dredged;
Achieved = 10 CUs dredged
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EPA Draft Report Findings
• Phase 1 indicated much greater mass of PCB in the areas
dredged than estimated. In fact, PCB-bearing oils were frequently
encountered.
• The depth of contamination (DOC) was greater than estimated in
the design (in one area DOC was 13 feet deeper than designed).
On average the depth of cut was 1.5 X deeper than designed.
– Inaccurate estimates primarily attributable to woody debris
interference with sediment sampling during design phase.
• If the actual DOC is better defined prior to actual dredging, the
contaminated material can be removed with fewer and fuller
bucket bites, and fewer passes over a given area. Fewer bucket
bites equates to less resuspension and greater productivity.
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EPA Draft Report Findings: Resuspension
Standards
Findings
• Near-field TSS - 100 m
Evaluation Level - 700 mg/L
• Av. TSS well below Evaluation
Level
• Near-field TSS - 300 m
Evaluation Level - 100 mg/L
• Av. TSS well below Evaluation
Level; 4 exceedances observed
(but not supported by continuous
turbidity measurements).
• Max. allowable Total PCBs in
water column -- 500 ng/L
• 3 exceedances; dredging activities
halted less than 4 four days.
• Far-field net suspended solids
concentration Evaluation
Level -- 12 mg/L
• Not exceeded
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Monitoring PCBs During Dredging:
Schuylerville, NY Data
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EPA Draft Report Findings: Resuspension
Standards
Findings
• Far-field Total and Tri+ • Exceeded at Thompson Island for
PCB load Control levels: majority of the dredging period.
1,080 grams/day and
At Waterford, loads were significantly
361 grams/day
lower -- exceeded control level ~ 20%
of time.
Note: load criteria were not revised
during Phase 1 to address the largerthan-planned PCB mass removed.
Overall target of no more than 1%
export to lower Hudson was
achieved.
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EPA Draft Report Findings: Residuals
Standards
Findings
• Affirmation of removal of all
PCB-contaminated
sediment inventory in target
dredging areas (“Certification Units” or CUs)
• Substantial removal of inventory
confirmed in all CUs. Where
inventory left in place, engineered
caps constructed to isolate the
remaining inventory.
• Arithmetic average Tri+
PCBs concentration in the
residual sediments ≤ 1
mg/kg
• Expect that ≤ 1 mg/kg can be
achieved in residual sediments
during Phase 2
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EPA Draft Report Findings: Productivity
Standards
Findings
• Target Phase 1 dredging volume =
265,000 CY
• Total volume removed = 283,000 cy
• Targeted Maximum Phase 1 monthly
volume = 88,350 CY
• Max. monthly Phase 1 volume
removed = ~77,000 CY. (Very likely
that the target of 88,350 CY would
have been achieved but for
shortages of empty scows.)
• Shoreline stabilization, backfilling,
and processing and shipment of
removed sediment accomplished
prior to the end of calendar year.
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• Due to difficulties at disposal site, not
all sediment shipped off-site by end
of 2009. Provisions should be made
for back-up disposal site for Phase 2.
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What Went Well
• Met or exceeded sediment volume & PCB mass goals
• Few shut-downs with limited impact on production
• ~70% of dredged area closed in compliance with the
Residuals Standard
• No measurable impacts to Lower River
•We learned enough in Phase 1 to improve the
project and do it well in Phase 2
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Phase 1 Challenges
• Higher than normal flows
• Extent of wood debris
• DoC consistently underestimated
• NAPL releases
• Limitations on scow unloading
• Extent of erosion since 2001 – 35K CY lost in the 18 planned
CU’s before start of dredging; system is dynamic, redistribution
occurs all the time
• % of bedrock/clay bottom
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Resuspension Standard: Summary of
Observations
• No significant release of solids during dredging
• Water column PCB concentrations were significantly above
baseline during dredging.
• PCB-bearing oil sheens were extensive and are likely a
significant vector for PCB release.
• Water column concentrations of PCB decreased
substantially downstream of Thompson Island to Waterford.
– Tri+ PCB Loads at Lock 5 and Waterford were significantly
lower than loads at Thompson Island, yet solids transport
increased slightly (though still within the baseline
variations)
• There were no observable impacts of dredging to PCB water
column concentrations downstream of Albany.
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Resuspension Standard Observations
(con’t.)
• Net load at Thompson Island was still small relative to
the overall mass removed : 440 kg vs. the 20,000 kg
removed (roughly 2 percent).
• The net load to the Lower Hudson was roughly 150 kg
total PCB.
• The resuspension goal of maintaining the Total PCB
export rate to 1 percent or less relative to the mass of
PCBs removed was achieved at Waterford and nearly
met at Schuylerville.
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Productivity Standard: Major Factors
Affecting Productivity During Phase 1
• Scow unavailability due to limited scow unloading
capacity at Dewatering Facility
• Presence of wood debris in sediment
• Limited capacity of mini-scows
• Underestimated DoC
• Fine grading to meet cut line tolerances
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Debris in Sediment
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Impacts of Underestimated DoC and
Fine Grading
• Underestimated DoC:
– Additional dredge passes
– Time lost in mapping, sampling, and designing new
cut lines
– CUs open longer
• Fine Grading:
– Reduced production rate
• Both factors also increased resuspension losses
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Phase 2 Productivity Standard Can be
Met by:
• Addressing uncertainty in DoC to minimize
passes
• Improving scow unloading capacity
• Minimizing fine grading and small cuts
• Conducting access dredging where needed
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Residual Standard – Summary of Findings
• Resuspension, Productivity and Residual standards are
related
• Basic problems arise from the uncertainty in the design DoC
– Core samples used for design were often incomplete,
yielding inaccurate design
• Modifications needed in the approaches for dredging and
post-dredging sampling
• EPA is recommending simplifications to the Residuals
Standard but not changes to the basic approach
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Closure Summary
Percent of Phase 1 Area Closure
Cap on
Cap due to
Archaeologically
Schedule
Sensitive Areas
Constraints
0.26%
25%
Cap per Residual
Cap on
Bedrock/clay
Standard
Backfill
63%
10%
2%
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Simultaneously Meeting Standards
• Efficient dredging of inventory with fewer cuts
(productivity) leads to fewer bottom disturbances
and smaller dredging releases (resuspension) and
quicker certification of post-dredging
concentrations (residuals) reducing duration of
exposed bottom surface (resuspension).
• Per Residual Standard, appropriate selection of cut
lines is important in minimizing re-dredging...and
therefore in meeting the standards simultaneously.
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OVERALL BENEFITS OF PROJECT
• Far more PCBs in the River than estimated
• The River is NOT “cleaning itself” at the rate predicted by
the model used in the 1990s.
– Sediments are not being buried..
– Surface concentrations are 3x higher, and water column
concentrations are 2-3 X higher, than 1990s model
predicted. Both show little or no decline over a decade.
• Even with an increase in the resuspension standard,
completion of the dredging project will confer significant
and lasting benefits.
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More Information
For information on Hudson River Dredging Project:
http://www.epa.gov/hudson/
For EPA’s Report on Phase 1:
http://www.hudsondredgingdata.com/Report
For GE’s Report on Phase 1:
http://www.hudsondredging.com/
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