US Army Corps of Engineers BUILDING STRONG ® Dredging with Turbidity Tests and the EPA in Green Bay...

US Army Corps of Engineers

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Dredging with Turbidity Tests and the EPA in Green Bay Harbor

Michael Staal, E.I.T.

Civil Engineer

U.S. Army Corps of Engineers

Detroit District

Lake Michigan Area Office –Kewaunee Sub-Office

October 24, 2012

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Detroit District

Covers 82,000 square miles of land

4,000 miles of Great Lakes shoreline

Maintain 94 harbors Primarily a civil works

district, including navigation, flood control beach erosion, etc.

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Green Bay, WI

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History of PCBs in Green Bay

In 1954, paper companies started using PCBs to make carbonless copy paper

Nearly 700,000 lbs of PCBs were released into the Fox River between 1954 and 1971

The use of PCBs was officially prohibited by federal environmental regulations in 1976

*Data from WDNR

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Green Bay PCB Concentrations

*Data from WDNR

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History of PCBs in Green Bay

In 2007, a Record of Decision and a Unilateral Administrative Order required the primary responsible parties to initiate clean up of the Fox River

EPA and USACE entered into a IA to set monitoring requirements for dredging in Green Bay

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2010 Dredging Map

Area 1

Area 2 Area 3Area 4

Mod. Area

Option 2 Area

Turbidity Testing Required

Total Volume Dredged 173,755 CY

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Turbidity Testing Requirements

►1 week of background testing, 8 hours a day, 1 test each 15 min.

►2 assessments every work day, at least 4 hours apart

►Take initial test 500 feet upstream of dredge►Then take a downstream test 250 ft -500 ft

from the dredge►Downstream test – Upstream test < 80 NTU

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14 CY Dredging Bucket

A Cable Arm Bucket with Seals and Baffles

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Steps the Contractor took to reduce Turbidity

Scows were sealed with spray foam insulation

Dredge material loaded in scows was controlled

Speed of dredging bucket was controlled.

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Turbidity Testing

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Turbidity Testing Results

Maximum Difference 54 NTU(after a 50 year storm)

Minimum Difference 0 NTU

Average Difference 17 NTU

Average Distance from Crane 399 feet

The EPA has decided that turbidity monitoring no longer be used for those areasof Green Bay and Fox River Dredging as long as the Corps operates in a similar manner of dredging.

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Fox River Dock

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Bayport Disposal Facility

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Lessons Learned Switching up testing times keeps

contractor honest Mechanical dredging can be used in a

manner that does not cause large increases in turbidity

Background testing is important. Knowing how the Fox River turbidity reacts to rain events, ships, etc. helped us understand the turbidity in the river better.