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2007 Water Resources Report

Rob Montgomery

River Flow & Lake LevelsTMDL Study

Floodplain mapping revisionsDredging 101

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Rock River FlowJuly 2005 – July 2007

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Rock River Flow1990 – 2007

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Lake Koshkonong StageJuly 2005 – July 2007

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Lake Koshkonong Stage1990 - 2007

100-yr 864

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Rock River TMDL Study• TMDL = Total Maximum

Daily Load

• Load allocations for sediment and phosphorus for impaired streams and waterbodies

• Analyzing target phosphorus loads– 0.08 mg/L for wadeable streams– 0.125 mg/L for non-wadeable

• Allocations to point and non-point sources

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Rock River TMDL Study• DNR to submit

TMDL to USEPA, funded by USEPA

• Technical analysis ongoing, technical advisory committee meeting upcoming

• Lake Koshkonong will benefit, but changes will be slow in coming

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Floodplain Mapping Revisions

• Generally based on new topography, but old hydraulic analysis

• Dane County, Rock County: new maps, 90 day appeal period over

• Jefferson County: Appeal period not yet announced

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Dredging 101

• Dredging can increase water depths and supply fill

• Expensive

• Usually conducted in critical navigation areas only

• Substantial permit requirements

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Types of Dredging

Mechanical (excavated)– Usually used for smaller areas– Slower production than hydraulic– Smaller disposal area

Hydraulic (suction – pumping)– Most cost-effective, especially for large

areas– Usually requires large disposal area

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Mechanical Dredging

JF Brennan

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Hydraulic Dredging

Dredge

Dredge Disposal

Area

Dredge discharge pipeline

Return Flow

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Hydraulic Dredge

JF Brennan Company

Cutterhead

Pump

Discharge pipeline

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Hydraulic Dredge Disposal Areas

• Often 1.5 x Dredge volume

• Sediment dewatering return flow

• Land acquisition

State of North Carolina

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Final use of dredge spoil area

• Spoil properties important

• Open Space, Agricultural, Wildlife area

Applied Marine Sciences

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In-Lake dredge spoil placement to create habitat

• Dredge spoil placed behind confinement berms

• Would involve substantial permitting process on Lake Koshkonong

Corps of Engineers

Project at Pointe Mouillee, MI Lake Erie

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Factors Affecting Hydraulic Dredging Project Costs

• Dredge spoil site acquisition, preparation

• Access and mobilization

• Dredge material properties

• Pumping system

• Restoration

• Permit Conditions

• Costs could range from <$10/cy to >$20/cy

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Hypothetical Hydraulic Dredging Project

• 1000 ft x 300 ft (~7 Ac) x 2 ft depth = 22,000 cy

• Disposal – 3 ft depth – 8 acres• Dredge & place: 22,000cy x $20/cy =

$440,000• Property acquisition: 8 acres x

$20,000 = $160,000• Total: ~ $400,000 to $600,000• Actual project costs could vary

WIDELY

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Implementing a Dredging Project on Lake Koshkonong

PLANNING • Prioritizing navigation improvement areas• Identify habitat improvement opportunities• Effects on wind driven waves and ice push• Funding• Permit strategy• Planning level engineering, costing

DESIGN• Sediment characterization• Permitting• Acquisition of land and access• Specialist contractor

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Questions

Thank You