TOWN OF NORWICH Norwich Pool Dam and Recreation Area PRESENTATION - - PowerPoint PPT Presentation

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TOWN OF NORWICH Norwich Pool Dam and Recreation Area PRESENTATION - - PowerPoint PPT Presentation

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TOWN OF NORWICH Norwich Pool Dam and Recreation Area PRESENTATION by Shawn Patenaude, P .E. August 20, 2012 1 2 Existing Conditions Impact from Tropical Storm Irene Amount of rainfall Overtopping Erosion of right embankment

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TOWN OF NORWICH

Norwich Pool Dam and Recreation Area

PRESENTATION by Shawn Patenaude, P .E.

August 20, 2012

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Existing Conditions

Impact from Tropical Storm Irene

  • Amount of rainfall
  • Overtopping
  • Erosion of right embankment

Conclusions from Visual Inspection and Desktop Analysis

  • Vintage concrete (1949)
  • Minimal reinforcement and cracks
  • Antiquated fmashboard design
  • Nonfunctional
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Project Approach

Address Deficiencies Through Design

  • Inadequate hydraulic spillway
  • Overtopping in 1979 and 2011 caused right embankment erosion.
  • Deteriorated spillway concrete has led to structural instability
  • Inoperable fmashboard system
  • Flashboards are braced reducing hydraulic capacity during fmood fmows.
  • Manual stoplog section is often utilized during inclement conditions.
  • Unprotected abutments
  • If the left embankment hadn’t eroded, overtopping would have been

widespread and additional damages would have occurred.

Conform to Regulatory Requirements

  • Adequate Hydraulic capacity (1% storm frequency)
  • 6" of rain in one 24-hour period
  • Address sediment transport
  • Operable low-level gates
  • Sediment management plan
  • Fish passage element
  • Constructed natural fjsh bypass
  • Fish ladder
  • Flow management
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Alternative 1 - Rehabilitate Existing Structure

Address Deficiencies

  • New concrete training walls
  • Raise right abutment
  • Denil fjsh ladder
  • Articulated concrete blocks on left embankment
  • New fmashboard system
  • Concrete overfmow section
  • Rising stem sluice gate
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Alt 1 pdf Alternative 1 - Rehabilitate Existing Structure

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Alt 1 pdf Denil Fish Ladder

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Articulated Concrete Blocks

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Alt 1 pdf Flash Board System

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Alt 1 pdf Concrete Overfmow Section

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Alternative 1 - Rehabilitate Existing Structure

Address Deficiencies

  • New concrete training walls
  • Raise right abutment
  • Denil fjsh ladder
  • Articulated concrete blocks on left embankment
  • New fmashboard system
  • Concrete overfmow section
  • Rising stem sluice gate

Conclusion of Alternative 1

  • Hydraulic capacity - water level during storm
  • Structural integrity
  • Fish bypass
  • Sediment
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Alternative 2 - Ogee Spillway Design

Address Deficiencies

  • Remove and replace entire dam
  • Raise right abutment
  • 50-foot-span ogee spillway
  • Constructed natural fjsh bypass
  • Articulated concrete blocks on left embankment
  • Rising stem sluice gate
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Alt 1 pdf Alternative 2 - Ogee Spillway Design

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Ogee Spillway

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Constructed Natural Fish Bypass

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Alternative 2 - Ogee Spillway Design

Address Deficiencies

  • Remove and replace entire dam
  • Raise right abutment
  • 50-foot-span ogee spillway
  • Constructed natural fjsh bypass
  • Articulated concrete blocks on left embankment
  • Rising stem sluice gate

Conclusion of Alternative 2

  • Hydraulic capacity - water level during storm
  • Structural integrity
  • Fish bypass
  • Sediment
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Alternative 3 - Labyrinth Weir Spillway

Address Deficiencies

  • Remove and replace entire structure
  • Raise right abutment
  • 40-foot, 3-cycle labyrinth weir
  • Denil fjsh ladder
  • Articulated concrete blocks on left embankment
  • Rising stem sluice gate
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Alt 1 pdf Alternative 3 - Labyrinth Weir Spillway

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Labyrinth Weir Spillway

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Alternative 3 - Labyrinth Weir Spillway

Address Deficiencies

  • Remove and replace entire structure
  • Raise right abutment
  • 40-foot, 3-cycle labyrinth weir
  • Denil fjsh ladder
  • Articulated concrete blocks on left embankment
  • Rising stem sluice gate

Conclusion of Alternative 3

  • Hydraulic capacity - water level during storm
  • Structural integrity
  • Fish bypass
  • Sediment
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Project Costs

Cost Elements Alternative 1 Rehabilitate Existing Dam Alternative 2 New Ogee Spillway Alternative 3 New Labyrinth Weir Dam Construction Costs (without fish passage) $324,000 $456,000 $375,000 Fish Passage Construction $100,000 $50,000 $100,000 Engineering Costs $50,880 $60,720 $57,000 TOTAL $474,880 $566,720 $532,000

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Questions and Discussion