PROJECT PREPARATION SubSurface Drainage Module

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PROJECT PREPARATIONSub-Surface Drainage Module

• Specifying Drainage Structures to Solve
  Groundwater Problem Areas on Trails

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Objective

• Objective of this topic is to educate those
  preparing projects on
• The importance of managing ground water in the
  vicinity of the trail tread
• Being able to identify problems
• Prescribing efficient solutions

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Fundamentals of Subsurface Water Issues

• Subsurface Water Issues
• Seasonal Water Tables
• Groundwater
• Soil Types
• Relocation for Avoidance

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Sub-Surface Structures

• Underdrains
• Turnpike
• Corduroy
• Ditches
• Wire Baskets

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Underdrains
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924-1 Underdrain

• Commonly referred to as a french-drain
• All kinds of new geotechnical materials being
  developed and available MTDC materials available

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Underdrain

• Intended Uses
• Intercept ground water
• Permanently lower water table
• Limitations
• Difficult to find rock for construction
• Could plug easily
• Maintenance
• Difficult to clean

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Underdrain Notice exposed rock on
left, incorporates ditching
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Underdrains Included with turnpike section
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Turnpike
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913-1 Turnpike Type 1

• Design Basics
• Material Options

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913-2 Turnpike Type 2

• Design Basics
• Material Options

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Turnpike

• Intended Uses
• Wet areas to provide dry tread
• Limitations
• Life span
• Materials
• Logs or rock
• Maintenance
• Need to maintain crown

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Turnpike Native log retainers, Includes ditching
and interior culvert for drainage
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Turnpike Native log retainers, Includes side
ditching, culvert, And lead-off ditching
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Turnpike Rock retainers with imported aggregate
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Turnpike rock retainers, includes ditch
with cross-drain at end
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Corduroy
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Corduroy

• Intended Uses
• Use as last resort
• Not recommended
• Limitations
• Need to maintain adequate cover, extremely
  hazardous to stock when exposed
• Short life span
• Maintenance
• Keep covered with dirt

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Corduroy Poor example of how to
construct, unuseable by stock
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Wire Baskets
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Wire Baskets
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Wire Baskets

• Intended Uses
• Provide tread support
• Footings for bridge abutments
• Limitations
• Proximity of rock to construction site
• Cost
• Could be expensive
• Maintenance
• Minimal maintenance

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Wire Baskets Tread foundations on wet ground
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Wire Baskets Tread foundations on wet ground
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Wire Basket Wall
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Wire Basket Wall
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End Sub-Surface Drainage