Construction Storm Water Controls

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Construction Storm Water Controls

• CET-3320
• Hydrology Hydraulics

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EPA Phase 2 Clean Water ActRegulations Require

• Construction Sites 1 Acre or Larger
• Must not be Allowed to Erode Freely
• Measures Must be Taken to Prevent Erosion
  Sediment from Leaving Construction Sites.

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Erosion Removal Loss of soil by the Action of
Water (and ice, gravity, wind)

• Sedimentation Settling Out of Soil Particles
  Which are Transported by Water.

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Types of Erosion
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What Must Be Done?

• The Owner must
• Submit a Notice of Intent (NOI) for Construction
  Activities
• Have Erosion Sediment Control (ESC) Plans
  Developed.
• Must Have a Written Storm Water Pollution
  Prevention Plan (SWPPP)
• Must Ensure that the Controls are Put in Place
  and Maintained.

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What Goes in the SWPPP?

• Site Information
• - Type of Improvements
• - Construction Activity Descriptions
• - Existing Site Conditions
• - Disturbed Area Weighted Cs
• Description of all Construction E SC Methods
• Description of Permanent E SC Methods
• Description of E SC Maintenance

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How to Prevent Erosion

• Best Way is Using Vegetation on the Ground

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Construction Planning Controls

• Goals
• Disturb as Little as Possible
• Cover (with vegetation) Anything Disturbed for
  Long Term. (Stabilization)
• Slow Water Down (Runoff Control)
• Catch Anything that does Erode Before it Gets
  Away. (Sediment Control)

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Control Measure Selection Process

• Identify Problem Area
• Determine Required Strategy
• Select Specific Control Measure

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Soil Stabilization Measures

• Seeding - Matting
• Sodding -Mulching
• Tree Preservation
• - Surface Roughening

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Runoff Control Measures

• Check Dams
• Slope Drains

• Temporary Dams
• Water Bar

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Check Dams

• - Small Rock Dam in Channel
• - Slows Velocity

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Temporary Diversion

• Directs Runoff from Above Steep Slopes
• Direct Runoff to Sediment Ponds

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Slope Drains

• - Pipe or Chute Placed on Slope to Convey Surface
  Runoff Down a Slope Without Causing Erosion

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Sediment Control Measures

• Sediment Basin
• Sediment Trap/Diversion
• Silt Fence
• Storm Drain Inlet Protection

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Sediment Basin

• Temporary Settling Pond
• -Slow Release of Runoff
• -Allows Sediment to Settle out
• -Up to 100 Acres

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Sediment Trap/Diversion

• TrapTemporary Settling Pond With Simple
  Stabilizing Spillway.
• Diversion Detour of Storm Sewer System to
  Provide an In-Line Sediment Basin.

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Silt Fence

• - Fences Catch Sediment of Shallow Flow that
  cant be Trapped by Other Means.

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Storm Drain Inlet Protection

• Prevents Sediment From Entering Storm Sewer System

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Some Agencies Have Established Minimum Standards

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Maintenance

• Measures must be Inspected
• Every 7 days
• Within 24 hours of a 0.5 rainfall
• Measures must be cleaned out at specific levels
  and repaired if damaged.

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Watershed Management

• Local agencies are also charged with the
  management of watersheds within their districts.
• The use of permanent pollutions prevention
  controls are now being designed into new sites
  and retrofit into existing ones.
• These Best Management Practices (BMPs) are
  required prior to plan approval.
• Usually required to hold a First Flush of
  polluted storm water for treatment.

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BMP- Permanent Ponds

• Several stages allow water time to slow and
  pollutants to settle out.

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BMP Open Channels

• Detains first flush allowing settling and
  groundwater recharge.

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BMP- Filter System

• Allows for direct groundwater recharge and
  filtering of sediments and pollutants.

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BMP Infiltration Trench

• Trenches allow recharge of groundwater and use
  the ground and media to filter sediment and
  pollutants.

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BMP Commercially Available Solutions

• Manufactured units are available to filter
  runoff before it leaves the site!
• Filters
• Baffles
• Separation Units

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Erosion Sediment Control Protects the
Environment

• Keeps Valuable Topsoil in Place
• Keeps Natural Watercourses Free Flowing and Clean
  
• Keeps pollutants from destroying ecologies and
  habitats in watersheds.