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Construction Storm Water Controls

Construction Storm Water Controls. CET-3320 Hydrology & Hydraulics . EPA Phase 2 Clean Water Act Regulations 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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Construction Storm Water Controls

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  1. Construction Storm Water Controls CET-3320 Hydrology & Hydraulics

  2. 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.

  3. 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.

  4. Types of Erosion

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

  6. What Goes in the SWPPP? • Site Information - Type of Improvements - Construction Activity Descriptions - Existing Site Conditions - Disturbed Area & Weighted C’s • Description of all Construction E & SC Methods • Description of Permanent E & SC Methods • Description of E & SC Maintenance

  7. How to Prevent Erosion • Best Way is Using Vegetation on the Ground

  8. 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)

  9. Control Measure Selection Process • Identify Problem Area • Determine Required Strategy • Select Specific Control Measure

  10. Soil Stabilization Measures • Seeding - Matting • Sodding -Mulching • Tree Preservation - Surface Roughening

  11. Check Dams Slope Drains Temporary Dams Water Bar Runoff Control Measures

  12. Check Dams - Small Rock Dam in Channel - Slows Velocity

  13. Temporary Diversion • Directs Runoff from Above Steep Slopes • Direct Runoff to Sediment Ponds

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

  15. Sediment Control Measures • Sediment Basin • Sediment Trap/Diversion • Silt Fence • Storm Drain Inlet Protection

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

  17. Sediment Trap/Diversion Trap:Temporary Settling Pond With Simple Stabilizing Spillway. Diversion: Detour of Storm Sewer System to Provide an In-Line Sediment Basin.

  18. Silt Fence - Fences Catch Sediment of Shallow Flow that can’t be Trapped by Other Means.

  19. Storm Drain Inlet Protection • Prevents Sediment From Entering Storm Sewer System

  20. Some Agencies Have Established Minimum Standards

  21. 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.

  22. 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 (BMP’s) are required prior to plan approval. • Usually required to hold a “First Flush” of polluted storm water for “treatment”.

  23. BMP- Permanent Ponds • Several stages allow water time to slow and pollutants to settle out.

  24. BMP – Open Channels • Detains first flush allowing settling and groundwater recharge.

  25. BMP- Filter System • Allows for direct groundwater recharge and filtering of sediments and pollutants.

  26. BMP – Infiltration Trench • Trenches allow recharge of groundwater and use the ground and media to filter sediment and pollutants.

  27. BMP – Commercially Available Solutions Manufactured units are available to filter runoff before it leaves the site! • Filters • Baffles • Separation Units

  28. 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.

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