Transcript 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.
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.
Types of Erosion
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.
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
How to Prevent Erosion
• Best Way is Using Vegetation on the
Ground
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)
Control Measure Selection Process
1. Identify Problem Area
2. Determine Required Strategy
3. Select Specific Control
Measure
Soil Stabilization Measures
- Seeding
- Sodding
- Matting
-Mulching
- Tree Preservation
- Surface Roughening
Runoff Control Measures
- Check Dams
- Slope Drains
- Temporary Dams
- Water Bar
Check Dams
- Small Rock Dam in
Channel
- Slows Velocity
Temporary Diversion
- Directs Runoff from Above Steep
Slopes
- Direct Runoff to Sediment Ponds
Slope Drains
- Pipe or Chute Placed
on Slope to Convey
Surface Runoff Down
a Slope Without
Causing Erosion
Sediment Control Measures
-
Sediment Basin
Sediment Trap/Diversion
Silt Fence
Storm Drain Inlet Protection
Sediment Basin
• Temporary Settling Pond
-Slow Release of Runoff
-Allows Sediment to Settle
out
-Up to 100 Acres
Sediment Trap/Diversion
Trap:Temporary Settling Pond With
Simple Stabilizing Spillway.
Diversion: Detour of Storm Sewer System
to Provide an In-Line Sediment Basin.
Silt Fence
- Fences Catch Sediment of
Shallow Flow that can’t be
Trapped by Other Means.
Storm Drain Inlet Protection
- Prevents Sediment
From Entering Storm
Sewer System
Some Agencies Have
Established Minimum
Standards
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.
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”.
BMP- Permanent Ponds
• Several
stages
allow
water time
to slow
and
pollutants
to settle
out.
BMP – Open Channels
• Detains first
flush
allowing
settling and
groundwater
recharge.
BMP- Filter System
• Allows for
direct
groundwater
recharge and
filtering of
sediments and
pollutants.
BMP – Infiltration Trench
• Trenches
allow
recharge of
groundwater
and use the
ground and
media to
filter
sediment
and
pollutants.
BMP – Commercially Available
Solutions
Manufactured
units are
available to
filter runoff
before it
leaves the
site!
• Filters
• Baffles
• Separation
Units
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.