Construction Storm Water Controls

coriandercultureMechanics

Feb 22, 2014 (3 years and 1 month ago)

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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




-

Matting

-
Sodding




-
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.