March 1, 2011

sadhospitalMechanics

Feb 22, 2014 (3 years and 10 months ago)

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Overview of
Stormwater

Management

March 1, 2011

Sources of
Stormwater

Runoff

1.
Sheet flow over impervious surfaces or other
structures

2.
Runoff including agriculture, urban areas,
construction, and forestry

3.
Municipal
Stormwater

Management
Systems


Large, small, and urban
m
unicipal
s
eparate
s
torm
s
ewer
s
ystems
(MS4s
)

4.
Industrial Facilities/Activities

5.
Construction Activities


Managing
Stormwater

Discharges through the
National Pollutant Discharge Elimination
System (NPDES) Permit

1.
Point Sources that discharge into waterways
are subject to permitting requirements



Municipal
Stormwater

Collections Systems including MS4s


Certain industrial discharges


Other outfalls that directly discharges into waterways

2.
Non
-
point Sources are subject to “general
permits”


Stormwater

runoff due to construction
activites

Typical
Stormwater

Outfall

Point Source

A Case Study


Managing
Stormwater

Runoff from a
Constructon

Site

Pollutants Commonly Discharged from Construction
Sites


1.
Sediment

2.
Solid and sanitary wastes

3.
Phosphorous (fertilizer)

4.
Nitrogen (fertilizer)

5.
Pesticides

6.
Oil & grease

7.
Concrete truck washout

8.
Construction chemicals

9.
Construction debris

A Case Study


Managing
Stormwater

Runoff from a
Constructon

Site


Permitting System

US EPA has issued a
“general permit”
that authorizes the discharge
of pollutants in
stormwater

discharges associated with construction
activity that disturbs one acre or more of land.


Site owners must submit a
Notice of Intent (NOI)
to operate under
the “general permit”


In NC, site owners can submit a
“land disturbance permit”
application in lieu of an NOI that contains methods to comply with
the general permit requirements.

Content of Land Disturbance Permits

Land disturbance permits contain administrative requirements
consistent with the requirements outlined in the General Permit,
including:



1.
Equipment

operation & maintenance practices to avoid

the release of fuels, lubricants, etc. onto the ground;



2. Material handling practices regarding the use of

pesticides, herbicides and fertilizers;



3. Building material
w
aste
h
andling;



4. Litter & sanitary
w
aste
h
andling;



5. Monitoring & reporting
r
equirements; and,



6. Site inspection requirements.



Best Management Practices (BMPs) to
Prevent Erosion and Sediment Runoff

Erosion controls designed to either:
(1)prevent erosion through protection
and preservation of soil or

(2)prevent sediment runoff before the
runoff is discharged from the site include:


Stabilization Practices

Structural Practices



Example of sedimentation
entering a storm drain

Best Management Practices
-
Stabilization

Stabilization reduces erosion potential by (1) intercepting water so
that it infiltrates into the ground instead of running off the surface
and (2) slowing the velocity of runoff, thereby promoting deposition
of sediment and includes such practices as:



1. Temporary seeding


2. Permanent seeding


3. Mulching


4. Sod stabilization


5. Vegetative buffer strips


6. Contouring and protection sensitive


areas



Best Management Practices
-
Structural Practices

Structural Practices involve the installation of devices to
divert, store, or limit runoff to prevent water from flowing on
disturbed areas where erosion may occur, and include:



1. Earth dikes


2. Silt fences


3. Drainage swales


4. Check dams


5. Pipe slope drains,


6. Temporary
stormwater

diversions



Stormwater

Management

Stormwater

m
anagement measures
are measures applied to reduce
pollutants in
stormwaster

discharged
from the site after completing
construction activities, and include:

1.
Onsite infiltration of runoff

2.
Flow attenuation

by vegetation or natural
depressions

3.
Outfall velocity dissipation devices

4.
Stormwater

retention basins

5.
Artificial wetlands

6.
Stromwater

detention structures.