Transcript Env 247 2011 Overview of Stormwater Management March 1, 2011

Env 247
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 municipal separate storm sewer systems
(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 –
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2.
Municipal Stormwater Collections Systems including MS4s
Certain industrial discharges
Other outfalls that directly discharges into waterways
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.
2.
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4.
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Sediment
Solid and sanitary wastes
Phosphorous (fertilizer)
Nitrogen (fertilizer)
Pesticides
Oil & grease
Concrete truck washout
Construction chemicals
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 waste handling;
4. Litter & sanitary waste handling;
5. Monitoring & reporting requirements; 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 management measures
are measures applied to reduce
pollutants in stormwaster discharged
from the site after completing
construction activities, and include:
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Onsite infiltration of runoff
Flow attenuation by vegetation or natural
depressions
Outfall velocity dissipation devices
Stormwater retention basins
Artificial wetlands
Stromwater detention structures.