Transcript Stormwater Chemistry and Water Quality

Stormwater Chemistry and Water
Quality
Georgetown County Stormwater
Division
Tracy Jones, P.E. – Division Manager
Zollie Green, P.E. – Senior Engineer
Shelly Jordan – Quality/Billing Coordinator
Chris Allen – Inspector
What we do?
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Plan Reviews
Inspections
Capital Projects
Drainage Complaints
Utility Fee
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Funds our division
What is Stormwater?
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Rain or snow that falls on streets,
parking areas, rooftops and other
developed land and either flows
directly into nearby streams or
travels through drainage systems.
The flows are then discharged,
untreated, into Georgetown
County’s drainage ways.
WHAT IS A WATERSHED?
An area of land that
drains to a single outlet.
Pee Dee Basin
(HUC4-0304)
Impervious Surfaces
Materials like cement, asphalt, roofing, and compacted
soil that prevent percolation of runoff into the ground.
Components of Impervious Cover in the Urban Landscape
Sidewalks
Roads
Driveways
Parking
Buildings
Center for Watershed Protection
Point Source
Pollution
Industrial/Commercial –
each discharge has its own
permit
Nonpoint Source
Pollution
Where does this go?
What is an Illicit Discharge?
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Georgetown County Stormwater
Ordinance defines an Illicit
Discharge as:
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“Any activity which results in a
discharge to the Georgetown County
Storm Water System or receiving
waters that is not composed entirely of
storm water, except a discharge
pursuant to an NPDES permit and other
allowable discharges as defined in this
Ordinance.”
Allowable Discharges
-Unless a significant contributor of pollutants
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Water line flushing
Landscape irrigation
Diverted stream flows
Rising ground water
Uncontaminated
ground water
infiltration
Uncontaminated
pumped ground water
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Discharges from
potable water sources
Foundation drains
Air conditioning
condensation
Irrigation water
Springs
Water from crawl
space pumps
“Uncontaminated” is the key word!
Sources of Stormwater Pollution
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Street Pavement
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Components of road surface degradation are
common constituents of urban runoff.
Motor Vehicles
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Contribute a wide variety of materials to runoff
flow.
 Fuels, lubricants, particles from tires or brake
lining, exhaust emissions which collect on the
roadway surface, corrosion products, parts
which fall from vehicles.
 Organics, nutrients and suspended solids
which have become attached to the vehicle
are washed onto the roadway by the action of
the rain or splashing from street runoff.
Sources (cont’d)
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Atmospheric Fallout
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Air pollution such as dust and particles from
industrial practices, acid particles, heavy
metals from fossil fuel power plants, emissions
from automobiles and planes, and from
exposed land.
Vegetation
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Waste matter is an important source of organic
and nutrient pollutants in urban stormwater.
 Leaves, grass, and other plant material
that fall or become deposited in urban
areas may become part of the stormwater
runoff flows.
Sources (cont’d)
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Land Surface
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The type of ground cover found in a drainage
basin as well as the amount of vehicular and
pedestrian traffic is a function of land use and
will have a direct effect on the quality of
stormwater runoff in that area.
Litter
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Consists of various kinds of discarded material
such as food containers, packaging material
and animal waste.
In some areas, animal waste has been shown
to be a major contributor of both nutrients and
bacterial contamination in runoff
Sources (cont’d)
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Anti-Skid Compounds and
Chemicals
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Governments in cold weather regions
deploy large amounts of salts, sand,
and ash to provide better traction and
to melt ice.
These materials accumulate along the
roadway during the winter months and
become part of the snow melt when
spring arrives.
 Fertilizers, insecticides and herbicides are
often used for maintenance of roadside
areas.
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Sources (cont’d)
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Construction Sites
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Erosion of soil from land disturbing
during construction activities is a highly
visible source of suspended matter in
stormwater runoff.
Soil erosion is a major source of
stormwater solids for both urban and
suburban areas.
Components of Stormwater Runoff
 Suspended
Solids (Sediment)
 Nutrients
 Metals
 Oxygen
Demanding Substances
 Oils, Greases and Hydrocarbons
 Pathogens
Suspended Solids (Sediment)
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Material such as sand, silt, clay and
organic matter with a particle size larger
than dissolved molecules or ions.
The largest contributor by volume to
nonpoint source pollution in the U.S.
Studies indicate that other pollutants are
often bound or adsorbed onto suspended
particles, such as phosphorous, heavy
metals and organic compounds.
Suspended Solids (Sediment)
Impacts
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Nonpoint
Sources
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Agriculture
Silviculture
Urban Runoff
Construction
Mining
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Causes a decrease in transmission of light through water
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Decreases primary productivity of aquatic plants and
phytoplankton upon which other species feed
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Obscures sources of food, habitat, hiding places, and
nesting sites
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Interferes with mating activities that rely on sight and
delays reproductive timing
Effects on respiration and digestion of aquatic species
Decreases survival rates of fish eggs and sizes of fish
populations which may alter species composition
Increases temperature of surface water which increases
stratification and reduces oxygen in the lower layers
May affect surface water sources for drinking water
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Increases drinking water costs
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Deposition can clog conveyance systems and reduce water
storage
Decreases value for recreational and commercial activities
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Reduced aesthetic value, sport and commercial fish
populations
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Decreased boating and swimming activities
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Interference with navigation
Nutrients
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Plant nutrient such as nitrogen and
phosphorous, are common constituents of
nonpoint source runoff.
Stimulates growth of algae and other
aquatic plants and accelerates the
process of eutrophication.
Enter runoff through fertilizers, plant
matter, detergents and washing fluids,
soil leeching, animal wastes, and seepage
from septic tanks.
Nutrients
Impacts
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Nutrients promote premature aging of lakes and
estuaries (eutrophication)
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Nonpoint
Sources
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Agriculture
Silviculture
Urban Runoff
Construction
Septic Tanks
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Algal blooms caused by nutrients and the resulting
decay of organic materials create turbid conditions
that eliminate submerged aquatic vegetation and
destroy habitat and food sources for aquatic
animals and waterfowl
Blooms of toxic algae, such as blue-green species,
can affect health of swimmers and aesthetic
qualities of waterbodies
Excess algal growth favors survival of less desirable
fish species over more desirable/sensitive species
Interference with boating and fishing activities
Reduced quality of water supplies, including addition
of tastes and odors
Reduced dissolved oxygen levels can suffocate fish
species
Reduction of waterfront property value
Heavy Metals
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Originate from the operation of motor
vehicles, direct fallout and the
degradation of highway materials.
Gasoline (Pb), diesel fuel (Cd), exhaust
emissions (Pi,Ni), crankcase and
lubricating oils (Pb, Ni, Zn), grease (Zn,
Pb), tire wear (Cd,Zn).
The most abundant are lead, zinc and
copper which account for 90% of
dissolved heavy metals.
Most metals are present in particulate
form
Heavy Metals
Impacts
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Nonpoint
Sources
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Agriculture
Transportation
Urban Runoff
Construction
Mining
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Dissolved metals can create short term
and long term toxic impacts to
receiving waters.
Accumulate in bottom sediments,
posing risks to bottom-feeding
organisms and their predators
Affect reproduction rates and life
spans of aquatic species
Disrupt food chains in aquatic systems
Affect recreational and commercial
fishing
Affect water supplies
Oxygen Demanding Substances
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Include numerous organic materials which
are decomposed by microorganisms
thereby creating a need for oxygen.
This biochemical reaction results in the
use of dissolved oxygen in the water.
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Imposes a BOD (biochemical oxygen demand)
on the limited oxygen resources available in
waterbodies.
Oxygen used can be replenished through
Photosynthetic production by algae and
other green plants.
Oxygen Demanding Substances
Impacts
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Nonpoint
Sources
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Agriculture
Urban Runoff
Silviculture
Septic Tanks
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May cause oxygen depletion and fish
kills if introduced in high
concentrations
May alter species composition to make
them more tolerant of low D.O.
conditions.
Increase growth of anaerobic
microorganisms which produce byproducts responsible for odors in water
Low oxygen levels may increase
solubility of phosphorous and heavy
metals in the water column.
Oils, Greases and Hydrocarbons
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Organic chemicals cause concern because they
cannot be easily decomposed through biological
action and may persist for long periods.
Hydrocarbons come from fractions of oils and
greases resulting from transportation and
industrial sources, benzene from gasoline,
synthetic detergents, pesticides, herbicides, wood
preservatives, a wide range of industrial
chemicals.
Because there is no mechanism by which nature
can rapidly cleanse itself of these compounds,
even low concentrations can accumulate in the
environment and reach dangerous concentrations.
Oils, Greases and Hydrocarbons
Impacts
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Nonpoint
Sources
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Agriculture
Urban Runoff
Silviculture
Construction
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All compounds can hinder photosynthesis in
plants
Can affect reproduction, respiration, growth
and development in aquatic species as well
as reduce food supply and destroy habitat
for aquatic species
If released to the aquatic environment
before degradation, many compounds can
kill non-target fish and other species.
Pesticides/herbicides bioaccumulate in
tissues of fish
Health hazard from human consumption of
contaminated fish/water
Pathogens
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Includes a wide variety of organisms such as
bacteria, fungi, viruses, protozoans capable of
transmitting disease and having an adverse
impact on human health.
Primary sources include, animal wastes, illegal
wastewater connections into stormsewer lines,
seepage of groundwater containing pathogens
into sewer lines and septic tanks.
The principle indicator of pathogen contamination
is coliform bacteria.
Murrells Inlet shellfish beds close after a heavy
rain due to high counts of fecal.
Pathogens
Impacts
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Nonpoint
Sources
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Agriculture
Urban Runoff
Septic Tanks
Introduction of disease-bearing
organisms to surface waters
Reduced recreational usage
Increase in treatment costs for drinking
water
Human health hazards
Removal of Pollutants
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Particulate Pollutants
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Unhindered settling of particles
Dissolved Pollutants
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Wide variety of chemical, physical and
biological processes are responsible
Chemical precipitation, adsorption onto
plant surfaces, suspended solids,
biological uptake by algae, bacterial
decomposition
Removal (cont’d)
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Oxygen Demanding Wastes
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Occurs through simple oxidation of
organic matter by aerobic bacteria and
fungi.
Generally complete within 3-5 days.
Heavy Metals
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Deposition of metals into sediments
pH must be kept at 6-8 to keep metals
bound to sediments
Removal (cont’d)
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Pathogens
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Die off, coagulation, predation by zooplankton,
and adsorption onto suspended matter with
deposition into the bottom sediments.
Best treatment is to investigate and reduce the
sources within the watershed.
Oils, Greases, and Hydrocarbons
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Retain by using oil skimmers at the discharge
point
Reducing pesticides by controlling the sources
of these compounds
Hydrocarbons often float on water surface and
are removed by volatilization.
What you can do to help
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Recycle
Pick up pet waste
Beach sweep
Volunteer
Raingardens & Bioretention
Get Involved!
SW Contact
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Stormwater office can be reached at:
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(843) 545-3524
[email protected]
www.georgetowncountysc.org
www.GeorgetownCountyCleanWater.com
–Coming Soon
Downstream pollution leads to
upstream source