Presentation on theme: "Stormwater Chemistry and Water Quality"— Presentation transcript:
1 Stormwater Chemistry and Water Quality Georgetown County Stormwater DivisionTracy Jones, P.E. – Division ManagerZollie Green, P.E. – Senior EngineerShelly Jordan – Quality/Billing CoordinatorChris Allen – Inspector
2 What we do? Plan Reviews Inspections Capital Projects Drainage ComplaintsUtility FeeFunds our division
3 What is Stormwater?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.
4 An area of land that drains to a single outlet. WHAT IS A WATERSHED?One of the Consortium’s goals is to maximize efficiency of stormwater education efforts using a regional watershed approach.You must first understand how a watershed works - A watershed is simply a natural drainage basin where all water flows into a common outlet.Watershed can be viewed on many different scales – basin, tributary, 1 branch of tributary, etc.An area of land that drains to a single outlet.4
5 Pee Dee Basin (HUC4-0304)Watersheds provide a framework for looking at natural resources independent of jurisdictional boundaries (state, county, municipal…).The county’s drainage area is a part of a very large basin, the Pee Dee Basin, which lies in 3 states – 2 million acres just in SC (11.6 million total acreage). The blue lines represent the major rivers and creeks.5
6 Quick review of the water cycle shows In an undisturbed environment, water falls to the ground either hitting the surface and running off, or percolating through the soil into the groundwater.Through both pathways, water makes its way into our creeks, ponds, wetlands, rivers, and oceans.6
7 As we develop and alter the landscape, this natural cycle is disturbed, impacting both water quality and water quantity.Increased runoff brings more frequent and more severe flooding.Decreased infiltration means less groundwater recharge and a decrease in base flow to streams.The result is that more pollution is reaching our waterways7
8 Impervious SurfacesPolluted runoff includes pollutants being washed off of hard surfaces.These hard surfaces are examples of impervious surfaces which include roads, sidewalks, rooftops, and parking lots.All of these prevent infiltration of runoff into the ground.Materials like cement, asphalt, roofing, and compacted soil that prevent percolation of runoff into the ground.8
9 Components of Impervious Cover in the Urban Landscape SidewalksRoadsParkingDrivewaysHere’s a few examples of impervious cover …What is your guess as to how much imperviousness?57% in this slideBuildingsCenter for Watershed Protection9
10 Point Source Pollution Nonpoint Source Pollution Traditionally, the focus of water quality control has been on POINT SOURCES of pollution. These point sources represent direct discharges from industrial facilities, sewage treatment plants, etc. In the last 30 years, since the introduction of the Clean Water Act, these point sources have been largely cleaned up. Despite this reduction in point sources, pollution problems have not gone away.This has caused a shift in focus to what is now the #1 water quality problem in the US, polluted runoff. Polluted runoff is one example of nonpoint source pollution, that is pollution that comes from diffuse sources. Some types of air pollution are considered to be nonpoint in nature.Polluted runoff is usually created when rainwater washes over the land and picks up a variety of pollutants along the way ending in a watershed or drainage area. Examples of nonpoint source pollutants include:- oil from cars- fertilizers from lawns and farms- garbage tossed on the side of the roadPolluted runoff is what we will focus on today, both because it is such a problem, and because it can be difficult to address due to the diffuse nature of its sources. To reduce these sources, we must first understand what they are and where they are.Industrial/Commercial – each discharge has its own permitNPDES TRI & PCSWhere does this go?10
11 What is an Illicit Discharge? Georgetown County Stormwater Ordinance defines an Illicit Discharge as:“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.”
12 Allowable Discharges -Unless a significant contributor of pollutants Water line flushingLandscape irrigationDiverted stream flowsRising ground waterUncontaminated ground water infiltrationUncontaminated pumped ground waterDischarges from potable water sourcesFoundation drainsAir conditioning condensationIrrigation waterSpringsWater from crawl space pumps
14 Sources of Stormwater Pollution Street PavementComponents of road surface degradation are common constituents of urban runoff.Motor VehiclesContribute 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.
15 Sources (cont’d) Atmospheric Fallout Vegetation 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.VegetationWaste 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.
16 Sources (cont’d) Land Surface Litter 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.LitterConsists 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
17 Sources (cont’d) Anti-Skid Compounds and Chemicals 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.
18 Sources (cont’d) Construction Sites 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.
19 Components of Stormwater Runoff Suspended Solids (Sediment)NutrientsMetalsOxygen Demanding SubstancesOils, Greases and HydrocarbonsPathogens19
20 Suspended Solids (Sediment) 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.
21 Suspended Solids (Sediment) ImpactsCauses a decrease in transmission of light through waterDecreases primary productivity of aquatic plants and phytoplankton upon which other species feedObscures sources of food, habitat, hiding places, and nesting sitesInterferes with mating activities that rely on sight and delays reproductive timingEffects on respiration and digestion of aquatic speciesDecreases survival rates of fish eggs and sizes of fish populations which may alter species compositionIncreases temperature of surface water which increases stratification and reduces oxygen in the lower layersMay affect surface water sources for drinking waterIncreases drinking water costsDeposition can clog conveyance systems and reduce water storageDecreases value for recreational and commercial activitiesReduced aesthetic value, sport and commercial fish populationsDecreased boating and swimming activitiesInterference with navigationNonpoint SourcesAgricultureSilvicultureUrban RunoffConstructionMining
22 NutrientsPlant 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.
23 NutrientsImpactsNutrients promote premature aging of lakes and estuaries (eutrophication)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 waterfowlBlooms of toxic algae, such as blue-green species, can affect health of swimmers and aesthetic qualities of waterbodiesExcess algal growth favors survival of less desirable fish species over more desirable/sensitive speciesInterference with boating and fishing activitiesReduced quality of water supplies, including addition of tastes and odorsReduced dissolved oxygen levels can suffocate fish speciesReduction of waterfront property valueNonpoint SourcesAgricultureSilvicultureUrban RunoffConstructionSeptic Tanks
24 Heavy MetalsOriginate 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
25 Heavy MetalsImpactsDissolved 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 predatorsAffect reproduction rates and life spans of aquatic speciesDisrupt food chains in aquatic systemsAffect recreational and commercial fishingAffect water suppliesNonpoint SourcesAgricultureTransportationUrban RunoffConstructionMining
26 Oxygen Demanding Substances 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.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.
27 Oxygen Demanding Substances ImpactsMay cause oxygen depletion and fish kills if introduced in high concentrationsMay alter species composition to make them more tolerant of low D.O. conditions.Increase growth of anaerobic microorganisms which produce by-products responsible for odors in waterLow oxygen levels may increase solubility of phosphorous and heavy metals in the water column.Nonpoint SourcesAgricultureUrban RunoffSilvicultureSeptic Tanks
28 Oils, Greases and Hydrocarbons 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.
29 Oils, Greases and Hydrocarbons ImpactsAll compounds can hinder photosynthesis in plantsCan affect reproduction, respiration, growth and development in aquatic species as well as reduce food supply and destroy habitat for aquatic speciesIf released to the aquatic environment before degradation, many compounds can kill non-target fish and other species.Pesticides/herbicides bioaccumulate in tissues of fishHealth hazard from human consumption of contaminated fish/waterNonpoint SourcesAgricultureUrban RunoffSilvicultureConstruction
30 PathogensIncludes 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.
31 PathogensImpactsIntroduction of disease-bearing organisms to surface watersReduced recreational usageIncrease in treatment costs for drinking waterHuman health hazardsNonpoint SourcesAgricultureUrban RunoffSeptic Tanks
32 Removal of Pollutants Particulate Pollutants Dissolved Pollutants Unhindered settling of particlesDissolved PollutantsWide variety of chemical, physical and biological processes are responsibleChemical precipitation, adsorption onto plant surfaces, suspended solids, biological uptake by algae, bacterial decomposition
33 Removal (cont’d) Oxygen Demanding Wastes Heavy Metals Occurs through simple oxidation of organic matter by aerobic bacteria and fungi.Generally complete within 3-5 days.Heavy MetalsDeposition of metals into sedimentspH must be kept at 6-8 to keep metals bound to sediments
34 Removal (cont’d) Pathogens Oils, Greases, and Hydrocarbons 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 HydrocarbonsRetain by using oil skimmers at the discharge pointReducing pesticides by controlling the sources of these compoundsHydrocarbons often float on water surface and are removed by volatilization.
35 What you can do to help Recycle Pick up pet waste Beach sweep VolunteerRaingardens & BioretentionGet Involved!
36 SW Contact Stormwater office can be reached at: (843) 545-3524 –Coming Soon