1. Low Impact Development and Stormwater Management in Pennsylvania Catherine Chomat, P.E. F. X. Browne, Inc Brian Oram, PG Wilkes University Dr. Robert Traver, P.E. Villanova University

2. Impacts of Stormwater Runoff on Aquatic Ecosystems

3. Impacts of Stormwater Runoff on Aquatic Systems Historical Perspective EPA 2000 Water Quality Report Water Quality-Ecosystem Impacts

4. Wastewater Treatment Since 1970… STP Construction$239 Billion STP Operations$234 Billion EPA Needs Survey $84 Billion Needed for new STPs for year 2008

5. Wastewater Treatment Populations Served by STPs 197285 million people 1988150 million people From 1972 to 1988… 4000 new sewer systems 2000 new STPs

6. Wastewater Treatment 1988:Less than 1% of U.S. Population discharges untreated wastewater Meeting Effluent Criteria Industrial93% Municipal87%

11. Summary of Quality of Assessed Rivers, Lakes, and Estuaries

12. Leading Causes and Sources* of Impairment in Assessed Rivers, Lakes and Estuaries

13. Development Activities Site Clearing and Grading Tree Removal Loss of Natural Depressions (Storage) Loss of Topsoil/Humus Loss of Pervious Area/Percolation Increase in Impervious Area Increase in Runoff

14. Development Impacts on Water Quality 1. Watershed Hydrology 2. Stream Geometry 3. Degradation of Aquatic Ecosystems 4.Pollutant Export During Construction 5.Pollutant Export After Site Development

16. Impervious Cover as an Indicator of Stream Health (Schueler 1995) CharacteristicSensitiveDegradingNon-Supporting Percent Impervious Cover 0% to 10%11% to 25%26% to 100% Channel StabilityStableUnstableHighly Unstable Water QualityGood to ExcellentFair to GoodFair to Poor Stream BiodiversityGood to ExcellentFair to GoodPoor Pollutants of ConcernSediment and temperature only Also nutrients and metals Also bacteria

17. 1. Watershed Hydrology 1. Reduced Infiltration 2.Increased Peak Discharges 2-5x Predevelopment 3.Increased Volume of Runoff Moderately Developed – 50% more runoff 4.Decreased Time of Concentration “Time Runoff Reaches Stream” as much as 50% lower 5.Increased Flooding Frequency & Severity Bankfull conditions: Natural…Once every 2 years Developed…3-4 times per year 6.Reduced Base Streamflow Due to Loss of Groundwater 7.Higher Runoff Velocity

18. Changes in Hydrology Due to Development

19. Hydrology Changes Due to Development

20. Parking Lot vs. Meadow ParameterParking LotMeadow Runoff Coefficient 0.95 0.06 Time of Concentration (minutes) 4.8 14.4 Peak Discharge (cfs) 2-Year 4.3 0.4 100-Year Storm 12.6 3.1 Runoff Volume (cu. ft.) 3,450 218 Runoff Velocity 2-Year Storm (fps) 8 1.8

23. COMPARISON OF RUNOFF VOLUME BETWEEN UNDEVELOPED AND DEVELOPED CONDITIONS STORM FREQUENCY (years) 24-HOUR RAINFALL (inches) ESTIMATED RUNOFF (inches) Undevel. Devel. RUNOFF AS PERCENT OF RAINFALL Undevel. Devel. 22.80.140.605%21% 104.00.531.3313%33% 1005.81.402.6424%46%

24. 2. STREAM GEOMETRY 1.Channel Widening Developed Area Streams: 2 to 4 times original size Streambank Erosion Increased Pollutant Loads 2.Increase in Floodplain 3.Undercut Streambanks 4.Siltation of Stream Stream Bedload Substrate Changes (Biota Changes)

25. Physical Impacts of Impervious Cover

31. 3.DEGRADATION OF AQUATIC ECOSYSTEMS 1.Cumulative Effects Scouring Sedimentation Velocity Streamflow Organic Matter - Biochemical Oxygen Demand Dissolved Oxygen Nutrients Toxics Chlorides

32. 3.DEGRADATION OF AQUATIC ECOSYSTEMS 2.Temperature Increase in % Impervious  Increases Temp. Adverse Impact on -Algae -Macroinvertebrates -Fish

33. Temperature % Impervious Area

35. 3.DEGRADATION OF AQUATIC ECOSYSTEMS 3.Fish and Macroinvertebrates – Decrease in …Diversity …Populations …Clean Water Species Increase in Pollution Tolerant Species

38. URBAN RUNOFF POLLUTANTS Sediments Nutrients Bacteria Organic Matter Hydrocarbons Metals Toxic Chemicals Chlorides 3. Degradation of Aquatic Ecosystems

39. SEDIMENTS Produced by:Construction Erosion Developed Area Erosion Washoff Streambank Erosion Problems:Turbidity Reduced Light Penetration Clogging of Gills/Filters (Fish & macroinvertebrates) Reduced Spawning Habitat Destruction Nutrients Metals Toxics Metals and Phosphorus Attach to Sediments

41. NUTRIENTS Nitrogen (TN, NH 3, NO 3, Organic-N) Phosphorus (TP, PO 4, SRP) Eutrophication of Lakes, Impoundments & Large Rivers PROBLEMS: Excessive Algae and Aquatic Weeds Dissolved Oxygen Depletion Taste & Odor Problems Fish Kills Loss of Recreation Toxins Increased Water Treatment Costs

43. Wet vs. Dry Weather

44. Stream Hydrograph Total Phosphorus Concentrations

45. Stream Hydrograph Total Suspended Solids Concentrations

46. BACTERIA Always Found in Urban Runoff Often Exceed Health Standards More Developed – More Bacteria Older Developed – More Bacteria Special Problem Areas: Combined Sewer Areas Sewer Overflow Areas

48. ORGANIC MATTER Biochemical Oxygen Demand (BOD) of Stormwater Runoff is High Causing: Decreased Dissolved Oxygen Stressed Aquatic Life Fish Kills Older, highly impervious areas – Highest BOD

49. Dissolved Oxygen in Stream 0.4 Inches of Rain

50. HYDROCARBONS Oil & Grease – Hydrocarbons Sources: Parking Lots Roads Gas Stations

51. METALS Toxic Affect on Aquatic Life Impact on Drinking Water Common Metals Lead Copper Zinc Caveats: 1. Only soluble form is toxic and available for biological uptake 2. Some are attached to sediment

52. TOXIC CHEMICALS NURP Studies: Scan of 120 Pollutants Small concentrations – no real problem Great Lakes – Contaminated Sediments Limited Data Base, Need More Data for Suburban, and Urban Ateas

53. CHLORIDES Snowmelt: 2,000-3,000 mg/L Chlorides  Soluble  Streams High Levels: Toxic to organisms

55. 4. POLLUTANT EXPORT DURING CONSTRUCTION Soil Erosion 35-45 Tons/Acre/Year – Uncontrolled 10 Times Agriculture and Developed Land

56. 5. POLLUTANT EXPORT AFTER DEVELOPMENT A. Impervious Area Washoff Dryfall & Wetfall Up to 90% Washoff Constituents Sediments Metals Nutrients Sources Buildings, Roofs, Pipes Pet Droppings Vegetative Matter Litter Debris “THE LAND TAKES A SHOWER”

57. 5. POLLUTANT EXPORT AFTER DEVELOPMENT B.Older Community – More Impervious Household Add-Ons C.Causes On-Site and Streambank Erosion

58. Unit Area Loads Total Phosphorus Load Use lb/ac/yr Forest0.1 – 0.35 Developed0.4 – 3.5 Commercial0.5 – 1.6 Agriculture0.36 – 1.52

59. Ultimate Concern Runoff Volume Velocity in Stream Streambank Erosion

60. Our Ultimate Goal