Andrea Ludwig, PhD, EIT Assistant Professor Biosystems Engineering and Soil Science University of Tennessee

Transcription

1 Andrea Ludwig, PhD, EIT Assistant Professor Biosystems Engineering and Soil Science University of Tennessee

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6 Urban Development Stormwater NPDES Permits Phase I (n=4); pop>100,000 Phase II (n=86); pop.10,000 or density>1,000/mi 2 6

7 (Booth et al., 2002) ( 7

8 Urban Stream Syndrome (Walsh et al., 2005) Flashy hydrology Elevated nutrient and sediment concentrations Altered channel shape Decreased biodiversity

9 Pollutants of Concern in Urban Stormwater Runoff Type Source Potential Impact Nutrients (N,P) Fertilizers Eutrophication Metals (Ni, Cd, Ba, Zn, Cu, Pb, Fe, Mn) Tire wear, brake liners, engine wear, gasoline, weathered roofing and infrastructure Toxic to aquatic life Sediment Construction sites Loss of habitat Pathogens Leaky sewers, pet wastes No contact waters, fish parasites Organics Yard wastes, leaky sewers Unhealthy shifts in DO Pesticides/Herbicides Lawns and recreational areas Toxic to aquatic life Petroleum Leaky cars, roadway spills Toxic to aquatic life Sodium, Calcium, Chloride Deicing salts Degrades soil health 9

10 Watershed Management Techniques and Practices Divide 1 st Order Stream Watershed Low Impact Development /Green Infrastructure Floodplain and Wetland Restoration Stream Restoration and Aquatic Buffers 2 nd Order Stream

11 What is Low Impact Development? Using sustainable design principles and engineered practices to mimic natural hydrology. Figure Credit: Maudy Budipradigdo, after Auckland Council 11

12 History of Green Infrastructure and Low Impact Development 1992 T. Scheuler Mitigating the Adverse Impacts of Urbanization on Streams: A Comprehensive Strategy for Local Government. In Watershed Restoration Sourcebook. Publication #92701 of the Metropolitan Washington Council of Governments, edited by P. Kumble and T. Schueler Low-Impact Development Design Strategies, Prince George s County, Maryland EPA Water Quality Score Card integrates Green Infrastructure. Now regulated capture volumes/rainfall depths for new and redevelopment projects. 12

13 DBA MS4 Municipal Separate Storm Sewer System LID Low Impact Development SCM Stormwater Control Measure BMP Best Management Practice 13

14 5. Post-Construction Management in New Development and Redevelopment Why? Uncontrolled and untreated runoff increases the type and quantity of pollutants, quantity of water delivered to waterways. What is required? Implement BMP strategies Regulatory mechanisms Ensure long-term operation and maintenance Determine appropriate BMPs and measureable goals Avoid, Minimize, Manage 14

15 Non-Structural Practices that Avoid and Minimize Stormwater Generation Site planning to preserve green space Protecting native soils or infiltrateable soils Preserving natural drainage patterns Maintaining urban forests and riparian buffers Minimize impervious surface footprint (Natural Land Trust) 15

16 Structural Practices to Manage Stormwater Goal: Maintain natural hydrology of a site Strategy: Implement and design practices to mimic natural hydrology Post-construction stormwater - Stormwater BMPs = Pre-construction hydrologic conditions 16

17 Extended Detention, Wet Ponds (VA DCR, 2000) 17

18 Dry Detention Pond Retrofit to Create Storage 18

19 Constructed Stormwater Wetlands (Stormwater Center) 19

20 Bioretention (Residential Rain Gardens) Metro Nashville 20

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23 Bioretention (Parking Lot) 23

24 Bioretention (Green Street Planters/Ultra Urban) A linear practices that filters roadway stormwater through media and vegetation. City of Sandy, Oregon 24

25 Bioswales or Water Quality Swales 25

26 Regenerative Stormwater Conveyance (RSC) Underwood & Associates Patent US

27 Permeable Pavements Belgard Hardscapes, Inc. 27

28 Combination BMP! 28

29 Increasing Retention with Low Impact Development Avoid, Minimize, Manage Site planning to preserve functioning hydrology. BMP solution as close to the source as possible. Preventative maintenance. 29

30 Retrofit Challenges Finding the space to create storage Altered soils The UNKNOWN!! 30

31 Residential, Lot-scale Practices Downspout Disconnection Rainwater Harvesting 31

32 Commercial and Mixed Use 32

33 Construction & Permanent Stormwater BMP Performance (only as effective as weakest link) Design Calculations Correct Incorrect Design Plans & Specifications Incorrect Correct Adequate Inadequate Operation & Maintenance Correct Incorrect Construction (As-built inspections) 33

34 Get the Community Involved! 34

35 Additional Resources Center For Watershed Protection Low Impact Development Center USEPA Water Quality Scorecard tm USEPA National BMP Menu s/ International Stormwater BMP Database 35

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