Urban Stormwater Management

Transcription

1 State Regulations and Sustainable Infrastructure April 16, 2011 Urban Stormwater Management Drivers Ecosystem Services LID and Light Imprint New Urbanism Comments MD Stormwater Regulations Larry S. Coffman LNSB, LLLP Stormwater Services Low Impact Development (LID) and Other Green Design Strategies

2 Stormwater Management Drivers 1. Chesapeake Bay Program TMDL (N, P & Sediment) * WIPs * Goal - NPDES Phase I - 30% Urban Retrofit NPDES Phase II - 20% Urban Retrofit 2. MDE 2010 Stormwater Regulations * Redevelopment - Treat 50% of Impervious Surfaces * Preference for ESD (LID) * Concept Plan 3. EPA New NPDES Stormwater Program Requirement * Volume Control * Green Infrastructure (LID) 4. Conventional SWM (Pipe & Pond) is not protective!

3 B-IBI w/bmps B-IBI w/o BMPs Watershed Urbanization (%TIA) Figure 2: Showing the lack of mitigating influence of structural BMPs on biologic conditions in Puget Sound lowland streams (Horner and May, 2000). Note, w/bmps refers to structural facilities only. [Honer / May 2001]

4 Watersheds containing less than 10 percent impervious surface maintain healthy streams (CWP Schuler).

5 Watersheds containing less than 10 percent impervious surface maintain healthy streams (CWP Schuler).

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7 Since 1985, sediment loads in the bay from urban or suburban sources have increased by 57 percent, while phosphorus loads have increased by 67 percent and nitrogen loads have increased by 90 percent. impervious surfaces comprise less than 5% of the total Bay watershed (EPA) Office of Inspector General 2007 The Envirocast Newsletter 2002

8 Oak Ridge National Laboratory

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10 Historic site of the Port of Bladensburg

11 Special Protective Area Limit Impervious (12%) Wide Stream Buffers Stormwater Controls

12 Ecosystem Integrity & Ecological Services / Functions Scale / Spatial / Temporal / Species Nutrients Temperature D.O. ph Turbidity Organics Toxics Biotic Factors Disease Reproduction Feeding Predation Competition Chemical Variables Ecosystem Integrity Energy Sources Flow Regime Habitat Structure Sunlight Nutrients Seasonal Cycles Organic Matter 1&2 Production Velocity Frequency Runoff Evaporation Ground Water Flow Duration Rain Intensity Canopy Siltation Gradient Substrate Current Instream Cover Sinuosity Width/Depth Channel Morphology Soils Stability Riparian Vegetation

13 Imperviousness & Threshold Theories It s not so simple - very complex! Source: Schuler and Claytor, 1995

14 Natural Conditions Courtesy May, U of W

15 Soil Ecosystem Services / Functions Physical / Chemical / Biological 1. Hydrology storage / evaporation / recharge / detention 2. Storing Cycling Nutrients (bacteria / fungi) phosphorous / nitrogen / carbon 3. Plant Productivity (vigor) 4. Water Quality filter / buffer / degrade / immobilize detoxify organic and inorganic materials Watershed s Ecological Services

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17 Ecological Services Water Quality Regulated Temperature - Regulated Runoff Volume Regulated Stream Flow - Regulated Habitat Diverse Ecological Services Water Quality Pollutes Temperature - Unregulated Runoff Volume Unregulated Stream Flow - Unregulated Habitat Degraded

18 Degraded and Dysfunctional Streams

19 Urban Development Washington D.C. Urbanization causes the systematic loss of ecological services Hydro- illogical Potomac River Anacostia River

20 Background 1992 Bioretention Guidelines 1997 County LID Guidelines 2000 National LID Guidelines

21 LID Ecosystem Based Stormwater Management Goal Maintain / Restore the Water Balance (Hydrologic Processes) Increase the Assimilative Capacity of landscape & Architecture Principles Optimize conservation Decentralized / Integrated Cumulative Impacts Same Engineering Principles at Smaller Scale Retain / Detain / Filter / Infiltrate / Treat / Prevent / Use New Development Process Conserve / Minimize / Timing / Integrate Practices / Prevent

22 Only LID (ESD) Provides The Tools To Restore Ecological Services

23 Single Family Residential LID Techniques Tools Conservation Minimize clearing Minimize grading Save sandy soils Amended soils Reforestation Disconnect impervious surfaces Limit use of concrete conveyances Vegetative swales Rain gardens Porous surfaces Reduce impervious surfaces Rain Water Harvesting Infiltration devices Detention devices Vegetative buffers Save drainage patterns

24 Multi Family Residential LID Techniques Tools Conservation Minimize clearing Minimize grading Save sandy soils Reforestation Disconnect Impervious Surfaces Limit use of concrete conveyances Vegetative swales Rain gardens Porous surfaces Reduce impervious surface s Rain Water Harvesting Infiltration Detention Devices Vegetative Buffers Save Drainage Patterns

25 Big Box Commercial LID Techniques Tools Porous pavers Tree box filters Green roofs Bioswales Disconnect impervious surfaces Vegetative swales Rain gardens / bioretention Porous surfaces Reduce impervious surfaces Rain Water Harvesting Infiltration devices Detention Devices Vegetative Buffers Save Drainage Patterns

26 High Density Mix Use LID Techniques Tools Conservation Minimize clearing Minimize grading Save sandy soils Reforestation Disconnect Impervious Surfaces Limit use of concrete conveyances Vegetative swales Rain gardens Porous surfaces Reduce impervious surface s Rain Water Harvesting Infiltration Detention Devices Vegetative Buffers Save Drainage Patterns

27 Light Imprint Tool Box Matrix LID Applications by Density Paving Drainage Storage Filtration

28 Alhambra

29 WHY IS LID SO ATTRACTIVE? Universally Applicable Economically Sustainable Ecologically Sustainable Lower Costs (Construction, Maintenance & Operation) Multiple Benefits (air / water / energy / property values) Silent on Growth Management Ideal for Urban Retrofit (quality and quantity) Water Supply Public Acceptance

30 Maryland 2010 SWM Regs. Issues 1. Cost Increases Redevelopment and Infill Additional Planning & Engineering Cost 2. Limited LID Options 3. Limited Credit for LIDs 4. Overly Prescriptive Design Standards 5. Deficient Design Standards (bioretention ) 6. Sizing method too conservative (over size LID) 7. Discourages Innovation

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32 Density is not a Stormwater BMP!!!! 2005 Smart Growth Study EPA NRCS Model (CN Averaging) Average Results / unit (solution to pollution is dilution) 10% / 25% Impervious Supporting Impact Reduction is protective No empirical data none All Hypothetical Arguments

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