10/16/2013. The Big Picture of LID and Green Infrastructure. Learning Objectives

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1 Low impact development (LID) the basic idea behind LID is to manage stormwater in a way that imitates the natural hydrology of a site. Details Matter Selection, Design, and Implementation of Low Impact td Development t(lid) James L. Sipes,, ASLA Sand County Studios Bill Wenk,, FASLA Wenk Associates Andrew Earl,, Ph.D., P.E., D.WRE, CPESC, Wright Water Engineers 11 Common LID Practices 1. Impervious surface reduction and disconnection 2. Permeable pavers 3. Pollution prevention and good housekeeping 4. Rain barrels and cisterns 5. Rain gardens and bioretention 6. Roof leader disconnection 7. Rooftop gardens 8. Sidewalk storage 9. Soil amendments 10. Tree preservation 11. Vegetated swales, buffers, and strips Natural Resources Defense Council Learning Objectives 1. Learn green infrastructure concepts and their implementation at site to regional scales. 2. Understand the process for selecting the appropriate stormwater control measure, given treatment objectives and physical context. 3. Learn about appropriate BMP construction details maintenance requirements for proper function of stormwater control measures. 4. Learn about successes and failures of stormwater management measures considering plantings and construction details. Structural BMPs include: Infiltration systems, such as infiltration basins and porous pavement Detention systems, such as basins and underground vaults Retention systems, such as wet ponds Constructed wetland systems Filtration systems, such as media filters and bioretention systems Vegetated systems, such as grass filter strips and vegetated swales Minimizing directly connected impervious surfaces Miscellaneous and vendor supplied systems such as oil/water separators Hydrodynamic devices Structural practices to control urban runoff rely on four basic mechanisms: 1. Infiltration 2. Filtration 3. Detention/retention 4. Evaporation Nonstructural BMPs include: The Big Picture of LID and Green Infrastructure Automotive product and household hazardous material disposal Commercial and retail space good housekeeping Industrial good housekeeping Modified use of fertilizers, pesticides, and herbicides Lawn debris management Animal waste disposal Mit Maintenance practices such as catch thbasin cleaning, street tand parking lot sweeping, road and ditch maintenance Illicit discharge detection and elimination Educational and outreach programs Storm drain inlet stenciling Low impact development and land use planning 1

2 Detention Basins Atlanta BeltLine Fourth Ward Park Detention Basins A NEW SUSTAINABLE STANDARD Infiltration Bioretention Cells STORM WATER BENEFITS cfs) Flow (c Design Peak Green vs. Standard Green vs. Existing Scenario Event Discharge Percentage of Peak Percentage of Peak 100 Existing 2-Lane yr Existing 2-Lane 100 yr 30.4% 34.2% 90 Standard 4-Lane yr Standard 4-Lane Green 4-Lane yr Green 4-Lane Existing 2-Lane yr 26.8% 40.7% Standard 4-Lane Green 4-Lane Existing 2-Lane yr 27.2% 43.3% Standard 4-Lane Green 4-Lane Yr. flood is 20 contained inside the median with no 10 roadway flooding 0 7:00:00 10:00:00 13:00:00 16:00:00 19:00:00 22:00:00 Time 2

3 Site and Landscape Considerations Stormwater Detention & Water Quality FLOODING REQUIRES DETENTION Treatment SMALL STORMS REQUIRE WQ TREATMENT Detention helps to prevent flooding Storage of large flood volumes Water Quality treatment helps to keep our rivers and streams clean Filtration of small storm volumes District systems West Union, IA Charles City, Iowa Metrics:» Eliminated need for storm drainage system» Connected downtown Metrics:» Eliminated need for storm drainage system» Enhanced historic character of neighborhood 3

4 District systems Menomonee Valley Redevelopment Hutchinson Park District systems Menomonee Valley Redevelopment Taxi Phase II Development Denver, CO District systems Menomonee Valley Redevelopment Taxi Phase II Development 4

5 Taxi Phase II Development Poor detailing/ Difficult sediment removal Proximity of trees and vegetation results in Taxi Phase II Development Poor plant selection / no plan for sediment removal Principles for Success Plan early for water quality Consider all scales evaluate site constraints Reduce runoff rates Enhance site, community, environment Design for maintenance Barriers to Success Ineffective design team Indifferent (even hostile) reviewing agencies extended process Outdated standards / lack of awareness of related design professions Liability Cost concerns Poor plant selection/ high level of pollutants 5

6 Adequate plan for sediment removal/appropriate plantings Appropriate planting, system accommodates moderate sedimentation/ potential for removal Appropriate planting/ lacking infiltration media / lacking an underdrain Engineering Approach to Green Infrastructure Urban Drainage and Flood Control District criteria manual, volume 3 udfcd.org Inappropriate plantings-potential for sediment removal HYDROLOGY FOR WATER QUALITY Pre Development Hydrology Vegetation is Nature s BMP: It slows the flow Roots hold soil together Allows water to percolate into the ground Allows water to evaporate Filters/traps sediment 6

7 HYDROLOGY FOR WATER QUALITY Post Development Hydrology Paving, Concrete, Impervious Surfaces: Decrease in natural vegetation (sometimes dramatic) Higher peak discharges and greater runoffvolume More frequent runoff (more runoff events per year) Concentrates flows Increases potential for erosion and pollutant transport. Why are Stormwater Management and LID Important? IMPACT OF URBANIZATION ON STREAMFLOW ATE STREAMFLOW RA Large Storm Higher Baseflow Higher and More Rapid Higher Peak and Discharge More Rapid Peak Discharge Small Storm More Runoff Volume More Runoff Volume Lower and Less Rapid Lower Peak and Less Rapid Peak Gradual Recession Gradual Recession Pre-development Post-development Runoff Reduction TIME Source: Schuler, T.R Controlling Urban Runoff: A Practical Manual for Planning and Designing BMPs. Washington DC: Metro Council of Governments. Four Step Process Directly Connected Impervious Area This is what we want to avoid! 7

8 Runoff Reduction Treat the Water Quality Capture Volume Minimize Directly Connected Impervious Area Runoff Directed to Landscape Number of Rainfall Events in the Denver Area Total Rainfall Depth (inches) Average Annual Number of Storm Events 0.0 to to to to to to to to >5.0 0 Total 75 Runoff Reduction Maximized Water Quality Volume Reduce Impervious Area 8

9 Water Quality Capture Volume (WQCV) WQCV = Capture volume (watershed inches) I = Imperviousness (%) a = Coefficient for drain time Drain Time (hrs) Coefficient, a 6 hours hours hours hours 1.0 Primary, Secondary and Incidental Treatment Process Provided by BMPs MDCIA Practices (without WQCV) WQCV Facilities Design dependent Bioretention Sand/ s Paveground Perviou Under- Pervious Grass Grass Wetland Pavement Wetland Ret. Green (Porous EDB Media ment BMPs Swale Buffer Channel (no Basin Pond Roof Landscape Filter (with (various storage) Detention) storage) types) Functions Pretreatment LID/Volume Reduction WQCV WQCV + Detention Effectiveness for Targeted Pollutants WQCV Evapotranspiration Adsorption/ Biological BMP Infiltration Sedimentation Filtration Straining Attenuation Absorption Uptake Grass Swale I S I S S P S S Grass Buffer I S I S S P S S Constructed Wetland I N/A P P S P S P Channel Green Roof I S P N/A P N/A I P Pervious Pavement P * P N/A N/A P N/A N/A N/A System Rain Garden P P S P P S S P ** Extended Dry Detention P I I P N/A S S I Basin Sand Filter Extended P P I P P N/A S ** N/A Detention Constructed Wetland P I P P S S P P Basin Retention Pond P I P P N/A N/A P S Underground BMPs Variable N/A N/A Variable Variable Variable Variable N/A P = Primary; S = Secondary, I = Incidental; N/A = Not Applicable * If storage is provided ** Depending on media WQCV Chart WQCV Varies with Drain Time hour Drain Time 0.40 WQCV (wat tershed inches) WQCV=a*(0.91i i i) 6-hr drain time a = hr drain time a = hr drain time a = hr drain time a = hour Drain Time Stabilize Drainageways hour Drain Time hour Drain Time Total Imperviousness Ratio (i = I wq/100) Best Management Practices (BMPs), Functions & Considerations Water Quality, Channel Protection & Flooding Sediment & Solids Nutrients Total Metals Bacteria Other Considerations Land Med Med Med Low High High High High High Low Low Low Requirements Capital Costs Low Low Low High High High High High High High High High Life cycle Costs Low Low Low Med Med Med Med Med Med Med Med High Maintenance Frequency/ Costs Low Low Low Med Med Med Med Med Med Med Med High 9