Map Reading 201: Where Does the Water Go?? Today s Presenters: John Rozum, NEMO Program Paula Stahl, Green Valley Institute A Key Skill for Land Use Commissioners As the map is rolled out at the P&Z meeting... Map Reading 101.. 201 Wonder what those lines mean? Where is this? I m hungry. Oh, geeze I ll never get home in time for the game Topics requested: Stormwater Systems Grading and Drainage Cut and Fill Road Design Design Guidelines and more Map Reading 201 Interconnected Systems Today s Topics: Stormwater Basics Plan Reading for Stormwater Conventional Systems Alternatives
Interconnected Systems Interconnected Systems Interrupted Systems Stormwater: Water from rain or melted snow that cannot be absorbed into the ground where it falls onto impervious surface.. streets and roads parking lots roof-tops Stormwater Management Plans GOAL: Minimize impacts from non-point pollution, Control down stream erosion and flooding, and Preserve the natural hydrologic cycle
Stormwater Systems: The Options Stormwater Systems: Conventional Conventional Cs Collect Convey Centralized Low Impact Streets and Roads Parking Lots Rooftops Stormwater Systems: Conventional Stormwater Systems: Conventional Collect Convey Centralized Most municipal systems Collect Convey to a Centralized Stream Plan Reading - Tips Plan Reading - Tips Water flows downhill... Water flows downhill... so the direction of flow is always perpendicular to the contour lines, since this is the steepest slope.
Roads Roads Roads Existing Topo 41 41 42 Roads 41 41 42 42 42 Roads Roads Two basic designs Crowned 20 18 16 14 12 Cross sloped 20 18 16 14 12 500 496 492 488 484 480 476 472 468 0+00 6+00 11+55 20 vertical scale increased to show detail Distance is 1155 Change in Elevation is 26 (494-468) Slope =2.25%
Roads Parking Lots 500 496 492 488 484 480 476 472 468 0+00 6+00 11+55 Distance is 1155 Change in Elevation is 26 (494-468) Slope =2.25% Stormwater Collection & Conveyance Stormwater Collection & Conveyance Plan Review Stormwater System Plan Review Stormwater System Water flows downhill... But sumps aren t perfect...
Plan Review Stormwater System Plan Review Stormwater System TF Top of Flange, or aka Rim or CBR System Schematic Bottom of Invert pipe usually is even with top of Outlet pipe TF 609.10 EO 600.50 INV or Invert where storm water enters catch basin OUT or Outlet where storm water leaves catch basin BP 559 Question: Any concerns? Rooftops Rooftops Collect Convey Centralized Rooftops Rooftops
As the map is rolled out at the P&Z meeting... Plan Reading Tip take ownership! Oh, that LUA workshop is going to come in handy! Interconnected System I bet there s a better way. Why Stormwater Matters Stormwater Systems: C s Collect Convey Centralized Conventional More Runoff Arriving Faster
Stormwater Systems: Low Impact Stormwater Systems: a better approach 3Ds Distributed Disconnected De-centralized Low Impact Development (LID): A site design strategy intended to maintain or replicate a site s natural hydrology systems through the use of small-scale controls integrated throughout the site to manage runoff as close to its source as possible LID Connecticut-style Subdivision Jordan Cove Glen Brook Green (Jordan Cove) Research/Demo Project LID Cluster Bio-retention cul-de-sac Low-mow areas Bio-retention gardens Shared Driveways & Porous Pavers Traditional Grass swales 12 Lots on 4 acres with 6.3 acres open space Using many LID strategies Street 24 wide, loop 16 wide But Does It Work? More Runoff Arriving Faster Jordan Cove Monitoring Results Before vs. after construction LID Traditional Flow Nitrogen Phosphorus Metals TSS nc Traditional LID Adapted from J. Clausen, UConn The big picture: LID significantly reduced flow and pollutant export!!
A NEW Way to Deal with Stormwater The Runoff Reduction Method Strategy includes: 1. Minimizing disturbance through Environmental Site Design 2. Runoff Reduction Practices 3. Pollutant Removal Practices Runoff Reduction Methods Minimizing disturbance through Environmental Site Design 1. Site Design that Minimizes Impervious Cover & Soil Disturbance 2. Conservation of Forested Areas 3. Reforestation of Cleared Areas Runoff Reduction Practices Pollutant Removal Practices Environmental Site Design Cluster design Zoning regulations to limit site clearing Environmental Site Design Minimize disturbance Buffer streams and wetlands Protects water bodies from development impacts Research shows that buffers can mitigate the effect of impervious surfaces, up to about 15% IC* In addition, there are many benefits beyond water quality *Schueler, et al. 2008. Chesapeake Stormwater Network Environmental Site Design Reduce impervious cover Decrease pavement requirements Use porous pavement on walks and overflow parking areas Runoff Reduction Methods Minimizing disturbance through Environmental Site Design Runoff Reduction Practices 1. LID Practices 2. Rooftop Disconnect 3. Sheet flow to Conserved Open Space Pollutant Removal Practices
Low Impact Development Reduce Runoff Practices Interrupt sheet flow Pervious parking Grass swales Green roofs Bioretention (rain gardens) Rain Barrels/Cisterns Runoff Reduction Methods Minimizing disturbance through Environmental Site Design Runoff Reduction Practices Pollutant Removal Practices 1. Filtering Practices 2. Constructed Wetlands 3. Wet Ponds 4. Wet Swales 5. Many LID Practices Low Impact Development Practices Bioretention/Rain Gardens Vegetated Swales, Buffers, and Filter Strips Permeable Pavements Dry Wells/Leaching Trenches Rainwater Harvesting Vegetated Roof Covers LID Practices Bioretention/Rain Gardens Flow entrance Ponding area Soil, mulch and plants Overflow path Vegetated areas designed to infiltrate and process stormwater
Key Bioretention Concepts Rules of Thumb: No closer than 10 to building foundation Basin depth should handle first 1 of runoff Inflow and outflow need to be detailed Soil perc should be tested and verified before construction Planting plan should specify appropriate plants Runoff Reduction: 40-80% Pollution Reduction: 25-50% Important factors with bioretention Infiltration capacity of native soils Underdrain Recommended in Bioretention Manual & CT SWQM May not always be necessary Depends on local soil conditions From 2004 CT Stormwater Quality Manual Design variation: high sediments Heavy sediment loading may clog infiltrating surface of bioretention A grass filter strip or sediment forebay can be installed to reduce this impact Design variation: hot spots Hot spots are areas with high loadings of certain pollutants Impervious liner can be installed and pipe access can be provided (MD Bioretention Manual) Design variation: low permeability soils Extra storage can be gained by installing crushed stone below the underdrain (MD Bioretention Manual) Important factors with Bioretention Seasonal high water table Soil compaction before, during construction
Important factors with bioretention Over-Engineering Low Impact Development Practices Bioretention/Rain Gardens Vegetated Swales, Buffers, and Filter Strips Permeable Pavements Dry Wells/Leaching Trenches Rainwater Harvesting Vegetated Roof Covers LID Roads LID Road Water Quality Swales Runoff Reduction: 40-60% Pollution Reduction: 20-40% ROW Road is crowned to direct water to edges Stormwater infiltrates into the swale Benefits: Promote infiltration Most effective sediment removal Installation cost comparable to piped system Easier to maintain and troubleshoot LID Roads Key LID Subdivision Concepts Types of Swales Grass Channel Dry Water Quality Wet Water Quality Rules of Thumb Need grades of 5% or less Wide bottom and gentle side slopes Portland Oregon
Resources to help you In summary We have drastically altered the hydrologic cycle Traditional treatment practices really don t help much Proper S.W. Management starts with Site Design LID practices work, they enhance aesthetics, increase property values, and can cost less!! Resources to help you Connecticut Stormwater Quality Manual Planning Design Sizing Specifications Model Regulations Resources to help you Jordan Cove Research and Demonstration Project http://jordancove.uconn.edu http://nemo.uconn.edu/tools The next time a map is rolled out.. I know there s a better way Now I really want to know where this is Swales are swell! To heck with the game, I m rooting for LIDs