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Building Raingardens

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  • 1.  
  • 2. Building Raingardens Presented to: Massachusetts Association of Landscape Professionals November 12, 2008
  • 3. Michael F. Clark, P.E., LEED-AP
    • Sr. Project Manager
    • Weston & Sampson, Inc.
    • E-mail: [email_address]
    • Phone: (941) 806-9418
  • 4.  
  • 5.  
  • 6. Raingardens – A definition
    • Raingardens are a bioretention cell.
    • Bioretention: An engineered process to manage stormwater runoff, using the chemical, biological and physical properties afforded by a natural, terrestrial-based community of plants, microbes and soil.  Bioretention provides two important functions: (i) water quantity (flood) controls; and (ii) improve water quality through removal of pollutants and nutrients associated with runoff.
  • 7. Raingardens: The simple definition. A shallow depressed planting bed designed to improve the quality of stormwater runoff through biological process of plant and soil interaction, and by infiltrating stormwater back into the ground.
  • 8. Raingarden Benefits
    • Increases the amount of stormwater that infiltrates into the ground, thereby recharging local and regional aquifers.
    • Minimizes flooding and drainage problems by reducing runoff.
    • Protects streams and lakes by reducing pollutants in stormwater.
    • Provides an aesthetically pleasing stormwater treatment system.
    • Provides wildlife habitat.
    • Can be implemented on the lot level by contractors, landscapers and homeowners.
  • 9. Pollutant Removal
    • Total Suspended Solids: 80-99%
    • Nutrients –Nitrogen: 38-50%
    • Nutrients – Phosphorous: up to 80%
    • Metals: 90 - 99%
    • Total Petroleum Hydrocarbons: 67 - 99%
  • 10. Design Considerations
    • Developed or undeveloped site.
    • Pollution Control Objective.
    • Watershed size.
    • Utility locations.
    • Bioretention Soil Mixture.
    • Permitting
    • Control of overflow runoff.
    • Soils and Geology.
    • Groundwater levels.
    • Maintenance.
    • Freshwater – Phosphorous.
    • Always – TSS, Oil and grease, litter, metals.
    • Not effective for roadway salt.
  • 11. Developed or Undeveloped Site.
    • Developed sites – Retrofits –
      • Utilize existing drainage structures to convey flow after infiltration. (Advantage) Underdrains can be utilized to convey water to existing drainage.
      • Locate Raingardens in locations (either vertically or horizontally) to treat runoff prior to discharge to existing drainage. (Disadvantage)
  • 12. Developed or Undeveloped Site.
    • Undeveloped sites
      • Minimize conventional drainage structures/detention ponds.
      • Locate Raingardens in landscape locations prior to discharge to existing drainage features.
      • Underdrains can be utilized to convey water to existing drainage, wetlands, or additional infiltration areas.
      • Raingardens can be modeled for infiltration, storage, and reduction of peak and total flows.
      • Goal is to preserve watershed character.
  • 13. Watershed Size
    • Raingardens need to be sized to accommodate flow from design storm and drainage area. Divide and conquer (more is better, larger is not).
    • Residential rule of thumb.
      • Class A Soils - 20% of drainage areas.
      • Class B Soils – 30% of drainage areas.
      • Class C Soils – 60% of drainage areas.
  • 14. Infiltration Rates – Rule of thumb
    • Class A Soils – 5 to 8 in/hour: Sand, Loamy Sand, Sandy Loam (well to excessively drained)
    • Class B Soils – 1 to 2 in/hour: silt loam, loam (moderately to well drained)
    • Class C Soils – 0.1 to 0.5 in/hour: Sandy clay loams (slow infiltration)
    • Class D Soils – no infiltration.
  • 15. Utility Locations
    • Contact DigSafe at www.digsafe.com or 1-888-dig-safe.
    • Contact local municipal utilities (water and sewer).
    • Review plans and walk site.
    • Locate septic system.
    • Meet Title 5 Setbacks.
  • 16. Bioretention Soil Mix
    • Coarse Sand. (2 parts)
    • Topsoil or compost (1-2 parts depending on fines and organic content).
    • Shredded hardwood. (1 part) Long-term carbon source.
    • Test mixture to insure adequate drainage. Modify as needed.
    • Design filter for underdrain. Minimize use of fabrics.
  • 17. Permitting
    • Planning Board. Waivers/Special permits may be needed.
    • Wetlands – Conservation Commission.
    • Board of Health – Title 5.
    • Building Department.
    • Commercial/Industrial – Consider 21E/MCP (contaminated soils?)
    • Others may or may not be applicable.
    • May need to educate permitting authorities.
  • 18. Control Overflow Runoff
    • Raingardens are depressions, typically 6 to 12 inches deep.
    • Raingardens are designed for frequent small storms and will overtop in larger events.
    • Locate along existing drainage ways.
    • Ensure that overflow drainage is directed away from structures / leachfield etc.
    • Utilize existing infrastructure if possible.
  • 19. Soils and Geology
    • Use NCRS Soils Maps – Determine hydrologic soil group.
    • Test pits, permeability tests.
    • Local experience.
    • Presence of bedrock and impermeable strata.
    • Look for soils that provide adequate drainage for your situation or use underdrain, if possible.
    • Consider position on landscape.
  • 20. Soils and Geology 3 days after 2” rain This water should have infiltrated. Rain garden constructed on very dense clay soils i.e. Glacial till or “hardpan”
  • 21. Groundwater Levels
    • Soil Evaluations.
    • Observation wells.
    • Local experience.
    • Position on Landscape.
    • Presence of seasonally high water tables?
  • 22. Bioretention Cell - Raingarden
  • 23. Site Location
  • 24. Excavation
  • 25. Excavation
  • 26. Final Subgrade
  • 27. Material Stockpiles
  • 28. Coarse Sand
  • 29. Topsoil/Compost Mix
  • 30. Hardwood Chips
  • 31. Soil Mixing
  • 32. Crushed and Pea Stone
  • 33. Underdrain Construction
  • 34. Placement of Bioretention Soil Mix Demonstration Raingarden at Lily Pond
  • 35. Planting June 2005 Demonstration Raingarden at Lily Pond
  • 36. First Rain Storm Demonstration Raingarden at Lily Pond
  • 37. September 2005 Demonstration Raingarden at Lily Pond
  • 38.
    • July 24, 2007
    Demonstration Raingarden at Lily Pond
  • 39. Other Examples Dennis, MA Silver Lake, Wilmington, MA King St, Cohasset, MA Manchester, NH Norfolk MA Leominster, MA
  • 40. Other Examples
  • 41. Lost Opportunity
  • 42. Cohasset BMP Implementation Project Rain Garden Prototypes Coyle & Caron LLC Landscape Architecture, Scituate, MA Plant Selection Criteria Aesthetic Considerations: Neighborhood style – architecture and landscapes. Front yard visibility. Color .
  • 43. Cohasset BMP Implementation Project Rain Garden Prototypes Coyle & Caron, LLC Landscape Architecture, Scituate, MA Plant Selection Criteria Environmental Considerations: Variable Soil Moisture : Long periods of drought. Short periods of inundation. Variable Exposure to Light : Full sun. Deep shade. Cold hardiness . Harsh Road Edge Conditions : Snow plowing and snow stockpiling. Salt tolerance. Native Plants . Biodiversity .
  • 44. Cohasset BMP Implementation Project Rain Garden Prototypes Coyle & Caron LLC Landscape Architecture, Scituate, MA Prototypes White Rain Garden Compact Cranberrybush Viburnum trilobum 'Compactum' American Elder Sambucus canadensis White Gayfeather Liatris spicata 'Floristan White' Henry's Garnet Virginia Sweetspire Itea virginica 'Henry's Garnet' Winterberry Ilex verticillata 'Winterred' Dense Inkberry Ilex glabra 'Densa' Annabelle Hydrangea Hydrangea arborescens 'Annabelle' Slender Deutzia Deutzia gracilis Variegated Red Twig Dogwood Cornus sericea 'Elegantissima' Redtwig Dogwood Cornus sericea Compact Summersweet Clethra alnifolia 'Hummingbird' Summersweet Clethra alnifolia
  • 45. Cohasset BMP Implementation Project Rain Garden Prototypes Coyle & Caron LLC Landscape Architecture, Scituate, MA Prototypes Pink Rain Garden Pinkshell Azalea Rhododendron vaseyii Swamp Azalea Rhododendron viscosum Purple Gayfeather Liatris spicata 'Floristan Violet' Kobold Gayfeather Liatris spicata 'Kobold' Dense Inkberry Ilex glabra 'Densa' Strawberry Fields Deutzia Deutzia sp. 'Strawberry Fields' Variegated Red Twig Dogwood Cornus sericea 'Elegantissima' Redtwig Dogwood Cornus sericea Pink Summersweet Clethra alnifolia 'Ruby Spice' American Beautyberry Callicarpa americana
  • 46. Cohasset BMP Implementation Project Rain Garden Prototypes Coyle & Caron LLC Landscape Architecture, Scituate, MA Prototypes Green & White Rain Garden Snowhill Sage Salvia sylvestris 'Snowhill' Dw.Purpleosier Willow Salix purpurea 'Nana' Grow Low Fragrant Sumac Rhus aromatica 'Gro Low' White Gayfeather Liatris spicata 'Floristan White' Annabelle Hydrangea Hydrangea arborescens 'Annabelle' White Coneflower Echinacea purpurea 'White Swan' Compact Nikko Deutzia Deutzia gracilis 'Nikko' Compact Kelsey Dogwood Cornus sericea 'Kelseyi'
  • 47. Cohasset BMP Implementation Project Rain Garden Prototypes Coyle & Caron LLC Landscape Architecture, Scituate, MA Prototypes Lily Rain Garden Kobold Gayfeather Liatris spicata 'Kobold' Purple Gayfeather Liatris spicata 'Floristan Violet' W. Amethyst Medallion Daylily Hemerocallis sp. 'Woodside Amethyst' Stella de'Oro Daylily Hemerocallis 'Stella de Oro' Rosy Returns Dw. Daylily Hemerocallis 'Rosy Returns' Indian Giver Medallion Daylily Hemerocallis sp. 'Indian Giver' Sweet Fern Comptonia peregrina Moonshine Yarrow Achillea sp. 'Moonshine'
  • 48. Maintenance
  • 49. Maintenance
    • Inspect at least twice a year. Early Spring and fall.
    • Remove sediment, litter, and other debris.
    • Replace mulch at least every other year. Hardwood chips.
    • Inspect plants. Remove diseased and dead plants. Prune.
    • Replace with species that have survived. Biodiversity important for microclimate.
    • No fertilizers!!!!!!!
  • 50. Thanks to:
    • Cohasset Water Department
    • US EPA
    • MA Department of Environmental Protection
    • Norfolk Ram Group, LLC
    • Coyle & Carron, LLC
    • Comprehensive Environmental
  • 51.  

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