Module 5: Bioretention Design Specs/Details

1. Module 5: Bioretention Design Specs/Details Melanie Mills, MLA Central Coast LIDI

2. Specifications & Standard Details Standard Details Design Specifications

3. Design Guidance Review

4. Expert Panel Review

5. Design Specifications • Facility Design and Dimensions • width, depth, slope, ponding • Hard Infrastructure • inlets, check dams, overflow structures • Facility Media • soil, aggregate base, mulch • Landscape • plant selection, irrigation

6. Standard Details • Facility Type • planter • sloped sided • Elements related to facility • walls • curb inlets • overflows • check dams

7. Standard Details

8. Facility Design & Dimensions • Bottom width – provide 2’ wide minimum flat bottom for facilities with side slopes and longitudinal slope • Allowable standing water – 72 hours. • Allowable ponding time is typically associated with mosquito vector control, and varies by location. Confirm with local vector control agency to confirm appropriate drawdown time for facility. • Energy dissipation – provide an aggregate or concrete splash pad at inlet per LIDI details. • For aggregate: 6” depth, 3" – 6" rounded, washed cobble • For sloped sided facilities, extend a cobble flow path from pad 1’ into bioretention area bottom.

9. Bioretention w/ Flat Bottom (Planter)

10. Bioretention w/ Sloped Sides(rain garden, linear swale)

11. Side Slope Grades • 3:1 max • needs shoulder • 4:1 recommended

12. Bioretention w/ Sloped Sides

13. Facility Elevations photo: bluegreenbldg.org Overflow elevation Curb gutter inlet elevation Top of curb Adjacent surface Finished grade in facility

14. Bioretention w/ Underdrain Planter • Class 2 permeable • No filter fabric • No filter layer • Underdrain • PVC SDR 35 • holes downward • cleanout

15. Bioretention w/ Underdrain Side Slope • Underdrain design considerations • design w/ future modification • adjustable orifice • open/close drain

16. Design Specifications Hard Infrastructure

17. Edge Infrastructure

18. Edge Infrastructure for Sloped Sides

19. Curb Cut Inlets for Planters Inlet design has evolved

20. Concrete Splash Pad

21. Curb Cut Inlets for Sloped Sides City of Portland, Environmental Services

22. Curb Cut Inlets w/ Gravel

23. Energy Dissipation Cobble • Use it for energy dissipation • at inlets • sloped sides/extend down to facility bottom • Avoid decorative use • difficult to maintain • weeds can establish in sediment/cobble

24. Inlet w/ Grate SW 12th Ave., Portland, Kevin Perry

25. Gravel Check Dam City of Portland, Environmental Services Mild longitudinal slope

26. Concrete Check Dam Pittsburgh Courthouse, photo: bluegreenbldg.org

27. Concrete Check Dams • Work w/ steep longitudinal slope • Series of bathtubs photo: Tracy Tackett, SPU

28. Check Dams • Other rigid materials • steel • clear plexiglass • concrete w/ wood

29. Overflow Structure w/ Beehive Grate photo: SvR Design Required for systems without overflow bypass Overflow raised to allow ponding Connects to downstream structure or stormdrain

30. Overflow Structure w/ Collar photo: Kevin Perry

31. Location of Overflow TOP 10 Not adjacent to inlet Raised to allow for design ponding

32. Design Specifications Facility Media Landscape

33. Aggregate • Optional use – per project requirements • Cal Trans Class 2 Permeable • No filter fabric • potential for clogging • inhibits infiltration • Aggregate filter layer not needed for Class 2 • If Class 2 not available, substitute Class 3 • provide 3” depth filter layer for Class 3

34. Future Standard Details • Layout details for bioretention • street edge with parking • curb extensions • bioretention with pedestrian crossing • parking lot layouts

35. www.centralcoastlidi.org