This PowerPoint describes each best practice, description of challenging sites, conveyances and flows, permitting, O&M

1. Stormwater Practices
for Challenging Sites
Sustainability for all the places between the buildings
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2. What I’m About to Tell You
How Residents Can Safely Manage Stormwater
•Housekeeping
•What’s a “Challenging Site”?
•Why do our properties impact water quality?
•Why is reducing runoff important?
•What practices can we implement on our own
properties?

3. About Me

4. About You

5. Challenging Sites are…
… any area not suitable for infiltration of runoff.
This includes:
• Steep slopes/landslides
• Clay soils
• High seasonal groundwater
• Inadequate setbacks
(ex. Buildings too close together)

6. The Water Balance Model
Water Quantity Before
25% baseflow
(infiltration)
50%
evaporation
0.5% runoff
100%average
Annualrainfall
25%groundwater
(infiltration)

7. Water Balance BEFORE Development
Simplified

8. The Water Balance Model
Water Quantity After
0” baseflow
(infiltration)
reducedevapo-
transpiration
100%rainfall
yearlyavg
98% runoff
2%evapo-
transpiration
Reduced
infiltration

9. Water Balance AFTER Development
Example: EVERYWHERE

10. “Before” & “After”
Runoff Compared
0.5% runoff
98%
runoff

11. Runoff: A Watershed Perspective
in the West Hills
• Flooding, landslides and stream bank erosion

12. The Water Balance Model
Water Quality Before
Some sediment

13. The Water Balance Model
Water Quality After
Sediment (air particulates)
Nutrients
Feces
Other debris
Sediment/turbidity
Hydrocarbons
Heavy metals (particles & soluble)
Other chemicals
Runoff volume
Sediment/turbidity
fertilizers
pesticides
herbicides
Runoff volume
13

14. Restore the Soil: Lawn Areas
Runoff prevented = 50%

15. Restore the Soil:
Perennial Garden Areas
Runoff prevented = 80%

16. Restore the Soil: Meadows
Runoff prevented = 65%

17. Compost Amended Slopes
Washington DOT
• Great for keeping soil in place on steep slopes, too!
http://www.wsdot.wa.gov/Design/Roadside/SoilBioengineering.htm

18. Lots of great information at
soilsforsalmon.org

19. Contained Planters
(Over Hardscapes)

20. Contained Planters (Over Impervious Area)
Runoff prevented = 50%

21. Minimize Impervious Pavement
Depaving
Runoff prevented varies
depending on what
replaces the pavement,
lawn or perennial garden.

22. Lots of great information at
depave.org

23. Tree Planting

24. Porous Walkway & Patio Surface Types
Homemade paversGrass-crete
Flexible Pavements
(GrassPave )
Commercial pavers
Boardwalks/decksWood chips
(pedestrian only)
Gravel

25. Typical Permeable Paver Section

26. Porous Walkways
Runoff
prevented =
90%

27. Ecoroof/Green Roofs?
• DIY Projects = areas where a single ply of impermeable
lining can be used or where failure isn’t too problematic

28. Ecoroof/Green Roof
Runoff prevented = 50%

29. Conveyances & Flows

30. Issues to look for
• Drainage problems, like water pooling in your yard.
• Bare spots

31. Issues to look for
• Erosion: Stream banks

32. Issues to look for
• Erosion: Garden areas

33. Historic Landslide Areas
One way to identify them
• Erosion: Landslides
Bent trunks sometimes indicate areas
where landslides occurred a long time
ago = likely to happen again

34. Permitting

35. Operations & Maintenance

36. What I Just Told You
How Residents Can Safely Manage Stormwater
•Housekeeping
•What’s a “Challenging Site”?
•Why do our properties impact water quality?
•Why is reducing runoff important?
•What practices can we implement on our own
properties?

37. Thank You!

38. Rain Barrels

39. Rain Barrels: Food for Thought

40. Rain Barrels: Landscape

41. Rainwater Harvesting: L andscapes
A Watershed Perspective

42. Rainwater Harvesting: Indoor Uses