This document summarizes lessons learned from green infrastructure projects in Omaha, Nebraska. It discusses various green infrastructure techniques used, including bioretention systems, permeable pavements, rain gardens, and more. Key lessons include following design details carefully, targeting "over-engineering" strategically, designing for maintenance, sequencing construction properly, and using real-time controls and valves to improve system efficiency. Overall, green infrastructure provides significant stormwater management benefits when designed and installed correctly.

1. Andy Szatko
Andy.Szatko@ci.omaha.ne.us
City of Omaha
Environmental Quality Control Tech I
Green Infrastructure Lessons Learned:
Experiences from Omaha

2. Green Infrastructure:
Defined
Preservation, connecting,
& mimicking of natural
processes that slow, sink, &
spread rain where it lands
3 Scales:
1. Watershed
2. Neighborhood
3. Site

3. Site Specific GI Project Types
§ Bioretention system
§ Rain gardens
§ Bioswales
§ Xeric gardens
§ Soil Conditioning
§ Green roofs
§ Porous/pervious
pavement
§ Rain barrels
§ Urban forest
§ Wet & dry ponds
§ Wetlands
§ Filter strips and
level spreaders
§ Sand filters

4. Post-Construction BMPs in Omaha
1,158

5. Post-Construction BMPs in Omaha
339
157
147
122
81
67
53
36 34
23 17 16 14 12 9 9 5 5 4 4 4
0
50
100
150
200
250
300
350
400
PCSMP BMP Type Distribution - all status
Total BMPs = 1,158

6. Bioretention System
• Infiltration ‘Trench’:
Bioretention Soil Mix (BSM)
& washed aggregate
• Conditioned soil
outside ‘trench’
• Valve
Omahastormwater.org/ORSDM
– Chapter 8

7. Bioretention is not a…
• Pond
• Wetland
• Swamp
• Mosquito breeding ground
• Just a landscape bed
• Bio-pond, -garden, etc…
• Bioswale

8. Bioretention System – Upturned Elbow
Omahastormwater.org/ORSDM
– Chapter 8

9. 5-29-09
Infiltration cell
Clean-outs High flow structure
Valve
Bioretention: In the field
Overflow

10. Prairie Lane Park
When bioretention “doesn’t work”

11. The site as it was being constructed…

12. Soil conditioning BEFORE
infiltration cell installation
Protect infiltration cell
after installation
Sequencing & protecting infiltration cell key

13. 2” clay lens at top
‘Clean’ BSM below
“Poor design”, “doesn’t work”…upon further review

14. Drains great below lens
Clay lens
Clay, in-situ soil tilled into BSM clogged system

15. Troweled into pipe
during paving MH floor
1 7/8” concrete ‘plug’ in
underdrain tap to MH
Don’t make things harder than they need to

16. Remove top 2”, place new BSM, & new sod

17. Works great now

18. Elmwood Park Green Infrastructure
Part of the Aksarben Village Sewer Separation Project

19. Elmwood Park Green Infrastructure – just installed

20. Offline bioretention = less stress on system

21. Elmwood Park Diversion – Adaptations
• Gardens holding up
great but can
handle more volume
• Gardens not level
• Bottom 0.1’ lower
than notch
Install a bracket around low-flow notch & stop
logs to increase capacity & provide flexibility

22. 4/18/15 After rain, better capacity & slower flow

23. QC is key, 2 of 7 ScourStop failing; early in 2014

24. QC is key, 6 of 7 failing by end of season 2014

25. Repaired 12/2014

26. Benson Gateway Bioretention
A project full of learning

27. Originally a street…

28. Catch street runoff into conveyance

29. Test the system after install

30. Poor drainage instantly

31. Anticipated flows like this...

32. Failure 1: …but we got this slow flow instead
FYI, this is first flush of some dirt in underdrain

33. Failure 1: Slotted pipe with dirty drainage aggregate

34. Fix1: Remove the infiltration cell & replace

35. Fix 1: Install 4” PVC w/¼” perf, washed ¾” rock

36. Fix 1: Geotextile as separation, only on top*
* - note the return up the sides; this was not intended

37. Fix 1: Replace the soil mix & finish the project

38. Plant everything up

39. Right away we get a ‘natural’ test of the garden

40. Slow flow once again…

41. Failure 2: Flat geotextile created ‘perched water table’

42. Cut slit at corner, pulled back, & drained fast

43. Fix 2: Remove fabric, mound rock, separate
w/burlap
• Burlap is recycled coffee bean sacks
• 1” gap on either side of burlap

44. Test it again before Ribbon Cutting event…

45. …but once valve opened, drained at same slow rate

46. Gotta be something else – time to look inside…

47. Cleaned out mulch from underdrain &…

48. …filled it once more for the Ribbon Cutting…

49. …& it finally worked (first flow of 2014)

50. Still working & looking good

51. Sewer Maintenance Demonstration
EPA ORD, USGS, UNL, City of Omaha
Collaboration

52. Project Partners
§ Collaborative project that
includes:
§ EPA Office of Research
& Development
§ US Geologic Service
(USGS)
§ University of Nebraska
§ City of Omaha CSO &
Stormwater Programs
§ Designed by: Olsson &
Associates
§ Installed by: Sudbek
Home Builders

53. Basic function of the project
Infiltration Cell (trench) w/1 ingredient – pea gravel
Weather Station
Inflow flume
Inflow flume
Infiltration
Cell
Storage area
Outflow flume

54. Planting Plan by Steve Rodie, Associate Professor UNO
Create an “Omaha aesthetic”
Utilize grasses, sedges & shrubs for simple maintenance

55. Bioretention System: 1-ingredient (no soil mix)

56. Bioretenetion site before

57. West swale set, work stops for season – late 2013

58. Infiltration cell installation continued

59. Lesson learned: Ensure system is watertight at
underdrains & utility crossings
Pea Gravel
Permeable pavement
storage area

60. Buffalo sod, beds mulched, & irrigating plants

61. PaveDrain = 2,170 gallons of designed capacity

62. Bioretention = 39,085 gallons of designed capacity

63. Demo pavement cleaning w/jet-vac truck 4/7/15

64. Time lapse camera for rain events & plant growth

65. 50th & Pine
Porous concrete parking lot, bioretention, real-time
controls, & monitoring
50th & Pine

66. Bioretention System
Drainage Area
~10,000 sf
Drainage area
~10,500 sf
Concrete
Porous
Omaha Fire Dept Education Center

69. storage for
incoming
storms
Ultrasonic Depth Sensors
Valve
Valve
Real time controls:
• Slide gate valve
• Monitor weather
forecasts to open or
close valve
• Ability to draw
down to create

70. Antecedent Dry
Conditions ~ 5 days
(1.0 inch storm)

71. 48 hour QPF >
0.5, valve
opens
6 hour QPF >
0.1, valve
closes

72. § Valves greatly improve efficiency of
system & give flexibility, i.e. put peak
ahead of storm
§ Learning curve w/real-time controls but
provide significant benefits
§ This was a retrofit; maximize the storage
you have
§ Infiltration possible in poor soils
§ Winter performance good, warmer temps
at depth
Conclusions

73. 24th St Bioretention
Case study in design approach & costs

74. Design approach: offline vs. online?
• 5 inlets
• 2 large gate inlets
• 6” underdrain, valves, & clean outs
• 2’ bioretention soil mix (BSM)
• 3 layers of aggregate
• 1 inlets
• 2 type A inlets
• 4” underdrain, valve, & clean outs
• Narrow 18” BSM & underdrain
• 1 layer of washed aggregate
Cost savings approx. 51%

75. Initial Take-aways…
• Targeted “over-engineering”
• Bioretention is not a traditional curb inlet
• Public education critical

76. Overall take-away points…
• Bioretention Systems
• Follow details & don’t take shortcuts
• Design approach sets the stage, set
appropriately
• Cost savings w/simple & functional design
• Don’t lay geotextile flat in profile
• If geotextile used, use open weave & light
• Avoid using slotted underdrain
• Use washed rock
• Think about maintenance during design
• Plants are integral, value them

77. Overall take-away points…
• Permeable pavements
• Simple maintenance, just different
• Excellent benefits in winter
• Significant volume benefits w/valves & real-
time controls (50th & Pine project)
• General
• Put in once site is stabilized
• Sequencing/staging important
• Have fun & enjoy it!

78. It’s more than just landscaping
Green Infrastructure