Green Infrastructure in Omaha 4 22-15
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Transcript of Green Infrastructure in Omaha 4 22-15
Andy Szatko [email protected] City of Omaha Environmental Quality Control Tech I
Green Infrastructure Lessons Learned: Experiences from Omaha
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
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
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
Bioretention System
• Infiltration ‘Trench’: Bioretention Soil Mix (BSM) & washed aggregate
• Conditioned soil outside ‘trench’
• Valve
Omahastormwater.org/ORSDM – Chapter 8
Bioretention is not a…
• Pond • Wetland • Swamp • Mosquito breeding ground
• Just a landscape bed • Bio-pond, -garden, etc… • Bioswale
Soil conditioning BEFORE infiltration cell installation
Protect infiltration cell after installation
Sequencing & protecting infiltration cell key
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
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
Fix 1: Geotextile as separation, only on top*
* - note the return up the sides; this was not intended
Fix 2: Remove fabric, mound rock, separate w/burlap • Burlap is recycled coffee bean sacks • 1” gap on either side of burlap
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
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
Planting Plan by Steve Rodie, Associate Professor UNO
Create an “Omaha aesthetic” Utilize grasses, sedges & shrubs for simple maintenance
Lesson learned: Ensure system is watertight at underdrains & utility crossings
Pea Gravel
Permeable pavement storage area
Bioretention System
Drainage Area ~10,000 sf
Drainage area ~10,500 sf
Concrete Porous
Omaha Fire Dept Education Center
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
§ 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
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%
Initial Take-aways…
• Targeted “over-engineering” • Bioretention is not a traditional curb inlet • Public education critical
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
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!