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

1,158

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

Bioretention System – Upturned Elbow

Omahastormwater.org/ORSDM – Chapter 8

5-29-09

Infiltration cell

Clean-outs High flow structure

Valve

Bioretention: In the field

Overflow

Prairie Lane Park When bioretention “doesn’t work”

The site as it was being constructed…

Soil conditioning BEFORE infiltration cell installation

Protect infiltration cell after installation

Sequencing & protecting infiltration cell key

2” clay lens at top

‘Clean’ BSM below

“Poor design”, “doesn’t work”…upon further review

Drains great below lens

Clay lens

Clay, in-situ soil tilled into BSM clogged system

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

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

Works great now

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

Elmwood Park Green Infrastructure – just installed

Offline bioretention = less stress on system

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

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

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

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

Repaired 12/2014

Benson Gateway Bioretention A project full of learning

Originally a street…

Catch street runoff into conveyance

Test the system after install

Poor drainage instantly

Anticipated flows like this...

Failure 1: …but we got this slow flow instead

FYI, this is first flush of some dirt in underdrain

Failure 1: Slotted pipe with dirty drainage aggregate

Fix1: Remove the infiltration cell & replace

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

Fix 1: Geotextile as separation, only on top*

* - note the return up the sides; this was not intended

Fix 1: Replace the soil mix & finish the project

Plant everything up

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

Slow flow once again…

Failure 2: Flat geotextile created ‘perched water table’

Cut slit at corner, pulled back, & drained fast

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

Test it again before Ribbon Cutting event…

…but once valve opened, drained at same slow rate

Gotta be something else – time to look inside…

Cleaned out mulch from underdrain &…

…filled it once more for the Ribbon Cutting…

…& it finally worked (first flow of 2014)

Still working & looking good

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

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

Bioretention System: 1-ingredient (no soil mix)

Bioretenetion site before

West swale set, work stops for season – late 2013

Infiltration cell installation continued

Lesson learned: Ensure system is watertight at underdrains & utility crossings

Pea Gravel

Permeable pavement storage area

Buffalo sod, beds mulched, & irrigating plants

PaveDrain = 2,170 gallons of designed capacity

Bioretention = 39,085 gallons of designed capacity

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

Time lapse camera for rain events & plant growth

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

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

Antecedent Dry Conditions ~ 5 days (1.0 inch storm)

48 hour QPF > 0.5, valve

opens

6 hour QPF > 0.1, valve

closes

§ 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

24th St Bioretention Case study in design approach & costs

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!

It’s more than just landscaping

Green Infrastructure