ewri - kansas city - 2009 construction and performance of bioretention cells g.o. brown, r.a....

EWRI - Kansas City - 2009

Construction and Performanceof Bioretention Cells

G.O. Brown, R.A. Chavez, D.E. Storm, and M.D. Smolen

EWRI – Kansas City - 2009

Objectives

Demonstrate use of bioretention cells to improve water quality; primarily P reduction.

Develop simple to follow design procedures.Quantify cell hydrology.Long-term test of fly ash in filter media.

8: at Grove onGrand Lake2: at Stillwater, including a control pair


General Design

3% to 5% of area.Sized for runoff:

½” in pool ½” in filter

1’ topsoil.Sand plug on 25% of surface for infiltration.Filter media a blend of sand and 5% fly ash.Overflow designed for 50 year, 1 hour storm.


A high-tech hole in the ground


Infiltration plugs minimizestanding water

Designed to onlypond water for 24 hr.

Addition of sand “plugs”on surface compensatefor lower conductivityof top soil.

25% of surface layer are sand plugs with a specification that none touch.

Proved to be easy to construct and effective.

plug


Class C fly ash significantly reducesP and metals in effluent

Batch sorption for Kd Column experiments

simulated leaching within the cell.

BCTs were fitted to find transport parameters.

Long-term effluent modeled with fitted parameters.


Phosphorous adsorption

Kd, mL/g Retardation

Peat moss -5.8 1

Teller loam 0.41 3

Dougherty sand 2.1 11

Expanded shale (MO) 1.2 7

Limestone 12 60

Expanded shale (KS) 280 1,400

Class C Fly ash 2180 11,000


Fly ash will provide long-termP reductions

Effluent P Concentration Exceeds

Lifetime, yr

Pavement Lawn

0.037 mg/L 4 11

0.5 mg/L 12 35

0.95 mg/L 36 99

•Lifetime of filter calculated assuming 1 ppm P inflow

•Runoff volume from pavement will be higher than lawns.

•Assumes reversible adsorption.


Fly ash significantly reduces K

Adding fly ash decreased the hydraulic conductivity of the sand exponentially

Maximum 5% fly ash in Dougherty

y = 40.41e-0.484x

R2 = 0.999

0.0

10.0

20.0

30.0

40.0

50.0

0.0 2.0 4.0 6.0 8.0 10.0Percent of fly ash, %

Ks, c

m/h

Ks=3.6 cm/hr

5.0% fly ash

Hydraulic conductivity ofsand – fly ash mix.


PlantingsWet and dry tolerantNo nitrogen fixersNo invasive speciesLow-maintenance requirementsOffer a color varietyPlants had to be easily attainable and replaceableIncluded some native species in the plant list.


Lots of discussion about the plants…

Plant Type Surface Area %

Trees 8 to 10

Shrubs 15 to 20

Flowering Perennials 1 to 5

Ornamental Grasses 10 to 15

Rock Accents 1 to 5

Of course, you could just plant grass.


Constructed Cells LandUse

Drainage Area

(acres)

Volume(m3)

Elm Creek Plaza Paved 0.62 128

Lendonwood Gardens Turf 0.54 19

Grove High School Paved 0.65 161

Grand Lake AssociationTurf & Paved

1.90 435

Cherokee Queen Riverboats Paved 0.45 108

Spicer Residence Turf 0.39 93

Clark Residence Turf 0.18 27

Early Childhood Center Turf 0.11 70

OSU Botanical Gardens, Cell A Paved 0.32 66

OSU Botanical Gardens, Cell B Paved 0.90 208


Construction


Construction costs

0

5,000

10,000

15,000

20,000

25,000

30,000

0 100 200 300 400 500Cell Volume (m3)

Cos

t ($)

Contractor

OSU

Linear(Contractor)Linear (OSU)

$7,500 + $51* volume

$1,600 * $47 * volume


Mixing fly ash proved difficult


Wide distribution in fly ash

8.00%6.00%4.00%2.00%0.00%-2.00%

99.9

99

9590

80706050403020

105

1

0.1

Actual Fly Ash Content

Per

cent

Mean 0.02889StDev 0.01509

N 99

AD 1.133

P-Value 0.006

Normal - 95% CIProbability Plot of Actual Fly Ash Content - Cell A

12.50%10.00%7.50%5.00%2.50%0.00%-2.50%-5.00%

99.9

99

959080706050403020

105

1

0.1

Actual Fly Ash Content

Per

cent

Mean 0.03177

StDev 0.02181

N 63

AD 0.800

P-Value 0.036

Normal - 95% CIProbability Plot of Actual Fly Ash Content - Cell B


Hydraulic testing


30 % reduction in peak flow


Water Quality Data are Inconclusive

Water quality data collected to date are generally inadequate to draw strong conclusions.

Problems arise due to the long response time of these cells and the difficultly of measuring both inflows and outflows over extended periods.

Long-term, we will take core samples of the cells and determine the species and quantity of pollutants trapped.

A comparison between the fly ash and sand filter control is possible for the initial operation.


Impact of fly ash on effluent Parameter Cell N Mean St Dev

pH Control 8 7.58 0.450Fly Ash 6 9.78 0.436

NO3-N(mg/l)

Control 8 3.44 2.53Fly Ash 6 5.95 3.03

Ortho-P(mg/l)

Control 8 0.115 0.0441Fly Ash 6 0.063 0.0816

Fe(mg/l)

Control 8 2.29 2.85Fly Ash 6 0.122 0.046

Cu(mg/l)

Control 8 <0.02 0.007Fly Ash 6 0.022 0.004

Pb(mg/l)

Control 8 <0.02 0.002Fly Ash 6 <0.02 0.016


Two-sample T-test (95%)

Parameter T-Value P-Value DFSignificant Difference?

pH -9.26 0.000 11 Yes (Higher)

NO3-N -1.64 0.135 9 No

Ortho-P 3.24 0.014 7 Yes (Lower)

Fe 2.15 0.069 7 No

Cu -3.05 0.011 11 Yes (Higher)

Pb -1.09 0.326 5 No


Next steps

Finish analysis of cell hydrology. Quantify impact of the spatial variability in

conductivity. Perform more field tests. Model results. Relate to watershed hydrology.

Sample cells to determine retention of pollutants.Explore filter additives that will reduce N.


AcknowledgementsFunding for this project was provided by the

Oklahoma Conservation Commission as part of a U.S. EPA Region VI, 319h grant.

Fly ashdonated byGrand RiverDamAuthority.

Modelingby ReidChristianson

ewri - kansas city - 2009 construction and performance of bioretention cells g.o. brown, r.a....

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