The Orange County Water District Riverbed Filtration Pilot Project

Jason Keller1, Michael Milczarek1, Greg Woodside2, Adam Hutchinson2, Adam MP

Canfield2, Robert Rice1

1GeoSystems Analysis, Inc2Orange County Water District

Orange County Water District

Recharges groundwater basin using Santa Ana River (SAR) water and other sources of water

• Over 1,000 acres of surface spreading basins

• Average recharge of 230,000 acre-ft/yr SAR flow comprised of tertiary-treated effluent and stormwater SAR water quality:

• Total Suspended Solids (TSS) varies from 5 to 400 mg/l

• Total Organic Carbon (TOC) typically 5 to 10 mg/l Spreading basin performance declines in exponential fashion

due to clogging Want to improve performance and recharge volumes

Riverbed Filtration System Pilot Project Objectives

Evaluate riverbed filtration technology to treat SAR water Design pilot scale riverbed filtration system

• Want a shallow collection system to induce recharge

• Want low tech, low cost Construct pilot project in SAR off-river channel

• Evaluate potential long-term performance

• Monitor:

– Clogging rates

– Influence on groundwater system

– Shallow water level response

– Increased recharge rates with filtered water

Santa Ana River ChannelOff-River

Channel

Design for 10 cfs (4,500 gpm) Guided by two-dimensional model (HYDRUS-2D)

– Variable depth and spacing of lateral drains– Foulant layer incorporated to evaluate formation of surface clogging

• Pipe flow capacities calculated using Manning’s equation

Pilot System Design

330 ft

80 ft

40, 80, or 160 ft

5 or 10 ft

Layer 3 - Silty Clay (Ks = 0.3 ft/day)

Layer 2 – Sand (Ks = 52 ft/day)

Layer 1 – Foulant (Ks = 3.2 or 0.7 ft/day)

Lateral Drain

0.3 ft bgs

50 ft bgs

80 ft bgs

330 ft

80 ft

40, 80, or 160 ft

5 or 10 ft

Layer 3 - Silty Clay (Ks = 0.3 ft/day)

Layer 2 – Sand (Ks = 52 ft/day)

Layer 1 – Foulant (Ks = 3.2 or 0.7 ft/day)

Lateral Drain

0.3 ft bgs

50 ft bgs

80 ft bgs

Deeper lateral placement depth increases system capacity

Lateral drain length needed are similar at 80 and 160 ft spacing

Desaturation increases as lateral spacing decreases

Model Results

0

500

1000

1500

2000

2500

0 20 40 60 80 100 120 140 160 180

Distance Between Lateral Drains (ft)

Fee

t o

f L

ater

al

diameter=12in, depth=5ft

diameter=12in, depth=10ft

diameter=6in, depth=5ft

diameter=6in, depth=10ft

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

Soil Water Pressure Head (m): -1 0 1 2 3 4 5

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

Lateral Drain

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

Soil Water Pressure Head (m): -1 0 1 2 3 4 5

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

Soil Water Pressure Head (m): -1 0 1 2 3 4 5

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

X (m)

depth

(mbgs)

-50 -25 0 25 50

0

1

2

3

Lateral Drain

6 inch diameter drains carry substantially less flow Reduced footprint with 80 ft spacing vs 160 ft spacing Gain in efficiency with depth reduced due to added cost for

deeper excavation and installation Pilot system built using 8 inch diameter lateral drains at 80 ft

spacing and 5 ft bgs

Pilot System Design

Monitoring system to evaluate riverbed filtration system performance

• 13 Monitoring Wells and piezometers

• Temperature at 1, 6 and 10 ft bgs in selected wells • Stream flow gaging

→Flow in – Flow out = GW recharge and drain capture (transmission loss)

Bi-weekly samples of raw source water and riverbed filtration system effluent collected and analyzed for water quality

Percolation testing using raw water and riverbed filtration effluent to evaluate percolation decay

Pilot Project Monitoring

Pilot Study Results

Water Quality

Riverbed filtration significantly improved water quality• Reduced TSS and turbidity by >99% and 96%• Decreased TOC, TKN, iron, and manganese by 50% or greater • Riverbed filtered water quality significantly better than other

treatment technologies evaluated– Cloth filter, flocculation-sedimentation, dissolved air flotation, ballasted

sedimentation

Water Quality ParameterInfluent Value

Range

Average Percent Removal

Turbidity 8 - 80 NTU 96%TSS 7 - 37 mg/L > 99%

Chlorophyll A 52 - 68 mg/M3 > 99%Total Organic Carbon (TOC) 6 mg/L 47%Total Kjeldahl Nitrogen (TKN) 0.8 - 0.9 mg/L > 99%

Iron 0.7 - 0.8 mg/L 80%Manganese 0.06 mg/L > 99%

Percolation Decay Percolation rates

50% of initial percolation within:

• Raw water ~ 7 hours

• Riverbed filtered water ~ 58 hours

Air entrapment during early period of riverbed filtration column.

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 120 140 160

Time (hour)

Per

cen

t In

itia

l P

erco

lati

on

Raw

Riverbed Filtration

Inlet Surface Flow and Pumping Rates

0

500

1000

1500

2000

2500

2/23/2009 3/9/2009 3/23/2009 4/6/2009 4/20/2009 5/4/2009 5/18/2009

Date

Pu

mp

ing

Rat

e (g

pm

)

0

10

20

30

40

50

60

Inle

t F

low

Rat

e (c

fs)

Drain Pumping Rate Flow Rate Over Inlet Weir

Test Period 1 Test Period 2

Phreatic Surface Depth-1.5

-0.5

0.5

1.5

2.5

3.5

4.5

5.5

2/23/09 3/9/09 3/23/09 4/6/09 4/20/09 5/4/09 5/18/09

Date

Ph

rea

tic

Su

rfa

ce

(ft

bg

s)

0

300

600

900

1200

1500

1800

2100

2400

Pu

mp

ing

Ra

te (

gp

m)

P-6 P-11 Ground Surface Pumping Rate

Test Period 1 Test Period 2

Pumping east laterals

Pumping all laterals

Surface flow begins

Surface flow interrupted

No surface flow, construct L berms

Restart surface flow

235.5

236.0

236.5

237.0

237.5

238.0

238.5

239.0

239.5

240.0

0 50 100 150 200 250 300 350 400 450 500 550 600Distance (ft)

Ele

vati

on

(ft

am

sl)

TP1: No Pumping TP1: Max Pumping TP2: No Pumping TP2: Max Pumping

P-8

P-6

P-1

1

MW

-2

P-7

P-9

P-1

0

MW

-1

MW

-3

Ground Surface

West East

232.5

233.0

233.5

234.0

234.5

235.0

235.5

236.0

236.5

237.0

237.5

238.0

238.5

239.0

239.5

240.0

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400Distance (ft)

Ele

vati

on

(ft

am

sl)

TP1: No Pumping TP1: Max Pumping TP2: No Pumping TP2: Max Pumping

P-1

2

MW

-4

P-1

3

MW

-2

MW

-5

Ground Surface

South North

Pumping and Phreatic Surface Summary

Under no-pumping conditions, unsaturated zone exists East side of drain system less productive than west side

• Water from west supplying east laterals Strong hydraulic gradient to north Phreatic surface depths deeper after pumping than prior to

pumping Pumping capacity responsive to surface water flows Maximum Pumping Capacity

• Test Period 1 (w/out L-berms) = 1,350 gpm

• Test Period 2 (w/ L-berms) = 2,000 gpm

• 30% - 40% of target collection rate (4,500 gpm)

Transmission Loss and Groundwater Recharge

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

2/23/09 3/9/09 3/23/09 4/6/09 4/20/09 5/4/09 5/18/09

Date

Flo

w R

ate

(cfs

)

Estimated Transmission Loss Drain Pumping RateEstimated Groundwater Recharge Rate

Test Period 2Test Period 1

Conclusions Riverbed filtration significantly improves water quality and

percolation performance System performance dependent on surface water flow rates

and depth• Maximum pumping capacity of:

– 1,350 to 2,000 gpm– 30% - 40% of target collection rate

• Lower than expected groundwater elevations• Strong south-to-north gradient reduced system efficiency

Drainfield east of the collection vault was less productive than west of the collection vault

Drain system induces infiltration during pumping and most of water collected from induced infiltration

Future Studies

Surface clogging may have contributed to a reduction in induced recharge

• Longer term study required to evaluate surface clogging influences

• Treatment options Effective surface water and groundwater depths System optimization System expansion planned

THANK YOU!