characterizing groundwater flow velocity and preferential flow zones

2650 East 40th Avenue • Denver, Colorado 80205 • www.geotechenv.com2650 East 40th Avenue • Denver, Colorado 80205 • www.geotechenv.com

GROUND WATER SAMPLING • WATER LEVEL & PRESSURE • WATER SAMPLE FILTRATION • GROUND WATER REMEDIATION • GEOPHYSICAL MEASUREMENTSGROUND WATER SAMPLING • WATER LEVEL & PRESSURE • WATER SAMPLE FILTRATION • GROUND WATER REMEDIATION • GEOPHYSICAL MEASUREMENTS

CHARACTERIZING GROUND-WATER

FLOW VELOCITY AND PREFERENTIAL

FLOW ZONES

The Nielsen Environmental Field School, Inc.

2012 North American Environmental Field Conference & Exposition (East)



Agenda

• Introductions





Jeff Popiel

President and CEO

[email protected]

303.320.4764



www.GeotechEnv.com

…a world leader in environmental technology,

manufacturing and product training since 1978.

Geotech Corporate HeadquartersDenver, Colorado USA



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Audience Introductions

• Name

• Company name

• Experience with site characterization



Why Characterize Groundwater Flow

• Plan efficient remediation

– Quantify extent and magnitude of underlying

contaminants

– Define exposure routes

– Define flow velocity

– Identify and assess risks



Criteria for Characterizing

Groundwater Flow• Site geology

– Distribution of geologic materials

– Stratigraphic and structural relationships

– Features that affect the subsurface migration of contaminants

• Rate and direction of ground water flow– All impacted aquifers

• Groundwater– Contaminants present

– Concentrations of contaminants

– Vertical and lateral extent of contaminants



Methods of Groundwater Flow

Characterization

• Groundwater level measurements

• Potentiometric maps

• Well clusters screened at different depths

• Seasonal and temporal factors

• Hydraulic conductivity

• Tracer tests



How Does the Borescope Work?

• Directly observes groundwater flow velocity

• Measures flow at selected depths within a well and thus the ability to measure flow from individual fractures

• Allows capture of an aerial and vertical distribution of groundwater flow velocities that is useful for the interpretation of contaminant migration in complex flow systems



Why is a Borescope Better?

• Hydraulic conductivity values calculated from most aquifer tests in fractured rocks are meaningless

• Groundwater flow directions in fracture porous media can be diagonal to the hydraulic gradient

• Groundwater flow and contaminant transport in fractured porous aquifers is complicated by flow in porous blocks

• Flow in sandstone or siltstone blocks may be in the direction of the hydraulic gradient while groundwater in the fractures will migrate in a direction parallel to the fractures



Conceptual Diagram

Source: Oak Ridge National Laboratory, “Characterization of a Fractured Aquifer Using the Colloidal Borescope”



AquaLITE 7.2x



AquaLITE 7.2xSoftware Outputs



Video digitizer

Computer

92 cm

9 cm

MSC047

GroundwaterFlow

SandPack

High-ResolutionMonitor

Manometer

EffluentWater Level

InfluentWater Level

Reservoir/SandMembrane Screen

5-cm FullyPenetrating Well


Electronic cable

Borescope

PackSand

132 cm

153 cm

Colloidal

Courtesy: ORNL



EXPERIMENT #4

EXPERIMENT #3

EXPERIMENT #2

Sand #5

Sand #3

Sand #4

Groundwater Flow

Layered Flow

Sand #3

Groundwater Flow

Fully vs Partially Penetrating Well

Sand #3

Groundwater Flow

Sand Pack Influence

Sand #2

Well Diameter ComparisonEXPERIMENT #1

Groundwater Flow

Sand #1


FullyPenetrating Well

No Sand Pack

Penetrating Well5-cm Fully

Screen

Screen

Coarse-GrainSand Pack

Penetrating WellPartially

Screen

Coarse-GrainSand Pack

Screen


Courtesy: ORNL



MeasuredThick-layer Solution, Dq = 0Thin-layer Solution, Dq = 0

No Diffusive LossThin-layer Solution, Dq = 0

MSC115

100

0.80

0.60

0.40

0.20

0.004 8 12 16 20 24 28 32 360

Time, days

Rel

ativ

e C

onc

entr

atio

n, c

/c0

Silt

Sand Flow Direction

Silt

Nylon Mesh

Nylon Mesh

Flushing Ports

Flushing Ports

Screen

0.2m

1.0m

Laboratory tracer test results using sodium chloridewith an average linear porewater velocity in thesand equal to 0.10 m/d. (Sudicky et al., 1985)

Courtesy: ORNL



110

50

Dep

th (c

m)

Dep

th (

cm)

60

70

80

90

100

120

110

120

100

90

80

70

60

50

0.01 0.1

Degree from expectedflow direction

Velocity in well (cm/s)

110

Degree from expected

60120

80100

flow direction

4020

4020 60

80100

Dep

th (

cm)

100

90

80

70

60

50

110

Velocity in well (cm/s)

120

Dep

th (

cm)

100

90

80

70

60

50

1.0

0.10.01 1.0

Fine (#4)

Medium (#3)

Coarse (#5)

Fine (#4)

Coarse (#5)

Medium (#3)

Fine (#4)

Medium (#3)

Coarse (#5)

Fine (#4)

Medium (#3)

Coarse (#5)

a) b)

c) d)

6010080 4040

20 20 6080

100

Courtesy: ORNL



Well Bore Well Borer

r ii

Well BoreWell Bore

Finite Skin orDevelopment Zone

Filter Pack

Filter PackFilter Pack

r

r

r

123 K

a b

c d

MSC102

r

r

r

1

2

3

1 2 3

1

2

3

K K

Groundwater Flow

Courtesy: ORNL



0 20 40 60 80 100 120 140

0

0.5

1.0

0

0.5

1.0

0

1.0

0.5

0

1.0

0.5

0

1.0

0.5

MSC028

Point #5

Point #4

Point #3

Point #2

Point #1

Time (hr)

Rel

ativ

e B

rC

once

ntr

atio

n (m

easu

red

/inje

cted

)

Screen

#1

#2

#3

#4

#5

Well

6

5

4

3

2

1

0

Dis

tanc

e F

rom

Bo

ttom

Of

Wel

l (m

)

Development of fresh water zone within thescreened interval of sampling well

(Bromide tests) After Robin and Gillham (1987)



0

0

FEET

400200

METERS

50 100

600

150



Courtesy: ORNL



Preferential Flow

• Preferential flow






843

875

883818

H O L L O W

R O A D

W-20

C

W-18

880

891B873

891A

877

871

870

876

B

R O

U T

E

3

A

811

882

R O U T E1

R O

U T

E

2

B

879

A

M70

W- 7

841

840

C O

R R

A L

H O

L L

O W

R O

A D

879

W-25N-18

W-25N-11

W-25N-13

W7B

W873-06W872-02

MSC116

Colloidal Borescope Well

Building

RoadStream

0 150120906030METERS

FEET400300 5002001000

N

Direction and Magnitude

N

N N

N

NN

of Groundwater Flow

25% 50%

BORESCOPE TEST SITE



90

120

150

180

210

240

270

300



X

X

X

X

X

X



X X X X X X X X X X X X X X X X X X X

X

XX

X

X X X

XX

XXX

X X

X

XX

X

X

X

X X

X XX

X

XXX

X

X

X

X

X X

X

X

X

X

0 15 01209 06 03 0METERS

FEET4 0 0300 5002001000



X

X

X

X

X

X

X

X

X

X

X

0 1501209 06 030METERS

FEET400300 5002001000



Tidal Influence on Groundwater Flow



Groundwater

Flow in a Perched

Aquifer



Summary

characterizing groundwater flow velocity and preferential flow zones

Documents

direction of ground

avenue denver

colorado usa

lateral extent of contaminants

environmental technology

site characterization

world leader

different depthsseasonal