UCRL-PRES-XXXXXX

This work was performed under the auspices of the U.S. Department of Energy by the University of California,Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

This work was performed under the auspices of the U.S. Department of Energy by the University of California,Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

A Stable Isotope Tracer Experiment Using Hetch-Hetchy Water

A Stable Isotope Tracer Experiment Using Hetch-Hetchy Water

Madrid1, V.M., Gregory1, S., Verce1, M.F., Radyk1, J., Singleton2, M, Eaton2, G., Esser2 B. K. 1Environmental Restoration Division, 2Chemical Sciences Division

Lawrence Livermore National Laboratory

UCRL-PRES-228848

Madrid1, V.M., Gregory1, S., Verce1, M.F., Radyk1, J., Singleton2, M, Eaton2, G., Esser2 B. K. 1Environmental Restoration Division, 2Chemical Sciences Division

Lawrence Livermore National Laboratory

UCRL-PRES-228848

D = -104‰ 18O = -14.0‰

D = - 44‰18O= - 3.4‰

Talk Outline

• Site Background

• Objectives

• Experiment Design

• Data

• Results

• Conclusions

Site 300 location map

T2 test area

Isotope studies at Site 300

3H

235U/238U

18O,D(H2O)

15N,18O(NO3)

Typical Site 300 Contaminant Source area

• 15 m x 15 m (50 ft x 50 ft)

• High contaminant concentrations

• Low Permeability

• Limited Recharge

Therefore, conventional pump & treat has limited effectiveness.

Site Air Photo VOC plume

T2 tracerexperiment

Overall Objective Evaluate feasibility of reagent injection as a source area cleanup technology using an existing well field.

Phase 1: Tracer Test

Emphasize

Performance

Monitoring

Emphasize

CleanupPhase 3: Multi-well, source area cleanup

Phase 2: Reagent injection

Injection rate

Area-of-influence

Tracer / ground water mixing

• Single well, continuous injection tracer test.

• Constant head injection about 5 m (17 ft ) above the

static water table.

• Inject isotopically distinct, low salinity Hetch-Hetchy

(H-H) water until it is detected in observation wells.

Tracer Experiment Design

D = -104‰ 18O = -14.0‰

D = - 44‰18O= - 3.4‰

Why Hetch-Hetchy Water? • Conservative tracer

• Large salinity & isotopic contrast compared to site

ground water

• Non–toxic

• Analysis is commercially available & inexpensive

Performance Monitoring

• Water levels: hourly

• Stable Isotopes:

18O weekly

D every 6 weeks

• Specific Conductance: weekly

• VOCs: monthly

T2 site map

[920.3]

[919.4]

[921.6]

[918.6]

[916.8]

[918.3]

922

920

918

Pre-injectionground water

elevation contour

Ground water flow

direction

dry

dry

Cross section A – A'

K = 10-4 - 10-6 cm/sec

K = < 10-6 cm/sec

Injectionwell

Outcrop of gravel / clay contact

Tps clay perching horizon

Calcium carbonate cemented gravel

Caliche-filled fractures

Friable, medium-grained sand

Tpsg gravel

1 meter

916

918

920

922

924

926

16-Nov-2004 15-Dec-2004 13-Jan-2005 11-Feb-2005 12-Mar-2005 10-Apr-2005 9-May-2005 7-Jun-2005

GW

E (

ft M

SL)

-T2A

-T2

-1825

-T2D

-T2B

-1833

START

STOP

RE-START

Pre-injection

Dual isotope sample

0

0.2

0.4

0.6

0.8

1

1.2

11/16/04

Daily

Rain

(in

ches)

dailyrain

Observation well hydrographs

18O time-series plot

18O

Start ofInjection

Dual isotope sample

Specific Conductance S

peci

fic C

ondu

ctan

ce (

µS

) Start ofInjection

Dual isotope sample

Pre-injection isotope signatures

Hetch-Hetchy Tracer

Ground water (pre-injection)S300 precipitation

(2006)

25%

50%

75%Tracer-g

round water mixing lin

e

D

18O

[(18Osample- 18Ogw)2+ (Dsample- Dgw )2]1/2

[(18OHH- 18Ogw)2+ (DHH- Dgw )2]1/2

= Tracer fraction

SMOW

Plot of all 18O & D data

Hetch-Hetchy Tracer

25%

50%

75%Tracer-g

round water mixing lin

e

D

18O

SMOW

Ground water (pre-injection)

Isotope plots for individual wells

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0-15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

tracer-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0-15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

18O

D

tracer1833

12

3

456

7

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0-15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0-15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

18O

D

tracerT2

18O

D

T2A

18O

D

tracer 1825

12

4

5

67

1

3

4

56

7

12

34

5

6

32

7

1: Jan 132: Mar 13: Apr 154: May 235: Jul 216: Aug 187: Sep 13

Startinjection

Stopinjection

Low salinityarrives

High salinityarrives

Time-series plot of tracer fraction

Start ofInjection

End ofInjection

Change in salinityobserved at T2 & 1825

Time-series tracer distribution

Pre-injection Jan 21 May 23

July 21

-1824-T2-1825

-1833

-T2A-T2B

-T2D

-T2C

5

102550

75

510

2550

510

2550

75

Post-injection Sep 13

Ground water flow direction

Injectionwell

Extent ofsaturation

May 23

July 21 Post-injection Sep 13

20,0

00

10,0

00

1,00

0

100

20,000

20,000

10,0

00

1,00

0

20,000

10,0

00

1,00

0

-1824

-T2-1825

-1833

-T2A

-T2B

-T2D

-T2C

Pre-injection Jan 21

Time-series VOC distribution

Results

• Under a sustained, induced gradient of 0.3, an injection rate of about 100 L /day & a tracer velocity of 0.1 m/day was achieved.

• An immediate (< 1 hour) ground water level rise was observed in all wells at the onset of injection.

• In some wells that exhibited an immediate water level response, no tracer was detected during injection.

• Salinity decreased in the nearest observation well, while in other wells salinity increased or remained essentially the same.

• At the end of injection, the nearest observation well contained about 25% tracer. Other wells contained tracer concentrations ranging from 0 to 12 %.

Conclusions• H-H reservoir water is a good, conservative tracer when

injected into an aquifer with significantly different isotopic composition & salinity.

• Rigorous monitoring of multiple, independent data sets was the key to understanding how this source area responded under stress conditions.

• Under a steep induced gradient, the saturated zone responded like a confined system.

• Differences in salinity trends & tracer arrival times suggest the injected H-H water took separate pathways to the observation wells.

• Reagent injection is feasible at Site 300, however, some plume displacement is unavoidable.

AcknowledgementsAcknowledgements

• Brad Esser, Mike Singleton & Gail Eaton Brad Esser, Mike Singleton & Gail Eaton for mass spectrometry & data analysisfor mass spectrometry & data analysis

• Steve Gregory, Billy Clark, & Kian Atkinson Steve Gregory, Billy Clark, & Kian Atkinson for field instrumentation & data collectionfor field instrumentation & data collection

• Matthew Verce, Steve Gregory & John RadykMatthew Verce, Steve Gregory & John Radykfor data analysisfor data analysis