FSA Groundwater Flow and FSA Groundwater Flow and Solute Transport ModelSolute Transport Model

Presentation to Scottsdale Citizens Group

March 19, 1999

Overview of NIBW Site HistoryOverview of NIBW Site History

Overview of WorkOverview of WorkComprehensive site characterizationSummary of Site conditions in RI/FSImplementation of ROD-required Remedy

– Capture and containment not achieved

Implementation of Enhanced Remedy– Capture and containment projected (preliminary data and

modeling)

Preparation of FSA– Additional support for capture and containment projections

(performance evaluation and modeling)

Components of ROD-Required Components of ROD-Required RemedyRemedy

MAU & LAU extraction at wells COS31, COS71, COS72, and COS75

Monitoring of UAU mass fluxSoil vapor extraction at Areas 7, 8,

and 12

Voluntary Components of the Voluntary Components of the Enhanced RemedyEnhanced RemedyCOS6 tie-in to the CGTF (MAU/LAU)Replacement LAU extraction at well

COS75ALAU extraction at well PCX-1MRTF for treatment of groundwater from

PCX-1, and PVWC#15 and #14UAU extraction at Area 7MAU extraction at Areas 7 and 12

FSA Groundwater Flow and FSA Groundwater Flow and Solute Transport ModelSolute Transport Model

PurposePurpose

Predictive tool for evaluating a range of remedial actions with respect to:– Capture and containment of the zones of

contamination (flow model) – Relative clean-up time (transport model)

What is a Groundwater Flow and What is a Groundwater Flow and Solute Transport Model?Solute Transport Model?Mathematical representation of physical

system and processesGroundwater flow model - solves for

distribution of headContaminant transport model - solves

for concentration of solute as affected by physical and chemical processes

Model Development ProcessModel Development Process

Development of conceptual modelModel constructionModel calibration Projection of future conditions

Development of Conceptual Development of Conceptual Model - Vadose ZoneModel - Vadose ZoneShallow soil gas sampling programsInstallation and sampling of vapor

monitor wellsInstallation and sampling of soil

vapor extraction wellsAnalysis of potential groundwater

threat

AREA 12

SVE

PROGRAM

Conceptual Model - Vadose Conceptual Model - Vadose ZoneZoneGenerally coarse-grained sedimentsPrevious movement of mass from the

vadose zone to UAU groundwater at source areas

No current impact to groundwater above MCLs

Development of Conceptual Development of Conceptual Model - UAUModel - UAU

Installation, testing, and monitoring of about 70 UAU monitor wells

Characterization of Southwest Margin

Inorganic water quality evaluation

UAU

WATER LEVEL

CONTOURS

APRIL 1998

UAU

TCE CONCENTRATION

CONTOURS

APRIL 1998

SCHEMATIC OF SOUTHWEST MARGIN

HYDROGEOLOGY

Conceptual Model - UAUConceptual Model - UAUGenerally coarse-grainedSmall saturated thickness in south, unsaturated

in north and west Flow from east to west or northeast to

southwest toward Southwest MarginDownward hydraulic gradients to MAUDownward flow toward underlying units at

Southwest MarginSmall TCE mass; decreasing over time

Development of Conceptual Development of Conceptual Model - MAUModel - MAUInstallation, testing, and monitoring of

more than 50 MAU monitor wells Installation and testing of MAU

extraction wells at two source areasAquifer testing at production wellsConduit well investigationsSimulprobe sampling programCoring program

UPPER MAU

WATER LEVEL

CONTOURS

APRIL 1998

LOWER MAU

WATER LEVEL

CONTOURS

APRIL 1998

UPPER MAU

TCE CONCENTRATION

CONTOURS

APRIL 1998

LOWER MAU

TCE CONCENTRATION

CONTOURS

APRIL 1998

BOREHOLE FLOW UNDER

NON-PUMPING

CONDITIONS

CORE SAMPLES FROM MAU MONITOR WELL PG-46MA

SIMULPROBE SAMPLER

MAU CROSS-SECTION

AREA 7

MAU CROSS-SECTION

AREA 12

Conceptual Model - MAUConceptual Model - MAU

Generally fine-grained with thin coarse-grained interbeds

More coarse-grained interbeds in upper MAU

Convergent flow toward OU extraction wells and Southwest Margin

Downward hydraulic gradients to LAUTCE primarily in upper MAU

Development of Conceptual Development of Conceptual Model - LAUModel - LAUInstallation, testing, and monitoring of

more that 30 LAU monitor wellsRegional water level surveyInstallation and testing of extraction

wells COS75A and PCX-1Fluid movement and depth-sampling

investigationsAquifer testing at production wells

LAU

WATER LEVEL

CONTOURS

APRIL 1998

REGIONAL LAU

WATER LEVEL

CONTOURS

1996

EXTRACTION WELL COS75A

INSTALLATION

EXTRACTION WELL PCX-1

INSTALLATION

HYDROGEOLOGIC DATA FOR

EXTRACTION WELL PCX-1

FLUID MOVEMENT LOGGING

SPINNER

FLOWMETER

TOOL

DEPTH

SAMPLING

BOREHOLE FLOW UNDER

PUMPING CONDITIONS

LAU CROSS-SECTION

Conceptual Model - LAUConceptual Model - LAUGenerally coarse-grained with fine-grained

interbedsIncreasing lithification and consolidation

with depthDecreasing permeability and yield with depthConvergent flow toward PVWC wellfieldTCE concentrations generally largest in

upper LAU

Model Development ProcessModel Development Process

Development of conceptual modelModel constructionModel calibration Projection of future conditions

Model ConstructionModel ConstructionDefine model domainAssign model boundary conditionsDevelop model gridDefine model layersAssign pumpage at production wells to

model layersAssign hydraulic parametersAssign initial water level and TCE conditions

FSA

MODEL

DOMAIN

AND

BOUNDARIES

(66 sq. mi.)

GENERAL HEAD

BOUNDARY

GENERAL HEAD

BOUNDARY

NO

FL

OW

BO

UN

DA

RY

N

O F

LO

W

BO

UN

DA

RY

FSA

MODEL

GRID

max = 1,320 ft

min = 200 ft

MODEL LAYERS

1

2

3

4

5

6

7

8

9

10

PUMPING

DISTRIBUTION

BETWEEN

MODEL LAYERS

UPPER MAU

(LAYER 3)

PERCENT

COARSE-GRAINED

SEDIMENTS

UPPER MAU (LAYER

3)

TRANSMISSIVITY

DISTRIBUTION

FROM

PUMPING TESTS

LAYER 3

TRANSMISSIVITY

DISTRIBUTION

FROM MODEL

Model Development ProcessModel Development Process

Development of conceptual modelModel constructionModel calibration Projection of future conditions

Model CalibrationModel Calibration

Process of adjusting parameters within bounds of data to obtain best match to observed conditions

Calibration period– 1990 through 1996– Selected based on data availability

COMPARISON OF

OBSERVED

(APRIL 1997)

AND SIMULATED

WATER LEVELSUAU

SIMULATED

OBSERVED

COMPARISON OF

OBSERVED

(APRIL 1997)

AND SIMULATED

WATER LEVELSMAU

SIMULATED

OBSERVED

COMPARISON OF

OBSERVED

(APRIL 1997)

AND SIMULATED

WATER LEVELS

LAU

SIMULATED

OBSERVED

COMPARISON OF

OBSERVED

(APRIL 1997) AND

SIMULATED TCE

CONCENTRATIONS

UAU

SIMULATED

OBSERVED

COMPARISON OF

OBSERVED

(APRIL 1997) AND

SIMULATED TCE

CONCENTRATIONSMAU

SIMULATED

OBSERVED

COMPARISON OF

OBSERVED

(APRIL 1997) AND

SIMULATED TCE

CONCENTRATIONSLAU

SIMULATED

OBSERVED

Model Development ProcessModel Development Process

Development of conceptual modelModel constructionModel calibration Projection of future conditions

Projection of Future ConditionsProjection of Future ConditionsPrepare pumping input files – Based on projections by water providers– Generally reflect 1996 conditions

Compare ROD Required and Enhanced Remedial Alternatives

Simulate range of potential additional Remedial Actions

Simulate combinations of Remedial Actions comprising potential Remedial Alternatives

Total Mass Removed, Year 2008

0

20000

40000

60000

80000

100000

120000

140000

ROD ENH

Alternative

Pou

nds

of M

ass

Rem

oved

SWMARG-NEW

NEW LAU-3

NEW LAU-2

NEW LAU-1

MILLER/McD

7EXNEW-2

7EXNEW-1

7EX-4MA

7EX-3MA

7EX -1&2

Granite Reef

12M-EX1

PVWC-14

PVWC-15

PCX-1

COS-75A

COS-75

COS-72

COS-71

COS-31

COS-6

Total Mass Removed, Year 2028

0

20000

40000

60000

80000

100000

120000

140000

ROD ENH

Alternative

Pou

nds

of M

ass

Rem

oved

SWMARG-NEW

NEW LAU-3

NEW LAU-2

NEW LAU-1

MILLER/McD

7EXNEW-2

7EXNEW-1

7EX-4MA

7EX-3MA

7EX -1&2

Granite Reef

12M-EX1

PVWC-14

PVWC-15

PCX-1

COS-75A

COS-75

COS-72

COS-71

COS-31

COS-6

EnhancedROD

L ayer 3 T C E L ev els, R eq u ired an d E n h an ced A ltern ativ es Y ear 202 8

R e q u ire d

E n h a n c e d

Layer 3 TCE Concentrations ROD-Required and Enhanced Remedies, Year 2028

L ayer 6 T C E L ev els, R eq u ired an d E n h an ced A ltern ativ es Y ear 202 8

R e q u ire d

E n h a n c e d

Layer 6 TCE Concentrations ROD-Required and Enhanced Remedies, Year 2028

Estimated TCE Wellhead ConcentrationsCOS 71

0

50

100

150

200

250

300

1990 2000 2010 2020 2030 2040 2050

Year

TC

E C

once

ntra

tion

(ug

/l)

Required Remedy

Enhanced Remedy

Estimated TCE Wellhead ConcentrationsCOS 72

0

50

100

150

200

250

300

1990 2000 2010 2020 2030 2040 2050

Year

TC

E C

once

ntra

tion

(ug

/l)

Required Remedy

Enhanced Remedy

Estimated TCE Wellhead ConcentrationsPVWC 15

0

20

40

60

80

100

120

140

1990 2000 2010 2020 2030 2040 2050

Year

TC

E C

once

ntra

tion

(ug

/l)

Required Remedy

Enhanced Remedy

Estimated TCE Wellhead ConcentrationsPVWC 14

0

20

40

60

80

100

120

140

1990 2000 2010 2020 2030 2040 2050

Year

TC

E C

once

ntra

tion

(ug

/l)

Required Remedy

Enhanced Remedy

Anticipated Schedule for FSA Anticipated Schedule for FSA ProcessProcess Draft FSA submitted 3/29/99 EPA comments received ~ 5/1/99 Final FSA submitted ~ 6/1/99 EPA issues Proposed Plan ~ 7/1/99 Negotiation of new/amended

CD begun~ 7/1/99

ROD issued ~ 9/1/99 Draft CD completed ??