Characterization and Modeling of the Cape Cod Aquifer EE&S 816

Characterization and Modeling of the Characterization and Modeling of the Cape Cod AquiferCape Cod Aquifer

EE&S 816EE&S 816

James K. HendersonJames K. Henderson

May 5, 2005May 5, 2005

What are Lead Scavengers?What are Lead Scavengers?

The lead scavengers 1,2-dibromoethane The lead scavengers 1,2-dibromoethane (ethylene dibromide, or EDB) and 1,2-(ethylene dibromide, or EDB) and 1,2-dichloroethane (DCA) were added to leaded dichloroethane (DCA) were added to leaded gasoline to prevent lead buildup in enginesgasoline to prevent lead buildup in engines

EDB and DCA have low allowable Maximum EDB and DCA have low allowable Maximum Contaminant Levels (MCLs) and are Contaminant Levels (MCLs) and are suspected carcinogenssuspected carcinogens

Almost 20 years after leaded gasoline was Almost 20 years after leaded gasoline was banned, available field evidence suggests banned, available field evidence suggests that EDB and DCA persist at some sites that EDB and DCA persist at some sites where leaded gasoline was releasedwhere leaded gasoline was released

MMR EDB PlumesMMR EDB Plumes

The Massachusetts Military The Massachusetts Military Reservation is one of the few sites Reservation is one of the few sites where EDB plumes have been where EDB plumes have been delineateddelineated

How are EDB plumes able to persist How are EDB plumes able to persist in the subsurface at low levels years in the subsurface at low levels years after their release?after their release?

ObjectivesObjectives

Characterize Cape Cod Characterize Cape Cod geology and hydrogeologygeology and hydrogeology

Model EDB plume behaviorModel EDB plume behavior

Cape Cod OverviewCape Cod Overview Cape Cod is a hook-shaped Cape Cod is a hook-shaped

peninsula that extends eastward from peninsula that extends eastward from the Massachusetts mainland and the Massachusetts mainland and curves north over a total length of curves north over a total length of approximately 110approximately 110

The population of Cape Cod is The population of Cape Cod is

229,545229,545 Over 4.6 million visitors come to Over 4.6 million visitors come to

Cape Cod every year Cape Cod every year Dave Hisz is from thereDave Hisz is from there

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Truro

Dennis

Wakeby

Bourne

Cotuit

Eastham

Orleans

Hyannis

Santuit

Waquoit

Mashpee

Chatham

N. Truro

S. Truro

Cataumet

Pocasset

Sagamore BrewsterSandwich

W. Dennis

S. Dennis

E. Dennis

Cummaquid

Teaticket

Megansett

Wellfleet

N. Eastham

S. Orleans

E. Harwich

W. ChathamW. Harwich

N. Harwich

Bass RiverCraigville

S. Mashpee

Forestdale

Bournedale

Osterville

Barnstable

E. Brewster

W. Brewster

S. Brewster

S. Yarmouth

W. Yarmouth

Hyannisport

E. Sandwich

New SeaburyE. Falmouth

W. Falmouth

N. Falmouth

Gray Gables

Centerville Harwich Port

Yarmouthport

Provincetown

W. Barnstable

Marstons Mills

Monument Beach

Sagamore Beach

Harwich Center

Sagamore Highla

Atlantic Ocean

Nantucket Sound

Cape Cod Bay

# Village NamesCape Cod Town BoundariesState Outline

4 0 4 8 Kilometers

DaveDave’s

House

Map of Cape Cod Map of Cape Cod

TopographyTopography

051 01 52 02 53 03 54 04 55 05 56 06 57 07 58 08 59 09 51 0 01 0 51 1 01 1 5

GeologyGeology

Four broad classes of geologic Four broad classes of geologic materials are present on Cape materials are present on Cape Cod: Cod: sand and gravel in glacial sand and gravel in glacial

outwash plainsoutwash plains fine-grained silt and clay fine-grained silt and clay

layers that underlie outwash layers that underlie outwash plainsplains

glacial till overlying bedrockglacial till overlying bedrock crystalline rock crystalline rock

StratigraphyStratigraphy

GeomorphologyGeomorphologyN

Cape Cod Bay

Atlantic Ocean

Natucket Sound

State Outline

Cape Cod GeomorphologySand and Gravel DepositsTill or BedrockSandy Till over SandEnd MorainesLarge Sand DepositsFine-grained DepositsFloodplain Alluvium

2 0 2 4 Kilometers

HydrostratigraphyHydrostratigraphy

Six interbedded lenses of highly Six interbedded lenses of highly permeable glacial outwash sand and permeable glacial outwash sand and gravel are the principal gravel are the principal hydrostratigraphic unit on the Cape hydrostratigraphic unit on the Cape

The Cape Cod aquifer is relatively The Cape Cod aquifer is relatively homogeneous and mildly anisotropic homogeneous and mildly anisotropic

Permeability CharacteristicsPermeability Characteristics

Lithology Porosity Horizontal K (m/day)

Ratio of Vertical K:Horizontal K

Silt or clay 0.68 – 0.72 0.0003 1:1

Very fine sand 0.43 30.5 1:30

Fine-grained sand 0.43 48.8 1:30

Medium-grained sand

0.39 61.0 1:5

Coarse-grained sand

0.34 – 0.38 85.4 1:5

Gravel 0.34 – 0.38 122.0 1:5

Hydraulic ConditionsHydraulic Conditions

Cape Cod Bay

Atlantic Ocean

Nantucket Sound

Long Pond

Wequaquet LakeMashpee & Wakeby Ponds

Johns Pond

Pilgrim Lake

Cliff Pond

Swan PondMystic Lake

Sheep Pond

Gull Pond

Great Pond

Hamblin Pond

Lawrence Pond

Coonamessett Pond

Seine Pond

Mill Pond

Walkers PondEel Pond

Jenkins Pond

Salt Pond

Scargo Lake

Flat Pond

Dennis Pond

Grass Pond

Clapps Pond

Cobbs Pond

Flax Pond

Micah PondNeck Pond

Shawme Lake Lower

Cedar Pond

Jones Pond

Dyer Pond

Rushy Marsh Pond

Simmons Pond

Snows Pond

Nye Pond

Bass River Ashumet Pond

Mill Pond

Follins Pond

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1 0 1 2 Kilometers

Streams and RiversSurface Water BodiesState OutlineCape Cod Town Boundaries

Hydraulic HeadHydraulic Head

Cape Cod Bay

Atlantic Ocean

Nantucket Sound

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State OutlineCape Cod OutlineStreams and RiversSurface Water BodiesGroundwater Flow Contours (3 m interval)

1 0 1 2 Kilometers

Water BalanceWater Balance

Published Value Computed Value

Flux (m/yr) % of Precip.

Flux (m/yr) % of Precip.

Precipitation 1.27 100 0.29 100

Recharge 0.7 55 0.22 76

Baseflow NA 0.29 100

Runoff NA 0.24 82

ET 0.6 47 0.13 45

Stormflow NA 0.06 20

Storage NA 0.004 1

Water QualityWater QualityConstituent Concentration (mg/L)

Dissolved Oxygen 10.0

pH 5.8

Total Dissolved Solids 39.0

Alkalinity (as CaCO3) 6.0

Bicarbonate (as HCO3) 7.0

Chloride (Cl) 8.1

Sulfate 5.2

Calcium 7.0

Magnesium 1.7

Sodium 5.5

Total Organic Carbon 2.1

Ferrous Iron 0.07

Manganese <10.0

Contaminant SourcesContaminant Sources

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Cape Cod Bay

Nantucket Sound

Atlantic Ocean

6 0 6 12 Kilometers

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MMRState OutlineCape Cod OutlineStreams and RiversSurface Water BodiesGroundwater Flow Contours (masl)MMR PlumesSuspected or Potential Plumes

# Industrial SitesWastewater Treatment Plants

Conceptual ModelConceptual Model

North South

Bedrock

Groundwater Flow Paths

Freshwater/Saltwater Interface

Saline Groundwater

Recharge Streams Cape Cod Bay

Fine-grainedSand/Silt

Glacial Till

Fuel-Spill 28 PlumeFuel-Spill 28 Plume

Discovered in 1992; source Discovered in 1992; source unknownunknown

Highest concentration of EDB is Highest concentration of EDB is 0.031 ug/l0.031 ug/l

Top of plume 60 to 100 feet below Top of plume 60 to 100 feet below ground surfaceground surface

Groundwater upwells into bogsGroundwater upwells into bogs

FS-28 PlumeFS-28 Plume

FS-28 Plume Conceptual FS-28 Plume Conceptual ModelModel

EDB Plume

Coonamessett Pond

Water Table

Fine-grained silt/sand

Coarse-grained sand/gravel

Bedrock

Graphic design rendering support provided by M. Iannacone and J. Soberaski

Release SimulationRelease Simulation

Simulate release of aviation fuel as Simulate release of aviation fuel as contaminated rechargecontaminated recharge

Run the model for 20 yearsRun the model for 20 years Expect to reproduce groundwater Expect to reproduce groundwater

upwelling into bogsupwelling into bogs

Model DevelopmentModel Development

Overview Model of Cape Cod

Calibration

Refinement (TMR)

Transport Simulation (MT3D)

Overview ModelOverview Model

Based on three DEMsBased on three DEMs 64 rows by 72 columns64 rows by 72 columns Each cell is one square kilometerEach cell is one square kilometer Of 4608 total cells, 2860 were Of 4608 total cells, 2860 were

imported as constant head using imported as constant head using StreamBCStreamBC

MMR Model LayersMMR Model Layers

Overview Model contd.Overview Model contd.

Overview Model, contd.Overview Model, contd.

Overview model reproduced six Overview model reproduced six groundwater moundsgroundwater mounds

Calibration using actual head targets Calibration using actual head targets unsuccessfulunsuccessful

Calibration achieved by adding three head Calibration achieved by adding three head targets and one flux targettargets and one flux target

Calibrated K = 224 m/dCalibrated K = 224 m/d Calibrated R = 0.002 (compare to 0.001, Calibrated R = 0.002 (compare to 0.001,

CUHydrograph)CUHydrograph)

MMR ModelMMR Model

TMR used to refine overview modelTMR used to refine overview model 100 by 100 grid used100 by 100 grid used Each cell is 220 by 240 metersEach cell is 220 by 240 meters Focus is FS-28 release areaFocus is FS-28 release area MT3D used to simulate EDB transportMT3D used to simulate EDB transport

FS-28 PlumeFS-28 Plume

StratigraphyStratigraphy

Model LayersModel Layers

Coarse Sand and Gravel, K = Coarse Sand and Gravel, K = 3030




Fine silt/sand, K = 1 m/dFine silt/sand, K = 1 m/d



Bedrock, K = 0.000001 m/dBedrock, K = 0.000001 m/d



Ground Surface

MMR Model Layers with TillMMR Model Layers with Till

Source DeterminationSource Determination

Source of FS-28 unknownSource of FS-28 unknown Location of bogs chosen as discharge Location of bogs chosen as discharge

point of FS-28point of FS-28 ModPath run in reverse (layer by ModPath run in reverse (layer by

layer) until flow ended at a single cell layer) until flow ended at a single cell (R50, C32).(R50, C32).

This cell selected at source of EDB This cell selected at source of EDB plumeplume

ModPath Results (forward ModPath Results (forward model)model)

Coonamessett Pond

ModPath Results, contd.ModPath Results, contd.

Coonamessett

Pond

FS-28 Transport SimulationFS-28 Transport Simulation




























ConclusionsConclusions

MT3D predicts impact to MT3D predicts impact to downgradient surface water, but also downgradient surface water, but also disperses the plume disperses the plume

This is likely a problem of upstream This is likely a problem of upstream weightingweighting

This may be resolved with calibration This may be resolved with calibration of the MMR model, which was not of the MMR model, which was not conducted hereconducted here

The effectiveness of other means of The effectiveness of other means of modeling FS-28 in Groundwater modeling FS-28 in Groundwater Vistas will be evaluatedVistas will be evaluated

Documents

Characterization and Modeling of the Cape Cod Aquifer EE&S 816