characterization and modeling of the cape cod aquifer ee&s 816
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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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Streams and RiversSurface Water BodiesState OutlineCape Cod Town Boundaries
Hydraulic HeadHydraulic Head
Cape Cod Bay
Atlantic Ocean
Nantucket Sound
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6
9
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12
2
15
18
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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
Coarse Sand and Gravel, K = Coarse Sand and Gravel, K = 7575
Coarse Sand and Gravel, K = Coarse Sand and Gravel, K = 100100
Coarse Sand and Gravel, K = Coarse Sand and Gravel, K = 150150
Fine silt/sand, K = 1 m/dFine silt/sand, K = 1 m/d
Fine silt/sand, K = 1 m/dFine silt/sand, K = 1 m/d
Fine silt/sand, K = 1 m/dFine silt/sand, K = 1 m/d
Bedrock, K = 0.000001 m/dBedrock, K = 0.000001 m/d
Bedrock, K = 0.000001 m/dBedrock, K = 0.000001 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
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
FS-28 Transport SimulationFS-28 Transport Simulation
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
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