American Water Works Association

Vertical Flowin WellsAmerican Water Works AssociationCalifornia-Nevada SectionAnnual Fall Conference 2016San Diego, California October 26, 2016Russell J. Kyle, MS, PG, CHGAssociate HydrogeologistWood Rodgers, Inc.

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OverviewBasics of Aquifer HydraulicsTypes of Vertical FlowPossible CausesImplicationsDiagnosisMitigation

May change order of these and add new headings2

Basics of Aquifer HydraulicsUnconfinedAquifer

ConfinedAquifer

Basics of Aquifer HydraulicsAquifer (Sand & Gravel)Ground SurfaceConfining Layer (Clay)

Static Water Level

Downward Vertical FlowAquifer (Sand & Gravel)Ground SurfaceConfining Layer (Clay)

Static Water Level

Upward Vertical FlowAquifer (Sand & Gravel)Ground SurfaceConfining Layer (Clay)

Static Water Level

Upward Flow

Possible CausesWell ScreenScreen Across Aquifers with Differing Hydraulic HeadOpened Sections of Well Screen Following Well Rehabilitation EventHoles in Casing not Welded Shut During ConstructionBarholesPeep HolesHoles in Casing from CorrosionFailed Sounding Tube ConnectionsChanges in Groundwater Conditions

Casing Peep Hole

Machined EndCasing CollarPeep HoleCasing

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Welded Peep Hole

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Failed Sounding Tube

Failed Sounding TubePatched Sounding Tube Port to Eliminate FlowAmbient ConditionsDepth of Water in 3-inch Sounding Pipe 27 feet bgsDepth of Water in Well 168 feet bgsHead Differential = 141 feetStrong Downward GradientVertical Flow of ~25 gpmHigh Pressures from Head Differential caused Bulging of Casing PatchesRequired Reinforcement PatchesPostulated Cause Cement Seam

Impacts from DroughtHigh Arsenic Known to be Associated with Shallow AquifersArsenic Decline Coincident with Severe Groundwater Level DeclineGroundwater Elevations

Arsenic Concentrations

Flow Through Gravel PackNot as Big an Issue as You May Think!

Example Calculation:K = 5,000 gpd/ft2i = (Dh/L = 50 ft/100 ft)A = 2.52 ft2 (28-inch bore, 18-inch casing)Q = 6,275 gpd (4.36 gpm)

Q = -K * i * AWhere: Q = flow rate through gravel, gal/dayK = hydraulic conductivity of gravel pack, gpd/ft2A = cross-sectional area of annular space, ft2i = vertical hydraulic gradient, ft/ft

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DiagnosisTime-Series Water QualitySpinner Flowmeter SurveyDepth-Specific Groundwater QualityDye Tracer Flow Survey (BESST, Inc.)Fluid TemperatureVideo CameraFlag Survey (Flow Direction)

Flow ProfileSpinner (flowmeter) surveyMeasures depth-specific flow contributionUseful for addressing future flow and WQ issues

Mass Profiling

MitigationConsider Head Conditions and Water Quality during Design PhaseIsolated Aquifer Zone TestingMonitoring WellsWell ModificationPermanent BackfillTemporary BackfillCasing PatchesInflatable Packer (Temporary)OperationsDont Let Your Well Sit Idle!Pumping Modification to Alter Flow Profile (Dynamic)Change in Pumping RateExtended Suction

Temporary Zone Sampling

AQUIFER 1

AQUIFER 2

~18Water LevelUpper Bentonite SealGravel EnvelopeTemporary WellLower Bentonite Seal

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Preliminary Exploration Monitoring Well

AQUIFER 1

AQUIFER 2

~12

GRAVELBENTONITESEALPERMANENTWELLCEMENTSEAL

GRADIENT ACROSS SEAL

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DesignGravel Envelope Well with Inter-Aquifer Seals

Does Not Prevent Intra-Well Groundwater FlowSource: Roscoe Moss Company

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Well ModificationAquifer (Sand & Gravel)Ground SurfaceConfining Layer (Clay)

Static Water LevelDeep Contaminants (metals, color)

Well ModificationAquifer (Sand & Gravel)Ground SurfaceConfining Layer (Clay)

Static Water LevelDeep Contaminants (metals, color)

Discharge

Sealing of LowerWell Screen(s)Source: Roscoe Moss CompanyTemporaryGravel & Cement CapPermanentCementAvoid Dead Zone in Bottom of Well

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Elevated Sulfide in Deep AquifersLow Sulfide in Shallow Aquifers

Hydraulic Gradient

VerticalFlow

Equilibrium of SulfideSulfide Concentrations Exhibit Logarithmic Decay Pattern Following Idle Period

Equilibrium of SulfideRemoval of All Sulfide Would Take approx. 69 Days

Equilibrium of Arsenic

Downward Flow (Ambient)Aquifer (Sand & Gravel)Ground SurfaceConfining Layer (Clay)

Static Water LevelShallow Contaminants (nitrates, VOCs)

Well ModificationAquifer (Sand & Gravel)Ground SurfaceConfining Layer (Clay)

Static Water LevelShallow Contaminants (nitrates, VOCs)

DischargeInstall Casing Patches

CasingPatches

Little or No O&MRelatively Permanent Solution for low head differentialsHas the potential to leak under high head differential

InflatablePackers

Attached to Pump Column to Isolate Section(s) of WellTemporary SolutionRequire Ongoing O&MRisk of Deflation

Flow ModificationGround Surface

Static Water Level

High Flow (Good Quality)Moderate Flow (Poor Quality)

2,800 GPMAcceptable QualityModerate Flow (Good Quality)Low Flow (Poor Quality)Better Quality2,000 GPM

Questions?

Russell J. Kyle, MS, PG, CHGAssociate HydrogeologistWood Rodgers, Inc.rkyle@woodrodgers.com(626) 379-7569