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Advanced Models of Bank
Filtration andStream/AquiferInteraction
Jack Wittman, Ph.D., CGWPIUPUI/WHPA, Inc.
Bloomington, Indiana
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Outline Why are we interested in
RBF? What have we learned from
field investigations?
What aspect(s) of RBFprovide the regulatorychallenge?
Model or measure?Model and measure?
What is the next challenge?
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Why RBF?
Surface water quality
variability Lower cost than straight
SW treatment
Treatment effects arecredited in LT2ESWTR
Pharmaceutically activecompounds
RBF enhances well yield and
improves water quality
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RBF in the US and Europe
European RBF
line of wells alongshore line
vertical wells
pumping ~500 gpm primary purpose is
treatment
long history ofapplication
US RBF
clusters of verticalsor collector wells
horizontal wells that
pump several MGD Historically the
purpose has been
high yield Relatively short
history (1940s), fewmunicipal
applications
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Field Investigations AWWARF funded research
Gollnitz and others Great Miami River, OH
Flow path study showed that water qualityimproves most at the stream/aquiferinterface
Hubbs and others Ohio River, Louisville KY
Found that the hydraulics of the systemwere altered by pumping (clogging) thatdetached water table from River
Jasperse and Constanz Russian River Heat can be used to estimate travel time
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Field Investigations
(continued) Verstraeten and others pharmaceutically
active compounds can move from surfacewater to wells (German and US research)
Massmann and others tritium/helium age
dating indicated that the water in a BerlinRBF system is a mix of ages.
Levy and others water quality improved
when stream detached from aquifer Maxwell and others transport modeling and
analysis is possible in natural settings but
only along stream lines
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Field Investigations
(continued)
Bouwer and others RBF is an effectivepretreatment step for DBP control
Effective for controlling DBP formation infinished water
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Field Investigations have
shown:
3 to 4 log removal of pathogens is common
Effective for:
PhAC
DBP Blue-green algae
Risk depends on the setting and the qualityof the source water
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Regulatory Issues
Regulatory perspective is
naturally conservative The major risks:
scour of the river bed
short travel times
coarse deposits in aquiferbetween river and well
poor water quality associatedwith breakthroughs ofpathogens
Assume no removal atinterface
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Risk and Regulation
Regulations focus on risk LT2 requires data
Data is variable
Sites are variable
Uncertainty and complexity
Emphasis is on minimumtime between river and wells
Modeling may help make
decisions
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Modeling Issues
Stream-aquifer interactions are 3-D and
locally variable Seasonal variability in pumping and river
stage alter flows
RBF systems (especially high capacitycollector wells) have regional effects
Need insight into the velocity distribution not the minimum time
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Analytic Element Model
Modeling collector wells with MODFLOW is a
difficult task Model developed that simulates horizontal
collector wells near streams (Bakker, Kelson
and Luther, 2005) Analytic line elements that are quasi 3-D in a
heterogeneous aquifer
Published in Groundwater and used inSonoma County, St. Joseph, Missouri, DesMoines, Iowa, and Pine Bluff, Arkansas and
Terre Haute, Indiana
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Sonoma County, California Collector wells along
the Russian River
Population growthrequires additionalcapacity
Not much land in alimited area
Evaluate newcollector welltechniques
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Sonoma County
r
rr
rr
#
$Z
$Z
$Z
$Z
$Z$Z
$Z
$Z
$Z
$Z
$Z
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Sonoma County
Original Proposed
Same pumping rate in each
butdiminishing returns onadditional length
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Des Moines, Iowa New well field needed
to accommodategrowth (10+ MGD)
Collector wells along
Des Moines River How many wells?
How much water?
Water Quality
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Des Moines, Iowa DMWW coordinated
the hydrogeologicinvestigation
WHPA helped in the
aquifer testing and theinterpretation
regional 2-d model
local 3-d models
aquifer yield
water quality
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Lateral Layout Comparisons
1.2
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Where do we go from
here? Improvements in the 3-D model for simulation of
semi-confined flow
Continuing project in Sonoma Countyevaluating residence time distributions
Original Proposed
