5.2. ERMUSR 02-12-2008.^~/
Elk River -==
Municipal Utilities
13069 Orono Parkway • P.O. Box 430
Elk River, MN 55330-0430
February 5, 2008
To: Elk Ricer Municipal Utilities Commission
Jerry Takle
Jerry Gumphrey
Jim Tralle
From: Bryan Adams
Subject: Review Water Resource Option
Phone: 763.441.2020
Fax: 763.441.8099
We contracted with Barr Engineering to do a cursory study to indentify water supply alternatives
for Elk River. Attached is a copy of this study for your review. Mr. Ray Wuolo will be at our
meeting to make a presentation and answer your questions.
This is a long document but worth your while reviewing in detail.
This study reviews the regional geology issues that has allowed staff to better understand the
particular characteristics of our current wells and where we are going with future wells. The
larger metro water perspective and how it affects Elk River is also enlightening.
Identificatz'on of Water Supply Alternatives for
Elk River
Prepared for
Elk River Municipal Utilities
January 28, 2008
Identificatz'on of Water Supply Alternata'ves for
Elk River
Prepared for
Elk River Municipal Utilities
January 28, 2008
I hereby certify that this report. was prepared
by me or under my direct supervision and that
I am a duly Licensed Professional Geologist and
Professional Engineer under the laws of the stake
of Minnesota.
Signature (.J. ~~ Ray W. Wuolo
Date:. Jan ry 28 2008, Reg. No. .,19897.
4700 West 77"` Street
Minneapolis, MN 55435-4803
BARR Phone: (952) 832-2600
Fax: (952)832-2bOl
_-
Identification of Water Supply Alternatives for Elk River
Table of Contents
1.0 Introduction ............................................................................................................................................ 1
1.1 Scope and Purpose ...................................................................................................................... 1
1.2 Report Organization .................................................................................................................... 1
1.3 Other Relevant Studies and Initiatives ...................................................................................... ..2
1.4 Regional Water Demand and Use ............................................................................................. ..2
2.0 Groundwater Supplies ........................................................................................................................... ..4
2.1 Regional Geologic Setting ........................................................................................................ ..4
2.2 Geologic Conditions in the Elk River Area ................................................................................ 7
2.3 Regional Aquifer Systems ........................................................................................................ 10
2.4 Regional Groundwater Contamination and Water Quality ....................................................... 15
2.5 Available Aquifers in the Elk River Area ................................................................................. 16
2.6 Regional Groundwater Use ....................................................................................................... 19
2.7 Groundwater Use in the Elk River Area ................................................................................... 20
3.0 Surface-Water Supplies ........................................................................................................................ 25
3.1 Regional Surface Water Supplies ............................................................................................. 25
3.2 Regional Surface-Water Reliability .......................................................................................... 25
3.2.1 Water Treatment and Contamination ........................................................................... 26
3.2.2 Low-Flows and Drought .............................................................................................. 26
4.0 Summary of Alternative Water Supply Options ................................................................................... 28
4.1 Continued Use of Mt. Simon-Hinckley Wells .......................................................................... 28
4.1.1 Description ................................................................................................................... 28
4.1.2 Technical Feasibility and Reliability ........................................................................... 28
4.1.3 Cost .............................................................................................................................. 28
4.1.4 Challenges and Other Considerations .......................................................................... 28
4.2 New Wells in the Surficial (Unconsolidated) Aquifer .............................................................. 29
4.2.1 Description ................................................................................................................... 29
4.2.2 Technical Feasibility and Reliability ........................................................................... 29
4.2.3 Cost .............................................................................................................................. 29
4.2.4 Challenges and Other Considerations .......................................................................... 29
4.3 Aquifer Storage and Recovery (ASR) ...................................................................................... 30
4.3.1 Description ................................................................................................................... 30
4.3.2 Technical Feasibility and Reliability ........................................................................... 3U
4.3.3 Cost .............................................................................................................................. 30
4.3.4 Challenges and Other Considerations .......................................................................... 30
4.4 Artificial Recharge by Infiltration Basins ................................................................................. 31
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4.4.1 Description ...................................................................................................................31
4.4.2 Technical Feasibility and Reliability ........................................................................... 31
4.4.3 Cost .............................................................................................................................. 31
4.4.4 Challenges and Other Considerations .......................................................................... 31
4.5 Collection and Treatment of Mississippi River Water .............................................................. 31
4.5.1 Description ...................................................................................................................31
4.5.2 Technical Feasibility and Reliability ........................................................................... 32
4.5.3 Cost .............................................................................................................................. 32
4.5.4 Challenges and Other Considerations .......................................................................... 32
4.6 Ranney Well and Treatment ..................................................................................................... 32
4.6.1 Description ...................................................................................................................32
4.6.2 Technical Feasibility and Reliability ........................................................................... 33
4.6.3 Cost .............................................................................................................................. 33
4.6.4 Challenges and Other Considerations .......................................................................... 33
4.7 Interconnect with Minneapolis Water Works ........................................................................... 33
4.7.1 Description ...................................................................................................................33
4.7.2 Technical Feasibility and Reliability ........................................................................... 33
4.7.3 Cost .............................................................................................................................. 34
4.7.4 Challenges and Other Considerations .......................................................................... 34
4.8 Alternate Source for Lawn Water .............................................................................................34
4.8.1 Description ...................................................................................................................34
4.8.2 Technical Feasibility and Reliability ........................................................................... 34
4.8.3 Cost .............................................................................................................................. 34
4.8.4 Challenges and Other Considerations .......................................................................... 35
4.9 Water Conservation .................................................................................................................. 35
4.9.1 Description ...................................................................................................................35
4.9.2 Technical Feasibility and Reliability ........................................................................... 35
4.9.3 Cost .............................................................................................................................. 35
4.9.4 Challenges and Other Considerations .......................................................................... 35
5.0 Evaluation of Paired Mt. Simon-Hinckley and Drift Wells .................................................................36
5.1 Thickness of the Eau Claire Formation ..................................................................................... 37
5.2 Thickness of Unconsolidated Deposits .....................................................................................37
5.3 Saturated Thickness and Permeability of Unconsolidated Deposits .........................................40
5.4 Estimated Well Yield for the Unconsolidated Aquifer .............................................................41
5.5 Suggestions for Further Site Evaluation ................................................................................... 42
6.0 Summary and Discussion .....................................................................................................................43
References ................................................................................................................................................... 46
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List of Tables
Table 1 Summary of Water Supply Alternatives
List of Figures
Figure 1 Location of Hollandale Embayment
Figure 2 Schematic Geologic Cross Section Through the Twin Cities Area
Figure 3 Uppermost Bedrock in the Vicinity of Elk River
Figure 4 Approximate Depth to Bedrock
Figure 5 Aerially Averaged Percentage of Sand or Gravel in Unconsolidated Deposits
Figure 6 Outcrop Area of the Mt. Simon-Hinckely Aquifer Where Recharge Likely Takes Place
Figure 7 Conceptual Cross Section of Aquifers, Aquitards, and Groundwater Flow
Figure 8 Relative Aquifer Yield
Figure 9 Groundwater Pumping in the Greater Twin Cities Area: 2005
Figure 10 Areas of Increased Pumping Between 1990 and 2005
Figure 11 Locations of High-Capacity Wells Put Into Service Since 1990
Figure 12 Metropolitan Council Estimates for Water Demand in 2004 and 2050
Figure 13 Groundwater Use in the Elk River Area
Figure 14 2005 Pumping of Appropriated Wells
Figure 15 Major Appropriated Groundwater Use in the Elk River Area: 1988-2005
Figure 16 Trend of Groundwater Withdrawals in the Elk River Area: 1988-2005
Figure 17 Appropriated Groundwater Withdrawal in the Elk River Area by Aquifer
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Figure 18 Domestic Wells in the Vicinity of Elk River, by Aquifer
Figure 19 Areas Served by Surface Water Supplies
Figure 20 Thickness (feet) of the Eau Claire Formation in the Vicinity of Existing and Proposed
Mt. Simon-Hinckley Wells in Elk River
Figure 21 Thickness (feet) of Unconsolidated Deposits in the Vicinity of Existing and Proposed
Mt. Simon-Hinckley Wells in Elk River
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1.0 Introduction
1.1 Scope and Purpose
This report was prepared for Elk River Municipal Utilities and summarizes a preliminary evaluation
of water supplies and alternatives for the Elk River area. The purpose of this evaluation is to provide
Elk River Municipal Utilities with an overview of the sources of water, the current use of these
sources, and projections on how these sources and uses may change in the future. This evaluation is
based on existing data and reports - no new data were collected. This evaluation is not intended to be
exhaustive or definitive. The intent of this evaluation is to provide an indication of the available
water alternatives, the uncertainties associated with these alternatives, and a prognostication on how
future conditions and growth may affect these alternatives.
Elk River is not in the seven county metropolitan area of the Twin Cities and is not in the jurisdiction
of the Metropolitan Council, who is undertaking substantive water-supply planning activities.
However, from awater-supply perspective, Elk River is definitely influencing (and being influenced
by) water-supply pressures within the seven-county-metropolitan area - from a population
perspective and from asurface-water and groundwater perspective. We have attempted to place Elk
River in the context of the regional water-supply conditions of the Twin Cities metropolitan area
because future challenges and future solutions will likely be regional in nature.
1.2 Report Organization
This report is organized according to the two main sources of water: groundwater and surface water.
These two sources are, in fact, closely related, but the regulatory framework for their utilization is
different. Sections are included that discuss the availability and occurrence of these two water
sources. An additional section is included that discusses different approaches for using these
resources and the regulatory, economic, and societal challenges that are associated with the different
alternatives.
We have attempted to keep the amount of technical "jargon" as limited as possible in this report. We
feel that it is important that the contents of this report be as instructive and useful as possible. We
have attempted to provide some definitions of some of the more important concepts within the body
of this text.
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1.3 Other Relevant Studies and Initiatives
Water supply and water sustainability issues are being evaluated with increasing urgency in
Minnesota and the Twin Cities metropolitan area. The U.S. Geological Survey and the University of
Minnesota are evaluating water sustainability on a regional and state-wide basis from the perspective
of groundwater recharge (groundwater recharge is the primary limiting factor for the amount of
available water). Biofuels (primarily ethanol) production, which requires substantial amounts of
water, is a significant driver for these efforts. These efforts are expected to continue for the
foreseeable future because the quantification of groundwater recharge is very difficult.
The Metropolitan Council has organized the informal Northwest Metro Groundwater working group
to address water-supply issues in northwestern Hennepin County and portions of Anoka County.
This area has had challenges in obtaining water supply for future growth (based on projections)
because many of the bedrock aquifers that are available to other communities in the metro area are
not present here. The Metropolitan Council has, over the past three to five years, initiated several
studies to better characterize the groundwater conditions in this area -many of which have been
executed by the Minnesota Geological Survey. More recently, the Metropolitan Council has been
assisting the City of Ramsey in identifying possible water-supply alternatives, with emphasis on a
surface-water source and treatment plant. The economics of developing asurface-water source would
likely require the participation of nearby communities.
The most recent (and most comprehensive) water-supply initiative is a regional water-supply
alternative analyses that is being performed by the Metropolitan Council, with participation from
state regulatory agencies. This study began in 2006 with a regional analysis of the seven-county
metro area's water-supply infrastructure (piping, wells, treatment plants, etc.). The second part of
this study commenced in 2007 and involves (1) the construction of a regional, multi-aquifer
groundwater flow model and (2) use of this model to aid in evaluating water-supply alternatives for
selected locations in the seven county metro area. This study is slated to be completed in the second
quarter of 2008 and being performed by Barr Engineering Company.
1.4 Regional Water Demand and Use
According to the Metropolitan Council (2005) regional water demand in 2003 for the seven-county
metro area totaled over 1.3 billion gallons per day (BGD). About 65 percent of the demand was for
power generation (from surface water) and this water was returned to the region's three major rivers
in almost the same volume as was withdrawn. The remaining 35 percent was withdrawn by
municipalities (waterworks) for domestic, commercial and industrial uses; self-supplied
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commercial/industrial uses; agricultural and non-crop irrigation; water-level maintenance; special
categories; and air-conditioning uses.
Approximately 880,000 people in the metropolitan area rely, at least in part, on surface water as their
drinking water source. The Mississippi River serves as the primary water source for the Minneapolis
Water Works (MWW) and the St. Paul Regional Water Services (SPRWS), which together serve 16
additional communities with. wholesale or retail water delivery. All of the water appropriated by
Minneapolis is drawn from the Mississippi River. However, groundwater sources provide
approximately two-thirds of the water consumed in the metropolitan area and serve about 1.6 million
people through approximately 100 municipal water systems. Tb.e Prairie du Chien-Jordan aquifer
provides most of the groundwater in the metropolitan network. The Franconia-Ironton-Galesville
aquifer, the Mt. Simon-Hinckley aquifer, and local glacial drift aquifers provide water where the
Prairie du Chien-Jordan aquifer is not present. About 290,000 people in the metropolitan area obtain
their water from private wells (Metropolitan Council, 2007a).
The metropolitan area is expected to grow by about 33% by 2030 and by about 60% by 2050. The
Metropolitan Council's projections for related municipal water-use demands include a 27% increase
by 2030 and 52% increase by 2050 (the rate of water use is projected to increase at a slightly lower
rate than population growth because of water efficient appliances and general water conservation).
Total water demand is projected to increase by only 16% between 2004 and 2030 and by 35% from
2004 to 2050, due to expected improved efficiency as well as reductions in withdrawals associated
with once-through cooling, quarry dewatering and agricultural uses during this period (Metropolitan
Council, 2007a).
The Metropolitan Council (2007a) expects that the largest increases in water use between now and
2030 will take place in areas served by the Minneapolis and St. Paul water-works systems, which use
Mississippi water. The Council projects the next tier of increases will take place in several rapidly
growing suburbs and rural growth centers. Projections show several older suburbs and most rural
areas experiencing nominal increases or even small decreases in water use, due to conservation
measures (e.g., low-flow toilets, etc.) and stable lawn-water needs. Similar water use trends are
expected to continue in the region through 2050.
Changing transportation corridors will likely experience concentrations of population growth. For the
Elk River area, this will likely be along the North Star commuter rail corridor and along Interstate 94
and Highway 10.
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2.0 Groundwater Supplies
"Phis section discusses the availability of groundwater supplies in the Elk River area. Groundwater
supplies are discussed in the context of the regional setting. Groundwater t7ows through bedrock and
through surficial sand and gravel deposits. Therefore, we have included a description. of the geology
of the area in this section.
2.1 Regional Geologic Setting
The Twin Cities metro area is situated above a relatively thick sequence of permeable bedrock units
that extend south into Iowa and east into Wisconsin. These bedrock units were formed by the
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deposition of marine sediments in a shallow sea about 450 to 600 million years ago. This sea covered
what is now Iowa, Illinois, Missouri, Indiana, lower Michigan, and southern Wisconsin. A bay of this
sea, called the Hollandale Embayment, extended up into southeastern and east-central Minnesota.
Within this bay, sea level periodically rose and fell in response to changes in climate. During periods
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of higher sea level, calcium-rich mud and clay was deposited in the sea bottom. As the seas
periodically fell, beach and near-shore marine environments encroached over the mud, depositing
sand.
Over the course of millions of years, the sands and mud formed into rock. The calcium-rich mud
formed limestone, the mud formed shale, and the sand formed sandstone. The sea-level fluctuations
(called "transgressions" and "regressions"), combined with the rock-forming processes, are
responsible for the "layer cake" stratigraphy of bedrock deposits that are found in the Twin Cities
area.
In the millions of years that followed, "tectonic" processes acted on the region to cattle the rocks to
be further buried. The Twin Cities structural basin formed as much deeper crystalline rocks that are
part of one arm of the Lake Superior rift basin dropped down. ~ The rocks near what is now
Minneapolis slowly became deeper than surrounding areas. A series of faults step the bedrock down
to this slightly deeper depth. These faults are most prevalent in southeastern Washington County and
southwestern Scott County.
There is some evidence to suggest that the transgression-regression sequences continued for periods
later than 450 million years ago, depositing sediment that became younger rock formations.
However, continental glaciation that took place beginning about 2 million years ago and ending
about 200,000 years ago, "planed off 'much of these younger rocks, leaving behind a hodge-podge of
clayey silt (called "glacial till") and gravelly sand (deposited from the flowing water of the melting
glaciers). Meltwaters from the glaciers, on occasion, ponded into massive lakes, such as Glacial
Lake Agassiz in northwestern Minnesota-eastern North Dakota. A natural rock and ice dam at the
southeast end of Glacial Lake Agassiz failed catastrophically, sending massive torrents of water
down what is now the Minnesota River Valley. Other, less energetic glacial streams incised
tributaries through bedrock, forming the Mississppi River. These unconsolidated glacial deposits
have not had enough time to form into rock. Processes of erosion and deposition by flowing water
About 700-million years ago, the beginnings of a new ocean began to form in what is now part of Lake
Superior. This process, however, stopped prematurely, leaving behind a rift valley, similar to the rift valley in
Ethiopia. 'The remnants of this "failed rift valley" is the Mid-Continent Gravity Anomaly then trends from
Lakes Superior, southwest through the Twin Cities and into Missouri. This arm of the failed rift valley has
been the location of periodic tectonic activity aver geologic time.
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continue to this day in the streams and river valleys of` the area. Some of the streams have cut down
into the rock. In several places, the streams deposited sand, gravel, and clay into these alluvial.
valleys and the stream has changed course, leaving behind a "buried bedrock valley" with. little
surface topographic expression.
A generalized cross section from northwest to southeast through the Twin Cities metropolitan area is
shown on Figure 2. The crystalline Precambrian bedrock consists of very old rocks (greater than
about 600 million year old) that are composed mostly of granite-like rocks. The Mt. Simon and.
Hinckley Formations (which typically are not differentiated from one-another) are sandstones.
Overlying the Mt. Simon-Hinckley Formations is the Eau Claire Formation, which is a relatively
Cow-permeability shale. The Ironton and Galesville Sandstones overlie the Eau Claire Formation,
followed by the Franconia Formation, which is a sandstone in some locations and a shale or
NORTHWEST
ELK RIVER
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0 Glacial drift {sand. gravel. clay)
[] Platteville Formation {limestone)
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Prairie du Chien Group (limestone)
~ Jordan Sandstone ` a ,~
®St. Lawrence Formation (shale)
~ Franconia Fm. (sandstone & limestone)
~ _"~ Ironton & Galesville Sandstones
Eau Claire Formation (shale) FAULTS
C~ Mt. Simon & Hinckley Fms. (sandstone) ~ I
Precambrian Crystalline Bedrock
Figure 2 Schematic Geologic Cross Section Through the Twin Cities Area (not to scale)
limestone in others. The St. Lawrence Formation (a sandy shale) overlies the Franconia Formation.
The Jordan Sandstone (which is typically about 90 feet thick) and the Prairie du Chien Group
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(doloir~itic limestone) make up the major aquifer system in the twin Cities. The St. Peter Sandstone
overlies the Prairie du Chien Group in some locations and in a few location (such as in Minneapolis),
the Platteville Formation is the uppermost bedrock.
2.2 Geologic Conditions in the Elk River Area
Elk River is located near the western edge of the Hollandai;. Embayment. Many of the bedrock units
that are present beneath Minneapolis and St. Paul are not preser.~ underneath Elk River (either they
were never deposited or were. long ago eroded awayl. A few miles west of Elk River, even the Mt.
Simon and Hinckley Formations are not present.
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Figure 3 Uppermost Bedrock in the Vicinity of Elk River
The uppermost bedrock unit in the vicinity of Elk River is shown on Figure 3. The Mt. Simon-
Hinckley Formations and the Eau Claire Formation are the uppermost bedrock [.[nits over most of Elk
River. the Ironton-Galesville Sandtone is the uppermost bedrock in the southeast corner of Elk River.
Approximately 4 miles west, near Big Lake, the uppermost bedrock unit is Precambrian Crystalline
rocks, which marks the western edge of the Hollandale Embayment.
The depth to bedrock in Elk River is generally greater than 50 feet and in several areas, the depth to
bedrock exeeds 200 feet, as shown on Figure 4. The brown and orange areas shown on Figure 4
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Figure 4 Approximate Depth to Bedrock (feet)
suggest an erosional. channel in the bedrock surface that was subsequently filled by unconsolidated
deposits. It is likely that this channel was formed by meltwater during the last glaciation and became
a tributary to the ancestral Mississippi River. It was subsequently filled by glacial deposits. The
preponderance of sand and gravel in Elk River suggests that the fill material is likely glacial outwash
deposits (sand and
to bedrock) shown
on Figure 4 corresponds approximately to the areas where the Eats Claire Formation has been eroded
away and the first bedrock unit is the Mt. Simon-Hinckley Formations, ash shown on Figure 3.
Unconsolidated glacial drift deposits are typically heterogeneous. In one location, the unconsolidated
deposits can be mostly sand or gravel and in a nearby location, only clay may be found. "these abrupt
changes from sand to clay in glacial deposits makes siting wells difficult in some locations because it
is difficult to predict how much water a well in these deposits might yield. Using the Minnesota
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Figure 5 Aerially Averaged Percentage of Sand or Gravel in Unconsolidated Deposits
Geological Survey's County Well Index (CWI) data base, an estimate of the distribution of sandy
areas and clayey areas can be made. The aerially averaged percentage of sand in a given area is
shown on Figure 5. High percentages of sand and gravel are found along the Mississippi River and
north, along Highway 10.
2.3 Regional Aquifer Systems
Aquifers are geologic units (or unconsolidated sediment) of sufficiently high permeability that can
transport useable quantities of water. Aquitards are geologic units (or unconsolidated sediment) of
relatively low permeability that cannot transport usable quantities of water. Examples of aquifers are
sandstones, fractured limestones, and sand. Examples of aquitards are shales (formed from mud) and
glacial till (silts and clays). Aquifers and aquitards generally must be of large enough aerial extent
that they can be mapped. Aquitards typically separated aquifers from one another. Groundwater
typically flows horizontally in aquifers and vertically in aquitards. The vertical flow in aquitards
represents leakage between aquifers. Groundwater always flows "downhill" -from areas of high
pressure to low pressure.
The major aquifers and aquitards in the Twin Cities area (from deepest to shallowest) are:
1. The Mt. Simon-Hinckley Aquifer.
The Mt. Simon Sandstone and the Hinckley Sandstone together make up the Mt. Simon-Hinckley
Aquifer. This is the deepest aquifer system in the Twin Cities area. It varies in thickness up to about
300 feet thick. The aquifer is underlain by lower permeability Precambrian rocks. The Mt. Simon-
Hinckley Aquifer is recharged primarily by infiltrating precipitation and downward leakage from
unconsolidated units where it "crops out" (i.e. is the uppermost bedrock aquifer) along the edges of
the Hollandale Embayment. The recharge area for the Mt. Simon-Hinckley aquifer is shown on
Figure 6. Elk River is in an area where the Mt. Simon-Hinckley Aquifer is recharged.
Groundwater in the Mt. Simon-Hinckley Aquifer generally flows toward the Minneapolis area, where
water leaks slowly upward through the overlying Eau Claire Aquitard into shallower aquifer systems.
The Mt. Simon-Hinckley Aquifer is unique in the Twin Cities area because it generally has a poor
hydraulic connection with the major river systems (i.e. the Mississippi, St. Croix, and Minnesota
Rivers) and is not readily recharged by leakage from overlying aquifers. Groundwater pumping out
of the Mt. Simon-Hinckley Aquifer in the Minneapolis area during the 1970's and 1980's was
depleting storage in this aquifer. As a result, the Minnesota DNR generally does not issues
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appropriations permits for this aquifer and has attempted to phase ottt pumping in all areas where
another aquifer or water supply is available.
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6 Outcrop Area of the Mt. Simon-Hinckely Aquifer Where Recharge Likely 'Cakes Place
Figure 7 is a conceptual cross section that portrays the aquifers, aquitards, and general movement of
groundwater in the Twin Cities area.
P:\Mpls\23 MN\71\2371 105 Water Supply Alternative Study\FinzlDeliverables\Al:ernatives_Report_final.doc
NORTHWEST hniKrariun nanp~ecipamiuu
1 1 1 ~ hniMr>tia~0anprecipfl:bioo SOUTHEAST
1111
_ __.
2. The Eau Claire Aquitard
The Eau Claire Formation is aloes-permeability shale that overlies the Mt. Simon-Hinckley
Formation. It is a significant regional aquitard that limits leakage between the Mt. Simon-Hinckley
Aquifer and overlying aquifer systems.
3. The Franconia-Ironton-Galesville Aquifer
The Ironton and Galesville Sandstones are moderately permeable. These two units are sometimes
treated as an aquifer system separate from the overlying Franconia Formation but more typically the
three units are lumped together as a single regional aquifer system (the lower portion of the
Franconia Formation is sometimes considered an aquitard). In some locations, this aquifer can
produce substantial quantities of water (e.g., Brooklyn Park and Champlain) but in other areas,
testing as shown very little yield potential. Where other aquifers are available (e.g., the Prairie du
Chien-Jordan aquifer system), the Franconia-Ironton-Galesville (FIG) Aquifer is not tapped but
P:\Mpls\23 MN\71\2371 105 Wa[er Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc I Z
Figure 7 Conceptual Cross Section of Aquifers, Aquitards, and Groundwater Flow
where these units are the uppermost aquifer, the DNR has strongly encouraged its use as a municipal
water supply -particularly in the northwest metro area.
The Minnesota Geological Survey (MGS) has conducted extensive evaluation of the FIG Aquifer in
the northwest metro area and has found that where the Franconia Formation or the Ironton-Galesville
Sandstones are the uppermost bedrock unit, they are more highly fractured and thus, more permeable.
Where these units are overlain by other bedrock units (e.g., the St. Lawrence Formation), the
fracturing is much more poorly developed and the ability to produce usable quantities of water is
substantially reduced. The fracturing appears to be associated with "lithostatic pressure relief' -the
fractures develop where the weight of the overlying bedrock had been removed.
4. The St. Lawrence Aquitard
The St. Lawrence Formation is afine-grained sandy shale of relatively low permeability. It is
considered a regional aquitard that separates the underlying FIG Aquifer from the overlying Prairie
du Chien -Jordan aquifer system. While of relatively low permeability, the St. Lawrence Aquitard
does allow substantial leakage between the two adjoining aquifers and in some locations it can
produce usable quantities of water.
5. The Prairie du Chien-Jordan Aquifer System
The Jordan Sandstone, combined with the overlying Prairie du Chien Group, is the most important
aquifer system in the Twin Cities. Many cities rely on this aquifer system to supply most or all of
their water needs (e.g., Eden Prairie, Plymouth, Chanhassen, Minnetonka, St. Louis Park, Edina,
Woodbury, Oakdale, Eagan, Burnsville, Apple Valley, Cottage Grove, etc.). The Prairie du Chien
Group is divided up into two Formations: the basal Oneota Dolomite (which is not very permeable)
and the Shakopee Formation (which is very permeable and transmits water in horizontal fracture
systems -particularly near the contact with the Oneota Dolomite). At a local scale, the Shakopee
Formation and the Jordan Sandstone are sometimes considered different aquifers but there is enough
leakage through the Oneota Dolomite for them to act as a single aquifer system at a more regional
scale. Many municipal wells are open to both units. Typical well capacities in this aquifer exceed
1,000 gallons per minute (gpm). The Jordan Sandstone is about 90 feet thick and the Prairie du Chien
Group is about 150 feet thick (unless it has been eroded down).
The Prairie du Chien-Jordan Aquifer System has proven to be very reliable because it typically the
uppermost bedrock unit, where present, and is readily recharged by precipitation that infiltrates
P:\Mpls\23 MN\7l\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 13
through the overlying glacial drift. This aquifer system is also in direct hydraulic connection with
major rivers. All groundwater that is not pumped (with the exception of the Mt. Simon-Hinckley
Aquifer) discharges into the major river systems in the Twin Cities.
6. The Basal St. Peter Aquitard
The lower 50 feet of the St. Peter Sandstone is a shale that is considered a regional aquitard. This unit
can yield domestic-quantities of water to wells in some locations.
7. The St. Peter Aquifer
The upper 100 feet of the St. Peter Sandstone is a very uniform, clean sand. In most locations, it can
yield domestic quantities of water but it is generally not permeable enough to be used as a domestic
water supply. It is typically present only near Minneapolis-St. Paul and in isolated locations in
Washington and Dakota Counties.
8. The Platteville-Glenwood-Decorah Aquitard
The Platteville Formation is a relatively low permeability dolomitic Limestone that is underlain by the
Glenwood Shale and in some locations it is overlain by the Decorah Shale. These units rarely
produce usable quantities of water but the Platteville Formation is the site of many springs along the
Mississippi River in Minneapolis.
9. Quaternary Buried and Water Table Aquifers and Aquitards
The glacial sediments (drift) in the Twin Cities area consist of tills (clays) and outwash (sand and
gravel). The outwash can be very permeable and can be used as an aquifer where it is present. The till
layers act as aquitards. Glacial outwash deposits can be of irregular and unpredictable extent. Glacial
stratigraphy is very complex, with tills interfingering with sands over very short distances. The water
table is typically in these deposits. In some locations, a till layer may overlie a buried outwash
deposit, resulting in a buried or "confined" glacial aquifer. Some communities produce substantial
quantities of water from these outwash deposits (e.g., Maple Grove, Brooklyn Park). They can be
subject to contamination (and have higher levels of nitrate) and they are more susceptible to drought
than bedrock aquifers. In many locations, the glacial sediment (or "Quaternary") aquifers are directly
connected to the bedrock aquifers. In 2007, pumping in the Prairie du Chien-Jordan Aquifer System
in Chanhassen depleted the storage in an overlying buried glacial aquifer that was connected to the
Prairie du Chien Group.
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 14
It is also important to keep in mind that in order for a glacial sediment aquifer to be usable, it not
only has to have permeable deposits
(sand and gravel) of a large aerial
extent, it also must be thick (typically at
least 30 feet thick) and it must he
saturated or have a substantial saturated
thickness. A sand and gravel unit that is
only saturated to about 10 feet is not a
good candidate for a water supply.
The Metropolitan Council (2007b)
ranked the availability of groundwater
water supplies in the seven-county
metropolitan area using criteria such as
number and productivity of aquifers,
presence of known contamination,
population growth, well-interference
effects, and presence of nearby natural
--
Potential AquNer Yield .:. ~rr .. ~
- RenlrkleA
l 3
~ woderar~. 4
~
~ ~F
~
A ~Id
~
HIgIr MOOerate
® HMS ~j I
t
i
J ,.~,
~..
y
.,{
~ry Nqh - _
~,i3 yr.
~.~.
~
-
.,3
, ~~
~
r ~
~~ ti
s~;
°t ~ I
.~
yy w-act
a
i ~~..:
M~`,
~
~
~ - ~ x;
.v ' ~1e~' ~
r
nY ~'
[. c ~~ i
A - ~ sj
~~
~n~,
~t~ ~~~~
,,
`-'
1---~--~~ ~-:-i
- -- - --- ~ ~'I~ -- - ---~
Figure 8 Relative Aquifer Yield (from Metropolitan
Council, z007b)
for
resources that are sensitive to groundwater withdrawals. 'Their map (included here as Figure 8) shows
areas of relative aquifer yield. The areas of highest aquifer yield are ir>, eastern Hennepin, Ramsey,
and Dakota Counties, where the Prairie du Chien-Jordan Aquifer System is available. Northwestern
Hennepin County and western Anoka County area are shown as having only "moderate" to high
moderate" potential aquifer yield.
2.4 Regional Groundwater Contamination and Water Duality
Contamination of groundwater impacts water-supply availability in some parts of the metropolitan
area. Non-point source pollutants, such as nitrate, pesticides, and herbicides have impacted
groundwater quality in agricultural (or formerly agricultural) areas of Dakota, Scott, and Washington
Counties, although no wells have been taken out of service duo to these contaminants. Nitrate, for
example, can be removed from water using reverse osmosis (RO) treatment. Pesticide and herbicide
levels are generally relatively lovv and higher levels are typically isolated and impact domestic wells.
The MPCA has identified many leaky underground storage tank (LL1ST) sites in the region.
Typically, these sites are not causes of coYitaminatiun to community water supply wells. Other
potential sources of contamination (e.g., dump sites, etc.) are in various stages of investigation and
P:\Mp1s123 MN\71\2371105 water Supply Alternative Study\FinalDeli~erables~Alternatives__Report_final.doc 15
clean-up. Locations of these sites need to be considered when locating new wells. Municipalities are
required by the Minnesota Department of Health to identify these potential sources of groundwater
contamination in their Wellhead Protection Plans.
There are three known areas of groundwater contamination that have affected municipal water
supplies in the metropolitan area: the Riley Tar Site in St. Louis Park; the U.S. Army TCAAP
trichloroethene (TCE) plume in Arden Hills and New Brighton; and the extensive perfluorocarbon
(PF) contamination in southern Washington County that has been linked to three landfills that
received perfuorocarbon wastes from 3M. The Riley Tar Site and the TCAAP Site were discovered
many years ago and are actively managed. The PF contamination in southern Washington County
was first discovered in 2004-2005 and has been the object of intense evaluation since then. The PF
contamination appears to be very widespread and may have permanent impacts on groundwater
supplies in Oakdale, Lake Elmo, Woodbury, Cottage Grove, and St. Paul Park. Studies by the MPCA
and MDH suggest the PF compounds may also enter groundwater from more widespread locations
associated with municipal landfills and fire-fighting and fire-training sites (PF compounds are
associated with fire-fighting materials).
Naturally occurring constituents in aquifers can impact the water quality of municipal groundwater
supplies. It is not unusual for municipalities to treat for the removal of iron and manganese from
groundwater before distributing. Many bedrock aquifers and some glacial aquifers have naturally
high levels of iron and manganese. Arsenic concentrations above health limits are a problem in out-
state groundwater supplies but are less frequently an issue in the metropolitan area. Arsenic is a
naturally occurring trace metal in shaley rocks that were deposits in marine environments. Higher
levels of arsenic are occasionally found associated with the Eau Claire Formation. Arsenic is a
known human carcinogen and is difficult to remove at very low concentrations.
Radium and other trace radio-nuclides are commonly found slightly above health limits in sandstones
such as the Jordan Sandstone, the Ironton-Galesville Sandstones, and the Mt. Simon and Hinckley
Sandstones. Elk River treats groundwater to remove radium.
2.5 Available Aquifers in the Elk River Area
Because Elk River is located along the periphery of the Hollandale Embayment, it does not have
available to it the important Prairie du Chien-Jordan Aquifer System. In the southeastern portion of
the city limits, the Franconia-Ironton-Galesville Aquifer is likely present and does likely have above-
average permeability because it is not overlain by the St. Lawrence Formation. However, the primary
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 16
aquifer in Elk River is the Mt. Simon-Hinckley Aquifer (which is currently being used by EIk River
Municipal Utilities.
O
0
O
Groundwater Use 2005
(Million Gallons)
0 0-10 O
• 10-2U
• 20-50
• 50-75
75 - 100
4' 100 - 500
500 - 1 .000
• > 1 ,000
~~
O
5 5 5 10 15 Miles
Figure 9 Groundwater Pumping in the Greater Twin Cities Area: 2005
The Eau Claire Formation overlies the Mt. Simon-Hinckley Aquifer in most of Elk River (see Figure
3). In the northern quarter of the City, north to Zimmerman, west to Big Lake, and north into
unincorporated parts of Sherburn County, the IV1t. Simon-Hinckley Aquifer is overlain by glacial
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 17
deposits. In these areas, the Mt. Simon-Hinckely Aquifer is recharged (and these areas may be
important recharge areas for the aquifer as a whole). Some stream loss from the Mississippi River to
the Mt. Simon-Hinckley Aquifer may take place in this area.
The Mt. Simon-Hinckley Aquifer has proven to be productive in the Elk River area. Some of Elk.
River's wells have begun to experience lowered hydraulic head (water levels in wells) in response to
pumping during the summer. The Mt. Simon-Hinckley Aquifer is locally recharged by downward
leakage from the overlying glacial drift (with is mostly permeable sand and gravel outwash) and
areas where the Eau Claire Formation is thinner and/or fractured to produce secondary permeability
features.
P:\Mpls\23 MN\71\2371 105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 1 g
Figure 10 Areas of Increased Pumping Between 1990 and 2005
The glacial drift represents another aquifer that may be useable as a municipal water supply., The
gla~-ial drift is typically very permeable sand and gravel in the F.lk River area (a westward portion of
the Anoka Sand Plain i. Recharge rates to this aquifer are likely higher than in many other parts of the
metro area t~ecause of the more permeable surficial soils. The Elk River and the Mississippi. River are
in direct hyc.rauli:; connection with the glacial drift aquifer, providing a stable discharge zone and
controlling +.he minimum groundwater levels, Like other shallow sand and gravel aquifers, glacial
drift aquifer, are susceptible to contamination from land use activities -particularly non-point
agricultural source pollutants such as nitrate and pesticide/herbicides. Treatment to remove nitrate
typically involves reverse osmosis or nano-filtration methods., which are expensive.
2.6 Regional Groundwater Use
In 2005 the greater Twin Cities m?tropolit~n area (including St. Cloud and Elk River) used
approximate 131-billion gallons of groundv~ titer. 'The distribution of groundwater pumping is :,hewn
on Figure 9. This is an
increase of approximately
34-billion gallons of
annual use since 1990, or
an increase of 26%.
Figure 10 illustrates where
the increased
appropriations have taken
place. In the outer-ring
suburbs of the Twin
Cities, increases have
largelg occurred as a result.
of the installation of new
wells, whereas increased
annual pumping of
existing wells accounts for
the increases in the inner-
ring suburbs, The
Interstate-94 corridor.
running northwest from
P:\Mpis\23 MN\7Z\23%1105 Water Supply ,~lie~native Study\FinalDeliverableslAlternatives_Repoct_final.doc 19
Figure 11 Locations of High-Capacity Wells Put Int•i Service Since 1990
the 'Twin Cities, is an area. where new public water-supply wells have increased total pumping.
Figure l 1 shows the locations of new high-capacity wells that have been put into service since 1990.
'The Metropolitan Council has not explicitly predicted future groundwater use in the seven-county
metropolitan area; however, Chey have predicted future water demand. Figure 12 is the Metropolitan
Council's estimate of water demand in 2004 and their projection for water demand in 2050. 'T'his
prediction does slot differentiate between groundwater use and surface-water use,
2000 Average Water Demand (MGD)
~ 001 -o.zo
~ 0.21 ..o.m
0.41 -O.BO
~~_~ 081-1.50
.~.j 151 ..250
® 2.51 - 5.00
-500--10.00
- 10.06-:0.00 ~
- 20.00 - 75.00 .
h YB
~ Z~
2050 Average Water Oemand (MGO)
~ ao1 -o.zo
~0.2o-6m
0.40-0.90
0.90 - 7.50
1 50 - 2.50
® 2.50 •5.00
- 5.00 - 10.00
- 10.00 - 2C 00 . _
20.00.84.00 t ~~ ~'~'
~ ++s.~~
r`~
ti
*~ - ,
r;~ ,_ Ott ~:
9i
0 5 10 ~AMIe~ t S in VI!Afn
Figure 12 Metropolitan Council (2007b) Estimates for Water Demand in 2004 and 2050
2.7 Groundwater Use in
the Elk River Area
Groundwater in the Elk River area is used
for municipal. water supplies (e.g., Elk
River Municipal Utilities, Ostego,
Albertville, Ramsey), irrigation
(especially sod-farm irrigation), aggregate
processing (mainly as wash water) and in
the Ramsey area, as part of the pump-out
system of a groundwater remediation
program. Locations of these groundwater
uses are shown on Figure 13. Of course,
a
~
s~
~
,a ~ ~~z~~p,
~~ ° fit. , . ~r~
..
~~
'
t,
~
,
' iY 9
~Y as
C
a
t
~
~ -~ ~~k R~~
a
~
~
•
L ~ aem a~ +i
~ ~ 6 . '~,.~ ~t~ tl w'i
~~
:o a.
b ,,, ~,o~~a..,.,
Tali . ~.o,~...~,,,~. ~.,,o.
. , a ,~..o~...,..,e
• a
9
G.+f
a ®a • t ,~
d o ~+
°a® a ,
a
ae • ae
n ¢m a o a ¢a
>~
1 2 3 4
• • ~~ o vo
a <d . ~ ~ .
S fl 9
~ ~ as^d 1.'~?_
a ! ~~
,~ '_,~
s~ 4
7 4'
~ .~l ~~~T
~.
A
. ~ ~~ .I
~ I i
~ f St..
r_,l~ ,
` . -~,. ,
t'~a get=.:
~sZ~ s ' ~!1~.~~_S
4
Figure 13 Groundwater Use in the Elk River Area
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 20
there are also many domestic wells in the area. Domestic well usage is typically low - in the range of
about 300 gallons per day. However, many domestic wells in the area can have an effect on
groundwater use and availability.
The Minnesota DNR. requires an appropriations permit for groundwater and surface-water
withdrawals that exceed 10,000 gallons over a 30 day period or 1 million gallons per year. Monthly
pumping volumes for these appropriations must be submitted annually to the DNR. Figure 14
summarized the total annual primping for 2005 for appropriated wells in the Elk River area.
Z i mrrieltna n
•
O ~AMM EP.. TOM
~SANi OR O.JEFFR~_Y ANO JAMES
KE, CITV
• ~IN GAR O..
- •
Annual 2005 Pumping ~ ~ ~ I~
ENO LC OM BE, IOMT
~OLC OMBE,
rrll ~OLCO OWIONT
~lIAAO. OL ANO DIANE
0
41M6B~ F111CELAl1E
Elk River
'~ BEEOATE 8IW BTRI -NCR INC
ON 1AN0~ O L
~K~_"~"~ ~0RIT 2, DIANE
`~ BBNEP Ca T QUB B/6.
~P
:pMA YtlNICRAI YTik
(Mllllon Gallons) •
r~~ /~
~NINTAGE GO Li COURSEI! ~~
• 1C] -. cJo OBULOW INC
O 50-100
/~^\\ Otsego
~a.J ~~~ - zo(] ~®SEG O, CITY OF
~ > zoo
(~ ~ IL /~ T LANG OEV ENT GO MP AHY
Q 1 ~ 3 4 MII I RS WA OARO ~R
/'''QC OlB 1111CT~T LIPAL UTILITIES
`<.JCi/C RWEII M LIPAL UTILITIES
~1`EIIT gRAfll Y
Saint F
ER.CRY OF
BEND MHP ~2amsey
-INKS 0.T~Y.0 RT N FP(/O~R~{`K/~G~)C LLC ~L
v,JRPMSEY. MYOFO
0
/JAS ~
Figure 14 2005 Pumping of Appropriated Wells
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverabies\Alternatives_Report_final.doc 21
800
700
600
N
C
O
soo
c
0
e
f
~ 400
a
.~
E
d
~ 300
200
100
^ SAND & GRAVEL WASHING 1
^ MAJOR CROP IRRIGATION
^ NON-CROP IRRIGATION
^ GREAT RIVER ENERGY
^PRNATE WATERWORKS
^ OTSEGO, CITY OF
^ ELK RNER MUNICIPAL UTILITIES
Figure 15 Maior Appropriated Groundwater Use in the Elk River Area: 1988-2005
1.600
1.400
,~ 1,200
c
0
A
V
c
u 1.000
f
N
800
e`
ro 600
3
v
e
0
'U~ 400
200
0
~yHH 1~y() `~.>2 , yc)A .~jc)l~ 1`)y)3' Z()p() •~C)02 ,i0U0.
Year
^ ELK RNER MUNICIPAL UTILITIES
^ OTSEGO. CITY OF
^PRNATE WATERWORKS
^ GREAT RNER ENERGY
^ NON-CROP IRRIGATION
^ MAJOR CROP IRRIGATION
^ SAND 8 GRAVEL WASHING
Figure 16 'Trend of Groundwater Withdrawals in the Elk River Area: 1988-2005
In the immediate vicinity of Elk River, water-supply pumping by Elk River Municipal Utilities is the
largest groundwater withdrawal, as shown on Figures 15 and 16. Groundwater withdrawals by Elk
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 22
0
,ao~' .qua'' ~oa° ya` ^aa`~ ~ay`~ ^aA'` aye ~~ ~a~~ ~~,~ ,~°j ~ooo ^oo° ~oo`~ ,o~>~ oo~' .1,00`'
Year
River Municipal Utilities have increased from 250 million gallons in the early 1990's to over 700
million gallons in 2005. Withdrawals by the second largest groundwater user (major crop irrigation)
t .600
1,400
1,200
a
c
0
a
V
e 1.000
A
n 800
v
m
600
4
C
7
0
~ 400
200
^ aualernaryfunconsolldated)
^ Franconia-Ironton-Galesv;lle
i ~ Mt. Simon-Hlnckiey
I
0
1988 1989 1990 7991 "992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 ?003 2004 2005
Year
Figure 17 Appropriated Groundwater Withdrawal in the Elk River Area by Aquifer
have remained relatively
.<°° - _
steady (slightly under 300
million gallons per year). ~°°° f - ---
Sand and gravel. wash.-
eoo ~ - -
water pumping has 3
increased from about SO s
a 6~ i -
million gallons per year in €
400
early 1990's to nearly 200 i
million gallons per year in I ,°°
2005. Since 2003,
~
municipal water-supply °
-- -T --
~ Cuntamnry
pumping by Otsego has Figure 18 Domestic Wells in the Vicinity of Elk River, by Aquifer
begun and will be
expected to continue to increase as Otsego builds out.
the
P:\Mpls\23 MN\71\23'71 I05 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 23
FIG Enu Clelre MI. SlmonHinckley
AquHSr
The trend of groundwater use in the Elk River area is increasing. Increasing groundwater use is likely
due to increased population served by municipal utilities and increased gravel mining activities.
The majority of appropriated groundwater in the Elk River area is from the Mt. Simon-Hinckley
Aquifer, as shown on Figure 17. Use of this aquifer has been increasing since 1988, whereas usage
from the Franconia-Ironton-Galesville Aquifer and the unconsolidated sand and gravel aquifer has
remained relatively steady (or, in the case of pumping from the unconsolidated aquifer, increasing
slightly over the past 4 years).
In the vicinity of Elk River, the Minnesota Geological Survey's County Well Index reports
approximately 1,800 dometic wells. About 55 percent of these wells are completed in the
unconsolidated Quaternary aqufier (Figure 18). Some domestic wells are completed in the Eau Claire
Formation, which is tyically considered an aquitard but in some locations where it is the uppermost
bedrock, it is sufficiently weathered to produce domestic quantities of water. If each of the 1,800
domestic wells pumps at an average rate of 300 gallons per day, the total annual groundwater
withdrawal from the domestic wells is about 200 million gallons.
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_f"inal.doc 24
3.0 Surface-Water Supplies
3.1 Regional Surface Water Supplies
Approximately 880,000 people in the metropolitan region rely, at least in part, on surface wafer as
their drinking water source. The Mississippi River serves as the primary water source for the
Minneapolis Water Works and the St. Paul Regional Water Services, which together serve 16
additional communities with wholesale or retail water delivery. All of the water appropriated by
Minneapolis is drawn from the Mississippi River. For St. Paul, the river represents about 70% of its
appropriated water supply with the remainder pumped from high-capacity wells, the Rice Creek
Chain of Lakes (Centerville Lake) and tributaries to Vadnais Lake (Metropolitan Council, 2007a).
Between 2004 and 2030, the Metropolitan Council expects that the largest increases in water use in
the Twin Cities area will occur in areas served by the Minneapolis Water Works and the St. Paul
Regional Water Services. St. Cloud also
uses treated Mississippi River water.
Several communities purchase some or
all of their water from Minneapolis or
St. Paul. Examples include the Joint
Water Commission (Crystal, New Hope,
and Golden Valley), Bloomington
(partial supply), Edina (partial supply),
and Roseville. The surface-water service
areas are shown on Figure 19,
All other communities rely on
groundwater, which does not require the
extensive treatment necessary fol~ any
surface water.
Metropolitan Council, 2007a)
The Minnesota River is used, in part by the City of Mankato, which collects surface water though
collector wells (also known as "Ranney Wells) advanced underneath the river bed.
3.2 Regional Surface-Water Reliability
'The water intakes for the Minneapolis Water Works are in Fridley and the intake from the
Mississippi River for the St. Paul Regional Water Services is in Columbia Heights (the water is
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalBeliverables\Alternatives_Report_final.doc 25
Figure 19 Areas Served by Surface Water Supplies (from
pumped to the Vadnais chain of lakes, north of St. Paul for storage prior to treatment) Under most
conditions, Mississippi River supplies far exceed the water needed by communities that rely on the
river. In times of drought or contamination, however, use of river water may be limited. The
Minneapolis Water Works currently has no alternative water sources to the Mississippi River. This
leaves its system vulnerable to events that may limit availability of supplies from the river. St. Paul
Regional Water Services maintains a reserve to supply approximately 60 days of its `practical' water
demand. It stores its reserve in the Rice Creek Chain of Lakes (Centerville Lake) and tributaries to
Vadnais Lake, where the water can be withdrawn for use if Mississippi River supplies are limited.
The St. Paul Regional Water Services is currently evaluating groundwater as a back-up supply
(Metropolitan Council, 2007a).
3.2.1 Water Treatment and Contamination
Surface water must be treated before distribution to remove water-borne contaminants, such as
bacteria, viruses, parasites, and a variety of natural and man-made constituents. Formerly, both the
Minneapolis Water Works and the St. Paul Regional Water Services used a lime softening process to
treat raw water. Minneapolis has invested considerably to change over to nano-filtration technologies
that a designed, in part, to remove newly emerging contaminants such as pharmaceuticals and
hormones. Both the Minneapolis Water Works and the St. Paul Regional Water Services are believed
to have considerable excess capacity to treat water, or can bring such capacity on line.
Surface-water sources on the Mississippi River are vulnerable to release of upstream contaminants
that may overwhelm the treatment system (e.g., an oil spill) and to low-flow conditions in the river
that may make it impossible for the water works' intakes to keep up with minimum demands.
Surface-water supplies are susceptible to both chronic contamination and accidental or intentional
releases of contaminants from a variety of sources. Water-treatment plants may shut intakes to allow
responders to mitigate an upstream release, with the duration of shut downs related to a number of
factors, including the types of contaminants as well as the volumes and locations of the spills
(Metropolitan Council, 2007a). The federal government requires all surface-water suppliers in the
United States to include filtration and disinfection in their treatment processes as final barriers of
defense against contaminants.
3.2.2 Low-Flows and Drought
In response to the 1988 drought, the Metropolitan Council prepared ashort-term water-supply plan
which establishes a critical flow of 554 cubic feet per second (cfs) in the Mississippi River at Anoka
to supply municipal water systems, generate power, and allow navigation. These minimum flows
P:\Mpls\23 MN\7l\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 26
assume that communities relying on the river as a source of drinking water would implement
conservation measures to reduce high summer demands. Intake flows of 85 million gallons per day
for the Minneapolis Water Works and 45 million gallons per day for the St. Paul Regional Water
System are likely possible during critical flow periods. Navigation lockages could be restricted or
suspended during low-flow periods. Historical records indicate that flows at Anoka have been as low
as 602 cfs in 1934, 529 cfs in 1976, 842 cfs in 1988, and 1,530 cfs during the drought period in 2006.
The 529 cfs measured in 1976 was an instantaneous flow resulting from automatic gate operations at
the Coon Rapids Dam. The lowest daily average recorded that year was 728 cfs. The short-term
water-supply plan includes a drought response plan that is triggered by a 72-hour average flow of
2,000 cfs at Anoka, with subsequent decision points occurring at 1,200, 1,000 and 750 cfs
(Metropolitan Council, 2007a).
Low-flow conditions in the Mississippi River at Fridley during the 1988 drottght reached critical
conditions. Governor Perpich was faced with the decision to release water from upstream reservoirs
at Pokegama and Winibabigoshish reservoirs. That impending decision was greeted with significant
controversy by businesses and residents of the upstream reservoir communities that have come to
rely on the reservoirs for tourism and tourism-related income. The 1988 drought passed without
releasing water from the reservoirs but the pending actions resulted in a review of contingency plans.
The Army Corps of Engineers (ALOE) developed draft drought contingency plans in 1992 for the six
Mississippi River Headwaters Reservoirs. The plans describe in detail how reservoir operating
decisions will be made during a drought. In 1994, in response to a request from the City of
Minneapolis, the ACOE prepared a study for determining the volume and travel time for various
releases from the headwaters reservoirs and how flows will recede at Anoka under a variety of
conditions. The report highlighted the limited potential of relying on the headwater reservoirs as a
source of water supply in the metropolitan area. For instance, if the flow at Anoka is 750 cfs and is
forecast to fall to 554 cfs in 37 days, an extra 100 cfs released from Lake Winnibigoshish and Leech
Lake (total of 200 cfs) would cause the flow at Anoka to rise to 760 cfs (a 10 cfs net increase) and
extend the time it would take the flow at Anoka to fall to 554 cfs by 19 days (Metropolitan Council,
2007a). The ALOE is required with various entities (e.g., DNR, tribal governments, resort owners,
etc.) before making its final decision on whether to release additional water. However, release from
the reservoirs has never been executed and it is unclear how that process would actually proceed if it
was undertaken.
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4.0 Summary of Alternative Water Supply Options
This section summarizes various alternatives for future water supplies for Elk River Municipal
Utilities. Each alternative includes a brief description of the infrastructure, the availability and
reliability, the benefits, and the challenges of implementing the alternative. These alternatives are
described in the context of (1) likely increases in future water demand by the Utilities' customers and
(2) likely increases in water demand for surrounding areas.
4.1 Continued Use of Mt. Simon-Hinckley Wells
4.1.1 Description
The Mt. Simon-Hinckley Aquifer is a proven water supply in Elk River. Additional wells could be
installed to provide additional supply. Wells can be installed on an as-needed basis. Additional wells
would need to be balanced with the need for adding additional water treatment (principally for
removal of iron, manganese, and radium). Wells need to be located with a consideration for piping,
land availability, storage, and service area infrastructure.
4.1.2 Technical Feasibility and Reliability
The technical feasibility is high and the reliability of the alternative is high. The potential for wells to
become contaminated is low (because of the presence of the overlying Eau Claire Formation). If one
well becomes contaminated, it is unlikely that the entire system will be affected.
4.1.3 Cost
Capital costs include the cost of drilling a well and the piping, electrical, and control appurtenances.
Additional cost may include expansion of water-treatment facilities or the construction of a second
water-treatment unit. Capital costs are relatively low. Operation and Maintenance costs are generally
low. Well systems and treatment facilities need to be installed to meet peak summer capacity, which
is a multiple of base (winter) demand. This results in expenditures for parts of the well system that
are used for only a portion of the year.
4.1.4 Challenges and Other Considerations
As pumping in the Mt. Simon-Hinckley Aquifer increases (through a combination of new wells by
Elk River Municipal Utilities and growth in surrounding areas), the aquifer's storage may begin to
deplete (i.e. recharge is less than pumping). Additional wells may cause well interference effects that
result from the intersection of the drawdown cones of adjacent wells, thereby causing a reduction in
the capacity of an individual well. If pumping conditions begin to cause a depletion in storage, the
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Minnesota DNR could place a moratorium on additional wells. These conditions do not appear to be
likely in the short term but they could manifest themselves in the next 10 to 15 years.
4.2 New Wells in the S~arficial (Unc®ns®lidated) ,14~quifer
4.2.1 Description
The sand and gravel of the surficial aquifer in the Elk River area is likely very permeable and capable
of yielding large quantities of water where the saturated thickness is greater than about 50 feet.
Locating these areas (and delineating their extent) would likely require a combination of surface
geophysical surveys and test drilling. Wells completed in the surficial aquifer could supplement the
existing Mt. Simon-Hinckley wells.
4.2.2 Technical Feasibility and Reliability
Utilizing surficial unconsolidated aquifers through wells is generally a proven method for obtaining
water supplies. surficial aquifers are generally more subject to reduced yields during extended
drought conditions. surficial aquifers are also more likely to become contaminated by land use
activities and typically have higher levels of nitrate and pesticides than bedrock aquifers (although
these levels are typically below drinking water standards). surficial wells have a higher likelihood
than bedrock aquifers to become contaminated by spills and leaks. Purnping in the surficial aquifer
could reduce recharge to the underlying Mt. Simon-Hinckley Aquifer.
4.2.3 Cost
The cost for a surficial well system would likely be slightly less than the cost for a similar Mt.
Simon-Hinckley well system, due to reduced drilling costs for shallower wells. However, the cost
differential is likely small. In some locations, a Mt. Simon-Hinckley well and a surficial aquifer well
could be located close together without causing yield losses due to well interference effects. This
could result in some cost savings in piping and land acquisition.
4.2.4 Challenges and Other Considerations
Pumping from the surficial aquifer may reduce recharge conditions (over the long term) to the
underlying Mt. Simon-Hinckley aquifer. Wells located very near the Elk River or the Mississippi
River may be deemed to be "under the direct influence of surface waters" by the Minnesota
Department of Health and may require much more stringent treatment.
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4.3 Aquifer Storage and Recovery (ASR)
4.3.1 Description
Injection of water into an aquifer through one or more wells and recovery by pumping of that water
at some later date. As originally envisioned by Elk River Municipal Utilities, treated water Mt.
Simon-Hinckley water would be injected in one well during the winter in order to make use of the
excess treatment plant capacity. During summer peak use, this treated water could then be recovered
thereby obviating the need for increased treatment plant capacity and storage of treated water.
ASR may also be implemented by injecting treated surface water or water from the surficial aquifer
into the Mt. Simon-Hinckley aquifer, although these methods are more unlikely from a permitting
standpoint.
4.3.2 Technical Feasibility and Reliability
ASR that utilizes treated Mt. Simon-Hinckley Aquifer water is technically feasible. Issues of
dissimilar water quality need to be addressed to minimize fouling of the wells. This is a method
employed in other parts of the county but not in Minnesota. The Minnesota Department of Health has
indicated that they would considering permitting an ASR system. U.S. EPA Region V regulates
injection well systems and requires extensive study before permitting.
Injection of water from surface water is much more technically challenging. First, this water would
likely need to be treated to drinking-water standard using asurface-water treatment plant. Second,
the issues of dissimilar water are compounded in cases of dissimilar water sources. Injection of water
from the surficial aquifer would require variances from the Minnesota Department of Health.
4.3.3 Cost
The cost of constructing and implementing ASR is likely prohibitive. Monitoring costs may be
significant and will likely require the installation of a monitoring well network. However, the
permitting costs and studies required to obtain permits may be very costly because ASR is not
routinely implemented in the upper Midwest.
4.3.4 Challenges and Other Considerations
ASR is not a routine technology and implementation will require significant evaluation and
monitoring. If ASR is implemented by other communities, the cost of permitting may come down as
regulatory agencies gain familiarity with the approach. Risk from unforeseen technical failures are
higher than with pumping well systems.
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4.4 Artificial Recharge by Infiltration Basins
4.4.1 Description
Raise regional groundwater levels, increase aquifer storage, and promote additional recharge to the
surficial aquifer and the Mt. Simon-Hinckely Aquifer by routing runoff and precipitation into
permeable basins (e.g., abandoned aggregate mines). Natural process will act on the infiltrating water
to remove suspended sediment and many water-borne contaminants. Increased water levels can
increase the available drawdown in existing wells, thereby increasing the lnaximum yield. Reduced
yield during extended droughts can be minimized.
4.4.2 Technical Feasibility and Reliabili#y
Promotion of infiltration in basins is a widely practiced in some watersheds in the metro area and is
an emerging best management practice. Infiltration basins improve the water quality of surface-water
bodies by reducing runoff during the first parts of high-intensity precipitation events. Reductions in
recharge caused by urbanization can be reversed and recharge can be increased even beyond natural
levels. Implementation is not complicated.
4.4.3 Cost
The cost of implementation is relatively small and sites for future infiltration can be incorporated into
land ttse plans. Basins are typically left dry but vegetated. Some land may be lost from future
development.
4.4.4 Challenges and Other Considerations
Increased infiltration may not necessarily translate into meaningful increases groundwater
availability to wells. In general, the water quality of infiltrated water is likely as good or better than
the water quality of infiltration through natural soils. However, the temperature of some infiltration
basin water may be higher. There is also the potential to raise water levels in the surficial aquifer to
such an extent that they might cause wet basement conditions near the infiltration basins (although
these conditions can be substantially mitigated through proper design). This approach would
indirectly affect available water supplies but would not necessarily represent a new water supply.
4.5 Collection and Treatment of Mississippi River Water
4.,5.1 Description
Construct an intake structure on the Mississippi River and treat the pumped water in a surface-water
treatment plant.
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4.5.2 Technical Feasibility and Reliability
A surface-water intake and treatment system is a proven technology -examples include St. Cloud,
Minneapolis, and St. Paul. Reliability issues similar to those associated with existing surface-water
works may result during low-flow periods.
4.5.3 Cost
The cost of a plant to treat surface water depends on a number of factors, including capacity, whether
or not to include softening, availability of land, and the location and type of intake structure. The
Kraemer & Sons Inc. quarry in Burnsville is planning construction of a 4 million gallon per day plant
to treat quarry dewatering water (which is considered to be under the influence of surface water and
requires surface-water treatment). The estimated cost of that plant is approximately $13 million (and
does not include softening). A plant in Elk River that is capable of supplying between 8 and 12
million gallons per day would likely be in the range of $20-million to $30-million, including intake
structures. As capacity increases, the cost per gallon treated would tend to go down. Thus, there
would likely be savings realized with a larger customer base.
4.5.4 Challenges and Other Considerations
Capital cost of implementation is likely the biggest obstacle for this alternative. The cost differential
for a small treatment plant compared to a large plant is not substantial. Therefore, per capita cost of
implementation could be reduced substantially if multiple communities combined resources to build
a single facility that would serve a large area. Risks associated with contamination and low flow
could be substantially reduced for Elk River with the continued maintenance of the existing well
system as a back-up water supply. Softening in the treatment plant would likely improve overall
water quality. Mixing of water from two sources (treated surface water and untreated groundwater)
could cause water-quality issues through a repetitive cycle of precipitation and dissolution in the
piping networks, leading to fluctuating water hardness, iron staining, and scaling.
4.6 Ranney Well and Treatment
4.6.1 Description
Ranney wells are horizontal collector wells advanced underneath the bed of river. In this case, one or
more collector well laterals would be advanced below the Mississippi River from a central caisson to
obtain Mississippi River water that has undergone some filtration through the river-bed bottom.
Treatment to surface-water quality standards would still be required because this water would be
considered "groundwater under the direct influence of surface water". However, some filtration steps
in the treatment process might be eliminated from the treatment plant by using Ranney wells.
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4.6.2 Technical Feasibility and Reliability
Ranney wells are a proven technology, employed by many communities, including St. Louis, Kansas
City, and Des Moines. Ranney wells typically replace intake structures that are subject to washing
out. Reliability issues associated
4.6.3 Cost
The Ranney well alone would likely cost $1,000,000 to $2,000,000. A treatment plant similar to the
surface-water alternative would also be necessary.
4.6.4 Challenges and Other Considera#ions
This alternative has a high probability of success. The advantage that this alternative has over the
surface-water alternative is in the reliability of the intake (i.e. not subject to wash-out) and the less
susceptibility of the water source to low-water conditions and contamination from spills or other
accidental releases.
4.7 Interconnect with Minneapolis Water Works
4.7.1 Description
The Minneapolis Water Works has an excess capacity for treated water and is likely amenable to
supplying (selling) other communities with softened, treated water. A treated water main would need
to be constructed from the Minneapolis to Elk River, most likely along the future North Star corridor.
4.7.2 Technical Feasibility and Reliability
This alternative involves constructing a water main over a distance of approximately 20 miles.
Significant cost savings might be achieved by installing a pipe line in conjunction with
improvements to the North Star rail corridor. Existing storage in Elk River would need to be
evaluated to determine adequacy because water transmission would likely be during the night in
order to obtain the best price for water. Reliability issues associated with the Minneapolis Water
Works would apply to this alternative. However, if Elk River Municipal Utilities maintained their
well network as a back-up supply, those risks would be substantially reduced. In addition, some
credit would likely be realized with Minneapolis in providing an emergency interconnect. As with
any long pipeline, there is a potential for short-term shut-down for repair or damage. The DNR is
strongly encouraging the City of Ramsey to pursue this alternative and is also encouraging Elk River
to participate.
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4.7.3 Cost
The cost of the pipeline would likely be about $ 20 million. Purchase of water would need to be
negotiated with Minneapolis but would likely be in the range of $3.00 to $ 4.00 per 1,000 (including
cost of service).
4.7.4 Challenges and Other Considerations
It is highly unlikely that Elk River Municipal Utilities would pay for all of the pipeline because other
communities in the area with more pressing water-supply needs would also likely be purchasers of
water from Minneapolis. Water from Minneapolis would be softened and would likely be of excellent
quality. Elk River Municipal Utilities may lose some potential revenue by no longer being the
supplier of source water.
4.8 Alternate Source for Lawn Water
4.8.1 Description
Water for lawn sprinkling greatly increases overall water demand in the summer and places demands
for larger water-supply infrastructure (e.g., more wells, larger treatment facilities). Lawn sprinkling
water comes from the same water distribution system as all other water supplies. Separating lawn
sprinkling water from drinking water provides opportunity to use a different (and perhaps untreated)
water supply, such as water stored in basins or river water. In order to implement such a system, a
second water distribution network would be required, with a nearly redundant pipe network.
4.8.2 Technical Feasibility and Reliability
While technically feasible, a second water distribution system is likely impractical in a community
that is already significantly developed. Water mains and service lines would need to be installed in
service areas. Safeguards would need to be instituted to minimize the likelihood that untreated water
was used for potable supplies.
4.8.3 Cost
The cost of implementing a second water-distribution system for lawn sprinkling would likely be
prohibitively high. In addition to piping and maintenance, a redundant system of elevated storage
would likely be required. If surface water was used for sprinkling, intake structures and pumps would
be required.
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4.8.4 Challenges and Other Considerations
An alternative source for lawn water may be feasible for a single development or a large water user.
A local well, installed in the surficial aquifer, or an intake in a retention basin, could provide non-
potable water. On a City-wide scale, such a system seems impractical.
4.9 Water Conservation
4.9.1 Description
Elk River Municipal Utilities already employs water-conservation measures. Water conservation is
most directly applicable to lawn sprinkling because this is the largest use of water during the
summer. More stringent water-conservation measures could be employed to further reduce summer
water demand, such as a permanent ban on irrigation and sprinkling, requirements for drought-
resistant plantings, etc. Amulti-tier cost of water is another alternative, whereby the cost per 1000
gallons increases proportional to use. We understand that Elk River Municipal Utilities is planning
on a three-tier program.
4.9.2 Technical Feasibility and Reliability
Severe and permanent water-conservation measures are difficult to enforce and are widely unpopular.
Cheating would likely be widespread. Enforcement would be an issue. Multi-tier cost of service is
generally only moderately effective unless unit costs increase substantially.
4.9.3 Cost
Additional costs would be realized for enforcement and education. Cost savings would likely be
realized overall for the utility by deferring future capital expenditures for wells and treatment.
4.9.4 Challenges and Other Considerations
Very stringent water conservation measures have generally been proven to be unpopular. Land
owners expect to be able to obtain nearly unlimited quantities of water at a low price. Water demand
is generally very inelastic in that substantial increases in the cost of water generally does not deter
use because it is still considered a bargain. Ordinances that require changes to landscaping to reduce
water consumption, such as xeriscaping, require community and political acceptance. Short-term
bans on sprinkling are typically acceptable during droughts but are typically tolerated only once or
twice.
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5.0 Evaluation of Paired Mt. Simon-Hinckley and
Drift Wells
This section describes in more detailed the concept of installing new wells in the sand and gravel
drift aquifer in close proximity to existing or proposed Mt. Simon-Hinckley wells. As previously
discussed, this approach could prove to be the most viable alternative to meeting future water needs
in Elk River.2 It has the following advantages:
1. Sand and gravel is plentiful in the Elk River area. There is a high likelihood that the sand and
gravel aquifer will be productive.
2. The Eau Claire Formation separates the Mt. Simon-Hinckley aquifer from the overlying sand
and gravel deposits. The Eau Claire Formation is generally a very competent separating
aquitard with minimal leakage. This allows for very little interference between wells installed
in close proximity to one another but in different aquifers.
3. Significant savings can be realized in locating wells in pairs. Piping runs are short. A
common well house might be possible at a given location. Wellhead treatment, if any, can be
shared. Some well controls can be shared. Power infrastructure to the well heads can be
shared. Land acquisition costs would likely be reduced. Operation and maintenance activities
could be reduced.
4. Installing wells in another aquifer improves water-supply reliability in the unlikely event that
one aquifer becomes contaminated.
5. Iron, manganese, and radium concentrations in drift aquifers are usually lower than in the Mt.
Simon-Hinckley aquifer. Opportunities for blending water from the different aquifers could
result in treatment savings. In Brooklyn Park, for example, blending drift aquifer water with
z Elk River recently received an annual appropriations increase from the DNR for the Mt. Simon-Hinckley
Aquifer from 875 million gallons to 1,600 million gallons using five new wells. This increased appropriation is
expected to meet demand through the year 2016. It is likely that future appropriations will need to be satisfied
from other sources.
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Franconia-Ironton-Galesville agtaifer water has allowed the City to forgo the construction of
additional treatment facilities.
6. Future appropriations from the drift aquifer are likely to be met more favorably by the DNR
because this aquifer is quickly recharged by infiltrating precipitation and pumping effects are
localized rather than regional.
7. As gravel mining operations in the area diminish, water availability from the drift will likely
become more plentiful.
There are two main disadvantages to the paired well approach. Drift aquifers, because they are
shallow, will be more susceptible to long-term drought conditions. Drift aquifers are also more
vulnerable to contamination from land-use activities, including leaky underground storage tanks,
urban runoff, and non-point source contamination form agricultural activities. In southern
Washington County, applications of anhydrous ammonia fertilizers from decades past have resulted
in elevated nitrate levels in the shallow groundwater.
5.1 Thickness of the Eau Claire Formation
Paired wells should only be considered where the Eau Claire Formation is relatively thick in order to
minimize well interference effects caused by leakage through the Eau Claire Formation. It is not
possible in this evaluation to determine precisely what the minimum thickness should be, but as a
guideline, the Eau Claire Formation should be at least 25 feet thick and preferably greater than 50
feet thick. The thickness of the Eau Claire Formation in the vicinity of the existing and proposed Mt.
Simon-Hinckley wells is shown on Figure 203. Based on existing information, the thickness of the
Eau Claire Formation is greater than 25 feet at all well locations except Existing Well #4.
5.2 Thickness of Unconsolidated Deposits
In order for an drift aquifer well to be productive, the unconsolidated deposits must be relatively
thick (although there are other considerations, such as saturated thickness and permeability). The
thickness of unconsolidated deposits is shown on Figure 21. The thickness of unconsolidated deposits
is generally over lU0 feet at each well location.
3 The locations of proposed wells were provided by Elk River Municipal Utilities.
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Proposed Mt. Simon-Hinckley Wells in Elk River
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_tinal.doc 'jg
Figure 20 Thickness (feet) of the Eau Claire Formation in the Vicinity of Existing and
_~
_~ -- -
~ - hi k es o~ U c ns lid to a osi~ s ±-
~ -
~ -~
~ -
® Pro os Mt. '
imon Hinc ley
- - 138 ~
ell L catio s ~ 93
i
__ - ~ t 318 - 3 3
- Exi
-- - I}- ing Ik r~i
- r W -Ils
-- 13 - 18
-
~----~---- _ 1
22 3 - 4
N D
i 8
I 8
-- - - -- a
--
' 3-
48
-
8 I
93
-
' 22~ 27
~
i --i~~
~-_-~- +- - ~ 23tr- _ i ~_ ~
~ -- I-
~ ~ _ I ~
--~_
i
Figure 21 Thickness (feet) of Unconsolidated Deposits in the Vicinity of Existing and
Proposed Mt. Simon-Hinckley Wells in Elk River
P:\Mpls\23 MN\71\2371105 Water Supply Alteenative Study\FinalDeliverables\Alternatives_Report_final.doc 3C)
5.3 Saturated Thickness and Permeability of Unconsolidated
Deposits
The maximum possible saturated thickness of the unconsolidated deposits is the vertical distance
between the top of the Eau Claire Formation and the water table. The elevation of the water table
varies from about 1,000 feet above mean sea level in the northern portion of the wellfield area to the
stage elevation of the Mississippi River (approximately 860 feet, above mean sea level). This
suggests that the maximum possible saturated thickness of the unconsolidated deposits is in the range
of approximately 125 to 250 feet. Provided that the permeability is sufficiently high, saturated
thickness is this range indicate that wells in the unconsolidated deposits would have relatively high
yields.
The actual saturated thickness, however, is the thickness of continuous unconsolidated deposits
below the water table that are permeable (generally sand or coarser). In most locations, there will be
layers of clay, which will result in the actual saturated thickness being lower than the possible
saturated thickness
Unconsolidated deposits that are mostly sand and gravel can be expected to have high permeabilities:
it the range of 30 to 100 feet per day. Silts and clayey silts generally have permeabilities less than 10
feet/day and clays can be expected to have permeabilities less tan 1 foot/day. In order for an area to
be considered a likely candidate for further evaluation as a paired well site, the unconsolidated
deposits in and around that area must be at least as permeable as medium sand. The following table
summarizes the estimates of saturated thickness and permeability at the well sites:
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Well Site Estimated Unconsolidated Estimated Estimated
Saturated Materials Average Transmissivity
Thickness (feet) Permeability (thickness x
(ft/day) permeability)
ftZ/da
#2 50 Sand on top of 50 2,500
cla
#3 60 Sand and clayey 30 1,800
sand
#4 20 Sand ravel 100 2,000
#5 180 Sand and gravel 50 9,000
with cla lenses
#6 90 Sand and ravel 100 9,000
#7 SO Sand with some 30 2,400
cla
#8 50 Sand and gravel 100 5,000
(buried drift)
#9 30 Fine sand 20 600
#10 60 Sand (buried 30 1,800
drift)
#11 & #12 120 Sand with ravel 70 8,400
#13 40 Sand with cla 25 1,000
5.4 Estimated Well Yield for the Unconsolidated Aquifer
A (very) approximate estimation for maximum sustainable well capacity is:
Well Capacity (gpm) = T/267 x 0.3 x Saturated Thickness (where T is the transmissivity)
Well Site Estimate Well
Ca acit ( m) Well Site Estimate Well
Ca acit ( m)
#2 140 #8 280
#3 120 #9 20
#4 50 #10 120
#5 1,820 #11 & #12 1130
#6 910 #13 50
#7 215
Based on this estimations, the best well sites to install pairs of wells (one well in the Mt. Simon-
Hinckley Aquifer and one well in the unconsolidated aquifer) are Wells Sites #5, #6, and #1 1-#12.
These estimates must be used with caution because geologic conditions can vary sharply over a short
distance. These wells site would be could candidates for further evaluation. Wells Sites #2, #3, and
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#4 should be avoided because these locations are too close to surface-water bodies and water-gt.lality
issues associated with drawing in surface water may occur. It is also important to note that only one
well in each aquifer should be placed at each well site. A well spacing of about 2,000 feet between
wells pumping in the same aquifer is important to keep well-interference effects to a minimum.
5.5 Suggestions for Further Site Evaluation
As a next step in evaluating the well sites for suitability as paired wells, the following (in order) are
recommended:
1. Construct hydrogeologic cross sections through promising well-site areas, using well logs
from existing wells, to better evaluate the aerial extent and connectivity of the permeable
deposits in these areas. Isopach (thickness) maps of each well site should be constructed).
2. Test wells at candidate well sites should be installed, along with one monitoring well in the
unconsolidated aquifer a short distance away from the test well. A series of controlled aquifer
tests should be performed at each well site to obtain better estimates of transmissivity,
storativity, specific capacity, sustainable well yield, and to determine the degree of
interaction between the unconsolidated aquifer and the Mt. Simon-Hinckley aquifer.
3. Water-quality tests should be performed on samples collected at various times during aquifer
tests to verify that the water-quality of the aquifer is suitable for apublic-water supply.
P:\Mpls\23 MN\7l\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 42
6.0 Summary and Discussion
Elk River Municipal Utilities currently obtains all of their water supply from seven wells completed
in the Mt. Simon-Hinckley Aquifer. These wells represent approximately 8.1 million gallons per day
of capacity. The Utility provides water to approximately 4,300 metered services in the southern
portion of the Elk River municipal boundary. Total annual consumption is about 875 million gallons.
At present, the Mt. Simon-Hinckley Aquifer is a reliable water supply that is capable of meeting
current demand. Elk River Municipalities recently received an appropriation increase from 875
million gallons per year to 16,000 million gallons per year to cover approximately the next 10 years
of projected demand. It is likely that this aquifer will be able to meet increases in demands for at
least the next 8 years, although increased demand may require the installation of new wells. Greater
confidence in this prognostication could be achieved by additional studies that involved computer
modeling of groundwater flow.4
Conditions that may adversely affect the Utilities' ability to lneet future demand with the Mt. Simon-
Hinckley Aquifer are:
1. Climatic changes that result in extended periods of drought, reducing recharge to the aquifer
and placing increased demand on groundwater to meet various water demands.
2. Increased pumping in surrounding areas that are not served by the Utilities, including
adjacent communities. Increased pumping could result in well-interference effects that reduce
the well yield of individual wells or initiate a more regional depletion of storage and
associated lowering of groundwater levels.
3. Increased urbanization that reduces recharge to the aquifers. Increased urbanization with
infiltration basins that collect storm water from impervious areas may actually increase
a The Metropolitan Council is working on a regional model of groundwater flow that includes the Elk River
area. This model is scheduled to be completed in early 2008. This model could be used as a basis for
constructing a more detailed model of the Elk River area for further evaluation.
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 43
recharge but if the storm water is routed by sewer systems to the rivers, recharge could be
reduced.
4. Further regulatory limitations on use of the Mt. Simon-Hinckley Aquifer in response to
regional lowering of water levels in the Mt. Simon-Hinckley Aquifer.
5. Unforeseen contamination of the aquifer. An example of unforeseen contamination of an
aquifer is the Woodbury-Cottage Grove area where a previously unknown contaminant (poly-
fluoro compounds) was discovered to be widespread in occurrence.
Elk River Municipal Utilities currently does not have aback-up water supply (neither do many other
communities). Interconnections with adjacent communities are highly encouraged by the Minnesota
DNR to provide emergency water in case of unforeseen circumstances. Elk River is less vulnerable in
this regard than, for example, Minneapolis, which relies on a single intake for their water supply -
Elk River has seven wells and it is unlikely that all seven would experience a simultaneous failure or
contamination.
The surficial aquifer could provide aback-up water supply via wells, although additional study
would be necessary to determine the viability of the surficial aquifer in the Elk River area.
Depending on the permeability of the Eau Claire Aquitard in this area, it may be possible to pair
surficial aqufier wells with Mt. Simon-Hinckley Aquifer wells without inducing significant well-
interference effects. Well Sites #5, #6 and #11-#12 appear to be the most promising and well yields
over 1,000 gallons per minute might be realized from these wells. Additional testing would need to
be performed to verify these estimates. The surficial aquifer is more susceptible to contamination and
to drought conditions than the Mt. Simon-Hinckley Aquifer.
Any use of surface water requires a level of treatment that is substantially more expensive than
treatment of groundwater. It is unlikely that Elk River Municipal Utilities could support the
construction and operation of a surface-water treatment plant and intake structure with its existing
customer base. The economics of a surface-water source might become viable if additional customers
could be added (e.g., by selling treated water to neighboring communities) or by partnership with
other communities in a jointly owned and operated plant.
Purchasing water from other parties to meet future demand may also be viable. It is unlikely that
nearby communities will have excess groundwater to sell to Elk River because communities in this
area are already experiencing limits on groundwater availability. Therefore, any purchased source
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 44
will likely be treated surface water from an entity that has excess capacity. St. Cloud has a 16-million
gallon per day lime-softening plant with plans for expansion in 2010. It is unknown if St. Cloud has
plans or would be amenable to selling treated water. Minneapolis Water Works has alime-softening
plant with micro-filtration treatment. The Minneapolis Water Works likely has sufficient capacity to
sell treated water to additional communities. Either source (St. Cloud or Minneapolis) would require
the construction of a relatively long pipeline. The cost of the pipeline could be substantially reduced
if it served additional communities in the Elk River area or in the area of the likely pipeline route.
Elk River Municipal Utilities would be in a somewhat advantageous position if it were to obtain
treated water from another source. By retaining the capacity to supply water from the existing wells
during emergencies, Elk River could substantially improve its overall water-supply reliability. It
would likely not be economically feasible to purchase treated water only for peaking purposes -any
purchase would likely be for base demand. Also, it is important to recognize that there may be
technical issues related to precipitation and dissolution with mixing water in the distribution system
from different sources {e.g., softened surface water and unsoftened groundwater). It is also important
to recognize that if a long-term drought condition does occur in the central Minnesota, the drought
conditions will likely adversely affect both surface-water supplies and groundwater supplies.
P:\Mpls\23 MN\71\2371105 Water Supply Alternative Study\FinalDeliverables\Altematives_Report_final.doc 45
References
Delin, G.N., and Woodward, D.G. 1984. Hydrogeologic Setting and the Po~ntiometric Surfaces of
Regional Aquifers in the Hollandale Embayment, 1970-1980, Southeastern Minnesota. USGS
Water Supply Paper, WS 2219.
Metropolitan Council, 2005. 2030 Water Resources Policy Management Plan, adopted May 25, 2005.
Metropolitan Council, 2007a. Water Supply Planning in the Twin Cities Metropolitan Area, Report
to the 2007 Minnesota State Legislature, January 2007.
Metropolitan Council, 2007b. Water Supply Planning in the Twin Cities Metropolitan Area,
Technical Report, January 2007.
P:\Mpls\23 MN\71\2371 105 Water Supply Alternative Study\FinalDeliverables\Alternatives_Report_final.doc 46
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