U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2004–5031

In cooperation with the U.S. Environmental Protection Agency, Region 5, 

and City of Milwaukee, Wisconsin

Simulation of Ground-Water Flow, Surface-Water 

Flow, and a Deep Sewer Tunnel System in the 

Menomonee Valley, Milwaukee, Wisconsin
Simulation of Ground-Water Flow, 

Surface-Water Flow, and a Deep Sewer 

Tunnel System in the Menomonee Valley, 

Milwaukee, Wisconsin

By C.P. Dunning, D.T. Feinstein, R.J. Hunt, and J.T. Krohelski

In cooperation with the U.S. Environmental Protection Agency, Region 5, 

and City of Milwaukee, Wisconsin

Scientific Investigations Report 2004–5031

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.
iii

Contents

Abstract .......................................................................................................................................................... 1

Introduction ................................................................................................................................................... 1

Purpose and Scope ............................................................................................................................. 5

Hydrogeologic Setting ........................................................................................................................ 5

Acknowledgments ............................................................................................................................... 7

Conceptual Models for Ground-Water Flow in the Menomonee Valley Brownfield ......................... 8

Methods ......................................................................................................................................................... 9

Stepwise Modeling .............................................................................................................................. 9

Analytic-Element Model ................................................................................................................... 10

Finite-Difference Model .................................................................................................................... 12

Model Calibration .............................................................................................................................. 13

Application of Stepwise Modeling .......................................................................................................... 13

Model Domains .................................................................................................................................. 13

Development of the Analytic-Element Model ............................................................................... 13

Construction .............................................................................................................................. 13

Calibration .................................................................................................................................. 14

Development of the Finite-Difference Model ................................................................................ 15

Construction .............................................................................................................................. 15

Calibration and Sensitivity ....................................................................................................... 17

Model Limitations ....................................................................................................................................... 21

Uncertainties in the Hydrogeologic System .................................................................................. 21

Uncertainties in MODFLOW Target Values ................................................................................... 21

Uncertainties of Discretization and Scale ..................................................................................... 22

Limitations Arising from Extraction of Boundary Conditions ...................................................... 22

Simulation of Ground-Water Flow ............................................................................................................ 23

Ground-Water Contributing Areas .................................................................................................. 23

Sources and Sinks ............................................................................................................................. 23

Traveltimes .......................................................................................................................................... 25

Implications for Contaminant Transport ......................................................................................... 29

Summary and Conclusions ........................................................................................................................ 31

References Cited ........................................................................................................................................ 32

Appendix. Calibration targets August 14, 2001 (well name, location, screen interval, 

model layer, measured and simulated head, residual) ........................................................... 35
iv

Figures

 1–2. Maps showing:

 1. Location of Milwaukee County, the Menomonee Valley Brownfield study 

 area, the Menomonee Valley Brownfield, and downtown Milwaukee, 

 Milwaukee County, Wis. ......................................................................................................2

 2. Location of downtown Milwaukee, surface-water features, 

 the Inline Storage System (ISS), U.S. Geological Survey streamflow-gaging 

 stations, Falk Dam, 27th Street, and zones of estimated average recharge 

 across the Menomonee Valley Brownfield study area, Milwaukee 

 County, Wis ............................................................................................................................3

 3. Stratigraphic section for the Menomonee Valley Brownfield study area, 

Milwaukee County, Wis. .............................................................................................................4

 4. Block diagram of a part of the Menomonee Valley Brownfield study area, 

including a part of the Inline Storage System, Milwaukee County, Wis. ...........................5

 5. Figure showing end-members for a conceptual model of the Menomonee 

Valley Brownfield study area, Milwaukee County, Wis. .......................................................8

 6. Map showing model domains in the Menomonee Valley Brownfield study 

area, Milwaukee County, Wis. .................................................................................................11

 7–8. Figures showing:

 7. Schematic hydrostratigraphic section across the Menomonee Valley 

 Brownfield study area, Milwaukee County, Wis. ..........................................................12

 8. MODFLOW section and layering, Menomonee Valley Brownfield 

 study area, Milwaukee County, Wis. ...............................................................................16

 9. Map showing locations of channel deposits, nested wells, and minipiezometers 

in the Menomonee Valley Brownfield study area, Milwaukee County, Wis. ...................17

 10a. Calibration plot of measured hydraulic heads plotted against MODFLOWsimulated heads in the unlithified sediments (layers 1 through 4), 

Menomonee Valley Brownfield study area, Milwaukee County, Wis. ..............................19

 10b. Calibration plot of measured hydraulic heads plotted against MODFLOWsimulated heads in the dolomite (layers 5 through 8), Menomonee Valley 

Brownfield study area, Milwaukee County, Wis. .................................................................20

 11–12. Figures showing:

 11. Water-table surface in the Menomonee Valley Brownfield study area, 

 Milwaukee County, Wis., simulated with MODFLOW, and calibrated to 

 August 14, 2001 hydraulic heads. .....................................................................................23

 12. Backward particle tracking from the Inline Storage System in the 

 Menomonee Valley Brownfield study area, Milwaukee County, Wis., 

 simulated with GFLOW ......................................................................................................24

 13. Map showing capture zones simulated with MODFLOW and MODPATH 

for the Inline Storage System (ISS) in the Menomonee Valley Brownfield 

study area, Milwaukee County, Wis. ......................................................................................25

 14a–16. Graphs showing:

 14a. Sectional view (row 38) of ground-water-flow directions simulated 

 with MODFLOW and MODPATH in the Menomonee Valley Brownfield study 

 area, Milwaukee County, Wis. ..........................................................................................26

 14b. Sectional view (row 43) of ground-water-flow directions simulated with 

 MODFLOW and MODPATH in the Menomonee Valley Brownfield study area, 

 Milwaukee County, Wis. ....................................................................................................27
v

 14c. Sectional view (row 48) of ground-water-flow directions simulated with 

 MODFLOW and MODPATH in the Menomonee Valley Brownfield study 

 area, Milwaukee County, Wis. ..........................................................................................28

 15. Three-dimensional view generated by ModelViewer of ground-water flow-

 patterns in the Menomonee Valley Brownfield study area, Milwaukee 

 County, Wis. .........................................................................................................................29

 16. Traveltime to the Inline Storage System (ISS) in the Menomonee Valley 

 Brownfield study area, Milwaukee County, Wis., simulated with MODFLOW 

 and MODPATH. ...................................................................................................................30

Tables

 1. Sources of data for the construction and calibration of GFLOW and 

MODFLOW models, Menomonee Valley Brownfield study area, Milwaukee 

County, Wis. .................................................................................................................................9

 2. Hydraulic conductivities and effective porosities for calibrated GFLOW 

and MODFLOW models, Menomonee Valley Brownfield study area, 

Milwaukee County, Wis. ...........................................................................................................14

 3a. MODFLOW calibration statistics for wells in the unlithified sediments of 

the Menomonee Valley Brownfield study area, Milwaukee County, Wis. .......................18

 3b. MODFLOW calibration statistics for wells in the dolomite of the Menomonee 

Valley Brownfield study area, Milwaukee County, Wis. .....................................................18

 4. MODFLOW vertical-gradient calibration for the Menomonee Valley 

Brownfield study area, Milwaukee County, Wis. .................................................................18

 5. MODFLOW calibration to measured dry-weather infiltration to phases 

of the Inline Storage System (ISS) in the Menomonee Valley Brownfield 

study area, Milwaukee County, Wis. ......................................................................................18

 6. Ranked sensitivities of the MODFLOW parameters in the Menomonee 

Valley Brownfield study area, Milwaukee County, Wis. .....................................................19

 7. Direction of vertical gradients between river (estuary) and ground water 

below riverbed, Menomonee Valley Brownfield study area, Milwaukee 

County, Wis. ...............................................................................................................................21

 8. Statistics for simulated traveltime of recharge to surface-water sinks and 

the Inline Storage System, Menomonee Valley Brownfield study area, 

Milwaukee County, Wis. ...........................................................................................................25
vi

Conversion Factors, Vertical Datum, and Abbreviations

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 43,560 square foot (ft2

)

Discharge

cubic foot per day (ft3

/d) 28.32 liter per day (L/d)

cubic foot per second (ft3

/s) 2,446,575.5 liter per day (L/d)

Hydraulic conductivity*

foot per day (ft/d) 0.3048 meter per day (m/d)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 1929).

*Hydraulic conductivity: The standard unit for hydraulic conductivity is cubic foot per day per 

square foot of aquifer cross-sectional area (ft3/d)/ ft2. In this report, the mathematically reduced 

form, feet per day (ft/d), is used for convenience.

Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.

Water year: Water year is the 12 month period from October 1 through September 30. The water 

year is designated by the calendar year in which it ends.

Other abbreviations used in this report

Kg/d kilograms per day

in/yr inches per year
Simulation of Ground-Water Flow, Surface-Water Flow, 

and a Deep Sewer Tunnel System in the Menomonee 

Valley, Milwaukee, Wisconsin

By C.P. Dunning, D.T. Feinstein, R.J. Hunt, and J.T. Krohelski

Abstract

Numerical models were constructed for simulation 

of ground-water flow in the Menomonee Valley Brownfield, in Milwaukee, Wisconsin. An understanding of 

ground-water flow is necessary to develop an efficient 

program to sample ground water for contaminants. Models 

were constructed in a stepwise fashion, beginning with a 

regional, single-layer, analytic-element model (GFLOW 

code) that provided boundary conditions for a local, eight 

layer, finite-difference model (MODFLOW code) centered on the Menomonee Valley Brownfield. The primary 

source of ground water to the models is recharge over the 

model domains; primary sinks for ground water within 

the models are surface-water features and the Milwaukee 

Metropolitan Sewerage District Inline Storage System 

(ISS). Calibration targets were hydraulic heads, surfacewater fluxes, vertical gradients, and ground-water infiltration to the ISS. Simulation of ground-water flow by use 

of the MODFLOW model indicates that about 73 percent 

of recharge within the MODFLOW domain circulates to 

the ISS and 27 percent discharges to gaining surface-water 

bodies. In addition, infiltration to the ISS comes from 

the following sources: 36 percent from recharge within 

the model domain, 45 percent from lateral flow into the 

domain, 15 percent from Lake Michigan, and 4 percent 

from other surface-water bodies. Particle tracking reveals 

that the median traveltime from the recharge point to surface-water features is 8 years; the median time to the ISS 

is 255 years. The traveltimes to the ISS are least over the 

northern part of the valley, where dolomite is near the land 

surface. The distribution of traveltimes in the MODFLOW 

simulation is greatly influenced by the effective porosity 

values assigned to the various lithologies. 

Introduction

The City of Milwaukee, Wis. is actively promoting 

the revitalization of the Menomonee Valley Brownfield, a 

1,500-acre industrial center, south and west of downtown 

(figs. 1 and 2). Of these 1,500 acres, 300 to 400 are currently abandoned or considered by the City to be underutilized. In 1998 the City of Milwaukee successfully applied 

to the U.S Environmental Protection Agency (USEPA), 

Region 5 for a Brownfields Assessment Demonstration 

Pilot Grant. The objective of the grant was to evaluate 

innovative methods of addressing ground-water contamination (real and perceived) within the Menomonee Valley 

Brownfield. 

The Menomonee River Valley (from here on referred 

to as “the valley”) is the natural, low-lying outlet of the 

Menomonee River as it flows to Lake Michigan. Prior 

to large-scale human settlement in the early 1800s, the 

valley was a ground-water-discharge area covered with 

marshes and tamarack swamps, and bordered by relatively 

steep bluffs on the north and south (Rodolfo Salcedo, 

Department of City Development, City of Milwaukee, 

written commun., 1998; SIGMA Environmental Services, 

Inc., 2002). The Menomonee River meandered eastward 

through the marshes of the valley to the shore of Lake 

Michigan. The development of Milwaukee as a major port 

and industrial center resulted in extensive changes to the 

natural topography of the valley. From 1835 to 1890, the 

bluffs bordering the valley were cut and graded. The material from the bluffs, as well as household and industrial 

wastes, were used to fill the marshes. Starting about 1865, 

the river channel within the valley was straightened and 

dredged, and canals and slips were constructed for navigation and port facilities. Today, the path of the river is controlled and the depth of the channel maintained over the 

eastern half of the valley. By 1900, the valley had become 

a regional coal distribution center, and for years, heavy 
2 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

industries operated in the area. These industries included 

foundries, power plants, coking and coal gasification 

plants, cement plants, junkyards, stockyards, tanneries, 

switching yards, engine repair shops, and chemical companies. Also common were various material storage piles, 

such as coal, clinker, sand, gravel, and salt. An extensive 

rail system, including a large rail yard, was built in the valley to support the movement of materials to and from the 

industrial sites. Industries in the valley became the major 

source of air and water pollution in Milwaukee. Valley 

industries once employed about 50,000 people, representing over 75 percent of the region’s industrial employment 

base. Today, just over 7,000 people are employed at valley 

manufacturing firms. The relocation or demise of many 

of the valley’s industries, and the establishment of newer 

industrial parks on Milwaukee’s outskirts, have resulted in 

many vacant or underutilized properties within the valley 

(Rodolfo Salcedo, Department of City Development, City 

of Milwaukee, written commun., 1998; SIGMA Environmental Services, Inc., 2002).

Milwaukee, like a number of large metropolitan 

areas, has a combined-sewer system in which storm-sewer 

flow and sanitary-sewer flow are collected in the same 

pipe system. Historically in Milwaukee, if the capacity 

of the combined-sewer system was exceeded during a 

rain event, storm and sanitary overflow would be diverted 

to the Menomonee River or other surface-water body. 

The occurrence of overflows became more numerous as 

Milwaukee and surrounding areas grew. To address this 

problem, the Milwaukee Metropolitan Sewerage District 

(MMSD) constructed the Inline Storage System (ISS), 

also known as the Deep Tunnel. The ISS was constructed 

in the Silurian dolomite (fig. 3) between 1986 and 1994, 

and its purpose is to collect combined-sewer overflow 

during rainstorms and store it for later treatment. The ISS 

comprises 19.4 mi of tunnels constructed in phases: the 

Crosstown IA and IIA, the North Shore, the Kinnickinnic, 

and the Lake Michigan Phases (fig. 2). These tunnels are 

17 or 32 ft in diameter and run west through the valley of 

the Menomonee River, north along the valley of the Milwaukee River, and south through the valley of the Kinnickinnic River (figs. 2 and 4). The Crosstown IA phase of the 

ISS (32 ft in diameter) underlies the Menomonee Valley 

Brownfield, at a depth of 200 to 300 ft. 

Industrial contaminants such as organic solvents, 

petroleum byproducts, tars, and metal waste are found in 

the soil in the valley. These contaminants can be dissolved 

by precipitation and move with the recharge to ground 

water (SIGMA Environmental Services, Inc., 2002). A 

primary objective of this study was to determine in what 

proportion the fate of recharge to the valley is divided 

between a deep sink (the ISS) and shallow sinks (surface-water features). The fate of potentially contaminated 

ground water in different parts of the valley is of interest 

WISCONSIN

Milwaukee County Menomonee Valley

Brownfield study area

Menomonee Valley

Brownfield

Kinnickinnic R

Downtown Milwaukee

Milwaukee R

Menomonee R

0 3 6 MILES

0 3 6 KILOMETERS

Figure 1. Location of Milwaukee County, the Menomonee Valley Brownfield study area, the Menomonee Valley Brownfield, and 

downtown Milwaukee, Milwaukee County, Wis.
ISS

Crosstown

II A Phase

ISS

Crosstown

I A Phase

ISS

Kinnickinnic Phase

Lake Michigan

ISS

North Shore

Phase

Downtown

Milwaukee

Falk Dam

27th

Street

ISS

Lake Michigan

Phase

Hydrography

Menomonee Valley Brownfield

Inline Storage System (ISS)

USGS streamflow-gaging station

0.6

3.0 Crosstown I A Phase

Crosstown II A Phase

North Shore Phase

Kinnickinnic Phase

Lake Michigan Phase

Estimated recharge in inches per year

0 2 MILES

0 2 KILOMETERS

EXPLANATION

Menomonee

River

Milwaukee River

Kinnickinnic

River

Base map from USGS binary base map (BBM) files

derived from USGS digital line graphs

Jones Island

Root River

Honey Creek

Wilson

Creek

Miller Park

Figure 2. Location of downtown Milwaukee, surface-water features, the Inline Storage System (ISS), U.S. Geological Survey 

streamflow-gaging stations, Falk Dam, 27th Street, and zones of estimated average recharge across the Menomonee Valley 

Brownfield study area, Milwaukee County, Wis.

Introduction 3
4 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

to regulators and developers because it influences decisions regarding the amount of monitoring and cleanup that 

is necessary before future development can go forward. 

An additional objective of this study was to estimate 

traveltimes from the points of recharge in the valley to the 

sinks. To accomplish these objectives, the U.S. Geological 

Survey (USGS), in cooperation with the City of Milwaukee and its consultants, and with support from USEPA 

Region 5, used numerical modeling to simulate shallow 

ground-water flow in the Menomonee Valley Brownfield. 

The results and interpretations of this study, as well as the 

modeling approaches developed, may be useful as a case 

study for similar combined-sewer systems.

(Pleistocene)

Kewaunee, Oak Creek

and New Berlin Formations

(Holocene)

sediments

Maquoketa Shale

Three distinct till units

Dolomite

Quaternary

Period

Geologic

time interval Stratigraphic unit Lithology Silurian and Devonian Periods

Soil, estuarine and alluvial deposits

Years

before

present

10,000

20,000

380 million

440 million

550 million

0

Fine-, medium- and coarse-grained,

proglacial-lake sediment

Complex and variable ice margin unit

680 million

Ordovician

Period

Prairie du Chien Group

Ancell Group

Sinnipee Group Dolomite with limestone and shale

Orthoquartzite sandstone with

minor limestone

Dolomite with some sandstone

and shale

Shale and dolomite

Elk Mound Group

Tunnel City Group

Trempealeau Group

Cambrian

Period

Precambrian

Eon

Undifferentiated Crystalline

Sandstone with some

dolomite and shale

Mayville Dolomite

Thiensville Dolomite

Racine Dolomite

Figure 3. Stratigraphic section for the Menomonee Valley Brownfield study area, Milwaukee County, Wis. (modified from 

Mudrey, 1982, and Need, 1983).
Purpose and Scope

The purpose of this report is to discuss the hydrogeology of the Menomonee Valley Brownfield and shallow 

aquifers, and present simulations of ground-water flow. 

The report includes a summary of selected hydrologic 

data; conceptualization of the hydrogeologic setting of 

the Menomonee Valley Brownfield and shallow aquifers; 

details on the modeling approach, model construction 

and calibration, and model limitations; and delineation of 

ground-water recharge areas for shallow and deep sinks. 

The traveltimes and paths for recharge to move from the 

surface of the Menomonee Valley Brownfield to sinks are 

also discussed.

Hydrogeologic Setting

An understanding of the hydrogeologic setting of 

the Menomonee Valley is integral to effective simulation 

of ground-water flow, surface-water flow, and the sewer 

tunnel system. Stratigraphy, recharge, the Inline Storage 

System, and surface- and ground-water flow systems are 

discussed in the following sections.

Stratigraphy. Crystalline bedrock, Precambrian in 

age, underlies southeastern Wisconsin and the Menomonee 

Valley (fig. 3). Sandstone and carbonate units of Cambrian and Ordovician age overlie the crystalline bedrock. 

These units consist of the Elk Mound Group, the Tunnel 

City Group, the Trempealeau Group, the Prairie du Chien 

Group, the Ancell Group, and the Sinnipee Group. Directly 

overlying the Sinnipee Group is the Maquoketa Shale, a 

layer with low hydraulic conductivity, that isolates strata 

above (Silurian and younger) from strata below (Ordovician and older). Silurian units underlying the Menomonee 

Valley Brownfield are the Racine and Mayville Dolomites; 

Devonian units are represented by isolated occurrences of 

the Thiensville Dolomite. The shallow stratigraphy of the 

valley consists of unlithified Pleistocene and Holocene 

deposits overlying dolomite bedrock (figs. 3 and 4). 

 In this study, the Menomonee River Valley is identified topographically as land surface below 600 ft elevation 

and is the present-day expression of a Silurian bedrock 

valley that has been partially filled and narrowed by Pleistocene glacial deposits. These deposits are predominantly 

fine-grained regional till units with some coarser-grained 

proglacial-lake and ice-margin deposits. Detailed Quaternary stratigraphic information for the valley is presented in 

Need (1983). During the Holocene, estuarine and alluvial 

sediments were deposited over the glacial sediments in the 

marshy backwater and shallow estuaries of the valley. The 

estuarine deposits are typically organic-rich to peaty, silty 

clay and clayey silt. The alluvial deposits originated as 

channel and point-bar sediments and range in texture from 

sandy silt to gravel. These estuary and alluvial deposits

have a combined thickness of up to 30 ft; they terminate 

abruptly against the bluffs north and south of the valley, and thin and pinch out gradually to the west as the 

land surface rises out of the valley (Southeast Wisconsin 

Regional Planning Commission, 1976; Need, 1983; and 

SIGMA Environmental Services, Inc., 1999). The bluffs 

along the valley have been reduced in many areas, and 

natural and manmade fill have been added to large areas 

North West

Fill and

estuary

deposits

Crosstown IA phase of the

Inline Storage System (ISS)

Menomonee

River

Pleistocene and

Holocene deposits

Dolomite

27th Street

Vertical exaggeration 2X

Milwaukee

River Estuary

NOT TO SCALE

Figure 4. Block diagram of a part of the Menomonee Valley Brownfield study area, including a part of the Inline Storage System, 

Milwaukee County, Wis.

Introduction 5
6 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

of the valley. Fill material consists of clay, silt, sand and 

gravel, and locally variable amounts of cinder, glass, wood, 

metal, rubble, brick, ash, and household-type trash. The 

combined thickness of the estuary/alluvial sediments and 

manmade fill materials can be as much as 60 ft (SIGMA 

Environmental Services, Inc., 1999). 

Recharge. An upper bound to the rate of groundwater recharge for southeast Wisconsin is 8–10 in/yr, 

determined as the net discharge from surface- and groundwater sources in gaged streams (Gebert and others, 1989). 

Recharge commonly will vary spatially as a result of 

differences in watershed characteristics such as vegetation, 

urbanization, and evapotranspiration. Recent estimates 

of recharge rates in southeastern Wisconsin range from 

0.0 to 4.0 in/yr over almost all of the Menomonee Valley 

Brownfield study area (Cherkauer, 2001). For this investigation, the estimated recharge values have been averaged 

and simplified to two zones, one of 3.0 in/yr and the other 

of 0.6 in/yr (fig. 2). 

Hydrologic effects of the Inline Storage 

System. The ISS fills with overflow from the combinedsewer system (storm-sewer flow and sanitary-sewer flow) 

during rainstorms and stores it for later treatment and 

discharge to Lake Michigan. Between storms the ISS is 

effectively empty and is a regional sink for the groundwater system. Dry-weather infiltration of ground water to 

phases of the ISS was evaluated by MMSD in the early 

1990s using dye tracers and other techniques (Camp 

Dresser and McKee, 1998). In early 2002, consultants for 

MMSD visually inspected the ISS to better distinguish 

dry-weather flow from other outfalls (RUST/Harza, April 

2002). This investigation found the total dry-weather 

ground-water infiltration rate to the ISS to equal 4.3 ft3

/s 

(2.8 million gallons per day). As part of the same investigation, hydrographs for 46 wells were studied for the years 

following completion of the ISS (after 1993) to evaluate 

the degree to which the ground-water system was adjusting to changing subsurface stresses. Most monitoring wells 

in the dolomite near the ISS showed modest to significant 

increases in head; fewer showed declines in head. Two 

dolomite wells more distant from the ISS show a modest 

upward trend. It is possible that some heads were increasing because post-construction grouting has reduced water 

discharges to the ISS. 

Surface-Water-Flow System. Surface-water 

features of the Menomonee Valley Brownfield study area 

include Honey Creek; the Milwaukee, Menomonee, Root, 

and Kinnickinnic Rivers; the Milwaukee River Estuary; 

and Lake Michigan (fig. 2). The Milwaukee River Estuary is the name given to the Milwaukee, Menomonee, and 

Kinnickinnic Rivers once they reach the elevation of Lake 

Michigan. Downstream from this point, the stages of the 

rivers are controlled by the level of Lake Michigan. The 

Milwaukee and Kinnickinnic Rivers meet the estuary at 

the boundary of the valley itself, so gradients in stage are 

not appreciable within the valley. The Menomonee River, 

in contrast, has a gradient in stage from where it enters the 

brownfield near Miller Park to a point roughly at the site 

of the Falk Dam (fig. 2)—a river distance of about 1.5 mi. 

Above this point, the river stage is controlled by base flow, 

dry-weather outfalls to the river, and stormflow. Below this 

point, the stage of the water flowing through the valley is 

dominated by Lake Michigan water levels and occasional 

wind setup. Wind setup is the vertical rise of the stillwater 

level on the leeward side of a body of water due to wind 

blowing over the surface (Bates and Jackson, 1980). Data 

from 1860 to 1986 show the mean annual level for Lake 

Michigan is 580.11 ft above mean sea level. The maximum 

annual level was 582.57 and the minimum annual level 

was 576.95 (Quinn, 1988).

 Ground-Water-Flow System. The three aquifer 

systems present in the Menomonee Valley Brownfield 

study area are: 

 (1) (the unlithifi ed aquifer consisting of the shallowest 

Pleistocene glacial and Holocene postglacial 

deposits;

 (2) the shallow Silurian dolomite aquifer; and

 (3) the Cambrian and Ordovician units, known 

collectively as the sandstone aquifer.

The unlithified aquifer is composed of sediments with 

three different origins: tills, outwash, and proglacial-lake 

deposits of Pleistocene age; alluvial and estuarine deposits of Holocene age; and fill material added to the valley 

over the last century. The Holocene materials and the fill 

are considered to be hydrologically similar and are treated 

as a single unit in the model. The glacial and postglacial 

deposits are variable in thickness—from 0 to 200 ft in the 

Menomonee Valley Brownfield study area. The fill averages 10 to 20 ft thick, though it can be as much as 50 ft 

thick locally. Saturated thickness of the unlithified aquifer 

can be as much as 180 ft. 

Published values of horizontal hydraulic conductivity 

(Kh) for till in and around the valley range over more than 

four orders of magnitude, from 0.0004 to 9 ft/d. Published 

Kh values for glacial outwash in and around the valley 

range over about three orders of magnitude, from 0.0016 
to 1.6 ft/d (though clean sands and gravels are up to 1,400 

ft/d). Published Kh values for the estuary, alluvial, and fill 

sediments range from 4.5 to 197 ft/d (Carlson, 2000). The 

geometric mean of a set of slug tests on wells open to these 

sediments within the valley is 3.8 ft/d (SIGMA Environmental Services, Inc., 2002, table 6.15). Reported values of 

vertical hydraulic conductivity (Kv) values for the till and 

estuary materials extend over a very large range (Carlson, 

2000, Appendix C). Carlson (2000) recommended that, for 

modeling purposes, till in the study area should be given a 

Kh equal to 0.4 ft/d and a Kv equal to 0.003 ft/d. 

The Silurian dolomite aquifer underlies the entire 

Menomonee River Watershed. The relatively impermeable 

Maquoketa Shale underlies this aquifer and unlithified 

glacial and postglacial deposits overlie it (fig. 3). Although 

the dolomite is generally of low permeability, secondary porosity (fractures and dissolution), particularly near 

the top of the unit, helps to make it a productive aquifer. 

Porosity is about 5 percent (Carlson, 2000). Published 

values of Kh for the dolomite range over four orders of 

magnitude, from 0.0001 to 2.2 ft/d; published values of 

Kv for the dolomite range over three orders of magnitude, 

from 0.00006 to 0.07 ft/d (Carlson, 2000). On the basis of 

literature review and modeling of the dolomite units, Carlson (2002) estimated a Kh of 5 ft/day and a Kv of 0.01 ft/d 

for the weathered upper dolomite in the study area covered 

by this study. The unweathered lower dolomite has a Kh 

between 0.3 and 1.2 ft/d and a Kv between 0.0005 and 

0.001 ft/d (Douglas Carlson, U.S. Geological Survey, written commun., 2000). 

The sandstone aquifer is composed of geologic 

units above crystalline bedrock and below the Ordovician 

Maquoketa Shale (fig. 3), which is a confining unit (Feinstein and others, 2002). Significant lowering of the potentiometric surface in the deep sandstone aquifer (declines 

of as much as 400 ft) as a result of municipal pumping has 

resulted in appreciable gradients across the Maquoketa 

Shale confining unit. Potentiometric heads many miles 

inland are below the level of Lake Michigan (Southeast 

Wisconsin Regional Planning Commission, 1976).

 Because it is separated from the shallow Silurian 

dolomite aquifer by the Maquoketa Shale confining unit, 

the sandstone aquifer is not included in simulations of 

ground-water flow in this investigation.

Predevelopment ground-water flow in the valley was 

generally from surrounding highlands to the Menomonee 

River or Milwaukee River Estuary and ultimately to Lake 

Michigan (Southeast Wisconsin Regional Planning Commission, 1976). The current potentiometric surface within 

the Silurian dolomite aquifer is below the level of Lake 

Michigan in parts of the study area, particularly in an area 

centered on the Menomonee Valley Brownfield (Milwaukee Metropolitan Sewerage District, 1998; Plomb, 1989). 

This is primarily the effect of high-capacity wells that 

have pumped within the valley until recently. As a result 

of pumping, significant downward gradients have probably existed within the Menomonee Valley Brownfield for 

many years, from the estuarine, alluvial, and fill sediments 

to the underlying glacial sediments and Silurian dolomite 

(Southeast Wisconsin Regional Planning Commission, 

1976; Camp Dresser and McKee, 1998). Although pumpage from the dolomite is currently much reduced from 

historical rates, the construction of the ISS has introduced 

an additional stress to the system. MMSD reports show 

that heads in monitoring wells in the dolomite near the 

ISS are appreciably lower than even the lowered potentiometric surface that resulted from a century of pumping 

(Camp Dresser and McKee, 1998). Strong downward 

gradients have been observed in piezometer nests installed 

in 1999 and 2000 by consultants to the City of Milwaukee 

(SIGMA Environmental Services, Inc., 2002). Recharge 

falling on the valley is subject to these vertical gradients, 

as well as to horizontal gradients driving water toward the 

river and estuary. 

Acknowledgments

The authors acknowledge the contributions of the 

following organizations and people: Jane Neumann of U.S. 

Environmental Protection Agency (USEPA) Region 5, provided guidance for project objectives and implementation. 

Jeffery Gohlke and staff of the Department of City Development for the City of Milwaukee provided project input. 

Mafizul Islam, Kristin Kurzka and Jodi VanderVelden of 

SIGMA Environmental Services, Inc., furnished much 

of the data and information that supported the modeling 

effort, as well as coordinated and carried out the collection of additional field data. Peter McAvoy of Milwaukee’s 

16th Street Community Health Center provided general 

support and feedback on project activities. Kevin Shafer, 

Susan Anthony, and Timothy Bate of the Milwaukee Metropolitan Sewerage District provided copies of engineering 

and scientific studies and assisted in the exchange of information between their staff and consultants, and the USGS. 

Menomonee Valley Partners provided general support and 

feedback on project activities. Colleague reviews were 

done by Douglas Yeskis, USGS, and Douglas Carlson, 

Louisiana Geological Survey. Graphic and publication 

assistance were provided by Michelle Greenwood, Jennifer 

Bruce, and Susan Jones, USGS.

Introduction 7
8 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

Conceptual Models for GroundWater Flow in the Menomonee 

Valley Brownfield

A conceptual model of the hydrologic system is a precursor to numerical model construction. In defining a conceptual model, many of the general characteristics of the 

Menomonee Valley Brownfield must be considered. In the 

conceptual model, the dolomite and unconsolidated sediments above the Maquoketa Shale are assumed to compose 

a single aquifer, although there are recognized variations in 

hydrologic properties of the individual units. Over the last 

century, the hydrology of the Menomonee Valley Brownfield has become much more complicated with the physical alterations to the estuary (channelization and filling), 

high-capacity wells producing from the Silurian dolomite, 

and the recent completion of the ISS. Downward vertical 

gradients have been present in the valley for many years. 

In addition, measured heads in minipiezometers installed 

at eight locations in river sediments (SIGMA Environmental Services, Inc., 2002) indicated that downward gradients 

were common across bottom sediments of the Menomonee 

River and Milwaukee River Estuary. Dry-weather infiltration of ground water into the ISS has been quantified, but 

whether its origin is local or distant is not certain. Given 

this background, the range of possible conceptual models 

for the Menomonee Valley Brownfield can be described by 

two end-members.

Conceptual model A. All recharge to the 

Menomonee Valley Brownfield flows ultimately to the 

Menomonee River, the Milwaukee River Estuary, or Lake 

Michigan (fig. 5a). In spite of measured downward vertical 

gradients, the dolomite presents a sufficient conductivity 

contrast to restrict flow from the valley through the dolomite into the ISS. Dry-weather inflow to ISS comes from 

distant sources.

Menomonee Valley Brownfield

ISS

Menomonee Valley Brownfield

NORTH SOUTH

NORTH SOUTH

A

B

Menomonee River

Menomonee River

ISS

NOT TO SCALE

NOT TO SCALE

Figure 5. End-members for a conceptual model of the Menomonee Valley Brownfield study area, Milwaukee County, Wis.:

(A) All recharge to the valley flows ultimately to Menomonee River, the Milwaukee River Estuary or Lake Michigan and dryweather inflow to Inline Storage System (ISS) comes from distant recharge. (B) All recharge to the valley flows vertically to ISS.
Conceptual model B. All recharge to the 

Menomonee Valley Brownfield flows ultimately to the 

ISS (fig. 5b). Vertical gradients are large enough and the 

conductivity contrast is small enough that the ISS is the 

sink that captures all the recharge to the Menomonee Valley Brownfield. All surface-water features, including Lake 

Michigan, contribute flow to the ISS.

The conceptual model that was the starting point for 

the modeling effort falls in between the described endmembers. The ISS probably has an influence on groundwater flow but probably does not capture all the recharge. 

A primary objective of the study was to determine in what 

proportion recharge to the valley is divided between these 

two sinks—the ISS and surface water features.

For simplicity, it was assumed for this study that 

overall the system is at steady state, so both upward 

and downward trends in hydrographs of local wells are 

ignored. A rough calculation of storage contributions 

based on water-level changes, rock volumes, and expected 

storage parameters shows that the flux going into and out 

of storage is very small relative to reported dry-weather 

ISS infiltration. For conservative values of specific storage, 

dolomite volume, and rate of head change, the storage 

released is only 1 percent of dry-weather infiltration. 

Methods

Numerical modeling was used to simulate groundwater flow in the Menomonee Valley Brownfield. Two 

different mathematical approaches, analytic element (AE) 

and finite difference (FD), were used in a stepwise fashion 

to improve the efficiency of the modeling effort. Data for 

model construction and calibration came from numerous 

sources (table 1).

Stepwise Modeling

As modeling tools have become more sophisticated, 

concerns have been raised with regard to the cost of model 

complexity, and informational benefits of increased model 

complexity (Bredehoeft and Hall, 1995; Hunt and Zheng, 

1999). One suggested method to help ensure that the 

level of complexity is appropriate is to follow a stepwise 

modeling concept (Haitjema, 1995; Sun and others, 1998), 

whereby initial ground-water-flow models are relatively 

simple; that is, coarsely defined, and used in an exploratory fashion to help design data collection, test model 

assumptions, and provide boundary conditions for smallerscale models. 

In this study, the application of stepwise modeling 

involves the construction of a regional ground-waterflow model that is linked to a local inset model within its 

domain (Hunt and others, 1998). In this investigation of 

the Menomonee Valley Brownfield, the regional hydrology 

is simulated using a one-layer AE code based on DupuitForchheimer assumptions (Haitjema, 1995), and the local 

model is simulated using a three-dimensional FD model 

with multiple layers. Flux boundary conditions for the FD 

model were initially extracted from the AE model. Both 

Table 1. Sources of data for the construction and calibration of GFLOW and MODFLOW models, Menomonee Valley Brownfield 

study area, Milwaukee County, Wis. 

Data Source

Geologic logs with stratigraphic contacts Need (1983); D.T. Feinstein (USGS, oral commun., 2002)

Stage data for surface-water features USGS topographic maps

Slug tests in unconsolidated valley sediments SIGMA Environmental Services, Inc. (2002)

Compendium of hydraulic conductivities

from slug/aquifer tests and models

Carlson (2000)

Inline Storage System (ISS) flux measurements Rust/Harza (2002)

Recharge estimates based on empirical equation

tied to base-flow separation in selected basins

Cherkauer (2001)

Water-level measurements in wells in unlithified deposits, 

including well nests measured during 2001

SIGMA Environmental Services, Inc. (2002)

Water-level measurements in wells in dolomite, measured 

during 1994

Camp Dresser and McKee (1998), Milwaukee Metropolitan Sewerage 

District (1998)

Minipiezometer data SIGMA Environmental Services, Inc. (2002)

Conceptual Models for Ground Water in the Menomonee Valley Brownfield 9
10 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

models employ the same conceptual framework and incorporate the same sinks, but the local model adds a complex 

vertical stratigraphy, pronounced vertical anisotropy, and 

stresses originating at different elevations corresponding to 

shallow and deep sinks. As the modeling effort progressed, 

insight gained from the FD model was applied to the AE 

model, and a new extraction of boundary conditions was 

used for a revised FD model. This process continued in 

stepwise fashion until the FD model included the necessary hydrogeologic detail in the valley and was calibrated.

Both AE and FD models simulate the contributing 

areas that supply recharge to each sink. The FD model is 

used to provide quantitative estimates relating to the fate 

of recharge on the valley and the traveltime to sinks. Thus, 

in this approach, the AE model is called on only to provide 

boundary conditions. Application of the stepwise approach 

to modeling ground-water flow in the Menomonee Valley 

is thoroughly discussed in Feinstein and others (2003).

Analytic-Element Model

The AE model was constructed to simulate the 

shallow aquifer (above the Maquoketa Shale confining 

unit) and its interaction with surface-water features. The 

software used in constructing the model for this study was 

GFLOW2000 (Haitjema, 2000). AE modeling methods have been extensively documented (Strack, 1989; 

Haitjema, 1995) and have been successfully used in hydrologic settings throughout Wisconsin (Hunt and Krohelski, 

1996; Hunt and others, 1998; Krohelski and others, 2000; 

Hunt, Graczyk, and Rose, 2000; Hunt, Lin, and others, 

2000). 

The GFLOW2000 (GFLOW) model is a single-layer, 

steady-state model in which the aquifer is assumed to be 

infinite. The model uses the Dupuit-Forchheimer approximation by which a three-dimensional-flow problem is 

reduced to a two-dimensional, horizontal-flow problem. 

For this approximation to be appropriately applied, the 

length of a flowline must be large compared to the aquifer 

thickness. Within the Menomonee Valley Brownfield, the 

460-ft thick shallow aquifer is about 3,000 ft wide north to 

south (across the valley) and about 18,000 ft long west to 

east (along the valley). Therefore, this aquifer is very thin 

relative to its horizontal extent, suggesting that groundwater flow in the valley is a horizontal-flow problem and 

can be appropriately evaluated by use of a Dupuit–Forchheimer approximation. This GFLOW model contains a 

conjunctive solution (Mitchell-Bruker and Haitjema, 1996) 

that considers the interaction of surface-water and groundwater flow. Because of the proximity of the rivers and 

estuary, the conjunctive solution is an important consideration for evaluating ground-water flow in the Menomonee 

Valley Brownfield.

Important hydrologic features (rivers, streams, and 

lakes) are represented in the GFLOW model domain as 

analytic elements or strings of analytic elements (linesinks). Each element provides an analytic solution to 

the ground-water-flow equation, and the superposition 

of many individual solutions provides a solution for the 

ground-water-flow system. The model domain consists 

of both a far field and a near field (fig. 6). The far field is 

beyond the area of interest but is included in the model to 

define hydrologic boundary conditions for the near field. 

Far-field elements are constant-head boundaries, and nearfield elements are head-dependent boundaries. Far-field 

elements are usually coarsely defined and consist only of 

water-level information that is estimated from USGS topographic data. The near-field is the area of primary interest 

and contains important local hydrologic inhomogeneities; 

that is, areas where recharge and (or) aquifer parameter 

values differ from regional values. A hydrologic inhomogeneity is represented in the GFLOW model by a closed 

set of elements, within which the nonregional parameter 

values are present. Near-field analytic elements are made 

to more closely match the geometry of surface-water 

features and therefore require more line-sink vertices and 

solutions. Solutions for near-field elements also require 

information on the width and resistance of the represented feature. Regional values for aquifer parameters and 

recharge rate are applied across the entire GFLOW model 

domain. Aquifer parameters for the single-layer AE model 

are based on a generalized hydrostratigraphic section of 

the shallow aquifer (fig. 7).

The GFLOW model domain is not discretized into a 

grid; therefore, an exact solution for the flow equation can 

be calculated at any point in the domain. As a result, interpolation of heads or velocities is not necessary. Flow can 

also be examined at various scales without changing model 

input parameters or boundary conditions. This allows one 

GFLOW model to function at both a regional and a site 

scale without modification. GFLOW simulations are evaluated with respect to available composite head information 

and gaged streamflows. Finally, GFLOW is well suited as 

a regional model of the Menomonee Valley Brownfield 

because it allows the extraction of boundary conditions 

from a simulation directly into MODFLOW. 
ISS

Crosstown

II A phase ISS

Crosstown

I A phase

ISS

Kinnickinnic

phase

ISS

North Shore

Phase

ISS

Lake Michigan

phase

Lake

Michigan

Extent of MODFLOW model domain

Extent of recharge to GFLOW model

Wilson

Far-field model elements

Near-field model elements

Menomonee Valley Brownfield

inhomogeneity representing higher

horizontal hydraulic conductivity

Menomonee

Honey

Kinnickinnic

Root

Milwaukee

River

River

River

River

Creek

Creek

EXPLANATION

2 MILES

2 KILOMETERS

0

0

Inline Storage System

Crosstown I A Phase

Crosstown II A Phase

North Shore Phase

Kinnickinnic Phase

Lake Michigan Phase

Figure 6. Model domains in the Menomonee Valley Brownfield study area, Milwaukee County, Wis.

Methods 11
12 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

Finite-Difference Model

The FD model was constructed to simulate the shallow aquifer (above the Maquoketa Shale confining unit) 

and its interaction with surface-water features and the 

ISS. The FD model, developed with the use of the computer program MODFLOW 88 (McDonald and Harbaugh, 

1988), is a multilayer model in which the aquifer is 

bounded by constant-flux boundaries extracted from the 

GFLOW model simulation. The multiple layers allow for 

vertical discretization representing hydrogeologic variation, as well as simulation of vertical gradients and flow.

Two particle-tracking programs were used to determine the flow paths of recharge as it moves from the water 

table to sinks, such as streams or the ISS. Both MODPATH (Pollock, 1994) and PATH3D (S.S. Papadopulos & 

Associates, 1991) are designed to work with MODFLOW 

model output and were used in this investigation. Output 

from MODFLOW simulations is used in MODPATH 

and PATH3D to compute paths for imaginary particles of 

water moving through the simulated ground-water system. 

In addition to computing particle paths, MODPATH and 

PATH3D keep track of the traveltime for particles moving through the system, making possible a wide range of 

analyses, such as delineating capture and recharge areas 

Pleistocene till

Holocene fill / estuary deposits

Weathered

Silurian

dolomite

Land surface = 750 feet

Land surface = 590 feet

525 feet

390 feet

130 feet

Pleistocene till

Pleistocene till

Silurian

dolomite

N S

NOT TO SCALE

Elevations are shown in feet above NGVD 29

Lake

Michigan

Milwaukee River

Menomonee River

Honey Creek

Kinnickinnic

River

Location of section shown below

Menomonee Valley

Figure 7. Schematic hydrostratigraphic section across the Menomonee Valley Brownfield study area, Milwaukee County, Wis.
or drawing flow nets (Pollock, 1994). A USGS computer 

program called Model Viewer (Hsieh and Winston, 2002) 

was used to render three-dimensional views of simulated 

pathlines.

Model Calibration

Three types of targets were used in model calibration: 

(1) hydraulic heads measured in wells completed in various stratigraphic intervals, (2) measured dry-weather 

infiltration (flux) into several phases of the ISS, and (3) 

measured vertical gradients in well nests within and outside the valley. The availability of infiltration targets from 

ISS measurements improves the ability of the model to 

distribute flow between the shallow surface-water system 

and the ISS. Moreover, because it is a flux target, dryweather infiltration to the ISS helps overcome the problem 

of nonunique solutions associated with correlated parameters. In particular, joint consideration of head and flux data 

allows estimation of hydraulic conductivity values to be, at 

least in part, isolated from evaluation of recharge. Matching the third target set, vertical gradients, is particularly 

important in this setting because of the large vertical head 

loss beneath the valley. All the hydraulic heads measured 

in the unlithified sediments used as targets in the MODFLOW model calibration were measured on a single day 

during a dry period— August 14, 2001 (appendix). For 

these targets, the variability in heads that may be expected 

from seasonal recharge events, surface-water fluctuations, 

and stormflow in the ISS has been eliminated. Hydraulic 

head data reported during 1994 were compiled for 33 wells 

completed in the Silurian dolomite (appendix). Because 

these data were collected on different dates during 1994, 

any one measurement may have been affected by recharge 

events or stormflow in the ISS.

The MODFLOW calibration was a two-step process. 

In the first step, initial values for Kh and Kz were chosen on the basis of published values. In the second step, 

Kh values were adjusted through a sensitivity analysis 

restricted to head calibration targets only, whereas Kz 

values were adjusted through a calibration process using 

head targets, ISS dry-weather infiltration targets, and 

vertical gradient targets. The GFLOW model cannot be 

calibrated in this way because the solution represents 

composite heads over the thickness of the aquifer rather 

than the water-table surface, the ISS inflow is fixed rather 

than model output, and GFLOW does not simulate vertical 

gradients. For this reason GFLOW is evaluated by comparison of results to available composite head and streamflow information, which is a less complex evaluation than 

is used for the MODFLOW model.

Application of Stepwise Modeling 

Model Domains

Boundary conditions in a GFLOW model are 

applied at surface-water features. Because the solution to 

a GFLOW model assumes an infinite aquifer, the model 

domain should extend beyond ground-water and surfacewater divides. The hydrologic boundaries used in this 

evaluation of the Menomonee Valley Brownfield are Lake 

Michigan; the Menomonee, Milwaukee, Kinnickinnic, and 

Root Rivers and their tributaries; and Honey Creek (fig. 6). 

The model domain (as defined by the GFLOW limits of 

recharge) covers about 195 mi2

, including western areas of 

Lake Michigan. 

The local domain covers about 26 mi2, which is 

appreciably smaller than the model domain. The local 

domain is defined by the extent of the MODFLOW 

model (fig. 6). The MODFLOW model consists of 87 

rows and 185 columns; each cell is 250 ft on a side. The 

Menomonee Valley Brownfield, the primary area of interest, covers about 2.3 mi2

. The MODFLOW grid is surrounded by specified-flux boundaries that were extracted 

from the GFLOW solution. Locations of surface-water 

bodies and the ISS are also shown in figure 6.

Development of the Analytic-Element Model

Construction

Average stages for hydrologic boundaries in the 

GFLOW model (rivers, canals, and lakes) were estimated 

from USGS 7.5-minute topographic maps. Near-field 

line-sinks incorporate riverbed resistance, which is locally 

determined as the thickness of the riverbed sediments 

divided by the vertical hydraulic conductivity of those sediments. Hydraulic conductivity of the aquifer consisted of 

a regional Kh outside the Menomonee Valley Brownfield 

and an inhomgeneity corresponding to the area with landsurface elevations of 600 ft or lower (fig. 6). The regional 

Kh, and that of the inhomogeneity, are determined by the 

saturated-thickness-weighted average of the horizontal 

hydraulic conductivities assigned to the various vertically 

layered units. The unit conductivities are listed in table 2, 

and the unit thicknesses correspond to the elevations in figApplication of Stepwise Modeling 13
14 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

ure 7. The recharge zones in the model are shown in figure 

2. The ISS is represented by a series of discharge-specified 

line-sinks that remove water at the dry-weather discharge 

rate reported for different phases of the ISS. Lake Michigan and the other far-field water bodies are constant-head 

boundaries in the far field of the GFLOW model. The 

near-field water bodies were specified in the model as 

head-dependent-flux boundaries with assigned elevations, 

resistances, and widths.

Calibration

The GFLOW model was calibrated by manually 

adjusting line-sink resistances throughout the near field, 

and hydraulic conductivity in the inhomogeneity; regional 

recharge rates and the dry-weather infiltration to segments of the ISS were fixed on the basis of previous work 

(Cherkauer, 2001; Rust/Harza, 2002). However, in the 

course of calibration, model simulations indicated that 

estuary line-sinks were contributing an unrealistic amount 

of water to the ISS and that Lake Michigan was contributing negligible amounts. Field evidence shows the opposite 

to be true (Cherkauer and Carlson, 1997). Gradients over a 

part of the shoreline of Lake Michigan adjacent to Milwaukee reversed from upward to downward after ISS construction, whereas ISS exchange with the Milwaukee and Kinnickinnic Rivers is affected to only a small degree (Douglas 

Carlson, U.S. Geological Survey, written commun., 2000). 

To bring the model closer to observed conditions, fluxes 

out of the estuary were limited where the ISS lies directly 

underneath. Within the Menomonee Valley Brownfield, 

this zone corresponds to the area east of 27th Street in 

figures 2 and 4. Fluxes were limited by specifying a loss 

rate for the affected bodies. The selected flux rate for these 

reaches corresponds to a downward gradient of 1 ft/ft 

between the near-surface water table and the water level in 

the ISS and a vertical hydraulic conductivity of 0.001 ft/d 

for the intervening material. This vertical conductivity 

value represents an average of the till and dolomite vertical hydraulic conductivities used in cross-section models 

recently calibrated to local conditions (Carlson, 2000). The 

total specified flux from surface-water bodies overlying 

the ISS is 0.11 ft3

/s, of which 0.10 ft3/s comes from surface 

water within the local domain. These rates are small compared to the 4.34 ft3

/s gained by the entire ISS, of which 

2.61 ft3/s discharges to the ISS within the local domain. To 

simulate the observed limited availability of water from the 

rivers and canals, these modifications increased the relative 

contribution of Lake Michigan to the ISS and increased the 

area over which recharge contributes to the ISS.

Because the unlithified and Silurian aquifers are simulated as one layer in the GFLOW model, composite heads 

are simulated between the water-table elevation (average 

altitude of about 590 ft) and the ground-water head in the 

dolomite (average altitude of about 295 ft). The gradient in 

the composite head field controls the movement of water 

from the far field to the near field of the model and from 

sources of water (such as recharge and Lake Michigan) 

to sinks of water (such as the ISS and some surface-water 

bodies). The data available against which to match the 

simulated composite heads are limited to one location in 

the Menomonee Valley Brownfield adjacent to the estuary. 

A well completed in dolomite at the elevation of the ISS, 

but 492 ft to the south, showed a head equal to 518 ft in 

Table 2. Hydraulic conductivities and effective porosities for calibrated GFLOW and MODFLOW models, Menomonee Valley 

Brownfield study area, Milwaukee County, Wis.

Unit Horizontal hydraulic conductivity,1

feet per day

Vertical effective hydraulic conductivity,2

feet per day Porosity3

Fill/Estuary 4.0 0.0010 0.2

Channel4 10.0 .1000 .2

Till .4 .0010 .1

Weathered dolomite 5.0 .0050 .05

Dolomite .65 .0004 .01

1Horizontal hydraulic conductivities used in both GFLOW and MODFLOW models.

2Vertical hydraulic conductivities calibrated to MODFLOW solution.

3 Effective porosities used to calculate traveltimes with MODFLOW and PATH3D.

4 Channel deposits only represented in MODFLOW model.

5Dolomite horizontal hydraulic conductivity is zoned in MODFLOW model.
August 2001. A well open to till less than 984 ft from the 

dolomite well but about 213 ft above the ISS, showed a 

head equal to 564 ft for that date. The head produced by 

GFLOW should be some composite of these two values 

close to the average of 544 ft. The simulated head at the 

location is 541 ft. 

A second way to evaluate the GFLOW model, particularly the suitability of the recharge zones, is through 

flux data. The base flow to the Menomonee River along 

the section between the two USGS streamflow-gaging 

stations shown in figure 2 can be estimated for pre-ISS 

conditions by use of flow-duration curves constructed from 

concurrent data collected in the early 1980s. The calculation yields a value of base flow for this section equal to 1.0 

ft3

/s. This estimate agrees well with the base flow of 0.78 

ft3

/s simulated by the GFLOW model for pre-ISS conditions.

Development of the Finite-Difference Model

Construction

In many respects, the MODFLOW model duplicates 

the input to the GFLOW model. Both models are steadystate representations of the flow system. The total volumetric rate of recharge entering the MODFLOW model 

domain is the same as the total volumetric rate of recharge 

that enters the corresponding area in the GFLOW model. 

The outline of the Menomonee Valley Brownfield Kh zone 

is the same for both models, and the Kh values assigned 

each of the units are also the same (table 2). The average 

thickness of units in the MODFLOW model corresponds 

to the thicknesses used to calculate the composite hydraulic conductivities in GFLOW. Lake Michigan is treated as 

a constant-head boundary in both models. The two models 

differ, however, with respect to how they simulate vertical flow, how near-river sediments are characterized, how 

recharge is zoned, and how boundary conditions are set. 

Although GFLOW supports some three-dimensional 

flow features (for example, it allows flow under the estuary 

to the ISS), it does not explicitly account for differences in 

resistance to vertical flow within the shallow deposits and 

the dolomite units. The MODFLOW model incorporates 

the full flow system by dividing the hydrostratigraphic 

units between eight layers, and by varying the thickness of 

the layers on the basis of data from geologic logs on file at 

the Wisconsin Geologic and Natural History Survey (Daniel Feinstein, USGS, oral commun., 2002). The configuration of the units along an east-west section that intersect 

the valley is shown in figure 8. The vertical hydraulic 

conductivities assigned to the fill/estuary, till, weathered 

dolomite, and dolomite units after calibration are included 

in table 2. 

The MODFLOW input contains a zone of high Kv 

and Kh in layers 1 and 2 corresponding to coarse channel 

deposits that are likely to be associated with the free-flowing reaches of the rivers (upstream from the Milwaukee 

River Estuary) in the model (fig. 9). The introduction of 

this zone was necessary to reproduce the measured vertical 

gradient in the only well nest in the free-flowing reach of 

the Menomonee River. The channel deposits are not represented in the GFLOW model.

All phases of the ISS represented in the MODFLOW 

domain are in layer 7. The ISS is represented as a series 

of drains (a head-dependent-flux boundary that removes 

water from the model) to facilitate comparison of simulated infiltration to reported values. In other words, ISS 

dry-weather infiltration is used as a flux calibration target. 

The conductance of the drains represents the resistance 

to flow through the grouted circumference of the ISS. 

Conductances are based on an assumed grout hydraulic 

conductivity equal to 0.0004 ft/d (the same value assumed 

for the vertical hydraulic conductivity of the dolomite) and 

a grout thickness of 1.0 ft. 

MMSD measured the dry-weather infiltration to 

each phase of the ISS (Rust/Harza, 2002). For purposes 

of model calibration, this information has been translated 

into target flux estimates for the western part of the Crosstown IIA phase (0.47 ft3

/s), for the Crosstown IA phase 

(1.16 ft3/s), and for the parts of the Northshore, Kinnickinnic, and Lake Michigan phases included in the MODFLOW model (0.54, 0.31, and 0.16 ft3

/s, respectively). 

Specified fluxes are assigned to all perimeter nodes 

of the MODFLOW grid, except for the last column of the 

grid because it intersects constant-head nodes associated 

with Lake Michigan. The fluxes for a given MODFLOW 

boundary node are equal to the comprehensive flux 

extracted from GFLOW for the width of the row or column 

location and are distributed between the eight MODFLOW 

model layers according to their relative transmissivity. The 

remaining boundary conditions in the MODFLOW model 

are head-dependent conditions assigned to surface-water 

nodes and the ISS drains. The resistance of the riverbed 

material is set to 1 ft/(ft/day). This resistance corresponds 

to a riverbed of sand that is 5 ft thick, with hydraulic conductivity equal to 5 ft/d.

Application of Stepwise Modeling 15
16 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

0 1 MILE

0 1 KILOMETER

580

620

660

700

540

500

460

420

380

340

300

260

ELEVATION, IN FEET ABOVE NGVD 29

MODEL LAYER NUMBER

Extent of MODFLOW model domain

Location of section shown below

Land surface

Valley

Lake Michigan

Fill/estuary

Till

Weathered dolomite

Crosstown tunnel

Dolomite

Dolomite

West East

1

2

3

4

5

6

7

8

Figure 8. MODFLOW section and layering, Menomonee Valley Brownfield study area, Milwaukee County, Wis. (Section extends 

entire west to east distance of MODFLOW model domain shown in figure 6.)
Calibration and Sensitivity

Calibration of the MODFLOW model depends on the 

match between measured and simulated heads, between 

the measured and simulated vertical gradient at well nests, 

and between the measured and simulated dry-weather 

infiltration for all or part of the five phases of the ISS. 

Measurements of water levels on August 14, 2001, 

provided head targets at 101 wells open to unlithified sediments, of which 79 represented water-table conditions and 

the others corresponded to depths averaging about 33 ft 

below the water table. Water levels are also available from 

1994 for 33 wells drilled in the dolomite, most of which 

are close to the ISS (appendix).

The data set from wells drilled in the unlithified sediments includes measurements at 12 nested well locations 

(fig. 9). The measured vertical gradient was downward 

at all but the westernmost nest location. The average 

downward gradient was equal to 0.09 ft/ft between the 

water table and the fill/estuary horizon at the mid-elevation in model layer 2; it was equal to 0.28 ft/ft between 

the water table and the till horizon at the mid-elevation in 

model layer 3. The increasing vertical gradient with depth 

reflects some combination of drainage to the ISS and the 

distribution of vertical hydraulic conductivities. Calibration results for the simulation that best matched the three 

sets of targets are shown in figures 10a, and 10b and tables 

3a, 3b, 4, and 5. The agreement between the observed and 

simulated heads is not as close for the wells in bedrock as 

it is for the wells in unlithified sediments (tables 3a and 

3b, and figures 10a and 10b). For the wells in unlithified 

sediments, the agreement is close not only with respect to 

the trend of the water-table surface but also with respect 

to the measured vertical gradients between the estuary and 

underlying till deposits (table 4).

The quality of the fit to wells drilled in bedrock is 

affected by at least three factors. First, bedrock head measurements are not synchronous with other targets used in 

model calibration. 

Second, although many of the wells drilled in bedrock 

SG

Menomonee River

N1

N2

N8

N10

N15

N6,7 N3,11

N14 N4

N12

N5,9

P

P

N1

P

P P P

P

P

P

N13

0 .5 1 MILE

0 .5 1 KILOMETER

MP

Upstream from FD

CP

WG BB

EP

RM

EXPLANATION

Nested well location and number

(number refers to table 4)

Minipiezometer location

Site identifier

Channel deposit

Kinnickinnic River Lake

Michigan

MP

Milwaukee River

Figure 9. Locations of channel deposits, nested wells, and minipiezometers in the Menomonee Valley Brownfield study area, 

Milwaukee County, Wis.

Application of Stepwise Modeling 17
18 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

Table 3a. MODFLOW calibration statistics for wells in the 

unlithified sediments of the Menomonee Valley Brownfield 

study area, Milwaukee County, Wis.

[Residual = observed – simulated; ft, feet]

Total number of wells 101

 wells in layer 1 79

 wells in layer 2 8

 wells in layer 3 12

 wells in layer 4 1

 wells in layer 5 1

Residual mean 2.25 ft

Absolute residual mean 3.63 ft

Residual standard deviation 5.63 ft

Most negative residual -7.84 ft

Most positive residual 29.03 ft

Number of negative residuals 43

Number of positive residuals 58

Number of residuals within +/- 2 ft 53

Table 3b. MODFLOW calibration statistics for wells 

in the dolomite of the Menomonee Valley 

Brownfield study area, Milwaukee County, Wis.

[Residual = observed – simulated; ft, feet]

Total number of wells 33

 wells in layer 5 6

 wells in layer 6 11

 wells in layer 7 15

 wells in layer 8 1

Residual mean 23.2 ft

Absolute residual mean 44.9 ft

Residual standard deviation 58.0 ft

Most negative residual -69.0. ft

Most positive residual 188.1 ft

Number of negative residuals 15

Number of positive residuals 18

Number of residuals within +/- 2 ft 15

Table 4. MODFLOW vertical-gradient calibration for the 

Menomonee Valley Brownfield study area, Milwaukee County, 

Wis.

[Negative values indicate upward gradient]

Well nest 1 Measured 

gradient

Simulated 

gradient

1. Water table-Estuary -0.043 -0.028

2. Water table-Till .03 .18

3. Water table-Estuary .06 .23

4. Water table-Till .07 .35

5. Water table-Estuary .12 .15

6. Water table-Estuary .22 .27

7. Water table-Till .27 .24

8. Water table-Till .27 .16

9. Water table-Till .28 .19

10. Water table-Till .28 .23

11. Water table-Till .30 .24

12. Water table-Till .30 .12

13. Water table-Till .36 .32

14. Water table-Till .41 .31

15. Water table-Till .58 .51

Averages: 

Overall .23 .23

Water table-Estuary .09 .16

Water table-Till .28 .26

1 Well nest is located by number in figure 9.

Table 5. MODFLOW calibration to measured dry-weather 

infiltration to phases of the Inline Storage System (ISS) in the 

Menomonee Valley Brownfield study area, Milwaukee County, 

Wis.

[ft3/s, cubic feet per second]

Inline Storage 

System phase

Measured 

infiltration1

ft3/s

Simulated 

infiltration

ft3/s

Crosstown IIA 0.46 0.60

Crosstown IA 1.16 .97

Northshore .54 .53

Kinnickinnic .31 .37

Lake Michigan .16 .26

Total within local 

MODFLOW model

 2.63 2.73

1Rust/Harza, 2002, Internal inspection of the Inline Storage System; 

report prepared for the Milwaukee Metropolitan Sewerage District.
are completed within a few feet of the deep tunnel, the 

model simulates water levels at an appreciably greater distance from the tunnel because model cells are 250 ft wide. 

Third, the ISS is not grouted everywhere, so gradients into 

the tunnel are variable from place to place. Given the difficulty in matching local conditions around the tunnel, the 

model was more closely calibrated to the estimated dryweather infiltration into the five phases of the ISS (table 

5) than to the adjacent ground-water levels. Because the 

tunnel infiltration is an integrated measure of the response 

of the ground-water system to the stress imposed by segments of the ISS, it is less affected by variations in local 

conditions.

The match between measured and simulated targets 

is reasonably close across the range of targets, and the 

overall calibration is considered acceptable. The calibrated 

horizontal hydraulic conductivities and recharge rate in 

the MODFLOW model are unchanged from those in the 

GFLOW simulation that provided the specified-flux conditions to the MODFLOW perimeter boundary. The head 

calibration is very sensitive to recharge and the distribution 

of vertical hydraulic conductivity (tables 1 and 6). Measured gradients between surface water and ground water 

provide a check on the model calibration. Streamflowgaging stations paired with minipiezometers inserted just 

below the riverbed yield the direction and magnitude of 

the hydraulic gradient connecting surface water to ground 

water at the locations shown in figure 9. The estuary and 

estuary canal locations were sampled seven times between 

June 2001 and September 2001. The two upstream locations were sampled in spring and summer 2000. The 

direction of the gradient over the measurement periods is 

shown in table 7. Upward gradients imply discharge of 

ground water to surface water. Downward gradients imply 

discharge of surface water to ground water. The model 

simulation matched the observed upward flow in the 

upstream locations and the generally downward flow in the 

estuary locations.

No attempt was made during the calibration process 

to match the magnitude of the observed hydraulic gradients. Seiche in the estuary (oscillation of water level 

initiated chiefly by local changes in atmospheric pressure, aided by winds and tidal currents [Bates and Jackson,1980]) causes the river and canal levels to change 

significantly over a short time, with a corresponding effect 

on the measured gradient at a given streamflow-gaging station. In addition, the variability in the deposits constituting 

the riverbed (sand in some places, industrial fill in others) 

means that matching even average observed gradients 

would require changing the hydraulic conductivity of the 

riverbed over several orders of magnitude from one moni500

550

650

600

700

750

500 650 700 750 550 600

Line of equal values

SIMULATED HEAD, IN FEET

OBSERVED HEAD, IN FEET

Figure 10a. Calibration plot of measured hydraulic heads 

plotted against MODFLOW-simulated heads in the unlithified 

sediments (layers 1 through 4), Menomonee Valley Brownfield 

study area, Milwaukee County, Wis.

Table 6. Ranked sensitivities of the MODFLOW parameters 

in the Menomonee Valley Brownfield study area, Milwaukee 

County, Wis.

[Head calibration is most sensitive to first-listed parameter (Recharge) 

and least sensitive to the last-listed parameter (Kh of the estuary deposits); Kh, horizontal hydraulic conductivity; Kg, hydraulic conductivity of 

grout; Kv, vertical hydraulic conductivity; ISS, Inline Storage System]

 Recharge

 Kh Weathered dolomite

 Kg Crosstown IA phase of the ISS

 Kh Inline Storage System dolomite

 Kg Northshore, Lake Michigan, and

Kinnickinnic phases of the ISS

 Kv Till

 Kh Till

 Kh Mayville Dolomite

 Kh Racine Dolomite

 Kv Racine Dolomite

 Kg Crosstown IIA phase of the ISS

 Kv Mayville Dolomite

 Kv Estuary deposits

 Kv ISS dolomite

 Kv Weathered dolomite

 Kh Estuary deposits

Application of Stepwise Modeling 19
20 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

tored location to another without knowing what values to 

assign between these locations. 

This gap in our knowledge of the system, however, 

does not affect the reliability of the model. A sensitivity 

analysis on riverbed hydraulic conductivity (in which it 

was varied everywhere from its base value of 5 ft/d—corresponding to a sand—to values as low as 0.005 ft/d—corresponding to a silt) demonstrated that the model calibration and model results are almost completely insensitive 

to the value selected. The match to water levels, to vertical 

gradients, and to tunnel inflow is largely unaffected. Model 

findings (for example, the simulated areas of contribution 

for the deep tunnel and the surface water) are nearly identical over the entire range of riverbed values. The reason 

for this insensitivity is that decreases in riverbed hydraulic 

conductivity are linked to corresponding increases in the 

simulated hydraulic gradient, so the model simulates the 

same direction and approximately the same magnitude of 

flow between the ground water and surface water throughout the model over the tested range. This insensitivity to 

riverbed hydraulic conductivity has been noted in other 

studies (an example is given in Hunt, 2000).

The value assigned riverbed hydraulic conductivity in the model has little influence on the simulated flow 

lines connecting Menomonee Valley Brownfield recharge 

to discharge locations. However, if this model were to be 

applied at a finer scale to better understand the exchange 

of ground water with surface water over time at a specific 

location, it would be necessary to collect sufficient data to 

reproduce the cyclic changes in estuary stage and to map 

the local variations in riverbed hydraulic conductivity.

Figure 10b. Calibration plot of measured hydraulic heads plotted against MODFLOW-simulated heads in the dolomite (layers 5 

through 8), Menomonee Valley Brownfield study area, Milwaukee County, Wis.

250

350

450

550

650

750

250 350 450 550 650 750

Layer 5

Layer 6

Layer 7

Layer 8

Line of equal values

SIMULATED HEAD, IN FEET

OBSERVED HEAD, IN FEET

EXPLANATION
Model Limitations

Simulation of hydrology in this complex urban environment unavoidably involves a number of uncertainties 

over and above the values assigned to model parameters. 

Uncertainties in the Hydrogeologic System

Assumed impermeability of Maquoketa 

Shale. An appreciable downward gradient exists across 

the Maquoketa Shale as a result of ongoing pumping from 

the underlying sandstone aquifer. In addition, the construction of some deep wells (abandoned and active) may provide a conduit across the Maquoketa Shale confining unit. 

As a result it is possible that the model underestimates the 

total recharge to the water table by the amount that moves 

downward from the shallow to deep aquifer systems. 

However, the downward leakage is known to be very 

small below the study area (Feinstein and others, 2004), 

while the downward flow across multiple aquifer wells is 

assumed to be a minor component of total recharge.

Uncertainties in MODFLOW Target Values

Bias in shallow (unlithified) hydraulic head 

data. The primary calibration data set for the model consists of heads measured on a single day (August 14, 2001) 

in wells open to the shallow (unlithified) sediments. A 

synoptic data set such as this is preferable to data collected 

over many dates under potentially very different hydrologic conditions; however, it is not known how representative these synoptic measurements are of long-term average 

heads. It is known that these heads generally fall between 

heads measured in the same wells for the only other two 

available measurement dates—one in the spring (June 

2000) when the water table was relatively high and one in 

the winter (December 1999) when the water table was relatively low. Thus, the August data represent intermediate 

conditions across the three available measurement periods. 

Bias in deep (dolomite) hydraulic head data. The 

calibration data set for deep wells drilled in bedrock is 

much less reliable than the data set for the shallow wells. 

These heads correspond to different dates of measurement 

in 1994 (rather than to a single measurement date in 2001 

as in wells drilled in unlithified sediments). Water-level 

conditions from that time are likely different than those in 

2001 because the hydrologic system is not in steady state. 

In addition, many of the deep wells drilled in bedrock 

are very close to the ISS (as little as 10 ft distant), so the 

water levels represent conditions just outside the tunnel 

rather than at the middle of the 250-ft by 250-ft model cell 

that encompasses the tunnel. For these reasons, the set of 

calibration targets in the dolomite bedrock serves at best 

as only a qualitative check on the ability of the model to 

approximate deep hydraulic conditions.

Uncertainty in vertical gradient targets. The 

presence of strong vertical gradients requires calibration 

to heads in different layers of the model. However, vertical 

discretization of the model and necessary interpolation of 

target heads at the center of screened intervals to the center 

elevation of model layers introduces additional uncertainty. 

MMSD estimate of ISS dry-weather infiltration. 

Uncertainty will always be associated with estimates of 

dry-weather infiltration, although the most recent evaluation (Rust/Harza, 2002) was designed specifically to 

quantify dry-weather infiltration and is believed to be an 

improvement over earlier estimates. Dry-weather infiltration has likely changed over time and for this reason 

corresponds to changing head. In this connection, it is 

noteworthy that the recent infiltration estimates made in 

early 2002 are close in time to the calibration-target water 

levels collected in the unlithified sediments in late 2001 

but are significantly separated in time from the set of 

calibration targets collected in 1994 for wells completed in 

the dolomite.

Table 7. Direction of vertical gradients between river (estuary) and ground water below riverbed, Menomonee Valley 

Brownfield study area, Milwaukee County, Wis. 

[Minipiezometer locations are shown on figure 9; Falk Dam site is about 

one- half mile upstream from the dam; gradient was observed only one 

day at the Falk Dam site; at all other sites, gradient was observed on 

seven dates between June 2001 and September 2001]

Site Observed 

direction

Simulated 

direction

Miller Park (MP) Up Up

Falk Dam (FD) Up Up

Central Repair (CP) Down Down

Wisconsin Gas (WG) Down Down

SIGMA (SG) Variable Down

Bridges and buildings (BB) Down Down

Emmpak (EP) Down Down

RACM (formerly Crabby 

Al’s) (RM)

Variable Down

Application of Stepwise Modeling 21
22 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

Uncertainties of Discretization and Scale

MODFLOW cell size in the valley. The 16,095 

model cells are uniformly 250 by 250 ft. This level of 

discretization does not allow incorporation of the myriad 

manmade features of the industrial Menomonee Valley that 

will influence local gradients and flow.

Limitations Arising from Extraction of 

Boundary Conditions

Linking of GFLOW and MODFLOW models. 

These models are parallel in that the average transmissivity 

of the MODFLOW model is the same as the spatially constant transmissivity assigned to the GFLOW model. Similarly, the average recharge to the MODFLOW model is 

identical to the spatially constant recharge to the GFLOW 

model. These parallels notwithstanding, the boundary conditions provided by GFLOW are subject to some error. The 

greatest source of error is that the distance from the major 

stress induced by the ISS to the local model boundary is 

less than the desired minimum of 3 times the characteristic leakage length, lambda (λ). Lambda is calculated by 

means of the following equation:

 (1)

where 

 λ is the characteristic leakage length (L),

 K is horizontal hydraulic conductivity of the aquifer

 (LT -1), 

 H is the thickness of the aquifer (L), and

 c is resistance, the ratio of confi ning unit 

 thickness (d) to its vertical hydraulic

 conductivity (K),

In calculating λ, average aquifer transmissivity was 

assumed to be 500 ft2/d, and vertical resistance through the 

glacial material and dolomite was equated to that used in 

the MODFLOW model (average 400 ft thickness divided 

by Kv=0.004 ft/d, yielding 100,000 days). The resulting λ

value is 7,100 ft. To minimize runtime, the MODFLOW 

grid was made fairly small. The 2-mi distance that separates the ISS in the valley from the north and south edges 

of the local model area is only 1.5 times the calculated λ. 

It follows that the stress from the ISS near the bottom of 

the section produces some vertical flow components at the 

boundary that are not reflected in the fluxes extracted from 

the GFLOW model. The vertical-flow effect decreases 

exponentially with distance from the ISS. Application of 

the exponential factor [1-e-x / λ

], where x/λ is set equal to 

1.5, indicates that about 78 percent of the vertical-flow 

component has disappeared at the MODFLOW boundary. (Haitjema and others, 2001, equation 4). Sensitivity 

analyses show that changes in the vertical distribution of 

the constant flux at the MODFLOW model boundary have 

virtually no effect on the simulated flow system within the 

Menomonee Valley Brownfield. 

Because the MODFLOW model derives the lateral 

flow into its grid from GFLOW, that it receives the same 

quantity of water as recharge as does the GFLOW model, 

and that the strength of the ISS sink is identical in both 

representations, it is expected that the overall capture zone 

simulated by the two models should be similar. In fact, as 

demonstrated in the following section of the report, capture 

zones for the ISS simulated by GFLOW and MODFLOW 

are very close in shape and extent.

MODFLOW results are reported in more detail than 

GFLOW results because MODFLOW provides more 

accurate estimates for traveltimes from source to sink, 

which are useful for consideration of natural attenuation 

of contaminants. Experience in this study also showed 

that although GFLOW was adequate to simulate capture 

zones for flow systems dominated by two-dimensional 

flow, a full three-dimensional analysis was needed to more 

rigorously predict the effect of the ISS on the base flow to 

overlying streams.

Vertical distribution of flux to the MODFLOW 

model. From the standpoint of mass balance, the GFLOW 

model should supply the proper amount of water across 

each part of the extracted MODFLOW model boundaries (for the given model inputs) to allow recharge and the 

surface water to supply the ISS. What is at issue is the 

vertical distribution of flux at each lateral boundary and 

the assumption that the constant flux from the GFLOW 

solution divides proportionally to the transmissivity of the 

MODFLOW layers. To evaluate the effect of distributing 

the flux in this way, several sensitivity runs were done 

in which the flux was distributed differently. In the first 

run, all the flux simulated by GFLOW was assigned only 

to the MODFLOW dolomite layers; in the second run, 

all the flux was assigned to the top weathered dolomite 

layer; and in the third run, all the flux was assigned to the 

glacial material across layers 1 through 4. In each case, the 

simulated ISS infiltration and head calibration statistics 

agreed closely with the original run. The ISS infiltration 

for the sensitivity runs ranges from 2.60 to 2.75 ft3

/s, with 

the base value equal to 2.73 ft3/s. The absolute residual 
mean of the head calibration targets for the sensitivity runs 

ranges from 3.35 to 3.51 ft, with the base value equal to 

3.48 ft. These small differences indicate that the distribution of the boundary flux has little effect on model results.

Simulation of Ground-Water Flow

The calibrated MODFLOW model was used to simulate shallow ground-water flow in the Menomonee Valley 

Brownfield study area, to address questions about sources 

and sinks for ground water, and to estimate traveltimes 

from the points of recharge in the valley to sinks. The 

simulated water table within the MODFLOW local domain 

ranges in altitude from about 570 to 800 ft (fig. 11). Watertable altitudes are around 570 ft in the Menomonee Valley 

Brownfield and rise quickly to the north, west, and south. 

The highest water-table altitudes are in the southwest corner of the MODFLOW domain.

Ground-Water Contributing Areas

At the regional scale, the GFLOW model simulated 

capture areas for particles flowing from the water table 

outside the Menomonee Valley Brownfield to the ISS. 

The simulated traveltime for these particles is as much 

as 600 years (fig. 12). In defining these capture areas, 

the assumed composite effective porosity for the till and 

dolomite is 0.05. Particle-tracking routines MODPATH 

(Pollock, 1994) and PATH3D (S.S. Papadopulos & Associates, 1991) were applied to the MODFLOW results to 

determine what part of recharge to the local domain flows 

downward to the ISS and what part circulates back upward 

to surface-water bodies. The capture pattern for the local 

domain is shown in figure 13.

Sources and Sinks

Within the local MODFLOW domain, the comparison of the total simulated infiltration to the ISS (2.74 ft3

/s) 

and total available recharge (1.36 ft3/s for the assumed 

recharge rate equal to 0.6 in/yr) demonstrates that the 

ISS is the major sink for ground water and that it captures much water that would otherwise discharge as base 

flow to streams. In addition to local recharge, sources for 

infiltration to the ISS include lateral flow into the model 

(originating largely as recharge outside the MODFLOW 

domain), flow from Lake Michigan, and losses from rivers 

and canals. The MODFLOW model provides the following 

sources of infiltration to the ISS as percentages: 36 percent 

from recharge within the model domain, 45 percent from 

lateral flow into the domain, 15 percent from Lake MichiFigure 11. Water-table surface in the Menomonee Valley Brownfield study area, Milwaukee County, Wis., simulated with 

MODFLOW, and calibrated to August 14, 2001 hydraulic heads.

790

770

750

730

710

690

670

650

610

630

590

570

WATER-TABLE ELEVATION, IN FEET ABOVE NGVD 29

Menomonee River

Kinnickinnic River

Menomonee River

Kinnickinnic River

Milwaukee RiverMilwaukee River

0 2 MILES

0 2 KILOMETERS

Lake

Michigan

Model Limitations 23
24 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

Lake

Michigan

Extent of MODFLOW model domain

Extent of recharge to GFLOW model

Wilson

Far-field model elements

Near-field model elements

Menomonee Valley Brownfield

inhomogeneity representing higher

horizontal hydraulic conductivity

Backward particle track

Menomonee

Honey

Kinnickinnic

Root

Milwaukee

River

River

River

River

Creek

Creek

EXPLANATION

2 MILES

2 KILOMETERS

0

0

Inline Storage System (ISS)

Crosstown I A Phase

Crosstown II A Phase

North Shore Phase

Kinnickinnic Phase

Lake Michigan Phase

Figure 12. Backward particle tracking from the Inline Storage System in the Menomonee Valley Brownfield study area, 

Milwaukee County, Wis., simulated with GFLOW.
gan, and 4 percent from other surface-water bodies. About 

73 percent of recharge within the MODFLOW domain 

(excluding the area occupied by surface-water nodes) 

discharges to the ISS, and 27 percent discharges to gaining 

surface-water bodies. This suggests that the conceptual 

model that best fits the Menomonee Valley Brownfield is 

one intermediate to the end-members discussed earlier (fig. 

5). The simulated flux from losing surface-water bodies 

overlying the ISS is 0.11 ft3

/s, which compares well with 

the corresponding GFLOW rate specified at 0.10 ft3/s and 

therefore increases confidence in the stepwise approach. 

Three east-west sections are presented that illustrate the 

flowpaths of recharge to the MODFLOW model domain 

(fig. 14a, b, and c). A three-dimensional representation that 

illustrates simulated flow paths from selected areas of the 

Menomonee Valley Brownfield is shown in figure 15.

Traveltimes

The patterns of discharge to surface sinks and the ISS 

simulated by the MODFLOW model are distinguished by 

the traveltimes involved. For the assumed values of effective porosity assigned different units (table 2), it is possible 

to calculate the range of traveltimes for recharge to the 

valley to circulate back to the surface and for recharge to 

the valley to discharge to the ISS (table 8). 

The median traveltime to surface water is 8 years; 

the median time to the ISS is 255 years. The distribution 

of traveltimes to the ISS based on the assumed effective 

porosities (table 2) is shown in figure 16. The traveltime 

EXPLANATION

Recharge captured by surface-water features

Recharge captured by Inline Storage System (ISS)

Inline Storage System (ISS)

0 1 MILE

0 1 KILOMETER

Lake

Michigan

Menomonee River

Kinnickinnic River

Menomonee River

Kinnickinnic River

Milwaukee RiverMilwaukee River

Figure 13. Capture zones simulated with MODFLOW and MODPATH for the Inline Storage System (ISS) in the Menomonee 

Valley Brownfield study area, Milwaukee County, Wis.

Table 8. Statistics for simulated traveltime of recharge to 

surface-water sinks and the Inline Storage System, 

Menomonee Valley Brownfield study area, Milwaukee County, 

Wis.

[Traveltime and range in years]

Surfacewater sinksInline Storage 

System

Average traveltime 30 230

Median traveltime 8 255

Range (90 percent of traveltimes fall within range) 1–99 34–355

Simulation of Ground Water Flow 25
26 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

15 0

75

75 75

VERTICAL EXAGGERATION APPROXIMATELY 66X

0 1 MILE

0 1 KILOMETER

West East

EXPLANATION

Inline Storage System (ISS)–

segment shown lies in row 43 and is projected

into this cross section

Flow path to Inline Storage System (ISS)–

each arrow head represents 75 years of travel time

Flow path to Menomonee River–

each arrow head represents 75 years of travel time

100

200

300

400

500

600

700

800

ELEVATION, IN FEET ABOVE NGVD 29

Dolomite

Weathered

dolomite

Estuary

Till

Lake Michigan

Land surface

Water table

Menomonee River

Honey Creek

Lake

Michigan

Row 38

Row 43

Row 48

Milwaukee River

Menomonee River

Honey Creek

Kinnickinnic River

Menomonee Valley

LOCATION OF ROW 38 (SECTIONAL VIEW BELOW)

Figure 14a. Sectional view (row 38) of ground-water-flow directions simulated with MODFLOW and MODPATH in the 

Menomonee Valley Brownfield study area, Milwaukee County, Wis.
150

15 0

VERTICAL EXAGGERATION APPROXIMATELY 66X

0 1 MILE

0 1 KILOMETER

West East

100

200

300

400

500

600

700

800

ELEVATION, IN FEET ABOVE NGVD 29

EXPLANATION

Inline Storage System (ISS)–

segment shown lies in row 43

Flow path to Inline Storage System (ISS)–

each arrow head represents 75 years of travel time

Flow path to Menomonee River–

each arrow head represents 75 years of travel time

Dolomite

Weathered

dolomite

Till

Lake Michigan

Land surface

Water table

Menomonee River

Estuary

Honey Creek

Lake

Michigan

Row 38

Row 43

Row 48

Milwaukee River

Menomonee River

Honey Creek

Kinnickinnic River

Menomonee Valley

LOCATION OF ROW 43 (SECTIONAL VIEW BELOW)

Figure 14b. Sectional view (row 43) of ground-water-flow directions simulated with MODFLOW and MODPATH in the 

Menomonee Valley Brownfield study area, Milwaukee County, Wis.

Simulation of Ground Water Flow 27
28 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin Estuary Honey Creek

100

200

300

400

500

600

700

800

ELEVATION, IN FEET ABOVE NGVD 29

EXPLANATION

Inline Storage System (ISS)–

segment shown lies in row 43 and is projected

into this cross section

Flow path to Inline Storage System (ISS)–

each arrow head represents 75 years of travel time

Flow path to Menomonee River–

each arrow head represents 75 years of travel time

30 0

30 0

30 0

0 1 MILE

0 1 KILOMETER

West East

Dolomite

Weathered

dolomite

Till

Lake Michigan

Land surface

Water table

Menomonee River

VERTICAL EXAGGERATION APPROXIMATELY 66X

Lake

Michigan

Row 38

Row 43

Row 48

Milwaukee River

Menomonee River

Honey Creek

Kinnickinnic River

Menomonee Valley

LOCATION OF ROW 48 (SECTIONAL VIEW BELOW)

Figure 14c. Sectional view (row 48) of ground-water-flow directions simulated with MODFLOW and MODPATH in the 

Menomonee Valley Brownfield study area, Milwaukee County, Wis.
from a given location is largely dictated by the length of 

flowpath in the unlithified deposits (where higher porosities result in slower velocities) as opposed to the fractured 

dolomite. The traveltimes to the ISS are least over the 

northern part of the valley where the dolomite is near the 

land surface. 

Implications for Contaminant Transport

A primary reason to model ground-water flow in 

the Menomonee Valley is to address questions that arise 

from the designation of the valley as a brownfield site. 

The soil in the valley contains industrial contaminants 

such as organic solvents, petroleum byproducts, tars, and 

metal waste. Recharge to the valley can dissolve these 

contaminants from the soil and transfer them to the ground 

water (SIGMA Environmental Services, Inc., 2002). The 

fate of potentially contaminated ground water in different 

parts of the valley is of interest to regulators and developers because it influences decisions about the amount of 

monitoring and cleanup that is necessary before future 

redevelopment can go forward. As a first step in an evaluation process, an advective transport analysis could be 

done in which the potential threat posed by ground-water 

contamination is determined by the traveltime from a 

point of recharge in the Menomonee Valley Brownfield 

to any destination. The advective traveltime (time it takes 

for the bulk movement of the ground water from the point 

of recharge to a destination) will be less than the actual 

time of movement for many contaminants, because these 

contaminants are subject to retarding mechanisms such 

as sorption. Destinations include discharge to the water 

table, to surface-water bodies, and to manmade structures 

such as the ISS. As the dissolved constituents move from 

recharge areas to discharge areas, their characteristics 

and concentration can be changed by mechanisms such 

as chemical transformation, volatilization, precipitation, 

sorption, dispersion, and dilution. This process is known 

as natural attenuation. The rate of natural attenuation of 

Traveltime

in years

East

North

Traveltime along flow paths

from point of recharge to

Inline Storage System (ISS)

Traveltime along flow paths

from point of recharge to

surface-water features

Lake Michigan

Inline Storage System (ISS)

300

225

150

75

0

Figure 15. Three-dimensional view generated by ModelViewer of ground-water flow-patterns in the Menomonee Valley 

Brownfield study area, Milwaukee County, Wis.

Simulation of Ground Water Flow 29
30 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

any particular contaminant will depend on its physical and 

chemical properties and those of the matrix. 

The results of the MODFLOW model provide the 

destination of ground-water flowpaths and approximate advective traveltime. A three-dimensional view of 

simulated ground-water-flow in the Menomonee Valley 

Brownfield is shown in figure 15. In the eastern part of the 

Menomonee Valley Brownfield, ground water is simulated as moving downward to the ISS. The ground water 

that infiltrates into the ISS is routed to Jones Island at the 

extreme eastern end of the valley (fig. 2), where all the 

water is treated at a wastewater plant before being discharged to Lake Michigan. In the western areas, recharge 

follows local flowpaths that circulate back to the water 

table and surface-water bodies (fig.15). Model results indicate that most of this flow goes into the Menomonee River 

or the Menomonee River Estuary.

This method of evaluating contaminant transport processes by simulating advective transport alone is subject 

to many limitations. In particular, the traveltime results are 

very sensitive to the assumed values of effective porosity. The results presented in table 8 vary linearly with the 

assumed porosity. Consequently, if the porosities for each 

unit were reduced by 50 percent (resulting, for example, 

in a porosity value for till of 0.05 instead of 0.10), then the 

simulated traveltimes would be reduced by 50 percent for 

ground water discharging to the surface and to the ISS.

The analysis also depends on the stability of the 

simulated flow system. The relatively long travel paths to 

the ISS depend on the long-term presence of the ISS. If 

River capture

Canal capture

Menomonee Valley Brownfield boundary

0–65

65–175

175–325

>325

EXPLANATION

Range of times of travel

0 .5 1 MILE

0 .5 1 KILOMETER

Menomonee River

Figure 16. Traveltime to the Inline Storage System (ISS) in the Menomonee Valley Brownfield study area, Milwaukee County, 

Wis., simulated with MODFLOW and MODPATH.
the ISS were to be closed (and filled so as not to be a sink) 

sometime in the future, the flow system would change, and 

water previously destined for the ISS may reverse course 

and discharge to surface-water features or to Lake Michigan.

Summary and Conclusions

The City of Milwaukee, Wis., is actively promoting 

the revitalization of the Menomonee Valley Brownfield, 

a 1,500-acre industrial center, about a quarter of which is 

abandoned or underutilized. An understanding of groundwater flow within the brownfield is requisite for evaluation 

of ground-water contamination. The U.S. Geological Survey (USGS), in cooperation with the City of Milwaukee 

and its consultants, and with support from USEPA Region 

5, used numerical modeling to simulate shallow groundwater flow in the Menomonee Valley Brownfield. Modeling objectives were to simulate the fate of ground-water 

recharge to the valley, and estimate the traveltime from 

points of recharge to the ground-water sinks.

Shallow ground-water flow in the valley is driven by 

sources, primarily recharge to the valley and lateral flow 

from outside the valley, and sinks, primarily surface-water 

features and the Milwaukee Metropolitan Sewerage District Inline Storage System (ISS). The ISS is a deep tunnel 

in the Silurian dolomite bedrock, 17 or 32 ft in diameter, 

which fills with combined storm-sewer flow and sanitarysewer overflow during rainstorms. This water is stored for 

later treatment and discharge to Lake Michigan. Between 

storms, the ISS is effectively empty and is a regional sink 

for the ground-water system.

Numerical models were used to simulate groundwater flow and to determine the fate of recharge falling 

on the Menomonee Valley. A stepwise modeling approach 

was used in this study, whereby a relatively simple, 

regional ground-water-flow model was used in an exploratory fashion to help design data collection, test model 

assumptions, and provide boundary conditions for a local 

multi-layer model. The regional model was constructed by 

use of the analytic-element modeling code GFLOW. The 

GFLOW model domain (as defined by limits of recharge 

and the far-field analytic elements) covers about 195 mi2

(square miles), including western areas of Lake Michigan. 

The local model is 8-layers and was constructed by use 

of the finite-difference modeling code MODFLOW. The 

MODFLOW model domain covers about 26 mi2

 and is 

centered on the Menomonee Valley Brownfield, which 

covers about 2.3 mi2

. The MODFLOW grid is surrounded 

by specified-flux boundaries that were extracted from the 

regional GFLOW solution.

The GFLOW model was calibrated by adjusting 

line-sink resistances and hydraulic conductivity values; 

regional recharge rates and the dry-weather infiltration 

to segments of the ISS were set based on previous work. 

Only one location was available to match GFLOW-simulated composite hydraulic heads. The GFLOW-simulated 

head at this location was 541 ft compared to a composite average of 544 ft. The GFLOW calibration was also 

evaluated in comparison to surface-water flow. Base flow 

to the Menomonee River along the section between the 

two U.S. Geological Survey (USGS) streamflow-gaging 

stations was estimated for pre-ISS conditions by means of 

flow-duration curves constructed from data collected in 

the early 1980s. Calculated base flow for this section is 1.0 

ft3

/s (cubic feet per second). This estimate agrees well with 

0.78 ft3/s, the base flow simulated by the GFLOW model 

for pre-ISS conditions.

The MODFLOW model was calibrated to measured 

heads (101 wells in unlithified sediments, 33 wells in 

dolomite), measured vertical gradients at 12 well nests, 

and measured dry-weather infiltration for five phases of 

the ISS. Head calibration in the unlithified sediments used 

water levels measured on August 14, 2001. Head calibration in the dolomite used water levels measured during 

1994. Final calibrated values for horizontal hydraulic 

conductivity and rate of recharge for the MODFLOW 

model are unchanged from the GFLOW simulation that 

provided the flux boundary conditions. MODFLOW head 

calibration was very sensitive to rate of recharge and the 

distribution of vertical hydraulic conductivity; however, 

the solution proved almost totally insensitive to the resistance assigned to nodes representing rivers and canals. The 

simulated flux from losing surface-water bodies directly 

above the ISS is 0.11 ft3

/s, which compares well with the 

corresponding GFLOW rate specified at 0.10 ft3/sec and, 

therefore, increases confidence in the stepwise approach.

About 73 percent of ground-water recharge within the 

MODFLOW domain discharges to the ISS, and 27 percent 

discharges to gaining surface-water bodies. MODFLOW 

simulates the following sources of infiltration to the ISS 

as percentages: 36 percent from recharge within the model 

domain, 45 percent from lateral flow into the domain, 15 

percent from Lake Michigan, and 4 percent from other 

surface-water bodies. The median traveltime for recharge 

falling on the valley to reach surface-water bodies is 8 

years; the median traveltime to the ISS is 255 years. The 

traveltime from a given location is largely dictated by the 

length of a flowpath in the unlithified deposits (where 

Simulation of Ground Water Flow 31
32 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin

higher porosities imply slower velocities) as opposed to 

the fractured dolomite. The traveltimes to the ISS are 

shortest over the northern and western parts of the valley 

where the dolomite is near the land surface.

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34 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin
Appendix 35

Appendix

Calibration targets, August 14, 2001

(well name, location, screen interval, model layer, measured and simulated head, residual)
36 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin MODEL X ORIGIN = 1,362,612 ft in UTM coordinates MODEL Y ORIGIN = 15,620,203 ft in UTM coordinates Well Xmodel Ymodel Column Row Measure point Layer Observed head Simulated head Residual Wells in unlithified sediments – August 14, 2001 is the date of all measurements Distant Wells #1436 39,364.00 21,542.00 158 1 613.31 1 613.31 584.28 29.03 #3790 19,850.00 873.00 80 84 634.17 1 634.17 642.01 -7.84 #4292 30,742.17 741.00 123 85 629.82 1 629.82 621.61 8.21 CLARK 24,475.00 13,471.00 98 34 662.14 1 662.14 656.02 6.12 FORESTRY 16,897.00 16,030.00 68 23 623.28 1 623.28 620.24 3.04 HTOWN 9,515.00 971.00 39 84 741.57 1 741.57 727.29 14.28 Bluff Wells BL_JK434 30,390.74 8,555.84 122 53 597.03 1 601.24 593.44 7.80 BL_JM081 19,968.26 8,287.00 80 54 608.85 1 612.30 610.21 2.09 BL_JM718 26,687.00 13,536.00 107 33 671.15 1 674.33 667.63 6.70 BL_JY481 16,124.00 11,321.00 65 42 630.72 1 651.71 636.63 15.08 BL_JY505 23,271.00 6,811.00 94 60 657.83 1 662.33 642.96 19.37 BL_JY551 19,218.26 9,850.00 77 48 596.04 1 608.67 595.13 13.54 BL_JY556 30,112.00 13,996.00 121 32 628.69 1 635.36 625.37 9.99 Valley Wells JI093 2,9275.00 11,438.00 118 42 572.64 1 577.12 579.17 -2.05 JI094 2,9565.20 11,442.64 119 42 573.35 1 579.12 579.17 -0.05 JI098 2,9971.00 11,404.00 120 42 572.49 1 575.85 579.17 -3.32 JI100 2,9361.00 11,371.00 118 42 574.45 1 581.12 579.17 1.95 JL774 31,146.09 10,634.97 125 45 576.19 1 582.50 579.14 3.36 JL775 31,114.00 10,368.00 125 46 576.95 1 581.38 579.23 2.15 JL776 30,971.00 11,103.00 124 43 577.41 1 581.55 579.17 2.38 JL958 29,533.94 11,371.00 119 42 574.43 1 581.05 579.17 1.88 JM108 28,521.00 12,060.00 115 39 575.84 1 578.84 579.40 -0.56 JM714 33,125.00 11,609.00 133 41 574.51 1 578.55 579.20 -0.65 JM715 33,066.00 11,511.00 133 41 574.93 1 578.73 579.20 -0.47 JM716 33,133.30 11,513.34 133 41 574.73 1 578.42 579.20 -0.78 JM719 28,501.00 12,126.00 115 39 575.76 1 578.98 579.40 -0.42

JM720 28,514.00 12,027.00 115 39 575.22 1 578.88 579.40 -0.52
Appendix 37

MODEL X ORIGIN = 1,362,612 ft in UTM coordinatesMODEL Y ORIGIN = 15,620,203 ft in UTM coordinates

Well Xmodel Ymodel Column Row Measure point Layer Observed head Simulated head Residual

Valley Wells (continued)JW045 29,518.00 11,470.00 119 42 573.85 1 580.52 579.17 1.35JY482 25,521.00 9,886.00 103 48 575.02 3 578.91 572.87 6.04JY521 22,497.00 11,929.00 90 40 591.53 3 593.32 589.01 4.31JY522 32,442.51 9,441.64 130 50 588.51 1 593.03 583.64 9.39JY523 32,487.00 12815.00 130 36 588.02 1 592.64 579.48 13.16JY531 23,718.00 9,993.00 95 48 575.98 1 579.46 580.71 -1.25JY541 33,122.64 11,479.17 133 42 574.43 1 578.37 579.20 -0.83JY542 33,105.49 11,427.00 133 42 574.26 1 578.43 579.20 -0.77JY543 29,830.00 11,404.00 120 42 573.42 1 576.43 579.17 -2.74JY545 29,826.00 11,444.00 120 42 573.67 1 576.09 579.17 -3.08JY546 29,849.00 11,437.00 120 42 573.25 1 575.26 579.17 -3.91JY547 20,440.00 8,878.00 82 52 581.47 1 582.31 584.04 -1.73JY548 20,440.00 9,009.00 82 51 580.95 1 582.32 585.43 -3.11JY550 20,424.00 8,943.00 82 52 581.29 1 582.33 584.04 -1.71JY555 19,677.00 10,491.00 79 46 583.04 1 585.11 586.97 -1.86JY558 29,055.00 10,912.00 117 44 576.38 1 578.87 579.08 -0.21JY560 29,115.00 10,912.00 117 44 573.29 1 578.90 579.08 -0.18JY561 29,203.00 11,010.00 117 43 579.04 1 580.51 579.09 1.42JY562 28,786.00 10,387.00 116 46 574.31 1 578.81 579.17 -0.36JY563 28,760.00 10,387.00 116 46 574.52 1 578.89 579.17 -0.28JY564 28,773.00 10,356.00 116 46 574.51 1 579.03 579.17 -0.14JY569 29,361.00 10,256.00 118 46 576.11 1 578.84 579.20 -0.36JY571 29,259.00 10,321.00 118 46 576.92 1 579.91 579.20 0.71JY572 29,075.00 10,190.00 117 47 577.93 1 581.28 579.23 2.05JY573 29,088.00 10,256.00 117 46 576.45 1 579.20 579.17 0.03JY574 29,092.00 10,354.00 117 46 577.55 1 580.43 579.17 1.26JY575 29,101.00 10,420.00 117 46 577.83 1 580.42 579.17 1.25JY576 29,105.00 10,485.00 117 46 577.74 1 580.77 579.17 1.60JY577 30,135.00 11,207.00 121 43 579.03 1 580.54 579.13 1.41JY581 28,629.00 11,207.00 115 43 577.98 1 578.72 579.17 -0.45
38 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin MODEL X ORIGIN = 1,362,612 ft in UTM coordinates MODEL Y ORIGIN = 15,620,203 ft in UTM coordinates Well Xmodel Ymodel Column Row Measure point Layer Observed head Simulated head Residual Valley Wells (continued) JY582 27,057.00 11,273.00 109 42 573.42 1 579.49 579.54 -0.05 JY583 27,247.00 10,748.00 109 45 576.53 1 580.61 579.55 1.06 JY591 28,547.00 12,027.00 115 39 576.40 1 578.78 579.40 -0.62 JY592 28,580.00 11,929.00 115 40 575.21 1 578.86 579.50 -0.64 JY593 28,590.00 12,060.00 115 39 573.88 2 579.09 573.78 5.31 JY594 28,619.00 11,994.00 115 40 575.25 1 578.55 579.50 -0.95 JY595 29,046.00 11,404.00 117 42 574.33 1 581.39 579.21 2.18 JY596 29,046.00 11,371.00 117 42 577.23 1 581.16 579.21 1.95 JY597 28,990.00 11,437.00 116 42 577.00 1 581.24 579.23 2.01 JY598 29,036.00 11,437.00 117 42 577.39 1 581.26 579.21 2.05 JY599 29,115.00 11,470.00 117 42 577.10 1 578.48 579.21 -0.73 JY600 29,108.00 11,437.00 117 42 575.12 1 578.90 579.21 -0.31 JY614 31,300.26 11,226.68 126 43 573.58 1 581.03 579.11 1.92 JY617 29,940.00 12,386.00 120 38 573.02 1 576.36 578.26 -1.90 JY618 29,938.00 12,382.00 120 38 543.94 3 572.91 560.66 12.25 JY631 26,835.00 12,482.00 108 38 570.44 1 576.03 578.19 -2.16 JY647 25,521.69 11,771.60 103 40 538.76 3 568.95 569.41 -0.46 Nested Wells (D=deep, S=shallow, W=water table) N1D_JY507 25,495.00 11,456.00 102 42 532.36 3 565.77 570.45 -4.68 N1S_JY506 25,483.00 11,443.00 102 42 562.34 2 573.45 575.77 -2.32 N1W_JY508 25,483.00 11,466.00 102 42 571.51 1 576.63 579.72 -3.09 N2D_JY502 33,114.00 11,615.00 133 41 510.18 3 560.06 558.72 1.34 N2S_JY501 33,115.00 11,605.00 133 41 561.05 2 576.86 572.11 4.75 N2W_JM717 33,125.00 11,609.00 133 41 575.07 1 578.53 579.20 -0.67 N3D_JY649 26,055.00 12,020.00 105 39 539.96 3 568.91 567.91 1.00 N3W_JY648 26,055.00 12,020.00 105 39 579.03 1 583.37 579.08 4.29 N4D_JY513 29,403.00 11,437.00 118 42 511.05 3 564.51 563.01 1.50 N4S_JL119 29,376.00 11,471.00 118 42 569.99 2 577.11 574.26 2.85

N4W_JW180 29,271.96 11,419.72 118 42 574.11 1 581.03 579.17 1.86
Appendix 39

MODEL X ORIGIN = 1,362,612 ft in UTM coordinatesMODEL Y ORIGIN = 15,620,203 ft in UTM coordinates

Well Xmodel Ymodel Column Row Measure point Layer Observed head Simulated head Residual

Nested Wells (D=deep, S=shallow, W=water table) 

N5D_JY619 27,153.00 10,511.00 109 45 529.09 2 570.59 575.28 -4.69N5W_JY557 7,182.00 10,702.00 109 45 577.43 1 581.04 579.55 1.49N6D_JY613 30,325.43 8,712.30 122 53 560.50 3 562.00 560.60 1.40N6W_MW-3 30,311.78 8,710.81 122 53 595.22 1 599.36 593.44 5.92N7B_JY644 25,182.00 12,513.00 101 37 545.19 5 585.67 567.14 18.53N7W_JY643 25,181.00 12,507.00 101 37 582.87 4 587.32 587.17 0.15N8D_JY646 26,008.00 12,106.00 105 39 533.96 3 570.77 567.91 2.86N8W_JY645 26,008.00 12,104.00 105 39 578.93 1 583.33 579.08 4.25N9D_JY510 19,325.00 10,470.00 78 46 558.98 2 585.54 586.32 -0.78N9W_JY511 19,325.00 10,470.00 78 46 578.84 1 585.01 585.97 -0.96N11D_JY612 30,658.00 10,281.00 123 46 523.04 3 558.15 561.37 -3.22N11W_JY611 30,658.00 10,286.00 123 46 572.28 1 578.98 579.27 -0.29N12D_JY616 28,478.00 8,947.00 114 52 549.95 3 581.53 566.59 14.94N12W_JY615 28,479.37 8,944.13 114 52 581.09 2 582.90 575.98 6.92N13S_JL777 31,018.00 10,677.00 125 45 553.99 2 572.04 573.24 -1.20N13W_JL773 30,849.97 10,693.00 124 45 578.20 1 582.23 579.17 3.06Wells in bedrock used to monitor Deep Tunnel – data gathered during 1994CT-MW-01 37,678 8,278 151 54 587.27 7 290.24 359.25 -69.01CT-MW-02 34,322 10,630 138 45 594.20 7 422.66 349.98 72.68CT-MW-03 32,369 11,303 130 42 585.94 7 352.74 338.26 14.48CT-MW-04 30,551 11,436 123 42 587.57 7 398.91 349.28 49.63CT-MW-05 25,514 11,318 103 42 589.58 7 330.50 360.39 -29.89CT-MW-06 20,660 11,141 83 43 640.21 7 350.74 397.48 -46.74CT-MW-07 18,913 14,484 76 30 664.80 7 336.05 396.93 -60.88CT-MW-08 14,286 15,713 58 25 633.96 7 396.31 416.96 -20.65CT-MW-09 8,475 18,250 34 15 661.02 7 434.32 450.71 -16.39CT-MW-10 23,787 11,260 96 42 597.68 7 355.06 364.42 -9.36
40 Simulation of Ground-Water Flow, Surface-Water Flow, and a Deep Sewer Tunnel System in the Menomonee Valley, Milwaukee, Wisconsin MODEL X ORIGIN = 1,362,612 ft in UTM coordinates MODEL Y ORIGIN = 15,620,203 ft in UTM coordinates Well Xmodel Ymodel Column Row Measure point Layer Observed head Simulated head Residual Wells in bedrock used to monitor Deep Tunnel (continued) CT-MW-11 34,322 10,630 138 45 594.02 6 453.70 471.34 -17.64 CT-MW-12 23,918 12,025 96 39 597.74 6 510.21 511.70 -1.49 CT-MW-13 20,655 12,082 83 39 640.52 6 581.36 531.92 49.44 NS-MW-01 33,301 12,292 134 38 590.21 6 532.72 470.89 61.83 NS-MW-02 33,296 15,889 134 24 592.34 6 536.30 486.74 49.56 NS-MW-03 35,857 19,589 144 9 630.09 6 479.73 496.65 -16.92 KK-MW-01 35,643 6,810 143 60 586.36 7 378.96 334.46 44.50 KK-MW-02 34,064 3,746 137 73 599.54 7 523.60 335.47 188.13 KK-MW-03 34,218 678 137 85 587.10 7 496.08 340.42 155.66 KK-MW-05 35,643 6,810 143 60 585.27 5 512.59 538.38 -25.79 LM-MW-01 39,397 1,467 158 82 595.42 6 579.47 500.13 79.34 NS-MR-05S 34,587 17,093 139 19 592.15 6 543.89 490.39 53.50 NS-MR-05D 34,587 17,093 139 19 591.91 7 413.87 383.01 30.86 CT-MR-06S 28106 11717 113 41 587.76 499.01 491.67 7.34 CT-MR-06D 28049 11717 113 41 586.88 7 516.10 73.10 143.00 CT-MR-07S 13462 14073 54 31 696.99 5 635.82 635.23 0.59 CT-MR-07D 13438 14083 54 31 698.04 8 582.06 526.11 55.95 I30-25-CT 31667 12575 127 37 NA 6 514.06 479.08 34.98 I30-CT-DS-6 25553 12514 103 37 NA 5 554.85 558.90 -4.05 I30-17-CT 10190 17064 41 19 NA 6 632.67 601.56 31.11 C44-PZ-06 33044 2391 133 78 NA 5 560.58 563.05 -2.47 C10-07-KK 34048 420 137 86 NA 5 544.52 571.66 -27.14 I30-10-NS 36927 20933 148 4 NA 5 549.00 558.99 -9.99
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