U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2018–5105

Prepared in cooperation with the City of Crystal Lake, Illinois

Hydrologic Influences on Water Levels at Three Oaks 

Recreation Area, Crystal Lake, Illinois, April 14 through 

September 27, 2016
Cover photographs:

Front: View of Three Oaks Recreation Area (South Lake) from James R. Rakow Road, September, 27, 2016.

Back: View of Three Oaks Recreation Area (South Lake) from James R. Rakow Road, September 27, 2016.
Hydrologic Influences on Water Levels at 

Three Oaks Recreation Area, Crystal Lake, 

Illinois, April 14 through September 27, 2016

By Amy M. Gahala

Prepared in cooperation with the City of Crystal Lake, Illinois

Scientific Investigations Report 2018–5105

U.S. Department of the Interior

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

DAVID BERNHARDT, Acting Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2019

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Gahala, A.M., 2019, Hydrologic influences on water levels at Three Oaks Recreation Area, Crystal Lake, Illinois, 

April 14 through September 27, 2016: U.S. Geological Survey Scientific Investigations Report 2019–5105, 22 p., 

https://doi.org/10.3133/sir20185105.

ISSN 2328-0328 (online)
iii

Acknowledgements

The author would like to thank Mr. Jack Lucchetti for granting the USGS permission to 

obtain water levels on the downgradient quarry property and for his countless explanations 

of the quarry operations and plans. Thank you to Mr. Andrew Resek for providing the supply 

withdrawal records for Wells 12 and 13. Thank you also to George Roadcap and Daniel Hadley 

of the Illinois State Water Survey for their collaboration on this project.
iv

Contents

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

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

Purpose and Scope ..............................................................................................................................3

Previous Investigations at Three Oaks Recreation Area...............................................................3

Description of Study Area ...................................................................................................................5

Geology..........................................................................................................................................5

Water Use and Quarry Operations............................................................................................5

Hydrogeology................................................................................................................................8

Hydrologic Data Collection...........................................................................................................................9

Analysis of Influences.................................................................................................................................11

Water-Level Responses to Precipitation Events ...........................................................................11

Water-Level Responses to Withdrawals .......................................................................................13

Water-Level Responses to Quarry Operation Activities...............................................................13

Water Levels and Quantification of Flow ................................................................................................14

Water-Table Map ................................................................................................................................14

Groundwater Flow ..............................................................................................................................16

Summary........................................................................................................................................................20

References....................................................................................................................................................21

Figures

1. Map showing the Three Oaks Recreation Area, downgradient quarries, and well 

locations in Crystal Lake, Illinois................................................................................................2

2. Graph showing average annual water levels at North Lake and South Lake 

of the Three Oaks Recreation Area and McHenry County observation well, 

421122088222701–43N7E-23.1d, 16–GRF–I from 2009 to 2015 ................................................3

3. Image showing Bathymetry, in feet below water surface, of North and South 

Lake at the Three Oaks Recreation Area, Crystal Lake, Illinois............................................4

4. Graph showing daily pumping rates for supply wells 12 and 13 from January 2010 

to May 2016, in Crystal Lake, Illinois..........................................................................................6

5. Map showing the downgradient quarry and proposed expansion plans at 

Allendale in Crystal Lake, Illinois ...............................................................................................7

6. Image showing dredge operations in Franke at the downgradient quarry in 

Crystal Lake, Illinois......................................................................................................................8
v

7. Image showing conceptual drawing of a flow-through pit, representative of the 

groundwater system at the Three Oaks Recreation area and the downgradient 

quarries in Crystal Lake, Illinois .................................................................................................9

8. Graph showing daily precipitation data from the rain gage at the Crystal Lake 

Waste Water Treatment Plant 2 near the Three Oaks Recreation Area, Illinois, 

April 14, 2016, to September 27, 2016.......................................................................................11

9. Graph showing daily water levels at South Lake well and daily precipitation from 

the Waste Water Treatment Plant 2 rain gage, Crystal Lake, Illinois, from April 14, 

2016, to September 27, 2016 ......................................................................................................12

10. Graph showing daily water levels at well 8.2c and precipitation from the rain 

gage at Waste Water Treatment Plant 2, in Crystal Lake, April 14, 2016, to 

September 27, 2016.....................................................................................................................12

11. Graph showing daily water levels at the Rakow Road well and precipitation from 

the rain gage at Waste Water Treatment Plant 2, in Crystal Lake, Illinois, April 14, 

2016, to September 27, 2016 ......................................................................................................13

12. Graph showing daily water levels at observation well 8.2c and total daily 

pumping by supply wells 12 and 13 in Crystal Lake, Illinois, May 15, 2016, to 

September 27, 2016.....................................................................................................................14

13. Map showing water-table map in the vicinity of the Three Oaks Recreation Area, 

Crystal Lake, Illinois, May 5, 2016.............................................................................................15

14. Image showing conceptual illustration of water levels at South Lake of the Three 

Oaks Recreation Area and the downgradient quarry, in Crystal Lake, Illinois.................16

15. Graph showing volume of water entering and exiting the Three Oaks Recreation 

Area, Crystal Lake, Illinois, April 14, 2016, to September 27, 2016 ......................................19

Tables

1. Surveyed groundwater and surface water-level measurements near the Three 

Oaks Recreation Area, Crystal Lake, Illinois, May 5, 2016 ...................................................10

2. Observation well-construction data for wells near the Three Oaks Recreation 

Area, Crystal Lake, Illinois.........................................................................................................10

3. Horizontal hydraulic conductivity calculated from single well aquifer tests at 

select wells surrounding the Three Oaks Recreation Area, Crystal Lake, Illinois...........17

4. Velocity of groundwater flow calculations within the vicinity of the Three Oaks 

Recreation Area, Crystal Lake, Illinois ....................................................................................17

5. Volume of flow calculations for the inflow and outflow of groundwater using 

horizontal hydraulic conductivity values from slug test data at the Three Oaks 

Recreation Area, Crystal Lake, Illinois ....................................................................................19
vi

Conversion Factors and Abbreviations

U.S. customary units to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.4047 square hectometer (hm2) 

acre 0.004047 square kilometer (km2)

square foot (ft2) 0.09290 square meter (m2)

Volume

cubic foot (ft3) 0.02832 cubic meter (m3) 

acre-foot (acre-ft) 1,233 cubic meter (m3)

acre-foot (acre-ft) 0.001233 cubic hectometer (hm3) 

Flow rate

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

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

International System of Units to U.S. customary units

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

Area

square meter (m2) 0.0002471 acre 

hectare (ha) 2.471 acre

square hectometer (hm2) 2.471 acre

square kilometer (km2) 247.1 acre

square meter (m2) 10.76 square foot (ft2) 

Volume

cubic meter (m3) 35.31 cubic foot (ft3)

cubic meter (m3) 0.0008107 acre-foot (acre-ft) 

cubic hectometer (hm3) 810.7 acre-foot (acre-ft) 

Flow rate

meter per day (m/d) 3.281 foot per day (ft/d)

cubic meter per day (m3/d) 35.31 cubic foot per day (ft3/d) 

liter per second (L/s) 15.85 gallon per minute (gal/min) 

cubic meter per day (m3/d) 264.2 gallon per day (gal/d) 
vii

Datum

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Elevation, as used in this report, refers to distance above the vertical datum.

Abbreviations

ILWATER Illinois State Geological Survey website database

ISWS Illinois State Water Survey

Kh horizontal hydraulic conductivity

MP measuring point

NAVD88 North American Vertical Datum of 1988

TORA Three Oaks Recreation Area

USGS U.S. Geological Survey

Hydrologic Influences on Water Levels at Three Oaks 

Recreation Area, Crystal Lake, Illinois, April 14 through 

September 27, 2016

By Amy M. Gahala

Abstract

Hydrologic influences on water levels were investigated 

at Three Oaks Recreation Area (TORA), a former sand-andgravel quarry converted into recreational lakes in Crystal 

Lake, Illinois. From 2009 to 2015, average water levels in 

the lakes declined nearly 4 feet. It was not clear if these 

declines were related to variations in weather (precipitation or 

evaporation) or other hydrologic influences such as municipal 

supply pumping or nearby quarry operations. Data were 

collected using three approaches to determine the possibility 

of such hydrologic influences. First, water levels were 

collected at 15-minute intervals at three wells equipped with 

pressure transducers from April 14 through September 27, 

2016. The continuous data allowed assessment of lake 

and well water-level responses to precipitation, pumping 

influences, and quarry operations. Second, a single-day 

synoptic water-level survey was completed to create a watertable map to determine groundwater flow directions. Third, 

single-well aquifer tests (slug tests) were completed on the 

three data-collection wells to estimate the aquifer’s horizontal 

hydraulic conductivity. Collectively, these data were used 

to estimate the velocity and volume of water entering and 

exiting TORA.

Groundwater levels increase rapidly in response to 

precipitation at wells adjacent to TORA, but the higher levels 

are lost quickly to discharge between precipitation events. 

There were minimal to no pumping influences from the 

nearby municipal supply wells evident in the hydrographs. 

Nearby quarry dredging operations also did not appear to 

directly affect the water levels at wells adjacent to TORA. 

The calculations that compare the inflows to the outflows at 

the TORA indicate that evaporation may be the dominant 

hydrologic influence; therefore, the TORA would be 

particularly vulnerable to periods of drought conditions. 

Introduction

In 2009, the City of Crystal Lake, Illinois, converted 

an unused sand and gravel quarry within the city limits 

into a recreation area for swimming and beach activities 

named the Three Oaks Recreation Area (TORA). The TORA 

is located south of U.S. Highway 14 and west of State 

Highway 31 in McHenry County (fig. 1). The TORA consists 

of two lakes, North Lake and South Lake, with groundwater 

generally moving from north to south, hereafter referred to 

as “downgradient.” The TORA is surrounded by residential, 

commercial, and industrial development, which obtain water 

supplies from the City of Crystal Lake’s municipal supply 

wells. Ongoing quarry operations are located south of the 

TORA. The U.S. Geological Survey (USGS), in cooperation 

with the City of Crystal Lake, conducted a local hydrologic 

investigation of the TORA, with data collected from April 14 

to September 27, 2016. The data were collected to identify 

the influences from precipitation, nearby groundwater 

withdrawals, and nearby quarry operations on water levels 

at the TORA and to quantify the velocity and volume of 

groundwater flow entering and exiting the TORA. This 

investigation will provide the necessary information to Crystal 

Lake’s resource managers for lake-management, planning, and 

configuration decisions.
2 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

North

Lake

South

Lake

South Lake well North Lake well

Franke Allendale

Perch Lake

Big Lake

Storage well

3.7d

Rakow Rd well

14.5f

17-ALG-S

28.6g

Fox River

Fox River Tailwater

8.2c 12

13

16-GRF-I located 2.3 miles west

Three Oaks

Recreation

Area

downgradient

quarry

MCHENRY COUNTY

KANE COUNTY

South Lake well

South Lake northern-SW northern-SW

South Lake southern-SW southern-SW

North Lake well

North Lake-SW

Franke Allendale

Perch Lake

Larson Fen

Big Lake

Crystal Creek

Wash area

Storage well

3.7d

8.2c

WWTP2 Rakow Rd well

14.5f

17-ALG-S

28.6g

Fox River

Fox River Tailwater

Fox

River

12

13

16-GRF-I located 2.3 miles west

JAMES R. RAKOW ROAD

SOUTH VIRGINIA ROAD PINGREE ROAD

SOUTH ILLINOIS ROUTE 31

PYOLT ROAD

88°20' 88°19' 88°18' 88°17' 88°16'

42°14'

42°13'

42°12'

42°11'

42°10'

0 0.25 0.5 0.75 1 MILE

0 0.25 0.5 0.75 1 KILOMETER

ILLINOIS

Map

area

MCHENRY

COUNTY

EXPLANATION

Well location with name

U.S. Geological Survey streamflow-

 gaging station with name

Crystal Lake Waste Water Treatment 

 Plant 2 raingage with name

Wash area

28.6g

Fox River

Base map image is the intellectual property of Esri and is

used herein under license. Copyright © 2015 Esri and its 

licensors. All rights reserved.

WWTP2

31

Figure 1. Three Oaks Recreation Area, downgradient quarries, and well locations in Crystal Lake, Illinois.
Introduction 3

Purpose and Scope

The purpose of this report is to describe hydrologic 

influences on water levels at the TORA in Crystal Lake, 

Illinois. This report is to provide Crystal Lake’s resource 

managers with an understanding of how precipitation, 

groundwater withdrawals, and nearby quarry operations 

may be affecting lake levels and water quality in the TORA. 

USGS collected continuous (15-minute) water-level data 

within and near the TORA from April 14 to September 27, 

2016 to identify water-level responses to precipitation events, 

groundwater withdrawals, and quarry operations. Additionally, 

a synoptic water-level survey was completed to establish 

water-level elevations, hydrologic flow paths, and hydraulic 

gradients in the TORA and estimate groundwater velocity 

and volumetric flow rates. Single-well aquifer tests were 

completed at selected wells to estimate hydraulic conductivity. 

All collected data were compared to develop calculations that 

estimate the rate and volume of groundwater flow entering and 

exiting the TORA from April 14, 2016, to September 27, 2016.

Previous Investigations at Three Oaks 

Recreation Area

A water-level model for the TORA was used to estimate a 

maximum historical lake stage of 866 feet (ft) and a minimum 

stage of 856 ft (Hey and Associates, Inc., written commun., 

August 31, 2015). Hey and Associates, Inc., also indicated 

that water levels at the TORA would decrease if the nearby 

quarry water level fell below 849 ft. The model used by Hey 

and Associates, Inc., was a water-level model that does not 

consider geology or aquifer properties. Water-level models use 

only water-budget inputs such as precipitation and evaporation 

to predict lake water levels.

Crystal Lake and Hey and Associates, Inc., collected daily 

groundwater and surface water level data from 2009 through 

2015 (Hey and Associates, Inc., written commun., September 

11, 2015). These data were compared to the continuous waterlevel data available from a nearby (4 miles [mi] southwest) 

well (421122088222701–43N7E-23.1d, 16–GRF–I) in the 

McHenry County Groundwater Monitoring Well Network. 

This comparison indicated that the average-annual water 

levels at the TORA appeared to have been declining since 

2009 similar to 16–GRF–I (fig. 2). In general, the averageannual water levels of the two lakes were consistent with those 

in well 16–GRF–I from 2009 to 2010. From 2013 to 2014, the 

water level in the well decreased slightly while it remained 

the same in the two lakes. However, in 2015, the water levels 

at North and South Lake declined by about 3 ft, while the 

average annual water-level changes at well 16–GRF–I were 

less than 1 ft, potentially indicating the TORA water-level 

declines were unrelated to regional influences.

Bathymetric (lakebed) measurements completed by 

the Illinois Department of Natural Resources Fisheries 

division (Vic Santucci, written commun., February 23, 

2006) determined that North Lake had an average depth of 

23 ft with a maximum depth of 40 ft and South Lake had an 

average depth of 19 ft with a maximum depth of 41 ft toward 

the eastern half of the lake (fig. 3). The lakebeds have a 

tiered, stair-step configuration that grades deeper toward the 

center of the lake and shallows toward the shores. This is the 

result of previous quarry operations at the TORA with the 

configuration dictated by the amount of fine-grained (clays 

and silts) deposits encountered during mining operations. It 

is common for quarry operators to avoid mining fine-grained 

deposits because they clog equipment and are not salable. 

Where encountered, the dragline or dredger is moved until 

sand and gravel is found. The surface area of North Lake 

is about 1,437,000 square feet (ft2; 33 acres) and South 

Lake of the TORA is about 12,271,000 ft2 (281.7 acres) for 

a total of 13,708,000 ft2 (Vic Santucci, written commun.,

2006). The volume of surface water at North Lake was 

estimated at 760 acre-feet (33,110,000 cubic feet [ft3]). The 

volume of surface water at South Lake was estimated to 

be 5,384 acre-feet (234,540,000 ft3) (Vic Santucci, written 

commun., 2006).

855.0

856.0

857.0

858.0

859.0

860.0

861.0

862.0

863.0

864.0

865.0

866.0

2009 2010 2011 2012 2013 2014

Water elevation in feet above

North American Vertical Datum of 1988

USGS 16-GRF-I

North Lake

South Lake

2015

EXPLANATION

Figure 2. Average annual water levels at North Lake and South 

Lake of the Three Oaks Recreation Area and McHenry County 

observation well, 421122088222701–43N7E-23.1d, 16–GRF–I from 

2009 to 2015. (Source: North and South Lake data from Hey and 

Associates, written commun., 2014; observation well data from 

U.S. Geological Survey, 2016).
4 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

North Lake

McHenry County

T43N R8E S9NE

Surface Acres: 33.0

Maximum Depth (ft.): 40.0

Average Depth (ft.): 23.0

Volume (acre-feet): 759.9

Shoreline Length (mi.): 1.3

Vic Santucci – 2/24/06

IDNR - Fisheries

2 5

35

40

25

30

18

12

20 15 10

9

2 2

South Lake

McHenry County

T43N R8E S9SW

Surface Acres: 281.7

Maximum Depth (ft.): 41.0

Average Depth (ft.): 19.1

Volume (acre-feet): 5,384.3

Shoreline Length (mi.): 3.4

Vic Santucci – 2/23/06

IDNR - Fisheries

41

27

24

9

5 5

15

20

25

25 20

15

10 10 15

40

30

25

35

30 35

Culvert

Culvert

Figure 3. Bathymetry, in feet (ft) below water surface, of A, North and B, South Lake at the Three Oaks Recreation Area, Crystal Lake, 

Illinois. (Figures sourced from Vic Santucci, Illinois Department of Natural Resources (IDNR), written commun., 2006).
Introduction 5

Description of Study Area

The land topography surrounding the TORA is hilly with 

elevations ranging from 905 ft to 940 ft (North American 

Vertical Datum of 1988 [NAVD88]) toward the north, and 

relatively flat toward the west with elevations ranging from 

895 ft to 901 ft NAVD88. South of the TORA, the land slopes 

gently until steep gradients are encountered just before the 

Fox River.

There are no streams or constant sources of drainage 

into the TORA. Three culverts direct stormwater runoff from 

the roads into the recreational area; two culverts are located 

on the east side of South Lake (draining storm runoff from 

Pingree Road [Rd]), and one is located on the southwest 

side of South Lake (draining storm runoff from Virginia and 

James R. Rakow Rd). Two additional culverts parallel to 

the southern shoreline of South Lake along an earthen berm 

direct stormwater runoff from James R. Rakow Rd (hereafter 

referred to as Rakow Rd) where, the stormwater runoff 

passively infiltrates into the groundwater along Rakow Rd. 

Stage and flow data are not available for these culverts during 

the period of study. A culvert connects North Lake and South 

Lake to the TORA, and historical water levels indicate that 

water elevation at North Lake is generally less than 1 ft higher 

than South Lake. Therefore, velocity and volume calculations 

presented in the Water Levels and Quantification of Flow 

section of this report include only the square feet and volume 

of South Lake.

Geology

The geologic units of interest to this investigation consist 

of: (1) an approximately 70 ft thick fractured bedrock of 

Silurian age that pinches out toward the south (Reinertsen 

and others, 1993) overlain by (2) proglacial outwash of the 

Wisconsin Episode that includes less than 80 ft of till, finegrained deposits up to 38 ft thick (Haeger Member), and 

coarse-grained outwash deposits (Henry Formation) less than 

10 ft to more than 180 ft thick (Curry, 2005a). From a larger 

areal perspective, the sequence of coarse-grained outwash 

deposits (Henry Formation) thicken toward the northwest 

and gradually thin toward the south and east of the TORA 

toward the Fox River. Much of the coarse-grained deposits of 

the Henry Formation have been mined (Curry, 2005b). The 

fine-grained deposits of the Woodstock Moraine and Barlina 

Moraine increase toward the Fox River. 

Well logs from several wells in the vicinity of the TORA 

are available from the Illinois State Geological Survey website 

database (ILWATER; Illinois State Geological Survey, 2016). 

North of the TORA, layers of sand and gravel extend to 

approximately 70 ft below land surface with clay encountered 

at depths of 50 to 70 ft to bedrock and bedrock encountered at 

about 250 ft below land surface. West of the TORA, well logs 

noted interbeds of sandy clays followed by silts and brown 

clay at about 89 ft below land surface. Depth to bedrock west 

of the TORA is approximately 230 ft below land surface. 

Southwest of the TORA, well logs noted the presence of about 

60 ft of sand and gravel, underlain by about 150 ft of clay and 

bedrock that occurs at 217 ft below land surface. Southeast 

of the TORA, sand and gravel thickens, extending to depths 

ranging from 104 ft to 130 ft below land surface. The well 

logs located along Rakow Rd primarily show sand and gravel 

about 70 ft below land surface overlain by a thin (0 to 8 ft) 

layer of brown sandy clay. 

Water Use and Quarry Operations

There are two supply wells (Crystal Lake wells 12 

and 13) about 170 ft apart from each other, located about 

1,200 ft west of the TORA, and about 800 ft southeast of the 

USGS observation well 42130108819150—43N8E-8.2c. 

This USGS observation well is referred to in this report as 

8.2c. The supply wells are both open to the shallow bedrock 

aquifer at 250 ft depth according to well logs available on 

ILWATER (Illinois State Geological Survey, 2016). Daily 

pumping records from supply wells 12 and 13 were provided 

by the City of Crystal Lake Public Works Department 

(written commun., November 2, 2016) for most of the period 

of study (May 15, 2016, through October 1, 2016). The 

cumulative extraction rates for the supply wells ranged from 

0 to 1,275,000 gallons per day, with an average extraction 

rate of 101,000 gallons from Crystal Lake well 12 and 

233,000 gallons from Crystal Lake well 13 and a cumulative 

average of 334,000 gallons per day from January 2009 through 

May 2016 (fig. 4) (City of Crystal Lake, written commun., 

June 1, 2016). Withdrawal rates have decreased from an 

average of 111,000 to 75,000 gallons for Crystal Lake well 12 

and from an average of 286,000 to 98,000 gallons for Crystal 

Lake well 13 from July 2014 to May 2016. Several other 

municipal supply wells open to the shallow bedrock aquifer 

are located north, west, and east of the TORA according to 

ILWATER. About 15 private (residential) water-supply wells 

are present northeast of the TORA according to ILWATER. 

Approximately five commercial wells are located just north 

of the TORA. No known industrial supply wells are located 

within the vicinity of the TORA (Illinois State Geological 

Survey, 2016; U.S. Geological Survey, 2016).
6 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

The nearby quarry is situated directly south of South 

Lake and will be referred to as the downgradient quarry for 

the remainder of this report. The following descriptions of 

the downgradient quarry operations and plans were from 

conversations with the downgradient quarry Plant Manager on 

May 5, 2016. The downgradient quarry has two active mining 

areas (pits): Franke and Allendale (fig. 5). Franke is the larger 

of the two pits and is located just south of Rakow Rd (and 

South Lake). The second pit, Allendale, is located east of 

Pingree Rd and south of Rakow Rd. Franke is approximately 

45 to 50 ft deep and is currently being excavated via dredging 

operations. The dredge extracts sediment and water at a rate 

of 500 tons per hour for 8 hours a day, typically 5 days per 

week, according to the downgradient quarry Plant Manager 

(Jack Luccetti, oral commun., May 5, 2016). All fine-grained 

deposits are avoided and not mined because it damages the 

mining equipment. The water is redirected back into the 

same pit (Franke) while the sediment is removed by way of 

conveyor belt (fig. 6). The water in Franke and Allendale is 

not drained. Prior to July 2015, Franke and Allendale were 

mined using a dragline at an approximate rate of 250 tons per 

hour. Dredging operations commenced after July 2015 and 

are expected to continue until all minable sand and gravel 

is extracted from Franke to a depth of approximately 55 ft, 

which is estimated to take about 5 years.

Allendale is approximately 25 ft deep. An additional 

25 ft is planned to be mined to similar depths as Franke using 

the dredge, after the mining of Franke is complete (fig. 5). 

Currently (2017), there remains approximately 25 ft of sand 

and gravel above the water table at Allendale that also is 

planned to be mined. Furthermore, it is possible that this area 

may be mined below the water table to similar depths as the 

rest of Allendale.

Other previously mined surface-water bodies located 

on the downgradient quarry property are Perch Lake and Big 

Lake (fig. 5). These previously mined pits were not mined 

as deeply as Franke and Allendale because the increase in 

fine-grained deposits was encountered at shallower depths 

(approximately 12 ft), according to the downgradient quarry 

Plant Manager (Jack Lucchetti, oral commun., May 5, 2016). 

These lakes are drained through culverts toward Larson Fen 

and Crystal Creek, due to a lack of storage capacity within the 

quarry site according to the Plant Manager (Jack Lucchetti, 

oral communication, May 5, 2016).

Other activities at the downgradient quarry include a 

wash area where the sand and gravel are washed before being 

dried and sorted (fig. 1). The water that is used to wash the 

sand and gravel is sourced from a pond, and the used water 

is pumped to a settlement pond upgradient and allowed to 

return by gravity to a pump house pond to be reused. The 

water is pumped at a rate of 2,500 gallons per minute from the 

pump house when in operation (fig. 1) (Jack Lucchetti, oral 

commun., November 2016).

The area to the west of Franke, south of S. Virginia Rd 

(fig. 5), and northwest of Perch Lake is an older quarry that 

is currently being filled with clean construction material 

and debris owned by Consolidated Materials, Inc. No 

measurements were obtained in this area. Additional quarry 

operations owned by a different company are located further 

south of Big Lake and east of Route 31 but were not included 

in this investigation due to a lack of access. It is probable that 

operations at these additional quarries will be limited to depths 

similar to Big Lake and Perch Lake due to the increase in finegrained deposits and thinning of the overlying sand and gravel 

alluvium toward the south.

0

200

400

600

800

1,000

1,200

1,400

03/13/2010 07/26/2011 12/07/2012 04/21/2014 09/03/2015

Withdrawal, in thousands of gallons per day

Date (month/day/year)

Well 12

Well 13

Total

EXPLANATION

Figure 4. Daily pumping rates for supply wells 12 and 13 from January 2010 to May 2016, in Crystal Lake, Illinois.
Introduction 7

88°19' 88°18' 88°17'

42°13'

42°12'

42°11'

0 0.1 0.2 0.3 0.4 0.5 MILE

0 0.1 0.2 0.3 0.4 0.5 KILOMETER

Base map image is the intellectual property of Esri and is

used herein under license. Copyright © 2015 Esri and its 

licensors. All rights reserved.

Three Oaks

Recreation

Area

South Lake

Franke

Pump house and

wash area

Larson

Fen

Perch

Lake

Big

Lake

Crystal Creek

Allendale

JAMES R. RAKOW ROAD

Area above water 

table to be mined 

(~20 feet) plus additional 

25 to 50 feet below 

water table to be mined

Additional 25 feet

below water table

to be mined

SOUTH VIRGINIA ROAD

PYOLT ROAD

SOUTH ILLINOIS ROUTE 31

PINGREE ROAD

Three Oaks

Recreation

Area

South Lake

Franke

Pump house and

wash area

Larson

Fen

Perch

Lake

Big

Lake

Crystal Creek

Allendale 

JAMES R. RAKOW ROAD

Area above water 

table to be mined 

(~20 feet) plus additional 

25 to 50 feet below 

water table to be mined

Additional 25 feet

below water table

to be mined

SOUTH VIRGINIA ROAD

PYOLT ROAD

SOUTH ILLINOIS ROUTE 31

PINGREE ROAD

Figure 5. Downgradient quarry and proposed expansion plans at Allendale in Crystal Lake, Illinois.
8 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

Hydrogeology

The coarse-grained outwash deposits of the Henry 

Formation comprise the Haeger-Beverly Unit. The HaegerBeverly Unit is the primary aquifer unit for shallow 

groundwater flow in the TORA (Meyer and others, 2013). 

The Haeger-Beverly Unit is underlain primarily by finegrained deposits of the Tiskilwa Formation (till) deposited 

by the Woodstock and Barlina Moraines. Underlying the till 

is the fractured bedrock aquifer, which can be hydraulically 

connected to the shallower Haeger-Beverly Unit where the 

Tiskilwa Formation is absent. 

The TORA lakes and downgradient quarries are known 

as flow-through pits or pit lakes. Groundwater flows through 

the TORA lakes and downgradient quarries by entering from 

the north, along with surface-water runoff, and exiting the 

TORA at the southern portions of the lakes (fig. 7). Pit lakes 

are a source of groundwater recharge but can also have a 

greater loss from evaporation because of their open water 

characteristics. Pit lakes are a lake boundary system that 

receives precipitation, loses water to evaporation, and allows 

groundwater to enter and leave the lake. Pit lakes are also 

zones of infinite permeability, in that the velocity of the water 

within the pit is not limited by a matrix of sediment or rock. 

An increase in the velocity can alter the groundwater flow 

paths (Younger and others, 2012). Green and others (2005) 

published one of the first and only comprehensive studies on 

the hydraulic impacts of quarries and gravel pits. In that study 

of five limestone quarries and two sand and gravel pits, the 

effects of quarry operations on water levels at the sand and 

gravel pit mines were determined to be minimal; however, 

that study also showed that groundwater-flow directions 

were diverted away from a nearby fen because of one of the 

excavated gravel pits. Therefore, the downgradient quarry 

operations and expansion plans could potentially alter the 

groundwater-flow directions at TORA. 

88°18'04" 88°18'02" 88°18'00" 88°17'58" 88°17'56" 88°17'54" 88°17'52"

42°12'22"

42°12'20"

42°12'18"

42°12'16"

0 0.025 0.05 0.075 0.1 MILE

0 0.025 0.05 0.075 0.1 KILOMETER

Base image from Google.

Imagery date June 26, 2016. 

Accessed May 3, 2017 through

Google Earth version 7.1.2.2041.

Dredge

Discharge of

extracted water

Conveyor

belts

Figure 6. Dredge operations in Franke at the downgradient quarry in Crystal Lake, Illinois.
Hydrologic Data Collection 9

Hydrologic Data Collection

On April 7, 2016, an observation well (Rakow Rd well) 

was installed by the Testing Service Corporation slightly north 

of Rakow Rd about 25 ft from the southern shoreline of South 

Lake (fig. 1). The Rakow Rd well monitors the groundwater 

exiting the TORA. The well was installed at a depth of 

38 ft below land surface. The geology described in the well 

log showed a brown sandy clay to a depth of 8 ft, followed 

by coarse-grained outwash deposits approximately 30 ft in 

thickness. The identified geology is consistent with existing 

well logs available from the Illinois State Geological Survey 

(2016) ILWATER database. South Lake well is an existing 

well owned and maintained by the City of Crystal Lake and is 

located about 10 ft from the northern shoreline of South Lake 

(fig. 1). The South Lake well has a depth 8.82 ft below land 

surface with a 5-ft screen interval at the bottom of the well. 

The existing USGS well 8.2c is located about 1,200 ft west of 

South Lake and is 46.1 ft below land surface with a 5-ft screen 

interval at the bottom of the well. The South Lake well and 

8.2c well represent the upgradient groundwater entering the 

TORA. These three wells were equipped with vented pressure 

transducers and data were collected from April 14, 2016, to 

September 27, 2016 (referred to as the period of record) and 

processed according to Cunningham and Schalk (2011). The 

transducers continuously measured and recorded water levels 

at 15-minute intervals to catalog water-level responses to 

precipitation, pumping, and quarry operations. The data are 

available in the USGS National Water Information System 

(U.S. Geological Survey, 2016).

Daily precipitation data were obtained from a rain 

gage at Crystal Lake Waste Water Treatment Plant 2, 

approximately 1.5 mi west of the TORA (The Weather 

Company, 2016) (fig. 1). Daily precipitation for the period 

of record ranged from 0.00 to 1.47 inches (in.) for a total 

of 22.06 in. Evaporation was estimated from Roberts and 

Stall (1967), which reported monthly average evaporation 

for the state of Illinois. Near the study area, the evaporation 

for the months April through September totaled 25.2 in. The 

volume of precipitation and evaporation was determined 

by converting the inches to feet and multiplying by the 

surface area of North and South Lake (13,708,000 ft2). 

Precipitation added 25,222,720 ft3 to TORA and evaporation 

removed 28,786,800 ft3 from TORA. Evaporation exceeded 

precipitation during the period of record by about 14 percent. 

On May 5, 2016, synoptic water-level measurements 

within about a 2-mi radius of TORA were collected by 

the USGS from observation wells and surface-water sites 

including the downgradient quarry property (table 1). 

Table 2 lists the pertinent well construction details for 

the observation wells measured for the synoptic waterlevel event, and the water-level data are available in the 

USGS NWIS (U.S. Geological Survey, 2016). A calibrated 

electronic sounding tape obtained depth-to-water readings. 

A TrimbleTM R8 GNSS global positional system with an 

accuracy of approximately +/– 1.5 centimeter was used 

to determine the elevation of the land surface and the 

surface water-level elevation referenced to NAVD88. For 

groundwater level measurements, the measuring point (MP) 

height was measured, recorded, and added to the land-surface 

elevation to calculate MP elevation. Groundwater elevations 

were calculated by subtracting the depth to water from 

MP elevation. 

Surface water-level measurements at TORA and the 

downgradient quarries were collected at seven surface-water 

(SW) sites (table 1; fig. 1). The water-surface elevation was 

determined with the TrimbleTM R8 GNSS global positional 

system on May 5, 2016, using a Virtual Reference System 

Real-Time Network based on the single-base Real Time 

Kinematic method (Rydlund and Densmore, 2012.) The 

data are available in the USGS NWIS (U.S. Geological 

Survey, 2016).

Surface runoff

into pit

Groundwater

inflow

Groundwater

outflow

Pit lake

Groundwater table

Water table

NOT TO SCALE

Figure 7. Conceptual drawing of a flow-through pit, representative of the groundwater system at the Three Oaks Recreation area and 

the downgradient quarries in Crystal Lake, Illinois.
10 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

Table 1. Surveyed groundwater and surface water-level measurements near the Three Oaks Recreation Area, Crystal Lake, Illinois, 

May 5, 2016.

[USGS, U.S. Geological Survey; Rd, Road; SW, surface water; NAVD88, North American Vertical Datum of 1988; IL, Illinois; N, North; S, South]

USGS station 

identification number USGS station name USGS field identifier Water elevation, in feet above NAVD88

Groundwater

421317088182301 43N8E-9.5f South Lake well1 861.54

421320088181001 43N8E-9.3f North Lake well 861.77

421244088180201 43N8E-9.2a Rakow Rd well1 853.77

421143088180101 43N8E-21.2g Storage-Well 829.20

421301088191501 43N8E-8.2c 8.2c1 875.34

421402088173501 43N8E-3.7d 3.7d 881.29

421228088160701 43N8E-14.5f 14.5f 842.48

421052088184101 43N8E-28.6g 28.6g 799.55

Surface water

421320088181002 North lake at Three Oaks at Crystal Lake, IL North Lake SW 862.20

421317088182201 South Lake N at Three Oaks Crystal Lake, IL South Lake northern SW 861.16

421244088180202 South Lake S at Three Oaks at Crystal Lake, IL South Lake southern SW 861.13

421220088175601 Franke Lake at Quarry at Crystal Lake, IL Franke 847.49

421217088173301 Allendale Lake at Quarry at Crystal Lake, IL Allendale 840.68

421132088175201 Big Lake Lake at Quarry at Crystal Lake, IL Big Lake 823.51

421144088181501 Perch Lake Lake at Quarry at Crystal Lake, IL Perch Lake 832.98

1

Observation well equipped with pressure transducer to collect 15-minute continuous water-level data.

Table 2. Observation well-construction data for wells near the Three Oaks Recreation Area, Crystal Lake, Illinois.

[USGS, U.S. Geological Survey; Rd, Road; ?, unknown]

USGS station 

identification 

number

USGS 

station name

USGS 

field identifier

Land-surface elevation, in 

feet above North American 

Vertical Datum 1988

Measuring-point elevation, 

in feet above North American 

Vertical Datum 1988

Depth of open 

interval, in feet 

below land surface

421317088182301 43N8E-9.5f South Lake well1 863.6 866.69 6–8.82

421320088181001 43N8E-9.3f North Lake well 865.6 869.16 6–8.82

421244088180201 43N8E-9.2a Rakow Rd well1 868 871.06 28–38

421143088180101 43N8E-21.2g Storage-Well 834.6 836.709 ?–21.5

421301088191501 43N8E-8.2c 8.2c1 900 899.7 41.1–46.1

421402088173501 43N8E-3.7d 3.7d 920 919.6 53.7–58.7

421228088160701 43N8E-14.5f 14.5f 870 869.5 53.2–58.2

421052088184101 43N8E-28.6g 28.6g 800 799.5 33.9–38.9

1

Observation well equipped with pressure transducer to collect 15-minute continuous water-level data.
Analysis of Influences 11

Analysis of Influences

Water-Level Responses to Precipitation Events

Daily precipitation data (fig. 8) were available from the 

Wastewater Treatment Plant 2 (The Weather Company, 2016). 

From April 14, 2016 to September 27, 2016, total precipitation 

was 22.06 in. Based on the area of North and South Lake 

(13,708,000 ft2) and the amount of total precipitation (1.84 ft), 

the amount of rain added to South Lake at the TORA was 

25,222,720 ft3 for the period of study.

Precipitation events greater than 0.1 ft raised the water 

level at the South Lake and Rakow Rd wells by about 0.2 ft 

or greater. Water levels within the South Lake well increased 

rapidly by a few tenths of a foot after a precipitation event, 

but the increased water levels were followed by very rapid 

recession between precipitation events (fig. 9). The rapid 

water-level increase because of precipitation indicates the 

infiltration rate is fast and the recharge is a localized short 

path (Conlon and others, 2005). A rapid increase in water 

levels is expected because of the surficial geology of sand and 

gravel and the short distance the infiltrating rain must travel 

to reach the water table at this shallow well (8.82 ft below 

land surface). 

Observation wells 8.2c and the Rakow Rd well are 

deeper (38 and 46.1 ft below land surface, respectively) with 

a larger unsaturated zone (height of soil above water table) 

than the South Lake well. Deeper wells with large unsaturated 

zones are generally less responsive to precipitation due to the 

greater distance the infiltrating water needs to travel. Water 

levels at observation well 8.2c show very little response to 

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

04/14/2016 05/14/2016 06/14/2016 07/14/2016 08/14/2016 09/14/2016

Precipitation, in feet

Date (month/day/year)

Figure 8. Daily precipitation data from the rain gage at the Crystal Lake Waste Water Treatment Plant 2 (WWTP2) near the Three Oaks 

Recreation Area, Illinois, April 14, 2016, to September 27, 2016.

precipitation (fig. 10). Precipitation events larger than 0.10 ft, 

increased the water level at times by about 0.20 ft or less at 

this location. In addition, water levels decreased gradually 

between precipitation events. Water levels in Rakow Rd well 

showed a moderate response to precipitation during the period 

of record (fig. 11).

Water-level elevations at South Lake well can be 

considered a proxy for the uppermost column of surface water 

at South Lake due to its short distance (10 ft) to the shoreline 

and shallow depth (8.82 ft). The South Lake well water levels 

fluctuated between 861.33 ft to 861.72 ft above NAVD88 

during April 14, 2016 to September 27, 2016. Water-level 

trends during the period of record showed an increase at South 

Lake well of 0.13 ft (fig. 9) and 0.63 ft at Rakow Rd well 

(fig. 11). The water levels at 8.2c ranged from 876.13 ft to 

876.71 ft above NAVD88 and decreased by 0.58 ft during 

the period of record, indicating limited recharge from 

precipitation. South Lake well also had a greater decrease 

(–0.46 ft) in water elevation during a period with fewer 

precipitation events (June 13, 2016 to July 20, 2016) than 

the other two wells (well 8.2c and the Rakow Rd well). The 

larger fluctuations of water levels between precipitation events 

at South Lake and the smaller overall increase in water level 

for the period of record at South Lake well than at the other 

two wells may be indicative of the influence of evaporation. 

The water-level increase at the Rakow Rd well may be 

indicative of the seepage of surface water through the lakebed 

into the groundwater, along with flow surrounding TORA, 

precipitation and surface runoff. Therefore, it is possible that at 

least some of the gains at the Rakow Rd well could represent 

the loss of water from South Lake. 
12 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

South Lake well

WWTP2

EXPLANATION

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

860.00

860.20

860.40

860.60

860.80

861.00

861.20

861.40

861.60

861.80

862.00

4/14/2016 5/14/2016 6/14/2016 7/14/2016 8/14/2016 9/14/2016

Precipitation, in feet

Groundwater elevation, in feet above

North A

merican Vertical Datum of 1988

Date (month/day/year)

Figure 9. Daily water levels at South Lake well and daily precipitation from the Waste Water Treatment Plant 2 (WWTP2) rain gage, 

Crystal Lake, Illinois, from April 14, 2016, to September 27, 2016.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

875.00

875.20

875.40

875.60

875.80

876.00

876.20

876.40

876.60

876.80

877.00

Precipitation, in feet

Groundwater elevation, in feet above

North American Vertical Datum of 1988

8.2c

WWTP2

04/14/2016 05/14/2016 06/14/2016 07/14/2016 08/14/2016 09/14/2016

Date (month/date/year)

EXPLANATION

Figure 10. Daily water levels at well 8.2c and precipitation from the rain gage at Waste Water Treatment Plant 2 (WWTP2), in Crystal 

Lake, April 14, 2016, to September 27, 2016.
Analysis of Influences 13

Water-Level Responses to Withdrawals 

In order to identify water-level responses related to the 

nearby withdrawals from the supply wells, total daily water 

withdrawal in gallons per day by the supply wells 12 and 

13 were compared to the water levels at each well. These 

supply wells are open to the shallow bedrock aquifer and are 

not screened into the glacial aquifer. However, several areas 

throughout McHenry County show hydraulic connectivity 

between these two aquifers in areas where the till is absent 

(Meyer and others, 2013). These two supply wells pumped 

an average of 169,000 gallons of water per day and withdrew 

a total of 22,984,000 gallons from May 15, 2016, to 

September 27, 2016 (Crystal Lake Public Works Department 

written commun., December 2, 2016).

Minimal pumping influences were observed in 

observation well 8.2c throughout the period of study (fig. 12). 

The water-level drawdown caused by pumping, which was 

determined by comparing groundwater levels before and after 

the onset of pumping, is as little as a few hundredths of a foot 

(0.03 ft) and not a substantial influence on water levels at the 

TORA. Larger water-level changes were observed in 8.2c 

toward the latter half of the data collection effort from around 

August 12, 2016, to September 27, 2016, (fig. 12). These 

larger water-level changes did not coincide with withdrawals 

from the supply wells 12 and 13. The cause of these later 

water-level fluctuations could be related to other pumping 

influences, although there are no known residential or 

industrial pumping wells in this area. Pumping influences were 

not observed in South Lake well or Rakow Rd well. 

Water-Level Responses to Quarry Operation 

Activities

Continuous water-level data collected from the South 

Lake well and Rakow Rd well did not show any instance 

of being directly affected by dredging operations at the 

downgradient quarry. However, indirect effects on the TORA 

water levels may occur as quarry operations continue to 

remove sand and gravel at Franke and expand vertically 

and horizontally at Allendale. The removal of additional 

sand and gravel at both Allendale and Franke will increase 

the permeability downgradient and further decrease the 

downgradient water elevations, which could then cause 

declining water levels at the TORA.

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

853.00

853.20

853.40

853.60

853.80

854.00

854.20

854.40

854.60

854.80

855.00

Precipitation, in feet

Groundwater elevation in feet above

North A

merican Vertical Datum of 1988

Rakow Rd well

WWTP2

04/14/2016 05/14/2016 06/14/2016 07/14/2016 08/14/2016 09/14/2016

Date (month/date/year)

EXPLANATION

Figure 11. Daily water levels at the Rakow Road well and precipitation from the rain gage at Waste Water Treatment Plant 2 (WWTP2), 

in Crystal Lake, Illinois, April 14, 2016, to September 27, 2016.
14 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

Water Levels and Quantification of 

Flow 

Water-Table Map

On May 5, 2016, surface- and groundwater-level 

measurements were collected to create a water-table map to 

identify the groundwater flow direction and the horizontal 

hydraulic gradients (fig. 13). The water-level elevations were 

located on a map and lines of equal elevation were drawn 

between the points. Topographic elevation data from Google 

Earth Pro® were used to estimate the water-level elevation 

at ungaged creeks and along the steep slopes toward the Fox 

River. The direction of flow is perpendicular to the contoured 

lines. Groundwater flow direction is generally northwest to 

southeast toward the Fox River.

The difference in surface-water elevation between 

South Lake southern SW and Franke was 13.65 ft. The large 

difference was created in part by the removal of the sands 

and gravels at Franke that had previously provided the matrix 

for the groundwater to flow and to be stored. Removing the 

sand and gravel reduced the storage capacity of the aquifer 

and increased this hydraulic gradient and groundwaterflow velocity between the two surface-water bodies. The 

horizontal hydraulic gradient, or slope, of the water table in 

an unconfined aquifer is the change in water level over the 

distance between the two water levels along the direction of 

flow. It is a unitless value as it measures feet over feet. The 

horizontal hydraulic gradient affects the velocity of the water. 

There was one area where the water levels drop substantially 

within a relatively short distance. The horizontal hydraulic 

gradient between the surface-water elevation at the southern 

shoreline of South Lake and Rakow Rd well was calculated 

to be 0.29, where a 7.36 ft change in water-level elevation 

occurs over a distance of about 25 ft. The steep drop from 

the surface-water elevation to the groundwater over the short 

distance also indicates the presence of lower-permeable 

material such as clays, silts, and organics that act to reduce 

the flow of surface water infiltrating into the groundwater and 

exiting South Lake (Gandy and others, 2004). The lakebed of 

South Lake likely consists of fine-grained deposits that were 

stirred into suspension by previous quarry operations and 

subsequently settled out and formed a thin layer of clays and 

silts. The presence of fine-grained deposits was confirmed 

by the Illinois State Water Survey (ISWS) from sediment 

grab samples using a clamshell sampler dropped from a boat 

collecting 13 samples of lakebed sediment from South Lake 

at various locations about 30 ft from the southern shoreline. 

The clamshell sampler can only collect up to about 4 in. of 

sediment from the lakebed, therefore the full thickness of 

the lakebed material is unknown. The ISWS also confirmed 

that at the areas away from the shoreline of South Lake, the 

lakebed (at least the upper 4 in. of the lakebed) consist of clay, 

silts, and organic matter, whereas coarser materials (sands 

and gravels) were predominately found toward the shoreline 

(Illinois State Water Survey, oral commun., 2016). 

0

200

400

600

800

1,000

1,200

874.8

875

875.2

875.4

875.6

875.8

876

876.2

876.4

876.6

876.8

Total withdrawal, in thousands of gallons per day

Date (month/day/year)

8.2c

Total withdrawal supply well

12 and 13

EXPLANATION

05/15/2016 06/15/2016 07/15/2016 08/15/2016 09/15/2016

Figure 12. Daily water levels at observation well 8.2c and total daily pumping by supply wells 12 and 13 in Crystal Lake, Illinois, May 15,

2016, to September 27, 2016.
Water Levels and Quantification of Flow 15

880

870

860

850

840

830

830

820

820

810

810

800

800

790

790

780

780

770

770

760

760

750

750

740

740

730

720

880

870

860

850

880

870

860

850

840

840

830

830

820

820

810

810

800

800

790

790

780

780

770

770

760

760

750

750

740

740

730

720

880

880

870

860

850

South Lake

861.16

861.54

North Lake

862.20

861.77

Franke

847.49

Allendale

840.68

Perch

832.98

Big Lake

823.51

Storage well

829.20

3.7d

881.29

Rakow Rd

853.77

861.13

14.5f

842.48

17-ALG-S

881.33

28.6g

799.55

Fox River

731.34

Fox River Tailwater

726.56

8.2c

875.34 Three

Oaks

Recreation

Area

downgradient

quarry

MCHENRY COUNTY

KANE COUNTY

South Lake

861.16

861.54

North Lake

862.20

861.77

Franke

847.49

Allendale

840.68

Perch

832.98

Big Lake

823.51

Storage well

829.20

3.7d

881.29

8.2c

875.34

Rakow Rd

853.77

861.13

14.5f

842.48

17-ALG-S

881.33

28.6g

799.55

Fox River

731.34

Fox River Tailwater

726.56

88°20' 88°19' 88°18' 88°17' 88°16'

42°14'

42°13'

42°12'

42°11'

42°10'

0 0.25 0.5 0.75 1 MILE

0 0.25 0.5 0.75 1 KILOMETER

EXPLANATION

Line of equal water-level elevation,

 dashed where inferred

Well location with name

 and water-level elevation

U.S. Geological Survey streamflow-

 gaging station with name and

 water-level elevation

780

28.6g

799.55

Fox River

731.34

Base map image is the intellectual property of Esri and is used herein under license.

Copyright © 2014 Esri and its licensors. All rights reserved. 

Datum of measured water-level elevations is in feet above the North American Vertical Datum of 1988.

Inferred water-level elevations were estimated from topographic elevation data from Google Earth Pro®

Crystal CreekCrystal Creek

Figure 13. Water-table map in the vicinity of the Three Oaks Recreation Area, Crystal Lake, Illinois, May 5, 2016.
16 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

Additionally, the USGS used a handheld auger to collect 

geologic samples to a depth of nearly 2 ft at three locations 

along South Lake’s shorelines near the Rakow Rd well. The 

uppermost 4 to 6 in. of the shorelines augured were coarsegrained sand with some clays that progressed to sand and 

gravel with less clay at depth, indicating that fine-grained 

deposits line the lakebed but the upper portion near the 

shoreline has less clay. This is because waves and scour may 

stir up the clays and silts lining the southern shoreline of South 

Lake allowing the upper portion to be more permeable than 

the lower portion of the lakebed. It should be noted that the 

northern shoreline is also subject to having more permeable 

sediments than areas of the lakebed away from the shoreline. 

This is in part because of beach activities along the northern 

shoreline, and the steep bathymetry (fig. 3) along much of the 

eastern half of South Lake, potentially limiting the deposits of 

fine-grained material. Along the southern shoreline of South 

Lake, the areas of thin or absent clays and silts in the upper 

portion of the southern shoreline would create a preferential 

flow path to the underlying coarser materials for the surface 

water to infiltrate into the groundwater along James Rakow Rd 

and into Franke. The thickness and distribution of this upper 

portion of coarser materials is unknown. Figure 14 illustrates 

how effectively the low-permeable layer at the bottom of 

South Lake impedes groundwater flow toward Franke. Note 

the steep drop-off in water level from South Lake to Rakow 

Rd well. This represents the higher hydraulic gradient at 

this location. 

Groundwater Flow

The horizontal hydraulic conductivity (Kh) controls the 

rate at which fluid will transport horizontally through the 

geology. The Kh was determined from single well aquifer 

tests, referred to hereafter as slug-tests, in an effort to calculate 

the rate of groundwater flow in and out of the TORA from 

South Lake. Tests were done at the Rakow Rd on April 26, 

2016, and on May 20th, at South Lake and 8.2c wells by 

USGS personnel. Slug-tests were conducted following 

guidelines and selected procedural guidelines for conducting 

an instantaneous change in head test with a mechanical slug 

and submersible pressure transducer presented in Groundwater 

Technical Procedures Document GWPD 17 (Cunningham 

and Schalk, 2011). Water levels of the slug tests at Rakow Rd 

well had an oscillatory response, which were analyzed using 

the KGS-High K option in a spreadsheet provided by Keith 

Halford (U.S. Geological Survey, written commun., 2016) 

based on methods described in Butler and others (2003). The 

other two slug-test results were analyzed with the Bouwer and 

Rice (1976) method for determining hydraulic conductivity in 

an unconfined aquifer. The saturated aquifer thickness at South 

Lake and Rakow Rd well was estimated to be 55 ft thick for 

the saturated sand and gravel, and 48 ft at the 8.2c well. The 

average Kh of the Haeger-Beverly aquifer north and west of 

the TORA is one to two orders of magnitude lower than the 

Kh of the Haeger-Beverly aquifer to the south of the TORA 

along Rakow Rd (table 3).

Rakow

Rd well

Land surface

NOT TO SCALE

Groundwater

Clays and organics

inflow

Groundwater

outflow

Franke

South Lake

Water table

Figure 14. Conceptual illustration of water levels at South Lake of the Three Oaks Recreation Area and the downgradient quarry, in 

Crystal Lake, Illinois.
Water Levels and Quantification of Flow 17

The velocity (V) of groundwater flow through the 

aquifer was determined from equation (1) by using water 

levels between paired observation wells and surface-water 

sites (table 4). 

V = KhI/n (1)

where,

V is the velocity or rate of the groundwater flow, 

in feet per day;

Kh is the horizontal hydraulic conductivity of the 

aquifer, in feet per day;

I is the gradient (change in water-level 

elevation divided by distance), in foot per 

foot; and

n is the porosity of the aquifer material through 

which the groundwater flows (0.38).

Previous studies indicate that the estimated 

porosity average for sand and gravel is 0.38 (Morris 

and Johnson, 1967). The estimated rate of groundwater 

entering from the north at South Lake well into South 

Lake surface water was 8.21 feet per day (ft/day) and from 

Table 3. Horizontal hydraulic conductivity calculated from single 

well aquifer tests (slug tests) at select wells surrounding the 

Three Oaks Recreation Area, Crystal Lake, Illinois.

[USGS, U.S. Geological Survey; Rd, Road; ft, feet]

USGS station 

identification 

number

USGS 

station 

name

USGS field 

identifier

Average 

horizontal 

hydraulic 

conductivity, 

in ft/day

421317088182301 43N8E-9.5f South Lake well 78

421244088182301 43N8E-9.2a Rakow Rd well 115

421301088191501 43N9E-8.2c 8.2c 2.95

the west at well 8.2c into South Lake surface water was 

0.02 ft/day (table 4). The velocity of groundwater flow to 

Franke from South Lake surface water was estimated to be 

about 12.11 ft/day (table 4). However, that velocity does not 

account for the lower permeable material such as silts, clays, 

and organics that line much of South Lake’s lakebed. The 

lower permeable materials would act to limit the horizontal 

flow out of the flow-through lake to the upper part of the 

lakebed through the more permeable material. Also, because 

the Kh of the native sand and gravel north and west of the 

TORA is lower than it is at Rakow Rd, the effect of the 

sediments may have less influence on the velocity (and 

volume of inflow) than they would on the south side.

The Kh of the fine-grained material was not directly 

measured by the USGS. However, seepage meter 

measurements were collected by the ISWS and resulted in 

an average discharge (Q) of 0.22 ft3/day (Illinois State Water 

Survey, written commun., 2016). The Kh was calculated 

by rearranging the Darcy equation (equation 2) to solve for 

Kh (Kh = Q/(A*I). There were no water levels collected at 

the time of the seepage measurement. Therefore, the water 

levels collected on May 5, 2016, were substituted to estimate 

the hydraulic gradient (I) which is the difference in water 

levels between South Lake southern SW and Rakow Rd well 

(7.36 ft) divided by the distance between the two locations 

(25 ft); A is the average area of the seepage meters, 2.76 ft2

(ISWS, written commun., 2016). The calculated Kh of the 

fine-grained deposits was 0.27 ft/day. As a result, the velocity 

of the water transported from South Lake surface water to 

Rakow Rd well through the fine-grained deposits was about 

0.21 ft/day (table 4). However, there may be areas of thin or 

absent clays where the Kh returns to that measured at Rakow 

Rd well of 115 ft/day. These areas are likely in the upper 

portion of the lakebed where wave action and scour stir up 

the clays and silts. This stirring can create a preferential flow 

path where greater amounts of lake water can drain toward the 

downgradient quarry.

Table 4. Velocity of groundwater flow calculations within the vicinity of the Three Oaks Recreation Area, Crystal Lake, Illinois.

[ft, feet; ft/ft, feet per feet; ft/day, feet per day; SW, surface water; Rd, Road]

Segment description Distance, 

in ft

Difference 

in water 

elevation, in ft

Horizontal 

hydraulic 

gradient, in ft/ft

Horizontal hydraulic 

conductivity, 

in ft/day

Porosity for 

sand and 

gravel

Groundwater 

velocity, 

in ft/day

South Lake well to South Lake northern SW 10 0.39 0.04 78 0.38 8.21

8.2c to South Lake southern SW 5,756 14.21 0.002 2.95 0.38 0.02

South Lake southern SW to Rakow Rd well 25 7.36 0.29 0.27 1 0.38 0.21

Rakow Rd well to Franke 475 6.28 0.01 115 0.38 3.03

South Lake southern SW to Franke 500 13.66 0.04 115 0.38 12.11

1

Illinois State Water Survey hydraulic conductivity applied to account for low-permeable clays and organics lining the lakebed.
18 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

Groundwater, surface water-level measurements, and 

Kh were used to calculate the volume of discharge from 

groundwater into South Lake and recharge from South Lake 

into groundwater by the solution of the Darcy Equation 

(Fetter, 1988). The Darcy Equation is:

Q = KhAI (2)

where,

Q is the discharge, into or out of the lake, in 

cubic feet per day;

Kh is the horizontal hydraulic conductivity of the 

geologic deposits transmitting water and is 

equal to the mean value determined from 

the rising-head slug tests. Kh values were 

divided into the separate areas to fully 

characterize the rate of groundwater inflow 

and outflow at the South Lake of TORA. 

South Lake well Kh was 78 feet per day 

(ft/day), 8.2c well Kh was 2.95 ft/day, and 

Rakow Rd well Kh was 115 ft/day. The Kh 

(0.27 ft/day) from South Lake southern 

SW to Rakow Rd well was applied to 

estimate the discharge of the lake through 

the lakebed toward Rakow Rd well; 

A is the cross-sectional area of flow between 

the aquifer and the lake and is equal to the 

length of the lakeshore along which water 

is being recharged or discharged multiplied 

by the maximum depth of the lake, 41 ft 

(Vic Santucci, written commun., 2006), in 

square feet; and

I is the horizontal hydraulic gradient, the 

difference in the water levels between the 

lake and wells divided by the distance 

between the well and the lakeshore, in foot 

per foot.

The surface-water and groundwater elevations measured 

on May 5, 2016, for groundwater entering (inflow) (South 

Lake well to South Lake northern SW and monitoring 

well 8.2c to South Lake southern SW) and the surface-andgroundwater exiting (outflow) TORA (South Lake southern 

SW to Rakow Rd well) were used to calculate the volumes 

of water for the period of record. Distance between the two 

points for the inflow to TORA from the north and west and 

the groundwater exiting the TORA along Rakow Rd were 

determined using the distance (length) measurement tool in 

Google Earth Pro®.

The volume of water entering and exiting the TORA per 

day was estimated from the Kh, horizontal hydraulic gradient, 

length of the north and south shorelines, maximum depth of 

South Lake (41 ft), as well as the area of the transect along 

flow direction of shoreline for inflow and outflow. The volume 

of flow for the period of record was estimated by multiplying 

the volume of flow per day by 167 days. Therefore, quantified 

volume for the period of record does not take into account 

changes in water levels that occurred between April 14 and 

September 27, 2016. The total inflow was subtracted from 

the total outflow and the difference represents the calculated 

change in storage at South Lake. The difference was divided 

by the surface area of south lake (12,270,852 ft2) to convert 

the change in storage to the change in water level, in feet, for 

the period of record. The calculated change in water level was 

compared to the measured change in water level for South 

Lake of 0.13 ft, represented by South Lake well. Applying 

the maximum depth of lake (equation 2) resulted in volumes 

that were largely overestimated. Inflow was 164,778,327 ft3

and outflow was 32,592,405 ft3 over the period of 167 days. 

The difference (132,185,922 ft3) was divided over the surface 

area of South Lake and resulted in a calculated change in feet 

of 10.77 ft for the period of record. The measured change 

in water level at South Lake was 0.13 ft and therefore, it 

was necessary to attempt to determine the thickness of the 

coarse-grained deposits where the preferential flow may be 

occurring. Revised volumes were determined by changing 

the maximum depth of South Lake (ft) for the segments with 

Kh of 78 ft/day and 115 ft/day to determine the potential 

thickness of the coarse-grained deposits not impeded by the 

fine-grained deposits. The thickness of the maximum depth 

was iteratively adjusted in only whole numbers until the 

calculated change in water level for the period of record was 

closer to the measured change in water level (0.13 ft). The 

refined results (table 5) indicate that the estimated thickness 

of the coarse-grained deposits is about 1 foot with a calculated 

change in water level of 0.25 ft, which is comparable to the 

measured change in water level of 0.13 ft. The volume of 

groundwater entering TORA each day was 5,915,102 ft3/d, 

from the north and west, while the volume of outflow from the 

TORA along the south and east was 2,863,065ft3 for the period 

of record (table 5; fig. 15). 

The total volume of South Lake is 234,540,000 ft3. The 

inflow from groundwater accounts for 3 percent while the 

outflow was 1 percent of the volume of South Lake. Inflow 

into South Lake was 52 percent greater than the outflow from 

South Lake. Evaporation exceeded precipitation by 14 percent. 

The lower permeable material creates an impediment that 

acts to slow down the rate at which the surface water at South 

Lake flows to Franke and may account for the difference in 

head between the two lakes. Additionally, the groundwater 

entering the TORA, based on these calculations, exceeds the 

amount of groundwater leaving the TORA likely because of 

the larger shoreline along the north and west of South Lake. 

Groundwater exits South Lake along the southern shoreline, 

which has a length that is about 40 percent smaller than the 

northern shoreline. 
Water Levels and Quantification of Flow 19

Table 5. Volume of flow calculations for the inflow and outflow of groundwater using horizontal hydraulic conductivity values from slug 

test data at the Three Oaks Recreation Area, Crystal Lake, Illinois.

[ft, feet; ft/ft, feet per feet; ft2, feet squared; ft/day, feet per day; ft2/day, feet squared per day; ft3/day, cubic feet per day; SW, surface water; Rd, Road]

Segment description

Horizontal 

hydraulic 

conductivity, 

in ft/day

Product of 

horizontal hydraulic 

gradient and 

horizontal hydraulic 

conductivity, 

in ft2/day

Length of 

lakeshore 

through which 

flow is 

occurring along 

flow transect, in ft

Maximum 

depth of 

South 

Lake, in ft

Area of 

transect 

along flow 

direction, 

in ft2

Volume of 

flow, 

in ft3/day

Volume in ft3

for period 

of record 

(167 days)

Inflow

South Lake well to South Lake 

northern-SW (coarse-grained 

deposits lining the lakebed)

78 3.04 7,823 21 7,823 23,782 3,971,581 

South Lake well to South Lake 

northern-SW (fine-grained 

deposits lining the lakebed)

1

0.27 0.03 7,823 41 320,743 9,622 1,606,922 

8.2c to South Lake southern-SW 2.95 0.01 4,916 41 201,556 2,016 336,599 

Outflow

South Lake southern-SW to 

Rakow Rd well (fine-grained 

deposits lining the lakebed)

1

0.27 0.08 3,870 41 158,670 12,694 2,119,831 

South Lake southern-SW to 

Rakow Rd well (coarse-grained 

deposits lining the lakebed)

115 1.15 3,870 21 3,870 4,451 743,234 

inflow 5,420 5,915,102

outflow 17,144 2,863,065

difference 18,276 3,052,037

1

Illinois State Water Survey hydraulic conductivity applied to account for low-permeable clays and organics lining the lakebed.

2

Estimated thickness of sand and gravel in the upper portion of South Lake along the shoreline.

Figure 15. Volume of water entering and exiting the Three Oaks Recreation Area, Crystal Lake, Illinois, April 14, 2016, to 

September 27, 2016.

0

1,000,000

2,000,000

3,000,000

4,000,000

5,000,000

6,000,000

7,000,000

IN OUT

Volume of flow, in cubic feet
20 Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, IL, April 14 through September 27, 2016

It is important to note that these values are generalized 

estimates because certain key water-balance components 

were not directly measured. These include: site-specific 

evaporation, surface-water runoff, inputs from the culverts 

that directly drain the surface-water runoff into South Lake, 

hydraulic conductivity of the low-permeable material lining 

the lakebed, and that the seepage measurement from the ISWS 

was only completed along the southern shoreline and results 

were assumed to be the same along the northern shoreline 

of South Lake. Additionally, the adjusted thickness for the 

coarse-grained deposits as determined by the calculations may 

not be the same along northern input segments as is it along 

the southern output segments. A full water-balance was outside 

the scope of this report. This study did not detect pumping 

influences or direct influences from the downgradient quarry. 

Therefore, these general estimations indicate that evaporation 

may be the predominant hydrologic influence on the TORA as 

it was estimated to have removed 14 percent more water than 

what precipitation added. Still, groundwater inflow exceeded 

the outflow to balance the losses to evaporation and outflow as 

shown by the measured increase in water level for the period 

of record. It is possible that prolonged periods of drought 

would be especially problematic given the loss of water to 

evaporation accounts for 11 percent of the volume of water 

of TORA. 

To improve the generalized estimates, a full water 

balance study would help identify the effective depth and 

width of the lake bathymetry’s sand and gravel deposits where 

horizontal flow occurs. Additionally, aquifer properties can 

be used in a groundwater model to further refine the volumes 

entering and exiting the TORA and to evaluate the effects 

of future changes in precipitation and the downgradient 

quarry operations.

Summary

Hydrologic influences were investigated at a former 

sand-and-gravel quarry that was converted to a recreational 

lake area in Crystal Lake, Illinois. From 2009 to 2014, 

average water levels have declined nearly 4 feet. It was not 

clear if these declines were related to variations in weather 

(precipitation or evaporation) or other hydrologic influences 

such as municipal supply pumping or quarry operations. 

Data were collected using three approaches to determine 

the possibility of such hydrologic influences. First, water 

levels were collected at 15-minute intervals at three wells 

equipped with pressure transducers from April 14 through 

September 27, 2016. The continuous data allowed for the 

assessment of responses to precipitation, pumping influences, 

and quarry operations. Second, a single day synoptic waterlevel survey was completed to create a water-table map for 

the determination of groundwater flow directions. Third, 

single-well aquifer tests (slug tests) were completed on the 

three data-collection wells to estimate horizontal hydraulic 

conductivity of the aquifer. Collectively, these data were used 

to estimate the velocity and volume of water entering and 

exiting the Three Oaks Recreation Area (TORA).

The groundwater-level responses to precipitation at 

South Lake well and Rakow Road (Rd) well were rapid and 

show that the water-level increases after precipitation events. 

The increase in water level was quickly lost to discharge, but 

overall gains during the period of record (April 14 through 

September 27, 2016) were observed in the South Lake well 

(0.13 ft) and Rakow Rd well (0.63 ft). There were minimal 

to no pumping influences from the nearby municipal supply 

wells open to the shallow bedrock aquifer evident in the 

hydrographs. There were also no direct hydrologic influences 

from the downgradient quarry observed in the hydrographs. 

However, indirect hydrologic influences from the 

downgradient quarry may occur if water levels at the quarry 

decline due to additional removal of the sand and gravel that 

acts to slow and retain the groundwater flow. The decline in 

water levels will increase the hydraulic gradient between the 

TORA and the Franke and Allendale quarry pits, which could 

cause water loss at the TORA.

Water-level elevations at South Lake well can be 

considered as a proxy for the uppermost column of surface 

water at South Lake. The larger fluctuations of water levels 

and the relatively smaller increase in water levels over the 

period of record at South Lake well compared to Rakow Rd 

well may indicate the influence of evaporation. The Rakow 

Rd well represents the average water level between the South 

Lake water level and Franke water level. At least some of the 

gains at Rakow Rd well could be the result of water loss from 

South Lake.

The synoptic water-level survey indicated that the 

groundwater flow direction is from northwest to southeast. 

There was one instance where the horizontal hydraulic 

gradient (0.29) was much greater than at any other location. 

This instance indicates a presence of lower-permeable material 

such as clays, silts, and organics that act to reduce the flow of 

surface water infiltrating to the groundwater and exiting South 

Lake. Higher horizontal hydraulic gradients can increase the 

flow velocity at which water is moved through the system.

The velocity of the groundwater entering the TORA at 

South Lake was 48 percent less than the velocity exiting the 

TORA. The volume of groundwater entering South Lake was 

estimated to be 52 percent greater than the water exiting South 

Lake along the southern shoreline toward Rakow Rd well. The 

longer shoreline to the north and lower-permeable materials 

act as a bottleneck that reduces the volume of flow exiting 

South Lake into Franke and may explain the difference in head 

between TORA and the downgradient quarries. Groundwater 

entering South Lake accounted for about 3 percent of the total 

volume of water at South Lake, while surface water exiting 

South Lake to Rakow Rd well and to Franke accounted for 

1 percent of the total volume of South Lake. The water-level 

increase of 0.13 ft measured over the period of record at 

South Lake well was comparable to the calculated increase of 

0.25 ft from the volumetric flow calculations and differences 

were likely due to assumptions and other unaccounted-for 

preferential flow paths and water balance components. 
References 21

In general, water-level measurements show that direct 

influences from pumping or quarry operations were not 

observed, and comparisons of inflow and outflow show that 

evaporation may be the dominant hydrologic influence at the 

TORA. Therefore, TORA would be particularly vulnerable 

to prolonged periods of drought. A full water balance study 

would help identify the effective depth and distribution of the 

lake bathymetry’s sand and gravel deposits where horizontal 

flow occurs. Additionally, aquifer properties can be used in a 

groundwater model to further refine the volumes entering and 

exiting the TORA and to evaluate the effects of future changes 

in precipitation and the downgradient quarry operations.

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For more information concerning the research in this report, contact the

Director, Upper Midwest Water Science Center

U.S. Geological Survey

8505 Research Way

Middleton, Wisconsin 53562

(608) 828–9901

https://wi.water.usgs.gov

Publishing support provided by the U.S. Geological Survey 

Science Publishing Network, Madison, Pembroke, Rolla, and 

Sacramento Publishing Service Centers ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20185105
Gahala—Hydrologic Influences on Water Levels at Three Oaks Recreation Area, Crystal Lake, Illinois, April 14 through September 27, 2016—SIR 2018–5105