Protecting Wisconsin's Groundwater Through Comprehensive Planning
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  Oconto County
  This report provides the most current information and data found, as of May 2007, unless otherwise noted.
  Oconto County groundwater findings reports Oconto County full report Switch to Oconto County executive summary


Wisconsin enjoys a generally clean and abundant groundwater resource.A2 This resource is present because of the state’s geologic history and climate; this resource is protected through strong state and federal regulations, and the cooperative efforts of water systems, trade associations, individual operators, planning commissions, and state and federal science agencies.

Drinking water in Wisconsin is provided by either public water systems or private wells. A public water system is defined as a system that provides public water for human consumption, if such a system has at least 15 service connections or regularly serves an average of at least 25 individuals daily at least 60 days out of the year. Wisconsin has nearly 11,500 public water systems which meet the daily water needs of about 4 million people.A1 The Wisconsin Department of Natural Resources (WDNR)A3 oversees these public systems, and additional information can be found online.  

Municipal water systems are regulated by the WI Department of Natural Resources, meaning that they have to regularly test their water and must notify the public if water exceeds certain drinking water standards. In the case of municipal wells, if water does exceed drinking water standards additional steps must eventually be taken to ensure that the standards are met before the water is distributed to the individual homes in the community. Municipal systems provide reasonable assurance that drinking the water will not result in any acute or chronic health effects. The municipal wells in Lena, Oconto and Oconto Falls draw water from bedrock. The Gillett municipal wells draw water from the sand and gravel aquifer. Of the Suring municipal wells, two draw water from the sand and gravel aquifer and one from the sandstone aquifer. These aquifers are described in the geology section of this paper.

Public water systems that are owned by a community are called municipal water systems.A4 Oconto County has 5 municipal water systems.  Table showing public water systems in Oconto County

In Oconto County, 26% of county residents get drinking water from five municipal water utilities while 74% of county residents get drinking water from private wells. Five municipalities in Oconto County have 15 municipal wells that provide drinking water to 9,939 residents, or 26% of county residents.

Private Wells

Oconto County Well Construction
Oconto County
well construction 1988-2004
Oconto County new well construction graph  
Oconto County
new well construction 1988-2004

There have been over 12,000 wells constructed in Oconto County alone, the vast majority of which are private wells. Approximately 27,700 county residents, or 74%, get their drinking water from private wells. The figure at right shows that from the period from 1988-2004 over 7,000 wells have been constructed, many of those newly constructed wells are concentrated in certain parts of the county.

The number of wells constructed each year in Oconto County has increased since 1988 as shown in the figure on the right.

Well construction which is regulated by the WI DNR (NR 812) is based on the premise that if a well and water system is properly located, constructed, installed and maintained the well should provide safe water continuously without the need for treatment. These regulations have specific guidelines regarding materials and methods used to construct a well, in addition to separation distances from potential sources of contamination. A coliform bacteria test is also required on all newly constructed private wells to ensure that the well is sanitary. This is a one time initial test and the only test that is required for private wells. While the majority of private wells in the state do produce high quality safe drinking water, some private wells may provide contaminated water to unsuspecting families."

After a well is drilled most homeowners are unaware of their responsibilities when it comes to owning a private well. The decision to test, and which contaminants to test for, is solely the responsibility of the individual well owner. If there is something wrong with the water supply it is the individual well owner’s responsibility to determine what the risks are and whether those risks are great enough to correct the problem or find an alternative source of drinking water.

Unlike municipal wells, private wells are not required to have a wellhead protection plan. The recharge area for private wells is generally local and discrete. Therefore, it is important for homeowners and well drillers to evaluate potential contamination sources when placing and deciding on the depth of a new well and casing in order to reduce the chances of drinking unsafe water. Incorporating such things as groundwater flow direction into the placement and design of a well are critical to providing the safest source of water possible. This is of particular concern for new subdivisions where the density is such that private wells often intercept effluent from upgradient septic systems. Simple groundwater flow models may enable wellhead protection strategies to be incorporated into new subdivision design. Considering the large increase in private wells, local governments should look for ways to take a proactive role in protecting public health by developing and incorporating drinking water protection policies for their community.

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WELLHEAD PROTECTION PLANS AND ORDINANCES   Table showing water systems in Oconto County

  • 1 of 5 municipal water systems in Oconto County has a wellhead protection plan: Suring.B1
  • 1 of 5 municipal water systems in Oconto County has a wellhead protection ordinance: Suring.B1
  • 26% of county residents get drinking water from five municipal water utilities.
  • 74% of county residents get drinking water from private wells.
For recommendations of groundwater protection policies and some outstanding examples of innovative groundwater protection policies adopted by other communities see Groundwater Protection Policies.

Wellhead protection plans are developed to achieve groundwater pollution prevention measures within public water supply wellhead areas. In some areas of the state, sophisticated groundwater flow modeling techniques were used to delineate source water areas for municipal wells. A wellhead protection plan uses public involvement to delineate the wellhead protection area, inventory potential groundwater contamination sources, and manage the wellhead protection area. All new municipal wells are required to have a wellhead protection plan. A wellhead protection ordinance is a zoning ordinance that implements the wellhead protection plan by controlling land uses in the wellhead protection area.B2

Of those municipal water systems that have wellhead protection (WHP) plans, some have a WHP plan for all of their wells, while others only have a plan for one or some of their wells. Similarly, of those municipal water systems that have WHP ordinances, some ordinances apply to all of their wells and others just one or some of their wells.


  • Oconto County has adopted an animal waste management ordinance.B3

Most Wisconsin counties have adopted an animal waste management ordinance that applies to all unincorporated areas of the county (areas outside of city and village boundaries). While the purposes of such ordinances vary among counties, a key purpose is often to protect the groundwater and surface water resources. This is accomplished by regulations such as:

  • Permitting of animal waste storage facilities;
  • Permitting of new and expanding feedlots;
  • Nutrient management;
  • Prohibiting:
    • Overflow of manure storage structures;
    • Unconfined manure stacking or piling within areas adjacent to stream banks, lakeshores, and in drainage channels;
    • Direct runoff from feedlots or stored manure to waters of the state;
    • Unlimited livestock access to waters of the state where high concentrations of animals prevent adequate sod cover maintenance.

More information is available from the WDATCP.


Your county may have additional policies in place for groundwater protection. A good way to find out is to check with the county conservationist and local zoning administrators.

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  • Over $12 million has been spent in Oconto County on petroleum cleanup from leaking underground storage tanks, which equates to $300 per county resident.C2

The Petroleum Environmental Cleanup Fund Award (PECFA) program was created in response to enactment of federal regulations requiring release prevention from underground storage tanks and cleanup of existing contamination from those tanks. PECFA is a reimbursement program returning a portion of incurred remedial cleanup costs to owners of eligible petroleum product systems, including home heating oil systems.C1

As of May 31, 2007, over $12 million has been reimbursed by the PECFA fund which equates to $300 per county resident, which is greater than the statewide average of $264 per resident.C2


  • No municipal water systems in Oconto County have spent money to reduce nitrate levels.

As of 2005, over 20 municipal water systems in Wisconsin have spent over $24 million reducing nitrate concentrations in municipal water systems.C3

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Water use in Oconto County
Water use in Oconto County
  • From 1979 to 2005, total water use in Oconto County has fluctuated from 5.8 million gallons per day to about 14.0 million gallons per day.*
  • The fluctuation in total water use over this period is due primarily to fluctuations in industrial use. Industrial use increased substantially from 1979 to 1990 but declined until 2000 and increased slightly by 2005.
  • The proportion of county water use supplied by groundwater has fluctuated from about 28% to 79% during the period 1979 to 2005.*

As part of the National Water-Use Information Program, the USGS stores water-use data in standardized format for different categories of water use. In 1978, the USGS entered into a cooperative program with the WDNR to inventory water use in Wisconsin. Since that time, five reports summarizing water use have been published (Lawrence and Ellefson, 1982D2; Ellefson and others, 1987D3; Ellefson and others, 1993D4; Ellefson and others, 1997D5; Ellefson and others, 2002D6; Buchwald and others, 2008D7).

Water use in Wisconsin in these summary reports is reported in the following categories: domestic, livestock, aquaculture, industrial, commercial, public use and losses, thermoelectric or mining. References describing the methods for collecting data and estimating water use are provided in the summary reports.

High capacity wells

There are 76 permitted high capacity wells in Oconto County. These wells belong primarily to municipal utilities, farms, golf courses, cheese plants and bottling plants.

USGS monitoring well

The groundwater level in one U.S. Geological Survey monitoring well in Oconto County, located near Bonita has varied within about a three-foot range from 1985-2005 with no defined trend. This well is shallow at 46 feet deep and is located near a river and dam which stabilizes water levels compared to surrounding areas.

Dry wells

Of more than 7,000 well that have been drilled since 1988, 147 wells indicated that the reason for constructing the well was to replace an existing well that had gone dry or was not able to produce enough water to meet the household water demands. The majority of the dry wells that needed replacement happened to be driven point wells. Driven point wells are generally shallower than drilled wells and are more susceptible to fluctuations in the water table during dry years. Driven point wells generally do not have the same pumping capacity as a drilled well and may not have been adequate to meet any increases in water use. In addition, driven points are also more likely to become plugged or encrusted over time which reduces yield and can lead to water quantity problems for well owners. It appears from this information that the well replacement was due more to the type of the original well than any overall water quantity concerns in Oconto County.

Groundwater quantity conclusions

Based on current water use that is less than 1979 water use and monitoring well data, it is unlikely that groundwater quantity issues will be a major concern for Oconto County. However, groundwater is a local resource and changes in land use which decrease recharge or large increases in water use could result in localized water quantity issues.

* Thermoelectric and mining data are not considered in water-use tables or figures on this web site. Thermoelectric-power water use is the amount of water used in the process of generating thermoelectric power. The predominant use of water is as non-contact cooling water to condense the steam created to turn the turbines and generate electricity. D1

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Susceptibility of groundwater to pollutants in Oconto County
Susceptibility of groundwater
to pollutants
in Oconto County
  • Susceptibility varies throughout Oconto County with the majority of highly susceptible groundwater areas in the northwest part of the county.

The figure on the right indicates the relative susceptibility of groundwater to contamination from sources located on or near the land surface. The map is based on several factors thought to influence susceptibility, including depth to bedrock, aquifer type, soil type, and depth to groundwater.

The majority of highly susceptible groundwater areas are in the north part of the county, with scattered highly susceptible areas elsewhere. Groundwater is generally less susceptible in the central and south parts of the county.

In Wisconsin, 70% of residents and 97% of communities rely on groundwater as their drinking water source. Wisconsin has abundant quantities of high-quality groundwater, but once groundwater is contaminated, it's expensive and often not technically possible to clean. Because of these factors, we need to be careful to protect our groundwater from contamination. Our activities on the land can contaminate groundwater - most contaminants originate on the land surface and filter down to the groundwater. In some cases however, groundwater can become contaminated from natural causes such as radioactivity due to the presence of radium in certain types of rocks.


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Nitrate-nitrogen concentrations in Oconto County
Nitrate-nitrogen concentrations in Oconto County
  • 91% of 941 private well samples collected in Oconto County from 1990-2006 met the health-based drinking water limit for nitrate-nitrogen.

Nitrate levels in Oconto County are generally low compared to other parts of the state. Of the 941 nitrate samples that have been collected in the county, 82 samples (11%) were above 2 mg/L and indicate that land use has likely affected groundwater quality; only 26 samples (3%) exceeded the safe drinking water standard. Much of the information about nitrate in the county is due to information, education and water testing services provided by the Oconto County UW-Extension Office over the years. Residents of Oconto County should be encouraged by the low levels of nitrate in groundwater; however there are areas for improvement. As shown in the figure at the right, most of the samples where nitrate levels were elevated were located in the central part of the county. This may be because karst areas (limestone outcroppings and sink holes) are more common in the central part of the county than in the south. These out crops are farmed around and may act as conduits from the land’s surface to the groundwater. While some nitrate leaching is expected under agricultural lands and septic systems, extra precautions should be taken or encouraged to ensure that nitrate does not reach problem levels in other parts of the county.

Introduction and Sources of Nitrate

In 2006, the WDNR and the Wisconsin Department of Agriculture, Trade and Consumer Protection (WDATCP) reported that nitrate-nitrogen (NO3-N) is the most widespread groundwater contaminant in Wisconsin, and that the nitrate problem is increasing both in extent and severity.F3 In Wisconsin's groundwater, 80% of nitrate inputs originate from manure spreading, agricultural fertilizers, and legume cropping systems.F4 On-site wastewater systems (septic systems) can also be a significant nitrate source in densely populated areas, areas where fractured bedrock is near the surface, or areas with coarse-textured soils.F5

Concentrations of nitrate-nitrogen in private water supplies frequently exceed the drinking water limit (federal and state Maximum Contaminant Level, or MCL) of 10 mg/L. In 2005, the WDNR combined data from three statewide groundwater databases and found that 11.6% of 48,818 private wells exceeded the nitrate limit.F3

Percent of drinking water samples with nitrate levels over the health standardLand use affects nitrate concentrations in groundwater. As shown in the figure on the right, an analysis of over 35,000 Wisconsin drinking water samples found that drinking water from private wells was three times more likely to be unsafe to drink due to high nitrate in agricultural areas than in forested areas. High nitrate levels were also more common in sandy areas where the soil is more permeable.F6 Groundwater with high nitrate from agricultural lands is more likely to contain pesticides than groundwater with low nitrate levels.F7

Health effects of nitrate

Ecosystem effects of nitrate




  • 80% of private well samples met the health standard for bacteria.
Statewide Map of Wells with Positive Bacteria
Percent of private well samples with positive bacteria for counties with 15 or more samples

Testing for coliform bacteria helps to determine if a private well is bacterialogically safe. All wells that supply drinking water should be absent of bacteria including coliform bacteria. Figure 8 shows the percentage of sampled private wells that have been contained bacteria for each county in Wisconsin. In Oconto County 19% of samples tested positive for bacteria.

In most cases a properly constructed well (Well Construction is regulated by NR 812) will prevent bacteria and other disease causing organisms from entering a well. Soils are usually able to filter bacteria out of water before it reaches the saturated zone. Unfortunately in areas with thin soils or in karst regions, bacteria can more easily contaminate the groundwater aquifer. Under these conditions even a properly constructed well may become contaminated with bacteria. Installing wells according to required distances from septic systems, animal feedlots and manure pits should help in avoiding potential bacteria problems. Also, ensuring that pets are not allowed in the area directly surrounding the well is a good precaution. Bacteria can also enter wells through sanitary defects such as compromised well caps or well casings.


  • A 2002 study estimated that 18% of private drinking water wells in the region of Wisconsin that includes Oconto County contained a detectable level of an herbicide or herbicide metabolite. Pesticides occur in groundwater more commonly in agricultural regions, but can occur anywhere pesticides are stored or applied.F24
  • There are no atrazine prohibition areas in Oconto County.F25

Definition and Use

A pesticide is any substance used to kill, control or repel pests or to prevent the damage that pests may cause.F26 Included in the broad term “pesticide” are herbicides to control weeds, insecticides to control insects, and fungicides to control fungi and molds. Pesticides are used by businesses and homeowners as well as by farmers, but figures for the amounts and specific types of pesticides used are not generally available on a county-by-county basis.

A 2005 report indicates that approximately 13 million pounds of pesticides are applied to major agricultural crops in Wisconsin each year, including over 8.5 million pounds of herbicides, 315,000 pounds of insecticides, one million pounds of fungicides, and 3 million pounds of other chemicals (this last category applied mainly to potatoes).F27 The report also shows that herbicides are used on 100% of carrots for processing, 99% of potatoes, 98% of cucumbers for processing, 98% of soybeans, 97% of field corn, 89% of snap beans for processing, 87% of sweet corn, and 84% of green peas for processing. Insecticides are used on 97% of potatoes, 96% of carrots, and 88% of apples. Fungicides are used on 99% of potatoes, 88% of carrots, and 89% of apples.

Top five crops by acreage grown in Oconto County in 2005-06
and average pesticide application per crop in Wisconsin.

Pesticides application rate

(statewide average)
Corn for grain
Corn for silage
Wheat all
Source: USDA QuickstatsF45 and USDA Statistics by StateF46

The number of pounds of pesticide applied per acre in Wisconsin varies greatly by crop, from 28 pounds/acre for apples to less than one pound/acre for oats and barley (see table below).F27

Total pounds of pesticides applied to
major crops in Wisconsin, 2004-2005.

Total pounds
of pesticides applied
Pounds of pesticides
applied per acre
Tart cherries
Carrots for processing
Snap beans
Sweet corn
Field corn
Green peas for processing
Cucumbers for processing
Cabbage, fresh

Atrazine Prohibition Areas

As of 2006, the WDATCP has prohibited the use of the popular corn herbicide atrazine on 102 designated atrazine prohibition areas in Wisconsin, covering about 1.2 million acres.F25 There are no atrazine prohibition areas in Oconto County.

Percentage of private wells with detectable herbicides or herbicide metabolites in Wisconsin thumbnail  
Percentage of private wells with herbicides or herbicide metabolites

Environmental fate of pesticides

Once a pesticide is applied, it ideally will harm only the target pest and then break down through natural processes into harmless substances.

However, the actual fate of pesticides in the environment may include evaporation into the air; runoff into surface water; plant uptake; breakdown by sunlight, soil microorganisms or chemical reactions; attachment to soil particles; leaching into groundwater; or remaining on the plant surface and removal at harvest.

The WDATCP conducted a private well water study from 2000-2001, looking for some of the most commonly used herbicides in Wisconsin.F29 From that study, the statewide estimate of the proportion of private drinking water wells that contained a detectable level of a herbicide or herbicide metabolite (breakdown product) was 37.7%. The map at the right shows the estimated percentage of wells containing herbicide or herbicide metabolites by region. The study did not look at less commonly used herbicides or any insecticides or fungicides. WDATCP is doing a similar study in 2007 that includes analysis for a greater number of pesticides.

Health effects of pesticides



  • 92% of 203 private well samples collected in Oconto County met the health standard for arsenic.F43

Of the203 water samples analyzed for arsenic in Oconto County, 96 have detectable arsenic and 17 samples (8%) are greater than the recently reduced safe drinking water standard of 10 parts per billion (ppb).F44 Most private wells in the county have unknown arsenic levels. In the Village of Suring Municipal Well #2 was taken off line in October 2006 because the three samples collected from the well in 2006 and analyzed for arsenic had levels at 13-14 ppb. This well cannot be used unless emergency conditions arise. The Village installed Well #3 with arsenic removal equipment and will blend water from Well #1 and Well #3 to stay below the standard. More information is needed to identify the extent of arsenic in the county and help people who may have elevated levels of arsenic to improve their drinking water quality.


Arsenic is an element that occurs naturally in some of Wisconsin’s aquifers and may contaminate well water drawn from those aquifers. It is a particular problem in parts of the Fox River valley of northeastern Wisconsin. However, arsenic has been detected in wells in every county in Wisconsin, and arsenic concentrations greater than the drinking water limit of 10 µg/L have been documented in 51 of Wisconsin’s 72 counties.F3

Health effects of arsenic

Release of arsenic into groundwater


For further information on arsenic, please visit the WDNR Arsenic in Drinking Water and Groundwater web site.


Information on volatile organic compounds, pharmaceuticals and personal care products, and chloride.

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Since groundwater gets into the ground at the land surface, it makes sense that what happens on the land surface can have impact on groundwater. A great many land use activities have the potential to impact the natural quality of groundwater, as shown in the table below. A landfill may leach contaminants into the ground that end up contaminating groundwater. Gasoline may leak from an underground storage tank into groundwater. Fertilizers and pesticides can seep into the ground from application on farm fields, golf courses or lawns. Intentional dumping or accidental spills of paint, used motor oil, or other chemicals on the ground can result in contaminated groundwater. The list could go on and on.G1 The rest of this section provides county-specific information about potential sources of groundwater contaminants.


Table showing activities that may contaminate groundwater


  • There are 40 open-status sites with contaminated groundwater and/or soil in Oconto County. These sites are composed of 23 Leaking Underground Storage Tank (LUST) sites and 17 Environmental Repair (ERP) sites.G2
Map of BRRTS sites in Oconto County
BRRTS sites
in Oconto County

Properties that were or are contaminated with hazardous substances can be found using the WDNR's Bureau for Remediation and Redevelopment Tracking System (BRRTS). The figure on the right shows the BRRTS map of contaminated sites in Oconto County. Royal blue diamonds on the map indicate open leaking underground storage tank (LUST) sites which have contaminated soil and/or groundwater with petroleum, which includes toxic and cancer-causing substances. However, given time, petroleum contamination naturally breaks down in the environment. Turquoise diamonds on the map indicate open environmental repair (ERP) sites which are sites other than LUSTs that have contaminated soil and/or groundwater. Examples include industrial spills or dumping, buried containers of hazardous substances, and closed landfills that have caused contamination. More information for the sites on the figure is available online.

About the BRRTS

What is a Hazardous Substance?

How to use BRRTS information in comprehensive planning

For more information, please see Environmental Contamination – The Basics, WDNR publication PUB-RR-674 July, 2004.


  • There are 3 concentrated animal feeding operations in Oconto County.G3

Dad's Farms, Suring
Suring Community Dairy
Suring Zahns Farms LLC, Gillett

By definition, CAFOs have greater than 1000 animal units. CAFOs are required under their Wisconsin Pollutant Discharge Elimination System (WPDES) permits to practice proper manure management and ensure that adverse impacts to water quality do not occur. Permit applicants must submit detailed information about the operation, a manure management plan, plans and specifications for all manure storage facilities, and a completed environmental analysis questionnaire. Once a WPDES CAFO permit is issued, operators must comply with the terms of the permit by following approved construction specifications and manure spreading plans, conducting a monitoring and inspection program, and providing annual reports.

Other potential groundwater contaminants from agriculture include fertilizers and pesticides. Large amounts of nitrogen fertilizers are used when fields are planted continuously with corn, and they can leach into groundwater as nitrate.

For more information, please visit the WDNR CAFO web site.


  • There are no licensed landfills in Oconto County.G4

The county may have additional facilities listed in the Registry of Waste Disposal Sites, available from the WDNR, that includes active, inactive, and abandoned sites where solid or hazardous wastes were known, or were likely, to have been disposed. The inclusion of a site on the Registry does not mean that environmental contamination has occurred, is occurring, or will occur in the future. The Registry is intended to serve as a general informational source for the public, and State and local officials, as to the location of waste disposal sites in Wisconsin.

About Wisconsin's Solid Waste Management Program


  • There are no Superfund sites in Oconto County.G6

What is Superfund?

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Now that you’ve inventoried groundwater data and analyzed it, what’s next? How do you use this information to lead to on-the-ground actions?

Now comes the key part of the planning process, where it’s important to involve as many community members as possible to develop and implement a plan of action to protect groundwater. The following sections of this web site are intended to help your community move forward together to protect groundwater.

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Oconto County full report Oconto County full report

For more information about this site, its contributors, and the data contained herein, click here.

For assistance concerning comprehensive planning, please contact Lynn Markham, UW-Stevens Point.
For assistance concerning groundwater, please contact Charles Dunning, USGS.
Page contact: Webmaster, USGS
Page last updated: January 14, 2008