Illinois EPA SWAP Factsheet: Well Data Fields Explained

An Illinois EPA SWAP factsheet is a public summary of the assessment for one drinking-water system. You look it up by county or by system name. It covers why the source matters, how susceptible it is to contamination, and what protection work is recommended. The agency’s search page says locational data and maps for wells and aquifers are removed from these summaries under its security policy, and it sends readers to local water officials for the complete report.

This page explains each well-table field (well ID, status, depth, minimum setback, pumpage, aquifer code, maximum setback), uses Farmer City as the worked example, and shows why the numbers matter to anyone opening a pit. Illinois law treats an excavation for stone, sand or gravel as a potential route of contamination, so a nearby community well can take ground out of a mine plan. The calculator below estimates how much.

What the SWAP program and mapping tool contain

SWAP stands for Source Water Assessment Program. The 1996 amendments to the federal Safe Drinking Water Act required states to set one up. Illinois EPA’s program page gives it four jobs: identify the areas that supply public drinking water, inventory potential contamination sources, judge how susceptible the water is, and tell the public the result.

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Illinois supplies in the assessment program

Number of public water supplies, as stated by Illinois EPA

The same page says more than 12 million people in the state rely on public supplies. It counts more than 1,700 community supplies and about 3,800 non-community supplies in the assessment program. A community supply serves residents year round; the Illinois Pollution Control Board quotes the legal test as at least 15 service connections used by residents, or at least 25 regular residents.

The program page links four public resources, and each answers a different question:

• SWAP web mapping tool: the map view of the program, with a separate visual help document.
• SWAP factsheets (data service): the search at dataservices.epa.illinois.gov, by water system type, county or part of a facility name.
• Resource Management Mapping Service: a second web map linked from the same page.
• Drinking Water Watch: a further state drinking-water resource, listed under the page’s water resources links.

People often search for a SWAP API or a bulk download of the wells database. The program page offers web maps and a factsheet search; it does not list an API or a download file. For data in bulk, ask the Groundwater Section at (217) 782-1020, the contact the page gives for SWAP questions.

How to look up an Illinois EPA SWAP factsheet

1. Open the factsheet search and choose Community or Non-Community.
2. Pick the county (Farmer City is in DeWitt County), or type part of the facility name. The same route works for any system, including Springerton, Bartlett, Enfield, Crossville, Weldon, Norris City and Waynesville.
3. Read the three summary parts: importance of source water, susceptibility to contamination, and source water protection efforts. The search page notes that protection summaries are not documented for non-community supplies.
4. Note the system’s PWS number. Farmer City’s is IL0390150 in its 2025 water report. It helps when you call any agency.
5. Ask the local water system for the complete assessment if you need more. That is the route the search page itself gives.

Infographic

From factsheet to well record in 4 steps

1. 1SearchFind the system by county or name.
2. 2ReadNote susceptibility and protection efforts.
3. 3AskRequest the full assessment from local officials.
4. 4VerifyCheck well records with the State Water Survey.

Well inventory columns: well ID, depth, pumpage and max zone

Some SWAP fact sheets republished by water systems do show a well table. The Pingree Grove fact sheet posted by that Illinois village is a useful specimen: it lists two wells, WL01631 and WL01632, as active, 1,345 feet deep, with a 200-foot minimum setback, a maximum setback of 0, aquifer description “Deep Bedrock” and aquifer code 8793. The table below explains each column and where to look for it in practice.

Aquifer code 0101 and other codes

Searchers often pair codes such as 0101, 0909, 1212 or 7097 with “sand and gravel”. Treat the description column as the answer, not the digits. It sits beside the code in the same table and states the unit in plain words, while Illinois EPA’s search page does not publish a code key. The Groundwater Section can confirm what any code stands for.

A material name also does not fix a depth. Only the well’s own record gives that. The Illinois State Water Survey describes three major aquifer systems in the state: sand and gravel, shallow bedrock, and Cambrian-Ordovician sandstone. A 1987 USGS summary reported that more than half of Illinois groundwater withdrawals came from the sand-and-gravel aquifers (mid-1980s data), an old figure but a clear sign of how much depends on them.

What Farmer City’s wells and reports show

The City of Farmer City’s water page says its supply comes from four wells named #11, OlsGold, McConkey and Luck, and that the system includes a 300,000-gallon elevated tank. The page also lists water reports from 2020 to 2025 and gives the utility office number, (309) 928-3412. The town had 1,828 residents at the 2020 census, so this is a small groundwater system.

The city’s 2020 Consumer Confidence Report is unusually useful, because it prints a source table and part of the assessment text:

The names differ slightly between that report and the current city page, so quote the well number and the five-digit ID when you ask about a well. For deeper background, see our separate notes on Farmer City’s aquifer code and Farmer City’s well data.

The same 2020 report states that a Well Site Survey published by Illinois EPA in 1989 identified ten potential contamination sources: a salvage yard, an above-ground fuel store, two grain elevators, a vehicle sales site, an auto repair site, two below-ground fuel stores, an electrical generator or substation, and a hazardous waste storage site. It also names inactive wells #4, #6 and #7 as potential routes. Illinois EPA determined that wells #2, #9, #10 and #11 are susceptible to inorganic, volatile organic or synthetic organic contamination, based on monitoring and available hydrogeologic data.

Susceptible does not mean contaminated. It describes exposure. The measured results are in the annual report, and they are the next thing to read.

Farmer City test results against federal limits

The 2025 report, dated 25 June 2026, lists no violations in its tables for the contaminants below. Arsenic was 3.64 parts per billion (ppb) against a limit of 10, and barium 0.886 parts per million (ppm) against 2, both sampled in March 2024. Combined radium was 1.56 picocuries per liter against 5. For lead, the 90th percentile was 13.5 ppb against an action level of 15, with 2 sites over and a highest result of 62.3 ppb. The report adds a lead notice: the city says it is using corrosion control treatment and replacing lead service lines. The same PDF also carries a monitoring violation notice for gross alpha testing, which the city describes as a late-paperwork issue, not a water quality problem.

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Farmer City results as a share of the limit

Highest level detected as % of the MCL shown in the 2025 report

A Maximum Contaminant Level (MCL) is the highest amount allowed in drinking water. The U.S. EPA’s national table sets nitrate, measured as nitrogen, at 10 mg/L. These limits are the yardstick for any system you look up: compare the highest level detected with the MCL, and check the sample date, since some tests are repeated only every few years.

Well setback zones: 200, 400 and 1,000 feet

A setback zone restricts land use around a well. Illinois EPA’s setback page says the law sets minimum zones of either 200 or 400 feet, and lets counties and municipalities using a community well set a maximum zone of up to 1,000 feet.

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Illinois well setback distances

Radius from the well, feet

The split between 200 and 400 feet depends on geology, not on who owns the well. In a Pollution Control Board rulemaking opinion (R05-9), the Board explains that section 14.2 of the Environmental Protection Act sets 200 feet around each community well, rising to 400 feet where the well draws from an especially vulnerable formation. So do not assume either number for a given well. Read the minimum setback column, or ask the Groundwater Section.

A well qualifies for a maximum zone if its lateral area of influence under normal pumping is larger than the minimum zone. The application needs the radius of influence, aquifer test data, geological logs and construction details, a description of the method, a draft ordinance and a local official’s signature. The zone takes effect once the county or municipality adopts an ordinance, and it has two years to do so after the agency confirms technical adequacy. The Board can also set a zone by regulation: the R05-9 opinion did so for wells serving Marquette Heights, which could not act by ordinance because its wells lie in North Pekin.

Why a sand or gravel pit counts as a potential route

This is where a drinking-water factsheet becomes a mining document. Section 3.350 of the Illinois Environmental Protection Act defines a potential route to include abandoned and improperly plugged wells, drainage wells, injection wells, and any excavation for the discovery, development or production of stone, sand or gravel.

▶ Clay explainer on the seven main environmental impacts of mining · 2:31

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US construction sand and gravel output

Million metric tons sold or used; 2024 and 2025 are estimates

The same section defines a new potential route in two ways: one that did not exist, or whose construction had not begun, on 1 January 1988; or one that expands sideways past its permitted boundary (or, if unpermitted, its 1 January 1988 boundary). The Board’s opinion states the effect: generally, absent a Board exception, new potential routes cannot be placed inside a community well’s minimum zone.

In practice this matters to three kinds of reader:

• License and land owners: an extension of an old pit can count as new, so a boundary that seemed safe may need checking before you expand.
• Consultants: test pits and exploration excavations can fall under the words “discovery” and “development”, so check well positions before the first trench.
• Investors and buyers: reported acreage is not the same as workable acreage if a community well sits close to the parcel.

Aggregate is a big, low-value business, so lost tons matter. USGS Mineral Commodity Summaries 2026 estimates 870 million metric tons of US construction sand and gravel in 2025, worth US$12.6 billion, from about 6,500 pits, with an estimated average value of US$14.50 per metric ton in 2025. Illinois produced 19.1 million metric tons of construction sand and gravel in 2019, 14.4 million of industrial sand and gravel, and 50.3 million of crushed stone, according to the USGS Illinois table. Crushed stone is the larger aggregate by tonnage there. For where operations sit nationally, see our US mining map by state; for how these deposits compare with others, see types of ore deposits.

How to get depth, pumpage and aquifer data for a well

1. Call the water system. The factsheet search page directs requests for the complete assessment to local water officials. In Farmer City, the city’s water page lists the office at (309) 928-3412 and names Chad Yeadon as Water Superintendent.
2. Call Illinois EPA. The SWAP page gives the Bureau of Water, Groundwater Section at (217) 782-1020. For maximum setback questions, the setback page lists the Hydrogeology Unit at (217) 785-4787.
3. Ask the State Water Survey. It holds over 370,000 well records. Its page says records for community supplies are not online, and it invites custom searches by email through its Well Records team, so have the property details ready.
4. Check the ILWATER map. The Illinois State Geological Survey’s service holds transcriptions of many well construction reports. The domestic wells database covers private wells, so do not expect municipal wells in it.
5. Look up withdrawals. The Survey’s groundwater resources map shows public supply wells as of 2013, with withdrawals in gallons per year as reported to the Illinois Water Inventory Program. Treat it as historic and confirm any figure before you rely on it.
6. Find an aquifer test. If a water supply owner lacks pump test data, Illinois EPA says copies can often be obtained from the drilling contractor or the Survey.
7. File a records request if needed. Illinois EPA’s security policy may still keep exact locations out of what you receive, so explain the site and purpose and ask what can be shared.

▶ Why maps, samples and site records belong in one place · 3:21

Screening a site before you open a pit

A short desk check saves money before any permit work starts:

• Draw the parcel boundary and list every community supply in the county from the factsheet search.
• Ask the operators and the Groundwater Section whether a well lies within 1,000 feet of the boundary, and whether a maximum zone exists.
• Confirm the minimum zone (200 or 400 feet) for each well, and the aquifer description.
• List old wells on the land. Abandoned and improperly plugged wells are themselves potential routes.
• Check whether the plan is new ground, an extension of a permitted boundary, or work inside the existing one.
• Run the calculator with the real radius, then get legal and hydrogeological advice on the result.

Satellite imagery can help with the surface side of this check, such as mapping existing pits, disturbed ground and water bodies around a parcel. It cannot show a well’s status or set a legal boundary. Farmonaut’s satellite-based mineral detection and mining site mapping produce exploration targets for a chosen area; they are not an environmental clearance. To scope an area, request a quote or contact the team.

▶ What Farmonaut Mining Pro shows for a chosen license boundary, with de-identified demo data · 4:56

Frequently asked questions

What is an Illinois EPA SWAP factsheet?

It is the public summary of a Source Water Assessment for one water system. It covers the importance of the source, its susceptibility to contamination and protection efforts. Locational data and maps for wells and aquifers are removed under the agency’s security policy.

Where is the SWAP factsheet search?

It is at dataservices.epa.illinois.gov/swap/factsheet.aspx, linked from Illinois EPA’s SWAP program page. Search by water system type and county, or by part of the facility name.

Is there a SWAP mapping tool API or database download?

The program page lists web mapping tools and a factsheet search, with no API or download file listed. Ask the Groundwater Section at (217) 782-1020 about data access.

What does max zone mean in a well table?

It is the maximum setback zone: a larger protected area of up to 1,000 feet that a county or municipality can set by ordinance, based on the well’s area of influence. The Pingree Grove sheet shows 0 in that column.

What does aquifer code 0101 mean?

Read the aquifer description next to the code, which names the unit in plain words. If a sheet shows the code alone, the Groundwater Section can confirm what it stands for. A code never tells you the depth of a particular well.

How deep are Farmer City’s wells?

The city’s page and water reports do not list well depths. Ask the city’s water office, or request a records search from the Illinois State Water Survey using the well number and ID, such as Well 10 (47647).

How many wells does Farmer City use?

The city’s water page says four: #11, OlsGold, McConkey and Luck. Its 2020 water report lists Wells 7, 9, 10 and 11.

Is the setback 200 or 400 feet?

Both exist. The Pollution Control Board describes 200 feet around each community well, and 400 feet where the well draws from an especially vulnerable formation. Check the figure for each well.

Can a gravel pit be dug inside a well setback zone?

Generally not if it is new. The Act lists excavations for stone, sand or gravel as potential routes, and new routes generally cannot go inside a community well’s minimum zone without a Board exception. Take legal advice on any specific site.

Does expanding an existing quarry count as new?

It can. A route that expands sideways past its permitted boundary falls within the definition of a new potential route in section 3.350.

Are Farmer City’s wells contaminated?

A susceptible rating is not a finding of contamination. The 2025 report’s contaminant tables show no violations, though the same PDF includes a monitoring violation notice that the city attributes to late paperwork, and a lead notice. Read the full report for lead sampling and every other result.