How to Choose a Well Site: Geology, Regulations and Drilling Costs

Knowing how to find a well site comes down to three checks: the geology has to supply enough water of acceptable quality, the location has to meet state and local permit and setback rules, and the spot has to be practical and affordable to drill and maintain. Start with nearby well logs and geologic maps, keep the well away from septic systems and other contamination sources, confirm permit requirements with your state water agency, and let a licensed driller make the final call.

This guide walks through each factor in the order most landowners should consider them.

Step 1: Define how much water you need

A well site that suits a single household may be inadequate for livestock or irrigation. The National Ground Water Association (NGWA) suggests that most homes need roughly 7 gallons per minute, and recommends a storage system holding at least a day's supply if the well cannot meet that rate. Add seasonal needs such as gardens, livestock, fire protection and any future buildings. Larger demands may require a different aquifer, a deeper well or a different permit category in some states.

Step 2: Read the geology

Geology sets the odds before anything else. According to the USGS, a usable aquifer must be both porous and permeable. Sand and gravel, porous sandstone, fractured rock and some limestones can yield water readily, while dense granite or thick clay may yield very little even when saturated.

Useful sources include:

• State well log databases. Most states require drillers to file well records. Look up wells near your parcel and note total depth, depth to water, formations and tested yield.
• Geologic maps from your state geological survey or the USGS, which show the rock types under your land.
• USGS groundwater data, which can show how water levels in monitored wells change over seasons and years.

The USGS also notes landscape clues: shallow groundwater is more likely beneath valleys than hilltops, and springs, seeps and water-loving vegetation can indicate water near the surface. In fractured-rock regions, wells a short distance apart can perform very differently, which is where a professional survey can help. Our article How to Find Underground Water on Your Land compares the research methods in detail.

Step 3: Respect setbacks and contamination risks

A productive well in the wrong place can draw in contamination. Setback distances are set by states and counties, so always check local code. As one example, the USDA Natural Resources Conservation Service practice standard for agricultural water wells calls for locating a well at least 100 feet from potential sources of pollution, or farther where local, state or tribal rules require it. The archived New Mexico version of that standard lists larger distances for some sources, such as 300 feet from an agricultural waste facility.

Common things to keep a well away from:

• Septic tanks and drain fields
• Livestock yards, manure storage and feedlots
• Fuel tanks, chemical storage and equipment wash areas
• Low spots that flood or collect runoff
• Property lines, buildings and overhead or underground utilities, per local code

Where site conditions allow, the NRCS standard also recommends placing the well up-gradient from contamination sources and away from flood-prone areas. Keep access in mind too: a pump rig may need to reach the wellhead years from now.

Step 4: Check permits and water rights

Permitting varies widely across the United States. Two examples show the range:

• Wyoming: the State Engineer's Office states that every groundwater well, including domestic and stock wells, has required a permit before drilling since 1969.
• Colorado: Colorado State University Extension notes that a well permit from the State Engineer's Office is required before drilling, with exempt domestic and livestock wells generally limited to 15 gallons per minute and restrictions on how the water may be used depending on parcel size.

Other states regulate through health departments, groundwater conservation districts or county permits, and some have few statewide rules for private domestic wells. Western states often tie groundwater use to water rights, which can limit irrigation or commercial use even when a domestic well is allowed. Ask your state water agency and county health department what applies to your parcel before you commit to a site.

Step 5: Narrow the spot with field data

On larger properties, or where nearby wells are inconsistent, field data can help prioritize candidate locations:

• A geophysical survey, typically resistivity or electromagnetic, interpreted by a hydrogeologist.
• A groundwater locator from our groundwater detectors collection, used for preliminary reconnaissance. Manufacturers state these units can indicate likely water zones and, in some models, water type; real-world results depend on soil, moisture, salinity and operator skill, so readings should be weighed alongside well records and professional advice.

See Groundwater Detectors Explained for what these instruments measure and their limits.

Step 6: Understand drilling cost factors

Well drilling costs vary too much by region and geology to quote reliably, so get several written quotes. The NGWA recommends contracts that itemize charges rather than a lump sum. Main cost drivers include:

The NGWA also advises against choosing a contractor on price alone and recommends confirming licensing or certification, insurance and references. Our guide to drilling a water well covers contracts, permits and what a survey should include.

Common well-siting mistakes

• Choosing convenience over protection. Placing the well next to the house or barn without checking where the septic field, fuel tank or manure pile sits.
• Ignoring drainage. A wellhead in a low spot can be flooded by surface runoff, which is a common route for bacterial contamination.
• Skipping the records. Drilling blind when neighboring well logs would have shown the typical depth, the productive formation and the risk of dry holes.
• Assuming wet season conditions last. A shallow water level measured in spring may drop substantially by early fall, especially in drought years.
• Relying on one indicator. Any single reading, whether from a dowser, a detector or a single survey line, is weaker than several lines of evidence that agree.

How to find a well site: checklist

1. Estimate peak and average water demand.
2. Pull nearby well logs and review the geologic map.
3. Mark septic, livestock, fuel and flood areas on a site plan.
4. Apply state and county setback distances to find allowable zones.
5. Confirm permit and water-rights requirements before drilling.
6. Use a survey or groundwater locator to prioritize spots within the allowable zones, if needed.
7. Get itemized quotes from at least several licensed drillers.
8. Plan for disinfection, a pumping test and laboratory water testing.

Frequently asked questions

What is the best place to put a well?

The best place is where geology suggests adequate yield, all required setbacks are met, the ground is up-slope of contamination sources and out of flood areas, and a rig can reach it. A licensed driller can confirm.

How far should a well be from a septic system?

It depends on your state and county code. Many agricultural standards use 100 feet as a general minimum, but local rules may differ. Check with your local health department.

Do I need a permit to drill a private well?

In many states, yes. Wyoming and Colorado, for example, require State Engineer approval before drilling. Rules vary, so confirm with your state agency.

Can a groundwater detector choose my well site?

It can help prioritize spots on large properties, but manufacturers' claims are not a guarantee. Combine readings with well logs, geology and a driller's advice.

Should I drill the well before building a house?

The NGWA recommends confirming water before investing in a home in areas where low-yield or dry wells are common.

Well permitting, water rights and construction rules change and differ by state, county and groundwater district. Confirm current requirements with your state water agency and local health department before you drill.

Sources

• >National Ground Water Association: Having a Well Drilled
• >USDA NRCS Conservation Practice Standard 642, Water Well (New Mexico, archived 2021 version)
• >Wyoming State Engineer's Office: Ground Water Division
• >Colorado State University Extension: Colorado well permit fact sheet (6.700)
• >USGS Water Science School: Aquifers and Groundwater