Land records · Parcel maps · October 5, 2026
What Is a Soil Survey? Reading Soil Maps for Land
A soil survey maps soil types and their properties, like drainage, depth, and septic suitability. How to use the NRCS Web Soil Survey for a parcel.
What is a soil survey? A soil survey is an inventory and map of the soils across an area, describing each soil type’s properties such as texture, drainage, depth to bedrock or water table, slope, flooding frequency, and suitability for uses like farming, septic systems, building foundations, and roads. In the United States, the Natural Resources Conservation Service (NRCS) publishes soil surveys for nearly every county, available free online through the Web Soil Survey. This page is general land-records background, not legal advice.
What a soil survey contains
| Item | What it tells you |
|---|---|
| Soil map units | Areas mapped as a named soil or soil complex |
| Drainage class | From excessively drained to very poorly drained |
| Depth to water table | How close seasonal groundwater gets to the surface |
| Depth to bedrock | Shallow rock limits digging and septic |
| Slope | Steepness range within the unit |
| Flooding and ponding | Frequency ratings |
| Interpretations | Ratings for septic fields, dwellings, roads, farming |
How to use the Web Soil Survey
- Open the Web Soil Survey and navigate to your area.
- Define an area of interest by drawing around the parcel or entering coordinates.
- View the soil map to see map units and their names.
- Open Soil Data Explorer for suitability ratings, such as septic tank absorption fields or dwellings with basements.
- Download or print a report.
Comparing the soil map with a parcel map helps you see which soils fall within your lot lines.
Limits of soil surveys
Soil surveys are mapped at a broad scale. A map unit can include small areas of other soils, and boundaries are approximate. They are planning tools, not site-specific tests. Septic design still requires an on-site soil evaluation or perc test, and foundations may need geotechnical investigation.
Why soil surveys matter for buyers
- Septic feasibility: “very limited” ratings for absorption fields signal possible trouble.
- Wet soils: poorly drained soils may hint at wetlands. See what is a wetland delineation.
- Basements: high water tables cause wet basements.
- Farming: prime farmland designations and productivity.
- Building costs: shallow bedrock or shrink-swell clay add cost.
See how to tell if land is buildable.
Soil surveys and other maps
Soil maps pair well with topographic maps and flood maps. See topographic map vs plat map. Together they give a quick read on land before you pay for site testing.
Reading soil names
Soil series are often named for a local place, and map unit names add texture and slope, such as a silt loam on 2 to 6 percent slopes. The slope range and texture in the name are useful quick clues.
Hydric soils
Soil surveys list hydric soils, which formed under saturated conditions. Their presence does not prove a wetland exists today, but it is a reason to look more closely before planning construction or drainage changes.
Bottom line
A soil survey maps soil types and their properties, with ratings for septic systems, buildings, and farming. Use the free NRCS Web Soil Survey for an early look at a parcel, then confirm with site-specific soil testing. Compare soil data with parcels on the Platbookmapper map.
What is a soil survey FAQ
Where can I find a soil survey for my property?
The NRCS Web Soil Survey offers free soil maps and reports online.
Can a soil survey tell me if a septic system will work?
It gives a general suitability rating, but a site test or perc test is needed.
What is a soil map unit?
An area on the map representing a named soil or group of soils.
Are soil surveys accurate for small lots?
They are broad-scale and approximate; on-site testing is more precise.
What does poorly drained soil mean?
Soil that stays wet near the surface for long periods.