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Northwest Arkansas Septic Suitability by Soil

The USDA soil survey rates every soil type in Northwest Arkansas for a conventional septic drain field. Of the 141 soils mapped across Benton and Washington County, 110 come back Very Limited, that is 78%. Search the full list free by soil name, county, or rating, and see exactly why each soil is limited. No signup, nothing to buy.

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Why Northwest Arkansas soils skew Very Limited for septic

A conventional septic drain field works by letting wastewater trickle down through soil that filters it before it reaches groundwater. That needs soil deep enough, dry enough, and permeable-but-not-too-permeable. Northwest Arkansas mostly does not have that. The region sits on Ozark karst: shallow soils over fractured limestone, steep slopes, seasonal high water tables, and rock that is close to the surface. The USDA National Cooperative Soil Survey rates each soil for exactly this use, and here the ratings come back overwhelmingly Very Limited. That is the whole reason so many local properties end up on engineered or aerobic systems instead of a simple gravity drain field, and it is why the Illinois River Watershed Partnership pays close attention to septic siting: a drain field that does not filter properly puts nitrate and bacteria into the same watersheds that feed the Illinois River and Beaver Lake.

Across the soils rated Very or Somewhat limited, the reasons USDA cites most often are slow water movement (91 soils), steep slope (50 soils), seasonal high water table (42 soils), and shallow depth to bedrock (37 soils). None of that means a lot cannot have a septic system. It means the system usually has to be designed for the soil, which is why Arkansas requires a soil pit evaluation before any permit. Our NW Arkansas Septic Permit Guide walks through that process, and the aerobic systems page covers the type of system these soils often call for.

Search every NW Arkansas soil rated for septic

The index below holds all 141 soil types the USDA maps across the two counties: 110 rated Very Limited, 21 Somewhat Limited, 0 Not Limited, and 10 Not Rated. Benton County has 43 mapped soils (34 Very Limited); Washington County has 98 (76 Very Limited). Type in a soil name or your soil symbol from a survey, filter by county, or filter by rating, and open a soil to see why it is limited.

78% of the 141 NW Arkansas soil types the USDA maps are rated Very Limited for a conventional septic drain field.
141 soil types
AeCAllegheny gravelly loam, 3 to 8% slopes (leesburg)Very limited
Washington County Why: Slow water movement
AeC2Allegheny gravelly loam, 3 to 8% slopes, eroded (leesburg)Very limited
Washington County Why: Slow water movement
AeD2Allegheny gravelly loam, 8 to 12% slopes, eroded (leesburg)Very limited
Washington County Why: Slow water movement, Steep slope
AgFAllegheny stony loam, 12 to 40% slopes (leesburg)Very limited
Washington County Why: Slow water movement, Steep slope
AgDAllegheny stony loam, 8 to 12% slopes (leesburg)Very limited
Washington County Why: Slow water movement, Steep slope
AlE2Allen loam, 12 to 20% slopes, erodedVery limited
Washington County Why: Steep slope, Slow water movement
AoFAllen stony loam, 12 to 35% slopes (nella)Very limited
Washington County Why: Steep slope, Slow water movement
AhFAllen-Hector complex, 20 to 40% slopes (nella)Very limited
Washington County Why: Steep slope, Slow water movement
AhFAllen-Hector complex, 20 to 40% slopes (nella)Very limited
Washington County Why: Shallow depth to bedrock, Steep slope, Seepage risk
AhGAllen-Hector complex, 40 to 55% slopes (nella)Very limited
Washington County Why: Steep slope, Slow water movement
AhGAllen-Hector complex, 40 to 55% slopes (nella)Very limited
Washington County Why: Shallow depth to bedrock, Steep slope, Seepage risk
AsC2Apison gravelly loam, 3 to 8% slopes, erodedVery limited
Washington County Why: Shallow depth to bedrock
ApBApison loam, 1 to 3% slopesVery limited
Washington County Why: Shallow depth to bedrock
ApC2Apison loam, 3 to 8% slopes, erodedVery limited
Washington County Why: Shallow depth to bedrock
SrEArkana-Moko complex, 8 to 20% slopes, very rockyVery limited
Benton County Why: Shallow depth to bedrock, Slow water movement, Steep slope
SrEArkana-Moko complex, 8 to 20% slopes, very rockyVery limited
Benton County Why: Shallow depth to bedrock, Large stones, Steep slope
BaEBaxter very gravelly silt loam, 12 to 20% slopesVery limited
Washington County Why: Steep slope, Slow water movement
BaFBaxter very gravelly silt loam, 20 to 45% slopesVery limited
Washington County Why: Steep slope, Slow water movement
CeCCane loam, 3 to 8% slopesVery limited
Benton County Why: Seasonal high water table
CnBCaptina silt loam, 1 to 3% slopesVery limited
Benton County Why: Seasonal high water table, Slow water movement
CaBCaptina silt loam, 1 to 3% slopesVery limited
Washington County Why: Seasonal high water table, Slow water movement
CaC2Captina silt loam, 3 to 6% slopes, erodedVery limited
Washington County Why: Seasonal high water table, Shallow depth to bedrock
CaCCaptina silt loam, 3 to 8% slopesVery limited
Washington County Why: Seasonal high water table, Slow water movement
CoCarytown silt loam, 0 to 2% slopesVery limited
Benton County Why: Seasonal high water table, Slow water movement
CkCherokee complex, moundedVery limited
Washington County Why: Seasonal high water table, Slow water movement
CsCherokee silt loam, 0 to 1% slopesVery limited
Benton County Why: Seasonal high water table, Slow water movement
ChCherokee silt loam, 0 to 2% slopesVery limited
Washington County Why: Seasonal high water table, Slow water movement
CvFClarksville extremely gravelly silt loam, 12 to 50% slopesVery limited
Benton County Why: Steep slope, Seepage risk
ClGClarksville extremely gravelly silt loam, 12 to 60% slopesVery limited
Washington County Why: Steep slope, Seepage risk
CrCleora fine sandy loamVery limited
Washington County Why: Flooding, Seepage risk
EcElsah cobbly soils (ceda)Very limited
Washington County Why: Flooding, Seepage risk, Poor filtering capacity
EgElsah gravelly soils (ceda)Very limited
Washington County Why: Flooding, Seepage risk, Poor filtering capacity
EgElsah soils, 0 to 3% slopes, occasionally and frequently floodedVery limited
Benton County Why: Flooding, Poor filtering capacity, Seepage risk
EgElsah soils, 0 to 3% slopes, occasionally and frequently floodedVery limited
Benton County Why: Flooding, Poor filtering capacity, Seepage risk
EnCEnders gravelly loam, 3 to 8% slopesVery limited
Washington County Why: Slow water movement, Shallow depth to bedrock
EnC2Enders gravelly loam, 3 to 8% slopes, erodedVery limited
Washington County Why: Slow water movement, Shallow depth to bedrock
EnD2Enders gravelly loam, 8 to 12% slopes, erodedVery limited
Washington County Why: Slow water movement, Steep slope
EnDEnders gravelly loam, 8 to 15% slopesVery limited
Washington County Why: Slow water movement, Shallow depth to bedrock, Steep slope
EoDEnders stony loam, 3 to 15% slopesVery limited
Washington County Why: Slow water movement, Steep slope, Shallow depth to bedrock
EnDEnders very gravelly loam, 3 to 12% slopesVery limited
Benton County Why: Slow water movement, Shallow depth to bedrock
EoFEnders very stony loam, 12 to 30% slopesVery limited
Benton County Why: Slow water movement, Steep slope, Shallow depth to bedrock
EoDEnders very stony loam, 3 to 12% slopesVery limited
Benton County Why: Slow water movement, Shallow depth to bedrock
ErFEnders-Leesburg complex, 20 to 40% slopesVery limited
Washington County Why: Slow water movement, Steep slope, Shallow depth to bedrock
ErFEnders-Leesburg complex, 20 to 40% slopesVery limited
Washington County Why: Steep slope, Slow water movement
ErEEnders-Leesburg complex, 8 to 20% slopesVery limited
Washington County Why: Slow water movement, Steep slope, Shallow depth to bedrock
FtFatima silt loam, occasionally floodedVery limited
Benton County Why: Flooding, Seasonal high water table, Slow water movement
FaE2Fayetteville fine sandy loam, 12 to 20% slopes, erodedVery limited
Washington County Why: Steep slope, Slow water movement
FeFFayetteville stony fine sandy loam, 12 to 35% slopesVery limited
Washington County Why: Steep slope, Slow water movement
FhFFayetteville-Hector complex, 20 to 40% slopesVery limited
Washington County Why: Shallow depth to bedrock, Steep slope, Seepage risk
FhFFayetteville-Hector complex, 20 to 40% slopesVery limited
Washington County Why: Steep slope, Slow water movement
HfHealing silt loam, 0 to 3% slopes, occasionally floodedVery limited
Benton County Why: Flooding, Slow water movement
HmCHector-Mountainburg gravelly fine sandy loam, 3 to 8% slopesVery limited
Washington County Why: Shallow depth to bedrock, Seepage risk
HmCHector-Mountainburg gravelly fine sandy loam, 3 to 8% slopesVery limited
Washington County Why: Shallow depth to bedrock, Seepage risk, Large stones
HmDHector-Mountainburg gravelly fine sandy loams, 8 to 12% slopesVery limited
Washington County Why: Shallow depth to bedrock, Seepage risk, Steep slope
HmDHector-Mountainburg gravelly fine sandy loams, 8 to 12% slopesVery limited
Washington County Why: Shallow depth to bedrock, Seepage risk, Steep slope, Large stones
HoFHector-Mountainburg stony fine sandy loams, 3 to 40% slopes, rockyVery limited
Washington County Why: Shallow depth to bedrock, Seepage risk, Steep slope
HoFHector-Mountainburg stony fine sandy loams, 3 to 40% slopes, rockyVery limited
Washington County Why: Shallow depth to bedrock, Steep slope, Seepage risk, Large stones
JaBJay silt loam, 1 to 3% slopesVery limited
Benton County Why: Seasonal high water table, Slow water movement
JaBJay silt loam, 1 to 3% slopesVery limited
Washington County Why: Seasonal high water table, Slow water movement
JaCJay silt loam, 3 to 8% slopesVery limited
Washington County Why: Seasonal high water table
JsJohnsburg complex, moundedVery limited
Washington County Why: Seasonal high water table
JoJohnsburg silt loam, 0 to 2% slopesVery limited
Benton County Why: Seasonal high water table
JoJohnsburg silt loam, 0 to 2% slopesVery limited
Washington County Why: Seasonal high water table
LfLeaf complex, moundedVery limited
Washington County Why: Seasonal high water table, Slow water movement, Flooding
LeLeaf silt loamVery limited
Washington County Why: Seasonal high water table, Slow water movement, Flooding
LrCLinker fine sandy loam, 3 to 8% slopesVery limited
Benton County Why: Shallow depth to bedrock, Slow water movement
LnC2Linker gravelly loam, 3 to 8% slopes, erodedVery limited
Washington County Why: Shallow depth to bedrock, Slow water movement
LnDLinker gravelly loam, 8 to 12% slopesVery limited
Washington County Why: Shallow depth to bedrock, Slow water movement, Steep slope
LkBLinker loam, 1 to 3% slopesVery limited
Washington County Why: Shallow depth to bedrock, Slow water movement
LkC2Linker loam, 3 to 8% slopes, erodedVery limited
Washington County Why: Shallow depth to bedrock, Slow water movement
MeMayes silty clay loamVery limited
Benton County Why: Seasonal high water table, Slow water movement
SoFMoko-Rock outcrop complex, 12 to 50% slopesVery limited
Benton County Why: Shallow depth to bedrock, Steep slope, Large stones
MoEMontevallo soils, 12 to 25% slopesVery limited
Washington County Why: Shallow depth to bedrock, Steep slope
MoDMontevallo soils, 3 to 12% slopesVery limited
Washington County Why: Shallow depth to bedrock
MuEMountainburg very stony sandy loam, 12 to 40% slopesVery limited
Benton County Why: Shallow depth to bedrock, Steep slope, Large stones, Seepage risk
MuDMountainburg very stony sandy loam, 3 to 12% slopesVery limited
Benton County Why: Shallow depth to bedrock, Large stones, Seepage risk
NeBNewtonia silt loam, 1 to 3% slopesVery limited
Benton County Why: Slow water movement
NfCNixa very gravelly silt loam, 3 to 8% slopesVery limited
Benton County Why: Seasonal high water table
NaCNixa very gravelly silt loam, 3 to 8% slopesVery limited
Washington County Why: Seasonal high water table
NfDNixa very gravelly silt loam, 8 to 12% slopesVery limited
Benton County Why: Seasonal high water table, Steep slope
NaDNixa very gravelly silt loam, 8 to 12% slopesVery limited
Washington County Why: Seasonal high water table, Steep slope
NoENoark very gravelly silt loam, 12 to 20% slopesVery limited
Benton County Why: Steep slope, Slow water movement
NoFNoark very gravelly silt loam, 20 to 40% slopesVery limited
Benton County Why: Slow water movement, Steep slope
NoDNoark very gravelly silt loam, 8 to 12% slopesVery limited
Benton County Why: Slow water movement, Steep slope
RgRazort gravelly silt loam, 0 to 2% slopes, occasionally floodedVery limited
Washington County Why: Flooding, Slow water movement
RaRazort silt loam, 0 to 2% slopes, occasionally floodedVery limited
Washington County Why: Flooding, Slow water movement
SbSamba complex, moundedVery limited
Washington County Why: Seasonal high water table, Slow water movement
SaSamba silt loamVery limited
Washington County Why: Seasonal high water table, Slow water movement
SfBSavannah fine sandy loam, 1 to 3% slopesVery limited
Washington County Why: Seasonal high water table
SfC2Savannah fine sandy loam, 3 to 8% slopes, erodedVery limited
Washington County Why: Seasonal high water table
SeSecesh gravelly silt loam, 0 to 3% slopes, occasionally floodedVery limited
Benton County Why: Flooding, Slow water movement
SnSloan silt loam, 0 to 3% slopes, occasionally floodedVery limited
Washington County Why: Flooding, Seasonal high water table, Slow water movement
SoSogn rocky silt loam (moko)Very limited
Washington County Why: Shallow depth to bedrock, Large stones
SpSummit complex, moundedVery limited
Washington County Why: Seasonal high water table, Slow water movement
SsASummit silty clay, 0 to 1% slopesVery limited
Washington County Why: Seasonal high water table, Slow water movement
SsBSummit silty clay, 1 to 3% slopesVery limited
Washington County Why: Seasonal high water table, Slow water movement
SsD2Summit silty clay, 3 to 15% slopes, erodedVery limited
Benton County Why: Seasonal high water table, Slow water movement
SsC2Summit silty clay, 3 to 8% slopes, erodedVery limited
Washington County Why: Seasonal high water table, Slow water movement
SsD2Summit silty clay, 8 to 12% slopes, erodedVery limited
Washington County Why: Seasonal high water table, Slow water movement, Steep slope
StE2Summit stony silty clay, 12 to 25% slopes, erodedVery limited
Washington County Why: Seasonal high water table, Slow water movement, Steep slope
StD2Summit stony silty clay, 3 to 12% slopes, erodedVery limited
Washington County Why: Seasonal high water table, Slow water movement
TaTaloka complex, moundedVery limited
Washington County Why: Seasonal high water table, Slow water movement
ToATaloka silt loam, 0 to 1% slopesVery limited
Benton County Why: Seasonal high water table, Slow water movement
ToATaloka silt loam, 0 to 1% slopesVery limited
Washington County Why: Seasonal high water table, Slow water movement
ToBTaloka silt loam, 1 to 3% slopesVery limited
Washington County Why: Seasonal high water table, Slow water movement
TsCTonti gravelly silt loam, 3 to 8% slopesVery limited
Benton County Why: Seasonal high water table, Shallow depth to bedrock
VsFVentris very gravelly silt loam, 15 to 40% slopes, rubblyVery limited
Benton County Why: Shallow depth to bedrock, Seasonal high water table, Slow water movement, Steep slope
WeCWaben very gravelly silt loam, 3 to 8% slopesVery limited
Benton County Why: Slow water movement
WeCWaben very gravelly silt loam, 3 to 8% slopesVery limited
Washington County Why: Slow water movement
WeDWaben very gravelly silt loam, 8 to 12% slopesVery limited
Benton County Why: Seepage risk, Steep slope

How to find your property's soil

You do not need to guess. The USDA Web Soil Survey lets anyone draw their lot on a map and pull the soil types under it for free. Match the soil symbol or name it gives you to the index above to see its septic rating and the reasons behind it. For an actual permit, Arkansas requires a soil pit evaluation on the specific site, because conditions vary within a single soil map unit. The permit guide explains who does that evaluation and what the permit process looks like.

Once you know your soil's likely rating, our septic tank installation guide walks through matching a system to the soil, the permit steps, and what each system type costs to build.

Sources

Buying or building on a lot in Northwest Arkansas? Get a local pro to read your soil and system options.

Call (479) 595-8904

Frequently asked questions

Where does this soil data come from?

Every rating, soil name, and limiting reason on this page comes directly from the USDA Natural Resources Conservation Service soil survey (the SSURGO database), pulled through the USDA Soil Data Mart. The rating is the standard USDA interpretation for septic tank absorption fields. The current survey versions are Benton County v23 (9/9/2025) and Washington County v22 (9/10/2025).

What does Very Limited actually mean for a septic system?

It means the soil has one or more properties that make a conventional gravity drain field difficult or unreliable, such as slow water movement, a shallow depth to bedrock, a seasonal high water table, or steep slope. It does not mean septic is impossible. It usually means the site needs an engineered or aerobic system designed around the soil, which is why Arkansas requires a soil pit evaluation before a permit.

Can I still build on a Very Limited soil?

In most cases yes, but the system has to be designed for the conditions rather than dropped in as a standard drain field. That is exactly what the required soil pit evaluation and the permit process are for. Start with the NW Arkansas Septic Permit Guide, then talk to a local septic professional about the system type your soil calls for.

How do I find the soil type under my property?

Use the free USDA Web Soil Survey. Draw your lot on the map and it lists the soil map units under it. Match the soil name or symbol to the index on this page to see its septic rating and the reasons behind it. For a permit, a soil pit evaluation on the actual site is still required.

Ask a local septic pro about your soil

Wondering what your property's soil means for a septic system? Tell us the address or the soil type and a local Northwest Arkansas septic professional will get back to you with a straight answer.

By submitting, you agree we may contact you about your request.

Prefer to talk? Call (479) 595-8904. Have septic plans or a survey to send? Email them to fayettevilleseptic.marketing@gmail.com.

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