Johnson County, Illinois

Survey Area IL087• Illinois

The dominant drainage class is Moderately well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Alfisols — moderately leached forest soils with a clay-enriched subsoil. This report summarizes the major soil map units across the survey area to help you understand what to expect when buying, building, or gardening in Johnson County, Illinois. Search your address to find the exact soil composition, drainage, and series details at your specific location.

Soil Map Unit	Acres	Drainage	Hydro Group	Dwellings	Septic
Wellston-Berks complex, 18 to 35 percent slopes	21K	Well drained	B	Very limited	Very limited
Hosmer silt loam, 10 to 18 percent slopes, severely eroded	19K	Moderately well drained	C	Somewhat limited	Very limited
Hosmer silt loam, 5 to 10 percent slopes, eroded	16K	Moderately well drained	C	Somewhat limited	Very limited
Zanesville silt loam, 10 to 18 percent slopes, severely eroded	15K	Moderately well drained	C	Somewhat limited	Very limited
Hosmer silt loam, 2 to 5 percent slopes	13K	Moderately well drained	C	Somewhat limited	Very limited
Belknap silt loam, 0 to 2 percent slopes, occasionally flooded	13K	Somewhat poorly drained	B/D	Very limited	Very limited
Grantsburg silt loam, 5 to 10 percent slopes, severely eroded	12K	Moderately well drained	C	Somewhat limited	Very limited
Grantsburg silt loam, 2 to 5 percent slopes	11K	Moderately well drained	C	Somewhat limited	Very limited
Hosmer silt loam, 5 to 10 percent slopes, severely eroded	11K	Moderately well drained	C	Somewhat limited	Very limited
Wellston-Berks complex, 10 to 18 percent slopes, eroded	10K	Well drained	B	Somewhat limited	Somewhat limited
Sharon silt loam, 0 to 3 percent slopes, occasionally flooded	9K	Moderately well drained	B	Very limited	Very limited
Grantsburg silt loam, 5 to 10 percent slopes, eroded	8K	Moderately well drained	C	Somewhat limited	Very limited
Hosmer silt loam, 10 to 18 percent slopes, eroded	7K	Moderately well drained	C	Somewhat limited	Very limited
Zanesville silt loam, 10 to 18 percent slopes, eroded	5K	Moderately well drained	D	Somewhat limited	Very limited
Bonnie and Petrolia soils, undrained, 0 to 2 percent slopes, frequently flooded	5K	Poorly drained	C/D	Very limited	Very limited
Grantsburg silt loam, 10 to 18 percent slopes, severely eroded	5K	Moderately well drained	C	Somewhat limited	Very limited
Bonnie silt loam, 0 to 2 percent slopes, occasionally flooded	4K	Poorly drained	C/D	Very limited	Very limited
Berks, Muskingum, and Weikert soils, 35 to 70 percent slopes	4K	Well drained	B	Very limited	Very limited
Zanesville silt loam, 5 to 10 percent slopes, severely eroded	4K	Moderately well drained	D	Somewhat limited	Very limited
Burnside silt loam, 1 to 4 percent slopes, occasionally flooded	4K	Well drained	B	Very limited	Very limited

Soil Orders in This Area

The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.

Alfisols

Moderately weathered forest soils with clay-enriched subsoil. Productive for agriculture, generally good for building and septic.

Entisols

Young soils with little development — found on floodplains, dunes, and steep slopes. Properties vary widely by setting.

Inceptisols

Young but developing soils found in mountains and river terraces. Variable properties — check drainage and bedrock depth.

Mollisols

Fertile grassland soils with thick, dark topsoil. Among the best for agriculture, building, and gardening.

What This Means

Building & Foundations

About 30% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.

Septic Systems

About 94% of soils are rated "very limited" for septic absorption fields. Despite good drainage overall, limitations may stem from shallow bedrock, steep slopes, or seasonal conditions. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.

Gardening & Agriculture

Well-drained soils on sloped terrain — good for most plants but watch for erosion. Terracing, contour planting, and mulching help retain moisture and topsoil. Drip irrigation is more effective than sprinklers on slopes.