Suffolk County, New York
The most common soil here is Riverhead, on about 17% of the land: a sandy loam, gritty and crumbly. Plymouth and Haven come next.
About 65% of the land drains well, and 4% stays wet for long stretches; groundwater comes within two feet of the surface under 5% of it.
USDA rates 68% of the land very limited for a standard septic drain field, and 10% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 3% of the land floods occasionally or more.
Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.
The soils you're most likely standing on
The biggest named soils in Suffolk County, New York, each drawn five feet deep from its official USDA description, in its recorded colors.
Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.
The biggest mapped areas
The dominant drainage class is Well drained and the dominant hydrologic group is A (high infiltration, low runoff). The most common soil order is Entisols — young soils with little profile development, often on floodplains or steep slopes. 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 Suffolk County, New York. 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 |
|---|---|---|---|---|---|
| Water | 161K | Not rated | Not rated | ||
| Riverhead sandy loam, 0 to 3 percent slopes | 69K | Well drained | A | Not limited | Very limited |
| Haven loam, 0 to 2 percent slopes | 60K | Well drained | B | Not limited | Very limited |
| Riverhead and Haven soils, graded, 0 to 8 percent slopes | 58K | Well drained | A | Not limited | Very limited |
| Carver and Plymouth soils, 3 to 15 percent slopes | 43K | Excessively drained | A | Somewhat limited | Very limited |
| Plymouth loamy coarse sand, 0 to 3 percent slopes | 39K | Excessively drained | A | Not limited | Very limited |
| Carver and Plymouth soils, 15 to 35 percent slopes | 34K | Excessively drained | A | Very limited | Very limited |
| Cut and fill land, gently sloping | 32K | Moderately well drained | Not rated | Not rated | |
| Riverhead sandy loam, 3 to 8 percent slopes | 32K | Well drained | A | Not limited | Very limited |
| Plymouth loamy coarse sand, 3 to 8 percent slopes | 27K | Excessively drained | A | Not limited | Very limited |
| Carver and Plymouth soils, 0 to 3 percent slopes | 25K | Excessively drained | A | Not limited | Very limited |
| Tidal marsh | 16K | Very poorly drained | Not rated | Not rated | |
| Haven loam, 2 to 6 percent slopes | 15K | Well drained | B | Not limited | Very limited |
| Plymouth loamy coarse sand, 8 to 15 percent slopes | 13K | Excessively drained | A | Somewhat limited | Very limited |
| Bridgehampton silt loam, 0 to 2 percent slopes | 10K | Well drained | B | Not limited | Very limited |
| Montauk loam, 3 to 8 percent slopes | 9K | Well drained | C | Somewhat limited | Very limited |
| Riverhead sandy loam, 8 to 15 percent slopes | 8K | Well drained | A | Somewhat limited | Very limited |
| Urban land | 6K | Not rated | Not rated | ||
| Beaches, sand | 6K | Very limited | Very limited | ||
| Fill land, dredged material | 6K | Not rated | Not rated |
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.
What This Means
Building & Foundations
Most soils are generally favorable for residential construction. Standard foundations are usually viable, though site-specific evaluation is always recommended.
Septic Systems
About 68% 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.