Guam Soil Surveys
The most common soil here is Guam, on about 28% of the land: a cobbly clay loam, firm and a little sticky. Akina and Pulantat come next.
About 92% of the land drains well, and 6% stays wet for long stretches.
USDA rates 95% of the land very limited for a standard septic drain field, and 91% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 4% of the land floods occasionally or more, and bedrock lies within 40 inches under 90% of it.
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 Guam, 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.
Guam has 1 USDA soil survey areas covering a wide range of landscapes and soil conditions. The most common soil order is Alfisols — moderately leached forest soils with a clay-enriched subsoil, making up roughly 33% of surveyed soils. Entisols — young soils with little profile development, often on floodplains or steep slopes account for another 25%.
In terms of drainage, 92% of Guam soils are classified as well drained. Drainage class affects everything from septic system design to basement feasibility to garden planning. Use the survey area pages below to see drainage details for specific counties, or look up any address for an exact soil profile.