Miami-Dade County, FL's soil, for a septic absorption field
Very limited
Soil across 54.3% of Miami-Dade County, FL rates "Very limited" in USDA's septic-absorption-field interpretation. Expect the ground itself to work against a plain gravity system; USDA's strictest bucket alone covers 54.3% of the county. Miami-Dade County covers 1,899.988 square miles and counts 2,838,461 residents.
This is a county figure, not a parcel figure
This is a countywide, area-weighted figure across every soil survey map unit in Miami-Dade County, FL - never a reading for one specific parcel. A site-specific perc test, usually $750-$1,850, is what a health department will actually require before permitting a lot in Miami-Dade County.
System cost, conventional vs. engineered
Given Miami-Dade County's rating, plan for the engineered-system range rather than the conventional one. The engineered-system range, $10,000-$40,000 (mound or aerobic treatment), is the more realistic number to plan around, against $3,000-$8,000 for a conventional system on the rare lot that passes.
Where this sits nationally
Nationally, Miami-Dade County, FL is the 2,833-most-constrained of 3,058 rated counties for septic soil. Within Florida alone it ranks 65 of 65.
Before you act on this
How this rating is built, and its real limits · Conventional vs. engineered septic systems