Septic soil in Williamsburg city, VA, by the numbers
Very limited
Soil across 59.1% of Williamsburg city, VA rates "Very limited" in USDA's septic-absorption-field interpretation. That reading means a conventional system is a poor bet here - 59.1% of Williamsburg city lands in the strictest "very limited" bucket USDA uses. Williamsburg city, VA is 8.938 square miles with a population of 16,030.
What Williamsburg city's reading doesn't cover
Two lots a mile apart in Williamsburg city can carry different soil, even though they share one countywide rating. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Williamsburg city will actually do.
What a system would cost here
With 59.1% of Williamsburg city rating "Very limited", a standard gravity system is not a safe assumption here. 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, Williamsburg city, VA is the 2,739-most-constrained of 3,058 rated counties for septic soil. Within Virginia alone it ranks 87 of 110.
Further reading
How this rating is built, and its real limits · Conventional vs. engineered septic systems