Septic soil in Santa Cruz County, CA, by the numbers
Very limited
Soil across 97.8% of Santa Cruz County, CA rates "Very limited" in USDA's septic-absorption-field interpretation. That reading means a conventional system is a poor bet here - 97.8% of Santa Cruz County lands in the strictest "very limited" bucket USDA uses. Santa Cruz County, CA is 445.106 square miles with a population of 262,406.
What Santa Cruz County's reading doesn't cover
Santa Cruz County's rating is an average across the whole county, not a promise about any one lot inside it. A local percolation test, typically $750-$1,850 (around $1,300 typical), is the only way to know what one lot in Santa Cruz County will actually do.
What a system would cost here
With 97.8% of Santa Cruz County 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, Santa Cruz County, CA is the 274-most-constrained of 3,058 rated counties for septic soil. Within California alone it ranks 1 of 57.
Related guides
How this rating is built, and its real limits · Conventional vs. engineered septic systems