Design guide
Drainage first,
asphalt second.
Nearly every pavement failure we dig up in the Valley has water in its history. Here's how drainage actually works on driveways and lots — and why we design the water path before we talk asphalt.
Updated July 2026 · California Asphalt Professionals · CSLB C-32 #760658 · Ballpark figures are planning aids, not quotes — the free site walk produces the real number.
The enemy underneath
Asphalt doesn't mind being wet; the base and clay under it do. Water that ponds on the surface finds every crack, saturates the base, and turns a load-bearing structure into mud with a lid. Add the Valley's expansive clays — swelling wet, shrinking dry — and standing water becomes a slow-motion demolition crew.
Slope is the whole game
Pavement sheds water with fall: roughly 1–2% minimum (about a quarter-inch per foot). Flat-looking driveways need deliberate crown or cross-slope; lots need the fall to actually reach an inlet or exit, not just wander. 'Birdbaths' — puddles that outlive the rain — are the diagnostic: each one marks a spot where slope failed, and each is fixable during resurfacing if someone measures instead of guesses.
Where the water goes
A good design gives every drop a destination: swales along rural approaches, curb openings on lots, trench drains at garage doors that sit below grade, and on ag properties, honest coordination with the irrigation that surrounds the pavement. In flood-irrigated orchard country we thicken and seal edges, because the water is coming whether the driveway likes it or not.
What this means for your estimate
When we walk a property, we're reading water before anything else: where it lands, where it wants to go, what it's already damaged. Sometimes the honest quote includes a hundred dollars of grading that saves a thousand in early failure. A paving bid with no drainage line-item on sloped or flat-problem ground isn't cheaper — it's incomplete.
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