Question 1

What's the minimum slope required for parking lots?

Accepted Answer

1% minimum (1 foot per 100 feet), though 1.5–2% is preferred. Insufficient slope causes water accumulation and accelerated pavement failure.

Question 2

Do we need a detention pond for every parking lot?

Accepted Answer

Not if using permeable pavement (infiltrates rather than runs off). Traditional asphalt lots >1 acre typically require retention/detention for EPA compliance.

Question 3

How often should catch basins be cleaned?

Accepted Answer

Monthly during growing season, quarterly otherwise. Neglect causes clogging and surface flooding.

Question 4

Is permeable pavement worth the cost?

Accepted Answer

Yes, over lifecycle. 50–100% upfront premium, but no detention pond needed (saves $50,000+) and pavement lasts 25–40 years vs. 15–20. Break-even 8–12 years.

Question 5

What's the biggest drainage maintenance mistake?

Accepted Answer

Neglecting catch basin cleaning. Clogged catch basins = no drainage = surface flooding = pavement failure. Monthly cleaning prevents 90% of drainage problems.

Parking Lot Drainage & Stormwater Management: Compliance, Design, Maintenance