What is an MS4 system?
A municipal separate storm sewer system means a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains) owned or operated by a County or other public body, including special districts such as a flood control district, designed or used for collecting or conveying storm water and which is not a combined sewer and which is not part of a Publicly Owned Treatment Works (POTW).

The County’s MS4 system consists mainly of flood control conveyances, drainage ditches, catch basins, storm drains, County owned streets, curbs and gutters.

Show All Answers

1. What is the Stormwater Program?
2. What is the Arizona Pollutant Discharge Elimination System (AZPDES) program?
3. What is stormwater runoff?
4. What is an MS4 system?
5. Why is stormwater regulated?
6. Does my construction site require a Stormwater Plan Approval from Maricopa County?
7. Do I require a Post-Construction Permit from Maricopa County?
8. How do I apply for Stormwater Plan Approval?
9. What is the National Pollutant Discharge Elimination System (NPDES) program?