Inlet protection is a temporary device or practice that filters or ponds runoff around a storm drain inlet so sediment settles or is captured before water enters the storm sewer. Because storm sewers usually discharge straight to streams, inlet protection is one of the most visible controls inspectors check.
What the EPA Construction General Permit requires
Under EPA's 2022 CGP:
- Install inlet protection on any storm drain inlet that carries stormwater from your site to a receiving water, provided you have authority to access it. Inlets that drain to a sediment basin, trap or similarly effective control don't need it.
- Clean, or remove and replace, inlet protection as sediment accumulates, the filter clogs, or performance is compromised.
- Where sediment accumulates next to the inlet protection, remove it by the end of the same business day it's found, or by the end of the next business day if same-day removal isn't feasible.
- Inlet protection can be removed during flood conditions or to prevent erosion.
Types of inlet protection
| Inlet type | Common devices |
|---|---|
| Grate inlets in paved areas | Filter bags or inserts under the grate; fabric covers sized for flow |
| Curb inlets | Weighted curb socks or compost socks across the opening; manufactured curb guards |
| Drop inlets in unpaved areas | Silt fence or wire-and-fabric enclosures, gravel or block-and-gravel filters, excavated sediment sumps around the inlet |
| Combination inlets | A grate insert plus curb protection |
Installation tips
- Match the device to the inlet type and size; a loose-fitting insert lets water bypass.
- Leave an overflow path so heavy storms don't back up into traffic lanes or properties.
- On streets, use devices that don't create traffic hazards and are approved by the road owner.
- Inlet protection is a backup. Upslope erosion control, perimeter controls and track-out control should keep most sediment away from inlets.
Maintenance
- Inspect at every SWPPP inspection and after storms.
- Empty filter bags before they're full, typically by lifting the grate with the bag's handles and dumping sediment in a stable area.
- Sweep sediment that collects around curb socks.
- Replace torn or clogged filters.
See sediment control BMPs for how inlet protection fits the whole system.
Sources and official references
Last reviewed: October 25, 2026 · Free general education based on the Clean Water Act, EPA NPDES rules and the EPA Construction General Permit. Your governing permit (EPA, state, tribal or local) controls. This is not legal advice, not EPA-approved, and not a California QSP/QSD or other state credential, and it does not issue a certificate. Nothing you enter on this page is saved or sent.