California MS4 Trash Reduction Requirements
California has some of the most stringent stormwater trash requirements in the country. All regulated MS4s (Municipal Separate Storm Sewer Systems) — both Phase I and Phase II — must comply with the State’s Trash Amendments.
Core Requirement: 100% Trash Load Reduction
California requires MS4 permittees to achieve a 100% reduction of trash discharges to receiving waters. This means preventing or capturing trash from stormwater systems equivalent to removing all particles 5 millimeters or larger. The goal is effectively no trash discharge from storm drain systems into creeks, rivers, bays, and the ocean.
Did you know? Approximately 80% of the trash found in our waterways begins as everyday litter that enters storm drains. Unlike sanitary sewers, storm drains flow directly into local creeks, rivers, and the Delta/Bay — without any treatment.
Why It Matters
The impacts of litter in our waterways are widespread and well-documented. Beyond being unsightly, trash in natural habitats can:
- Obstruct stream flow
- Block fish migration
- Interfere with boating, swimming, and other recreational uses
- Degrade water quality
Wildlife are especially vulnerable. Fish, birds, and other animals can suffer from entanglement, choking, and malnutrition from ingesting plastics. Trash may also contain hazardous substances such as oils and grease, heavy metals, and toxic chemicals — all of which can harm both wildlife and humans.
Be Part of the Solution
Every piece of litter prevented from entering a storm drain helps protect our creeks, rivers, and bays. Proper disposal, reducing single-use plastics, and keeping business and neighborhood areas clean can make a measurable difference.
What Makes This Issue Unique
Unlike trash in landfills, stormwater litter receives no treatment, travels quickly into ecosystems, and is much harder to remove once dispersed. What we drop on land doesn’t stay on land.