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Healthy Streams Can
Start in Our Streets


Community Trash Monitoring
with Pasadena City College

Trash is pervasive in the streets, streams, and rivers of our local watersheds, impacting the health of our waterways. Since 2018, CWH and our partners have assessed the extent of harmful litter at streams in the Los Angeles River Watershed. Building on this effort, CWH has moved to engage future scientists, leaders, and voters on trash issues. 


What We're Doing

Beginning in August 2020, Council for Watershed Health partnered with Pasadena City College (PCC) to:

  • Coordinate and train local students to assess their own communities for trash

  • Provide a hands-on opportunity for students to engage in a local water quality issue and scientific research through community-based learning

  • Implement a trash assessment that is consistent with existing methods using trash surveys that map, count and categorize trash types

With a better inventory of trash extent within the watershed backed by data, communities can contribute to regional trash mitigation knowledge and efforts such as bag and plastic straw bans. Learn more about the history of local trash reduction policies and other actions below.

Getting Up-to-Speed with Trash Issues

Trash is a non-point source pollutant that is deposited on our streets and natural areas directly through littering or indirectly by runoff and wind. Runoff transports trash to our rivers and ocean through gutter and storm-drain systems. The path that trash-carrying runoff takes also depends on watershed features. With a gust of wind, litter and refuse from uncovered or overflowing trash bins also make their way into local water bodies.

To help control and reduce the amount of trash in our waterways, a trash TMDL was put into place that requires cities and municipalities to put screens, nets and other trash capture devices along our storm drains. Despite these efforts, urban storm drain systems contribute to an estimated 60% to 80% of human-created debris in ocean environments. These trash issues cost 90 west coast communities more than $520,000,000 each year.


Note the features of a watershed in this diagram.

Key Concepts

Nonpoint source (NPS) pollution

Street and storm drain systems

MS4 Permits


Impacts of trash

Trash reduction policy & other actions

The 5 R's & circular economy

Key concepts

Did you know?

The Los Angeles River has one of the nation’s first Total Maximum Daily Loads (TMDLs) for trash, empowering stakeholders to challenge the ecological, health, and aesthetic impacts of litter in the LA River Watershed. 

Student Takeaways

"All Littering Leads to the Ocean"

For Students: We know it can feel awkward picking up trash when no one else is doing it. To get more comfortable, try picking up trash in pairs and make it a weekly or monthly habit. Organizing a group that picks up trash together is more fun and might signal others in the community to do the same. If you find yourself doing it alone, remember it only takes one person to inspire another.

Student Takeaways

Trash Assessment Results

Plastic food packaging was the most prominent type of trash and significantly higher than all other trash categories.

Street Sweeping

  • Students that said their location was last swept 1 month ago had significantly higher trash counts compared to all other self-reported sweeping frequencies.

  • There are more large item counts at sites that report less frequent street sweeping.

Trash Sources

  • Assessments that identified homeless encampments as a trash source had significantly higher trash counts than survey locations that identified bins, businesses, and construction sites as trash sources.

  • Locations that noted homeless encampments as sources of trash had significantly higher counts of paper trash items and smoking materials than all other trash sources, with the exception of urban. 

Top Trash Items
September 2020 - December 2021

TRASH ITEM (1).png

Trash Categories

Copy of TRASH ITEM.png

Note: In addition to the top trash items listed in the table, students also encountered high levels of yard waste and leaves in their neighborhoods. We have left these counts out of the table to capture trash with greater environmental impacts.

Maps & Findings

Map of Top Trash Items - Student Data
Trash Count Totals and Top Items by 2016 Census Tracts *Totals are based on counts, not volumes of trash


Watch this video to learn about our work at CWH
and this community trash monitoring effort!

What You Can Do

What You Can Do

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