California is one of the only states actively managing trash in its rivers. Several community groups in the Pinole, CA and a scientist collaborated on a Thriving Earth Exchange community science project. Its purpose was to assess the trash in Pinole Creek and identify policy opportunities for the Pinole City Council. The key scientific questions were: how much trash was in the creek, what types of trash were most abundant, and where were areas of highest concern? The team enlisted additional community volunteers at in-person local events and local nonprofit listservs. We used a randomized sampling design and a community science adapted version of The Trash Monitoring Playbook, to survey the trash in the creek. We estimated there were 37 m 3 and 47,820 pieces of total trash in the creek channel with an average concentration of 2 m 3 per km 2697 pieces per kilometer. This gave the community an understanding of the scale of the problem and the resources needed to address it. Plastic and single-use trash were most abundant, and the community members expressed high concern about plastic single-use food packaging and tobacco-related waste. The community used the data to identify locations in the creek where trash was abundant and prioritize follow-up study locations. Seven new policies were recommended to the Pinole City Council. The City Council unanimously voted for the proposed policies to be reviewed by the Municipal Code Ad-Hoc Committee. And that is when community science turned to policy.