The Arroyo Seco Water Reuse Project is a collaborative project between the cities of Pasadena and South Pasadena, with Pasadena serving as the lead agency. The project consists of two locations along the Arroyo Seco Channel – the San Rafael and San Pascual sites - that will address water quality issues and assist in complying with a state-mandated requirement to reduce the bacteria levels from tributaries that flow into the Los Angeles River. These sites were selected due to their large drainage area size (5,005 acres), their proximity to San Rafael Creek and Arroyo Seco Channel, their pollutant treatment potential, and the opportunity to revitalize and introduce new public spaces along the Arroyo Seco Trail.
Through sampling of the outfalls to the channel in dry weather conditions, the San Rafael Creek outfall to the Arroyo Seco Channel has been identified as consistently having bacteria levels above the allowable limits set by the Los Angeles Regional Water Quality Control Board for fresh waters designated for recreational use. This project will aid in reducing the bacteria load flowing into the Arroyo Seco Channel and subsequently to the Los Angeles River utilizing nature-based approaches to the best extent feasible.
Project Map
Project Co-Benefits
The Arroyo Seco Water Reuse project delivers meaningful co-benefits, including improving water quality, restoring native tree and plant species and native habitat, enhancing recreational spaces for the community, and promoting sustainable water management practices, all of which contribute to a healthier ecosystem and a more resilient urban environment.
- Water Quality Improvements: The project significantly reduces bacteria levels and other pollutants, such as zinc in the Arroyo Seco Channel from its tributaries. This leads to cleaner water entering into the Los Angeles River and contributes to improved water quality.
- Habitat Restoration: By replacing invasive species with native, drought-tolerant plants, the project restores diverse habitats like chaparral, sage-scrub, and riparian zones. This supports biodiversity and strengthens the local ecosystem.
- Community and Recreational Benefits: The project enhances walkability and community access to recreational spaces. Enhanced walking paths and restored natural habitats offer a more enjoyable outdoor experience for residents and visitors to the area.
- Sustainable Stormwater Management: Utilizing nature-based solutions, the project captures, treats, and infiltrates stormwater, helping to recharge groundwater and reducing reliance on potable water. This promotes sustainable stormwater management practices.
Conceptual Design
San Rafael Site
San Pascual Site
Project Timeline
Project Background
The project site is within the Upper Los Angeles River (ULAR) Watershed, which spans approximately 485 square miles of urban land. Runoff from this area drains into the Los Angeles River and eventually the Pacific Ocean.
In 2010, the Los Angeles Regional Water Quality Control Board set a Total Maximum Daily Load (TMDL) for indicator bacteria in the Los Angeles River watershed, which includes the Arroyo Seco Channel. To meet these TMDL waste load allocations, the ULAR group implemented a Load Reduction Strategy (LRS) focused on reducing bacteria from storm drain outfalls.
The San Rafael Creek outfall into the Arroyo Seco Channel was identified as a priority outfall due to its consistent contaminant discharges. The proposed action is to eliminate 100% of the dry weather flows from this outfall.
DRAFT ENVIRONMENTAL IMPACT REPORT
- Appendix A-1 - Notice of Preparation
- Appendix A-2 - Public Comments on NOP
- Appendix B-1 - Construction Mass Daily Emissions
- Appendix B-2 - i-Tree Output
- Appendix C - Biological Resources Assessment Report
- Appendix D - Cultural and Paleontological Resources Records Searches
- Appendix E-1 - Hydrology and Hydraulics Report
- Appendix E-2 - Stormwater Capture Study Technical Memorandum
- Appendix F-1 - San Rafael Geotechnical Evaluation
- Appendix F-2 - San Pascual Geotechnical Evaluation
- Appendix G - Noise Supporting Documentation
- Appendix H - Traffic Evaluation
- Appendix I - TCR Supporting Documentation
Appendix A-1 - Notice of Preparation
Appendix A-2 - Public Comments on NOP
Appendix B-1 - Construction Mass Daily Emissions
Appendix B-2 - i-Tree Output
Appendix C - Biological Resources Assessment Report
Appendix D - Cultural and Paleontological Resources Records Searches
Appendix E-1 - Hydrology and Hydraulics Report
Appendix E-2 - Stormwater Capture Study Technical Memorandum
Appendix F-1 - San Rafael Geotechnical Evaluation
Appendix F-2 - San Pascual Geotechnical Evaluation
Appendix G - Noise Supporting Documentation
Appendix H - Traffic Evaluation
Appendix I - TCR Supporting Documentation
Department Lead and Funding
Unlike other stormwater projects in Pasadena, this project is driven by a TMDL and was an unfunded mandate by the Los Angeles Regional Water Quality Control Board. Thanks to the support of Senator Anthony Portantino’s office, the Cities of Pasadena and South Pasadena received a $3.5 million grant from the State of California, Department of Parks and Recreation’s Urban Counties Per Capita Program, under a subprogram specifically designated for the Arroyo Seco. The Cities received further funding through Los Angeles County’s Safe, Clean Water Program (Measure W) for $9.33 million. In addition, both Cities provided Local Return dollars to the project, with about $1.37 million from Pasadena and $438 thousand from South Pasadena. Together, these grants will fully fund the project through construction.
The Safe, Clean Water Program provides local, dedicated funding to increase local water supply, improve water quality, and protect public health. For more information regarding Los Angeles County’s Safe, Clean Water Program please go to https://safecleanwaterla.org
Community Outreach and Public Meetings
The public is invited to attend upcoming public meetings to learn about the project design and provide feedback. For information on the upcoming meeting dates and times, please refer to the Upcoming Events section for updates.
Thank you for attending the Arroyo Seco Water Reuse Project EIR Scoping Meeting on Wednesday, May 28th, 2025, at the South Pasadena Community Room. To learn more on what was shared at this meeting, please view EIR Scoping Meeting.pdf.
Thank you for attending the Arroyo Seco Water Reuse Project Community Meeting #2 on Thursday, April 27th, 2023.” To learn more on what was shared at this meeting, please view the Arroyo Seco Water Reuse Second Community Meeting Graphic Boards.pdf and Arroyo Seco Water Reuse Second Community Meeting Presentation.pdf
Community Event #2 meeting materials also featured project renderings where participants could reimagine the proposed changes to the San Rafael site.
Community Event #2 meeting materials featured project renderings where participants could reimagine the proposed changes to the San Pascual site.
Thank you for attending the Arroyo Seco Water Reuse Project Community Meeting #1 on Thursday, May 26th, 2022. To learn more on what was shared at this meeting, please view the Arroyo Seco Water Reuse Project First Community Meeting Presentation.pdf
Community Meeting #1 featured a map of the project study area that identified two main sites, San Rafael (Site 1) and San Pascual (Site 2).
Community Meeting #1 highlighted the existing conditions of both project sites.
