SCH Number 2023110605

Project Info

Title

Arroyo Seco Water Reuse Project

Description

The proposed Arroyo Seco Water Reuse Project would develop two regional stormwater capture and treatment facilities (man-made treatment wetlands and infiltration basins) located within existing open space-zoned areas near the Arroyo Seco Channel. Additionally, as part of the Project, an off-site water harvester and related infrastructure would be installed within the existing, gated maintenance yard at the public Arroyo Seco Golf Course in South Pasadena. The Project would provide water quality benefits for multiple jurisdictions within the 5,005-acre drainage area in which the two sites are located. For both sites, the Project would include native landscaping; hardscape elements including reclaimed wood log benches, post-and-rail fencing, and concrete seat walls faced with natural stone; informational signs as a watershed education opportunity; and expand the existing trail network to enhance regional trail connectivity through the Lower Arroyo Seco. The Project sites are located within the Upper Los Angeles River (ULAR) Watershed. Runoff from this watershed drains to and runs through over 50 linear miles of the Los Angeles River and then to the Pacific Ocean. The Arroyo Seco Channel is a major tributary to the Los Angeles River. On July 9, 2010, the Los Angeles Regional Water Quality Control Board (RWQCB) adopted resolution No. R10-007 incorporating a total maximum daily load (TMDL) for indicator bacteria in the Los Angeles River watershed. A TMDL is the calculation of the maximum amount of a pollutant allowed to enter a waterbody and not affect that waterbody’s ability to meet and maintain water quality standards. Outfalls along the Arroyo Seco Channel were modeled for indicator bacteria and the San Rafael Creek outfall was identified as a priority outfall; these outfalls have routine problematic discharges that drive the total bacteria load. Runoff in San Rafael Creek would be diverted into the San Rafael site, pre-treated, and a portion of this runoff infiltrated for groundwater recharge. The portion not infiltrated would be treated, discharged into the Channel, and then diverted downstream into the San Pascual site for infiltration and additional treatment prior to discharge back to the Channel. The operation of these two regional stormwater management sites would result in an annual average water supply benefit of 320 acre-feet (af). Of this, there would be approximately 258 af of groundwater recharge and approximately 30 af (or less than 10 percent of captured water) would be captured off-site for irrigation reuse at the golf course to reduce potable water demand. In addition to fulfilling regulatory obligations placed on Pasadena to provide cleaner water in the Arroyo Seco and Los Angeles River channels, other Project benefits include increased habitat and reestablishment of natural plant communities, improved trails, increased public access to open space areas, and educational opportunities utilizing interpretive materials focused on hydrology and native habitat.

3 documents in project