Arroyo Seco Canyon Project Areas 2 and 3


The Project is being proposed to repair and replace the City’s water infrastructure facilities in the Upper Arroyo Seco that were damaged by debris flows caused by storms following the 2009 Station Fire. Disrepair and damage to these structures has greatly reduced the City’s capacity to divert water from the Arroyo Seco and spread it for groundwater recharge and pumping credits. The proposed improvements would allow for increased utilization of the City’s pre-1914 surface water rights from the Arroyo Seco and maximize the beneficial use of this important local water resource. The Project involves the construction of a new diversion weir and intake in the same location within the Arroyo Seco as the current facility (Area 2) which will span the width of the streambed and include an operable weir crest gate. In Area 3, the proposed Project includes the reconfiguration and expansion of the existing spreading basins in order to accommodate the increased diversion of stream flows for infiltration into the Raymond Groundwater Basin.

Upon completion of the proposed Project and into the foreseeable future, the City intends to keep the existing structural bridge overlay on top of Bridge No. 3 along the Gabrielino Trail (which connects Areas 2 and 3).  Furthermore, the City may need to remove some or all of the historic bridge to protect public safety. During construction of the proposed Project, there may be times when portions of the Altadena Crest Trail, Gabrielino Trail/Access Road, Arroyo Seco Trail, and the unnamed trails/maintenance roads would be partially or fully closed to the public due to construction activities. Upon completion of the proposed Project, the temporarily disrupted trail network would be restored.

Long-term operations in Areas 2 and 3 would not be substantively different than the current conditions.


Notice of Availability (June 2020)

Draft EIR (No Appendices)

CASE MANAGER: Elisa Ventura