Conceptual Design for the Arroyo Seco Canyon Project

Click HERE to download the full Conceptual Design Report

Habitat Restoration

An area of human disturbance to the natural environment over the last few decades, this restoration plan will improve habitat for wildlife and the Arroyo Seco Ecosystem.

A stream restoration plan was developed for about 1,000 linear feet of the Arroyo Seco stream in the headworks area. The conceptual plan view for the proposed stream restoration elements is depicted on Figure 5.3

A cross section view of the Arroyo Seco River through the restored area depicts the dynamic stream course interacting with a variety of habitat zones given different runoff magnitudes. The recreational users of the area will be able to immerse themselves in the natural area during the majority of the year, while high flows will replenish the habitat during winter rains.

Diversion Alternatives

Using an "Inflatable Dam" the surface water diversion from the Arroyo Seco for municipal water supply will be far more environmentally friendly allowing for aquatic wildlife migration and natural stream hydrology. The system will also be more efficient, allowing Pasadena to take full advantage of their water rights by diverting high flows that would otherwise runoff into the Pacific Ocean.

Parking Lot and Spreading Basins

With the Jet Propulsion Laboratory moving their employee parking to an on site, multi-level, facility the existing parking lot will be replaced by parking spaces for recreational users of the park, and with spreading basins for groundwater recharge.

Parking lot preferred alternative - Under this alternative configuration, a reduced size parking lot will be located on the northern end of the existing JPL East Parking Lot. This parking lot will include approximately 50-75 spots and accommodate space for trees to provide shading. This alternative also incorporates the vehicle routing and guard check needs for JPL employees that use the access road to enter JPL through the east-side entrance.

Spreading Basins - The existing spreading basins do not have enough capacity to take advantage of PWP's surface water rights. Additional spreading basin capacity can maximize the use of the City's surface water rights within the available space of the JPL parking lot.


The new restroom will serve recreational users of the Gabrielino Trail. This will improve water quality, and will be a great feature of convenience enhancing the overall recreation experience for park users.

As a result of stakeholder input, geotechnical issues in the area and structural issues of nearby bridges, the restroom will be located at the public parking area. This toilet will tie into existing disposal lines.

Click HERE to view more figures and tables from the Conceptual Design Report