Recovering Fossils During Excavation for Substation Project

The Southern California Edison (SCE) El Casco Substation Project (ECSP, Substation) is located in San Timoteo Canyon, west of Beaumont, in western Riverside County (County), California. The proposed ECSP was subject to approval by the California Public Utilities Commission (CPUC), which approval was subject to the California Environmental Quality Act (CEQA). SCE constructed the ECSP in compliance with the project Final Environmental Impact Report (EIR) and the requirements of the ECSP Paleontological Resources Treatment Plan. This project, along with the monitoring that it documents, and the ultimate curation of the collection with the Western Science Center, represents compliance with, and completion of the ECSP Mitigation requirements.

In 2009, LSA was contracted by SCE to execute mitigation measures adopted in the El Casco System Project (ECSP) Final Environmental Impact Report (FEIR) and formulated in the Paleontological Resources Treatment Plan. The purpose was to monitor all ground-disturbing excavation and activities in order to recover and identify significant resources within the project area and to ensure the scientific integrity of the recovered resources during the course of construction and construction excavation within the project area. At the Substation site, LSA staff monitored excavation for any artifacts and fossils that might be encountered during earth-disturbing activities.

Fossils recovery by LSA for SCE at the El Casco Substation yielded 77 taxa of plants, mollusks, fish, amphibians, reptiles, birds, insectivores, rodents, deer, camels, horses, sloths, and two saber cats. This exceptional assemblage from a single sedimentary interval has only 13 taxa in common with the taxa reported from all five Members of the entire San Timoteo Formation.

The assemblage includes:

• More than 12 species of plants, primarily riparian and aquatic
• Stickleback fish, whose presence indicates ancient drainage systems
• Eight genera of previously unreported riparian and aquatic slugs and snails
• Three salamander species and a frog not previously reported from the Formation
• First records from the Formation of giant tortoise, pond turtle, three lizards, and snakes
• Duck, rail, and scrub jay not previously reported from the Formation
• First records of shrews and broad-footed moles from the Formation
• One vole recording its first entrance into the southwestern states
• A giant camel and a fossil llama
• Two species of giant ground sloth
• Carnivores, rare in any fauna, including partial skeletons of two different saber cats, the dirk-tooth cat (Homotherium sp.) (Appendix I-D: Figure 42–51) and the ancestral Saber tooth cat (Smilodon gracilis).

Construction of the El Casco 220/115/12 kV Substation within the Norton Younglove Reserve in the County included:

• Associated 220 kV and 115 kV interconnections, and new 12 kV line getaways (i.e., distribution lines, connections out of the Substation)
• Replacement of approximately 13 miles (mi) of existing single-circuit 115 kV Substation transmission lines with new, higher-capacity double-circuit 115 kV subtransmission lines and replacement of support structures within existing SCE ROW in the Cities of Banning and Beaumont and unincorporated areas of the County
• Replacement of approximately 1.9 mi of existing single-circuit 115 kV subtransmission lines with new, higher-capacity double-circuit 115 kV subtransmission lines and replacement of support structures within existing SCE ROW in the City of Beaumont and unincorporated areas of the County
• Rebuilding the 115 kV switchracks at Banning and Zanja Substations in the Cities of Banning and Yucaipa, respectively
• Replacement of approximately 0.5 mi of existing single-circuit 115 kV subtransmission lines with new, higher-capacity double-circuit 115 kV subtransmission lines and replacement of support structures within existing SCE ROW in the City of Beaumont and unincorporated areas of the County
• Installation of new telecommunications equipment at El Casco Substation and the existing SCE Mill Creek Communications Site, install fiber optic cables in public streets and on existing SCE structures between the Cities of Redlands and Banning

The development of the El Casco Substation required grading approximately 28 acres (ac) to create the relatively flat 14 ac pad for the Substation and to address potential landslide problems related to the 180 ft high hill at the south margin of the project.

Client
Southern California Edison

Services
Archaeological/Paleontological Monitoring