Cascades PG&E Substation Wall Installation

The project would provide a special use permit to Pacific Gas and Electric (PG&E) to improve the transformer oil spill prevention structures at the Cascades Substation along El Portal Road. This project is a Spill Prevention, Control and Countermeasure (SPCC) Barrier that will reduce the potential risk of an oil splash resulting from a transformer malfunction. A masonry wall will replace the current fencing on the northwest, southwest, and southeast sections of the site. Instead of a wall, a drive-over berm will be constructed at the northeast side of the site to catch any runoff/oil spray coming from that direction and direct it into a SPCC pond which currently exists at the site. Due to wall construction and an increase of inflow from storm water runoff, a portion of the pond will be reconstructed to meet all SPCC requirements. Asphalt berms are currently in place to direct oil spray into the SPCC pond. Due to the poor condition of these asphalt berms, they will be replaced with concrete berms.

Project actions consist of the following:

1. Replacement of the existing fence (at the northwest, southwest, and southeast sides of the site) with a masonry wall.
a. This will consist of 120 linear feet of masonry wall.
b. Walls will stand 15' above the bottom elevation of the transformer.
c. Grade beams will be incorporated in line with the masonry wall.
d. Outrigger beams perpendicular to the wall will be located at intermediate points of the wall.
e. Pier foundations will be located at the end of the outrigger beams.
f. Work on the pier and shallow foundations will be performed by hand digging (unless a drill rig can be accommodated).
2. Construction of a drive-over berm and trenching with grating at northeast section of the site.
3. Modification of the existing SPCC pond walls as needed to accommodate the new wall barrier.
4. Replacement of the existing asphalt berms with concrete berms.
5. Patching of the existing SPCC ponds walls as needed.