I transcribed an interview with Chief Bridge Engineer, John Walters, Chief Bridge Engineer at of the California Department of Transportation.

I sent him this:

The Pet Cemetery is protected by seven 100′ steel-reinforced, prestressed concrete beams. Each beam weighs approximately 160,000 pounds. The seven are separated by crossed wooden beams and tied together with heavy cables, forming a stiff, integral system. Columns and steel beams support the concrete beams and extend down to bedrock, 60′ below the surface. A wooden and corrugated steel roof protects the Pet Cemetery from falling debris.

He sent me back:

The primary structure for the Pet Cemetery protective cover consists of eight 105 ft long pre-stressed precast reinforced concrete beams, supported primarily by steel beams on concrete columns. The concrete columns are founded on sixty foot deep 2 ft diameter cast in drilled hole reinforced concrete piles. Each precast beam weighs approximately 165,000 pounds. The precast beams are strutted and braced by 8 x8 timber cross beams and tied together with 5/8 inch wire rope cable. This forms an integrated and stable structural system. A 5/8 inch thick plywood cover set on top of this system protects the Pet Cemetery from falling debris.

For our handout, I revised his version to read:

The primary structure over the Pet Cemetery consists of eight 105′ pre-stressed precast reinforced concrete beams, supported primarily by steel beams on concrete columns. The concrete columns are founded on sixty foot deep reinforced concrete piles. Each precast beam weighs approximately 165,000 pounds.  The precast beams are strutted and braced by timber cross beams and tied together with cable.  This forms an integrated, stable structural system that can support a 2 million pound load.  A 5/8 inch thick plywood cover set on top of this system protects the Pet Cemetery from falling debris.

Here’s a snapshot of the email from him, which contains a few additional facts: