The use of three bores on a busy freeway with four lanes each direction can slow traffic because of lane drops down to two lanes in one or the other directions. The so-called "busy" direction gets four lanes across two tunnels, while the less busy direction gets a single tunnel with just two lanes. The trouble is that both directions are becoming equally busy at all times.

Barricades were constructed to mask the new tunnel from view by approaching traffic. Behind this barricade, nothing had been bored in this direction yet.

The traffic heading west toward Oakland was granted two tunnels and four lanes that day. Notice the barricades in the near roadway that closes off the eastbound lanes to two lanes through a single tunnel.

A huge crane was just behind the last over-pass before the existing tunnels.

The actual new bore could be seen on the approach heading west on the eastern side of the original tunnels. The technique for digging is in three phases. First the top excavated, then later the bottom two layers.

The new 4th bore as viewed from the freeway running west from Orinda toward Oakland on the Orinda side.