When CAHSR references a base tunnel for the SGs they are talking about the primary tunnel starting somewhere around Aqua Canyon road (2500ft) and Lake View Terrace (above 1500 ft)

FUD Wrote:
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> A tunnel through the San Gabriels, like BOB2 has
> advocated for in the past, would effectively be a
> base tunnel even though the altitudes at each end
> would be significantly different. That's because
> the land at each end is at the base of the
> mountains, so it's impossible to go deeper.
> Palmdale is at about 2500' elevation; Sylmar and
> other spots along the western base of the
> mountains in the San Fernando Valley area at
> 1000-1500' elevation.
>
> A Tejon tunnel would not be a base tunnel, because
> the line would surface at the top of the mountains
> in order to cross the San Andreas Fault. It would
> be, at minimum, two tunnels: one from the San
> Joaquin Valley floor to near Gorman, and another
> from the south side of the fault down to Santa
> Clarita.
>
> The last study I saw for HSR between Palmdale and
> the San Fernando Valley still had several
> alternatives, including one with multiple tunnels
> and lots of earthwork that more or less followed
> the current Metrolink line. IIRC, at least one
> alternative involved a long tunnel through the San
> Gabriels.