The parallel I-5 tunnel cost would depend on if you tried to put in a "deep" underground station at UCSD.

I go back to 1980, when Nat Read, my old pal, then at American High Speed Rail, proposed to build a 140-160 HSR from LAUPT to SD for $3 billion, including the Miramar bypass, Del Mar bypass, and "long" tunnel bypass of San Juan and San Clemente (go over and under near the toll road and I-5 and down the canyon to San Onofre). I was going through my old files and found the line survey sheets Nat gave me. Of course, we've had some inflation since then.

My current "guess" without a "deep" station at UCSD for a Miramar bypass, would probably be in the neighborhood of about $200 million per mile (which is the rule of thumb I used for the bluffs, without a more complete geotechnical analysis of the specific conditions and requirements), is a very "rough one", based on other recent similar tunnel "only" project costs.

So we are probably talking in the neighborhood of a billion to bypass Miramar, and put in a significantly shorter double track 125 capable tunnel, roughly parallel to the surface route of I-5. coming out at Sorrento Valley.

The existing Miramar segment ROw, and the branch to Miramar NAS, could be used for a conversion to a LRT extension to create a direct rail transit connection from Downtown, to San Diego's "future" new and badly needed international airport at Miramar.....?

LOSSAN and SANDAAG have rightly put funding into upgrading that very slow and congested segment via Miramar, to extend DT and improve operating speed and travel time. And, given the budget constraints these "real" needs face (as opposed to $16 we will spend for Pacheco...????), it is the only thing they can really do right now. But,(IIRC?) what we used to refer to as the "Jim Mills" memorial tunnel (Senator Jim Mills proposed doing this for LOSSAN nearly 40 years ago) could save at least another 8+ minutes of running time, depending upon operating speeds.

Union Station phase one, with a nearly 10 minute time saving for every passenger and every train movement is still the most cost effective rail project in the, and if the Gas tax goes down, it will again become an "un-funded" project, that will not be completed by the 2028 Olympics.

Billions for the "runaway money train" to get to San Jose, and nothing whatsoever for Southern California, while we all sit in gridlock every day on the I-5, which was completely closed down in the OC this morning...…

Heckuva a job...…. Because we have the best "gubmint" that money can buy, right?