Caltrain SF extension disaster salvage: DTX via Seventh Street and Howard Street

• Alignment plan Transbay — to Seventh and Bryant, via Howard Street, passing under Moscone Center and under Muni Central Subway. (PDF)
• Alignment plan Seventh and Bryant — to Caltrain Tunnel 1, via existing Caltrain right-of-way beneath Interstate 280 "China Basin Viaduct" structure. (PDF)
• Alignment profile. (SVG)

Features of note

• Cut and cover open trench from tie-in to existing. tracks ot Tunnel 1 (Mariposa Street) to Seventh and Townsend
  • Trenched under 280, with limited and manageable but unavoidable bent relocation.
  • 350m curve radius under 280, civil design speed 70kmh (imposed by freeway viaduct column placement)
  • Tracks pass clear under 16th Street, which bridges the trench at the existing road/pedestrain elevation.
    Ditto existing Mission Bay Drive and newly restoed Berry Street (the latter presently severed by train tracks.)
    Ditto the large "Division Street" outfall box sewer remains at existing elevation, bridging over rail trench.
  • Trenched (and optional) two platforn track single 310m island platform station adjacent to Seventh Street south of Townsend Street.
  • Fully enclosed underground construction (= $$$ for fire safety) avoided to maxmimal extent in favour of open-to-sky trenches.
  • "Transit oriented development" of commerical and residential buildings over rail tracks and especially railway stations and complex station approach tracks NEVER comes close to pencilling out — this is a tarpit of uneconomic wishful thinking, together with outrageous rent-seeking extraction of millions of dollars of real estate "value" by way of hundreds of millions of dollars of rail project budget.
  • Far, far worse than useless station mezzazine level nonesense avoided here as such nonesense must be everywhere — direct human-to-train access from street level to platform level.
  • Optional expansion to three through tracks is feasible, with either a no-platform bypass track or an additional side 310m platform.
  • (Optional-optional expansion to an additional 420m platform with two terminal tracks is technically possible, and is sketched in, but is not justifiable.)
  • One parcel property take at north-east corner of Seventh and Townsend (not even a rounding error in the project "budget") with construction and permenent operating easements to three additional parcels (still surface parking in 2023.)
  • "Railyards" city blocks between Seventh and Fourth and Townsend and King Streets otherwise unused by Caltrain post cutover to Transbay extension.
  • "Shoo-fly" access to existing Caltrain terminal station via phased relocated parallel tracks under 280, threading the needle between viaduct volumns, is possible through nearly the entire construction process, with total service interruption for final construction and cutover limited to a a timeframe measured in weeks, not years.
• TBM bore from Brannan and Seventh to Third and Howard.
  • Deepest point -97ft ASL track elevation, passing west-east under south-north Muni Central Subway bore deep beneath Howard Street / Fourth Street intersection, much as Muni Central Subway passes under the BART/Muni subway box under Market Street two blacks north.
  • Track elevation -93ft to -73ft ASL passing under footings of subterraean Moscone Center halls and loading docks beneath Howard Street between Fourth Strret and Third Street.
  • 510m curve radius, civil design speed 110kmh
  • 1.78%/2.86% track grades (1.89%/3.00% curve "compensated")
• Cut and cover station throat box from Third to Second Street
• Maximum flexibiliy (minimum possible train route conflicts = maximum possible train throughput) station throat configuration.
  Minimum radius 200m, 40kmh design speed.
  Seven turnouts standard UIC standard 500m diverging radius straight frog 1:14 design.
  Three turnouts standard UIC standard 300m diverging radius curved frog 1:9 design.
  Five turnouts identically curved (per standard UIC practice and within UIC design limits) from standard 500-1:12 design to 200m diverging radius and 333m non-diverging radius with 1:12 frog.
  
• Two parcel property takes at north-west corner of Second and Howard (not even a rounding error in the project "budget".)
• Undercutting into the Transbay train box for necessary for 90m to allow tracks to descend early enough to pass under the Muni Central Subway with maximum compensated grade of only 3.21% (200m radius, 2.86% uncompensated) which is well below 4% used on mainline rail alignments designed by skilled, professional, successful, competent rail engineers in constrained urban environments (eg Zürich Löwenstrasse underground station's approach tunnels and flyover.)
• Displacement of zero Transbay stuctural columns
  This is an utterly miraculously low impact, by blind luck in the face of unlimited PTG/TJPA/PCJPB/CHSRA unprofessionalism and incompetence in rail and civil "design" of the Transbay Terminal.
  Crippling, self-inflicted limits to passenger vertical circulation to and from the platforms still remain, of course.
• Appallingly, woefully, unnecessarily self-inflicted, terribly, irremediably misconceived and misdesigned Transbay rail box and platform track alignment and platform configuration otherwise unaltered.