Eengineers trying to find the most efficient bullet-train route from Bakersfield to Palmdale encountered unexpected difficulties, including steep grades and a previously undisclosed wetlands protection requirement costing as much as $1 billion.
The rail authority's has self-imposed limit (but also practical engineering limits) of 3.5 percent average grade for sections measuring about four miles.
The Tehachapi Mountains are a tough climb, even for a train that can travel up to 220 mph. The primary alternative, the Grapevine, also has steep grades that agency officials have said would require extensive tunneling and viaducts, both of which would be very expensive.
A progress report the rail authority received from its contracted engineers in the summer of 2013, building a high-speed rail through the wetlands would require environmental remediation work costing about $100,000 per acre.
* to build California's high-speed rail with magnetic levitation or Hyperloop would make things like track sharing in the SF and LA area all but impossible. Although Hyperloop could be placed into smaller and lighter tubes which could be elevated and placed beside existing track.
* Hyperloop would need to use its technical advantages to enable a straighter route with flatter grades
* When the agency undertook a study in 2011 comparing the two alternatives' relative strengths, the city of Palmdale filed a lawsuit alleging the rail authority may not use its federal grants and state bond money to revisit an earlier announced decision to build an alignment through the Antelope Valley.
China has built high speed rail through significant mountain sections but they have used significant tunneling and land appropriation to get as straight and flat as possible to minimize the slowdowns.
The Shitai Passenger Railway is a 190-kilometre long (120 mi) high-speed railway in China, running from Shijiazhuang to Taiyuan at 250 kilometres per hour (160 mph). The railway opened on April 1, 2009.
The railway crosses the Taihang mountain range in Taihang Tunnel, which, at almost 28 kilometers (17 mi) long, is (as of 2010) the longest railway tunnel in China.
The Qinghai–Tibet railway, Qinghai–Xizang railway or Qingzang railway is a high-elevation railway that connects Xining, Qinghai Province, to Lhasa, Tibet Autonomous Region, in the People's Republic of China.
China is looking at tunneling under Mount Everest in order to make a rail connection to Nepal.
SOURCES - Wikipedia, Quora, Bakersfield