For 50 years, Caltrans has tried to connect the 710 and 210, saying it's a critical missing link.
However, South Pasadena residents repeatedly use the courts to block the freeway expansion on environmental grounds. A surface freeway would cut through the city, eliminating hundreds of homes, some schools and thousands of trees.
The idea now is to use new European boring machines, like the ones that dug L.A.'s transit tunnels, to tunnel under Alhambra, El Sereno and South Pasadena.
Caltrans drilling crews began boring a 250-foot test tunnel on Tuesday, one of many test holes that will be drilled in the next couple of weeks between Alhambra and Pasadena.
The bore samples will allow geologists to determine whether an underground freeway is possible through the area.
The eight-lane freeway tunnel would be 4.5 miles long and hundreds of feet deep. $700 million from Proposition R, which voters approved last November in L.A. County, has been allocated to the project, but the state has yet to give its approval.
The cities of South Pasadena and La Canada-Flintridge are still not on board with the project, contending that no money should be spent on this project, even the test drilling, until the environmental impacts of a tunnel are fully studied.
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