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" This winter, test borings are expected to begin for one of the most audacious tunnel projects ever proposed. One concept calls for a set of three tunnels--two for cars and one for both trucks and high-speed light rail--that would stretch for 12 miles, burrowing beneath the Santa Ana mountain range, and carrying up to 70,000 cars a day between California&amp;#039;s Riverside and Orange counties. The route would run in the same general direction as the 91 freeway, which is one of the most congested thoroughfares in the country. Once completed, it would be the longest traffic tunnel in North America, ahead of Boston&amp;#039;s comparatively puny 3.5-mile Big Dig. The tunnel proposal, currently called the Irvine-Corona Expressway, has been making the rounds for seven years. It was first studied officially by the Riverside County Transportation Commission in June 2004, and its future now depends on those test borings. If the ground soil and bedrock contain too much water, tunneling could be deemed overly difficult. For opponents of the project, water content is the least of the expressway&amp;#039;s problems. For example, the massive tunnels would cross multiple fault lines, but none of them are active.  At any rate, well-built tunnels are among the safest places to be in an earthquake, according to H. Tony Rahimian, an engineer and consultant for both Riverside and Orange counties&amp;#039; transportation agencies. &amp;quot;The ground has a dampening effect,&amp;quot; he says. &amp;quot;During an earthquake, the whole tunnel moves at once.&amp;quot; Regularly spaced exits would lead to an evacuation tube, to help drivers escape. To counter worries that vented exhaust fumes will choke the surrounding Cleveland National Forest, the proposal includes ceiling-mounted air purifiers that would scrub the air. To offset the carbon footprint of those purifiers, power could be recovered as hydroelectricity from the downhill flow of water in one of the tunnels. If the borings hold up, and the project survives an extensive chain of reviews, construction could last until 2023, with a price tag of at least $5.8 billion. For now, work is already under way to widen Route 91, but Rahimian insists the tunnel should be considered. &amp;quot;There are good concepts out there,&amp;quot; Rahimian says, &amp;quot;but we can&amp;#039;t know whether this project is viable without test results.&amp;quot; Proposed Route If it&amp;#039;s ever built, the Irvine-Corona Expressway will cut through 12 miles of soil, sand and 200-million-year-old rock, sloping downward to prevent flooding and possibly to allow for a gravity-fed water line. The actual route and elevation are subject to change, but the current path crosses several inactive faults, shown as black vertical lines in the illustration above, which is not drawn to scale. In addition to relieving traffic congestion in Southern California, the Irvine-Corona Expressway could accommodate oil, power and water lines. In one proposal, each passenger tunnel would be one-way, while the truck and light-rail tunnel would run in both directions. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/technology/infrastructure/a4090/4224670/>