At a Caltrans public open house Thursday, experts explained that creating a new route around Last Chance Grade will involve stringent, multi-year studies to plot a new path through a scattering of known landslide areas.
Those studies, according to the experts, have to be done right the first time or they could add years to the already long project timeline of 2039.
Audience members heard from panelists and were able to talk to them at the close of the meeting.
Panelists were area CHP Commander Larry Depee; Steven Mietz California State Parks district superintendent; John Driscoll, representing U.S. Rep. Jared Huffman; state Sen. Mike McGuire; Matt Schmitz Federal Highway Administration director of project delivery; Del Norte County Supervisor Gerry Hemmingsen; Last Chance Grade Project Manager Jaime Matteoli; BGC Engineering Geologist Scott Anderson; Victor Bjeljac, California State Parks district superintendent II; and Caltrans District 1 Director Matt Brady.
Find a way through
Matteoli recalled that in 2015, a list of alternative routes was chosen and later narrowed down to six in 2016.
He said with the $10 million now allocated to begin the environmental studies, Caltrans needs to determine the affected areas of each alternative, ranging from plants and cultural area, to bank cutouts and culverts.
“So, what are the steps we need to take to begin those multi-year environmental studies?” he said, nothing the affected areas need to be determined first. “It’s really important we know where we’re studying. If we get that piece wrong... we have to start over with multi-year studies, so it’s really important we get that piece right, or else we’re adding years to the project.”
Matteoli said geotechnical investigations are a big part of those studies.
Showing maps of the proposed alignments, Matteoli said Caltrans is “trying to find ways to get over, around or through” the slide areas of U.S. 101. He said one of the alternatives would be a 1.3-mile tunnel through part of the mountain, just outside the slide area, which would cost more than $1 billion.
Another involves going around the slide area to the east, avoiding old growth redwood trees. He said while Caltrans does not want to cut the trees, one alternative would be to cut through about a quarter-mile of them, at a cost of $300 million. He said the shortest option is about three miles in length, while the longest is about eight miles.
He said while Caltrans had a good understanding of the potential environmental impacts of the alternatives, they needed to know more about what was happening below ground.
Showing a map of the alternative alignments laid over a map of known landslide areas, Matteoli said, “There’s really no way to get around slides without going over other existing landslides, so we need to know — if we’re going to put this alternative here, are we going to reawaken an old landslide? Are we going to have to shift that alternative?”
He said doing the preliminary investigations also helps Caltrans refine and validate alternatives. He said shifting a project to another area could also add years to the project, making it imperative to get studies done correctly the first time.
Matteoli explained Expert-Based Risk Assessment is a tool that helps the state narrow down options by helping determine which ones best suit project needs.
The assessment was performed by an independent panel of geotechnical experts with a combine experience of 180 years, Matteoli said, noting the assessment generated a couple of new alternative routes.
One of those experts is Scott Anderson, who led a team of five geotechnical experts in preparing a geological risk assessment for the alternative alignments.
Showing a splotched map of the grade area, Anderson said, “All of the dots that you see on these images are bad things. They’re all landslides.”
Anderson explained the boldest and darkest areas of the map wer where experts know the landslides to be active and would threaten any highway infrastructure.
“If you look at this, you’ll see that the boldest and the darkest ones are where we currently have the highway,” he said.
Anderson said the phenomenon could be because the creation of the highway is causing slides, or that the map simply shows areas where the most studies have occurred.
He said the assessment allows experts to put numbers on their judgement. He said new technology, such as Light Imaging Detection and Ranging (LIDAR) was used to create images of the mountain face, but without the obstructive trees and vegetation. Another technology, called a Hololens, allowed researchers to overlay engineering drawings into a three-dimensional, space and “walk around” in the virtual area.
“You can go places you can’t go,” he said. “There are no roads where these alternative alignments are.”
He said the experts broke the projects down into sections for analysis and reassembled them to complete the assessment.
“Nobody knows what answer is going to come out at the end because they are only studying one piece at a time,” Anderson said. “It’s not until we use probabilistic rules to reassemble the problem that the answer becomes clear.”
He said the experts looked at the following, based on the geotechnical data:
How likely is the alternative to require expensive maintenance after construction?
What is the chance that it will undergo repairs that cause delays to motorists?
What is the chance that, after construction, the alternative will fail causing long-term closure?
The three potential impacts to each of the six alternatives were looked at in 10- and 50-year time frames, he said. It was noted during the meeting that a failure/closure on Last Chance Grade would cause a 320-mile detour, adding six hours to the time it takes to get from Klamath to Crescent City.
Showing a graph where all alternative routes reached the top in regard to cost, Anderson said, “in the opinion of the panel, it was almost a certainty that in 50 years, this was going to be an expensive piece of highway for Caltrans to maintain.”
In regard to repairs/delays and possibility of closure over 50 years, the tunnel had little risk of full closure. Alternatives closer to the coast, as well as inland alternatives, had a very high likelihood of closure.
“We don’t see there’s a way to get around a high-cost highway here,” he said, noting the likelihood of delays and closures varies.
As to the likelihood of future closure, from least to highest risk went F, A1, L, X, A2 and C3.
Alternative F is the tunnel option, while A2 runs a curvy course to the east of the existing highway, would be 3.2 miles long with two bridges, run .6 miles through parks land, take out three acres of old growth redwoods, and cost $240 million.
A map of those alternatives, as well as the full risk assessment, can be found at lastchancegrade.com.
“We did this with probably the least amount of information that could be reasonably used,” Anderson said. “Caltrans is continuing to get more information and with more information, we can make better judgments, but it’s unlikely to flip the order of what we have seen tonight.”
following some questions and further explanation, audience members got a chance to see the nature of terrain surrounding Last Chance Grade as they looked at three dimensional images using virtual reality technology. Anderson and other panelists narrated as they went through three-dimensional images of the coastal mountain range and the challenges posed by the steep and remote terrain.