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Not over yet 

Slide-prone Cuesta Grade to be fixed by next year

Although the Cuesta Grade improvement project was technically completed in October 2003, construction crews are back on Highway 101 this summer fixing a damaged section. Caltrans officials deny that the original project was poorly designed or constructed.

Instead officials attribute the need for repairs to an unforeseen "preexisting slide condition inside the hill [that was] exacerbated by an incredible amount of water," said Marta Bortner, Caltrans public information officer.

The city of San Luis Obispo received 40.89 inches of rain last water-year, which started in July '04 and ended in June '05. That's more than 17 inches over the average yearly rainfall of 23.40 inches, according to the Western Regional Climate Center.

The heavy rains triggered a slide on the eastern side of the northbound lane of the Cuesta Grade. Bortner said the slide did not damage the highway, but there was enough rock debris coming off the hill side to force Caltrans to close the newly built third lane and line the highway with seatrains, or cargo containers. The large metal containers, attached together like Legos, were installed to temporarily block debris from falling into the road and traffic, said Bortner.

Once the heavy rains quit, Caltrans brought in geologists and structural engineers to study the situation. According to Bortner, Caltrans officials found a slide plane high on the slope above the area that actually slid out last year. Slide planes can exist below the surface of the ground, said Bortner.

Which raises the question, why didn't the original Cuesta Grade design accommodate the slide planes?

"What [the engineers] did was the best design they could with the limited information they had at the time," said Bortner. "Always when you work with these types of hills you're going to run into subterranean stuff you didn't know was there."

Caltrans officials put out bids this spring for the Cuesta Grade Improvement project, with plans to remedy the slide. Once engineers finished with the design, processed the paperwork, and accepted a bid, construction crews were able to begin the project on July 11. Caltrans will use $3 million from an emergency account to fund a "soil nail wall" that will stop the slide plane from dropping debris on the new third lane.

Bortner said the wall will anchor the slope and include an aesthetic treatment as well.

Caltrans will spend over $25 million in road repairs in SLO, Monterey, and Santa Barbara counties after last year's rains. Road damage in Santa Barbara County is eligible for federal relief funding due to a presidential disaster declaration. The $3 million required to fix the Grade comes out of an emergency fund, Bortner said.

The Cuesta Grade project was started in 1999 and completed in 2003. The project cost $45 million, with $35 million spent on construction.

Since the partial closure of the third northbound lane last spring, Bortner said the heaviest traffic occurred last weekend during the Mid-State Fair when a chemical spill on I-5 diverted additional traffic to 101.

Bortner compared to the improvement project on the Grade to the annual slide repair work on Highway 1 around Big Sur. But unlike that situation, Bortner said that once the current project on the Grade is completed it shouldn't require any more work.

The improvement project is scheduled to be completed by the end of November and the third lane will be opened by next year, said Bortner. 


Staff Writer John Peabody can be reached at

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