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Published March 23rd, 2016
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Rheem Blvd. to Close for Three Months for Long-needed Repairs
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| By Sophie Braccini |
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| Graphic provided |
In good news for commuters using Rheem Boulevard between St Mary's Road and Moraga Road: A new plan to repair the failed part of the roadway will disrupt traffic for only three months instead of the six previously forecast.
At the Moraga Town Council meeting March 9, the engineering team selected by SummerHill homes, Engeo Inc., assured council members that this proposed engineering of the roadway would stabilize it for the long term; they were clear that it would not, however, remediate an entire hillside that's prone to landslides.
This section of Rheem Blvd. between Moraga Road and St. Mary's Road has been a bumpy one for years. It was not maintained when the town resurfaced the rest of Rheem Boulevard. Engeo President Uri Eliahu explained that for decades two landslides from above the road have been shifting the roadway horizontally and downward. Vice Mayor DaveTrotter added that this section of road started failing within weeks of its construction by the county in 1948.
SummerHill owns the 179 acres of the Rancho Laguna II property, now called Bella Vista, that abuts that section of Rheem Boulevard. One of the conditions of approval for that company to build 27 homes there was their participation in the cost of reconstruction of that portion of the roadway, as well as its management of the project.
"In the first approach (approved last year) the entire roadbed and landslide beneath the road would have been removed and replaced with a geogrid reinforcing, such as a Polystyrene Mesh," Eliahu told the council. "It would arrest the lateral movement of the roadway." This option required EBMUD to relocate the water main and PG&E to either move or secure its poles. The difficulty to coordinate the work with the utility agencies and saturated soil conditions due to El Nino compelled SummerHill to look for an alternative.
The new solution will consist of drilling 106 large diameter piers every six feet through the landslide debris, then horizontally supporting those with tension cables that will be drilled diagonally down into the bedrock beneath the slide to provide lateral restraint for those piers. The piers will also be connected together with a continuous grade beam. Eliahu added that with this plan there would be no need to relocate the utilities. The soil below the road would remain, but asphalt and the base underneath the asphalt will be removed and a new base and new asphalt surface reconstructed.
"We have heard stories that there might be garbage underneath that road and other debris," said Eliahu. "We have drilled 18 borings and didn't find anything. Whatever is under the road will stay under the road."
He added that this new way of repairing the road would limit risks of reactivating the two landslides.
"We were comforted that doing it the other way would be an effective solution for the road from slipping again," Trotter said. "Is this new solution going to be as effective?"
Eliahu called this method "a tried and true approach,"
"The big geogrid buttress is like an open heart surgery," he said. "This (new approach) is a conservative design intended to handle very large loads, and it will definitely arrest the horizontal movement."
Eliahu warned nonetheless that there is an active landslide on that hill, and that the repair of the road is not going to stabilize the whole hill. "But by stabilizing the bottom it does add to the stability to the entire slope," he said. "Future failure could occur and if the slide mass wants to come down, it could come down on the road."
Town staff will work with the developer to get the required permits and work could start as early as May or June.
The total estimated cost of the project is $2,585,000, $100,000 less than was estimated for the options adopted last year. The developer will pay $933,500. The town will contribute the rest. A waiver of development impact fee will provide $390,000, Measure J will fund $729,000 and $359,000 is funded by the 1 percent tax measure.
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Lamorinda Weekly, Moraga CA