Auger Boring in Big Sur
California weather is the reason many people move to the most populous state in the union. Climate change is often cited for the severe weather that has afflicted the Golden State with wildfires and drought conditions over the last decade. The rainy season for California seems to shorten and disperse less precipitation during this period. An often-referred to saying “When it rains it pours” is the case, as well in California.
The combination of drought, wildfire and forestry management often leads to disaster and devastation when the rains come. Infrastructure, namely roads and water run-off, are overwhelmed when mudslides and heavy debris flow from the drought, wildfire and forestry management conditions. CALTRANS is addressing the problem throughout the state and Papich Construction and Pacific Boring were chosen to alleviate the issue on California’s scenic HWY 1 near the Big Sur area.
In January 2021, the Central Coast of California experienced heavy rains. During one of the downpours, a large section of HWY 1 was completely washed away into the Pacific Ocean. The Rat Creek area of HWY 1 was devastated by the flowing debris, which included boulders, trees, and large mudslides. The economic, environmental and tourism impact for the Rat Creek area was substantial and CALTRANS moved quickly to re-establish the section HWY 1.
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Pacific Boring, located in Caruthers, California, was contacted by Papich Construction to provide the trenchless tunnels and bores to alleviate future washouts on that section of HWY 1. Pacific Boring utilized several methods, including auger boring a 60-in. steel casing 260 ft at a 15 percent downhill grade. Auger boring was chosen due to the location of the bore, steep grade, trench set-up and suspected fill with large boulders under HWY 1.
“The site of the bore was in a deep ravine; this caused several challenges for spoil removal. A mini-excavator was used to load a conveyor and bring materials to the surface and hauled away. A pit was not excavated since the bore was being launched from the ravine into the highway embankment. A 44-ft long pad for the boring machine was graded to the slope of the bore, with ¾-in. crushed rock. A large thrust wall was constructed at the back of this pad using beam and plate. The area behind the thrust wall was backfilled and a pad was built for the 100-ton RT crane used to set the 60-in. casing and the machine in the hole. The casing was 60-in. outside diameter with ¾-in. wall. The weld joints were single bevel butt weld from the outside.
The site chosen for the auger boring proved to have all the intended obstacles and more. Auger boring gives better face access to observe the obstacles encountered. Boulders were encountered within the first 40 ft of boring. The medium-size boulders were conveyed by the auger to the spoil discharge area, the steep downhill grade often caused the boulders to become lodged between the auger and spoil ejectors. The boulders often had to be manually removed with slings to clear the area between the auger and ejector paddles. The access to the face of the bore proved invaluable as many large boulders were encountered and drilling and blasting techniques were used by the CALTRANS team to continue the bore.
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Pacific Boring chose a Michael Byrne Mfg. D72-1.5 Auger Boring Machine to perform this difficult bore. The D72-1.5 was selected because of its power, thrust and torque, featuring a John Deere 250 HP Tier 4 final engine, Stella Drive Hydraulic power pack and a Michael Byrne B16 gearbox with more than 250,000 ft lbs of torque. The 72-in. machine also features an Akkerman hydraulic power pack. This feature enables the machine to power an Akkerman 240A Guided Bore Machine by flipping a switch to Guided Bore mode from Auger Bore mode. A critical disc brake system is now used on new Michael Byrne Mfg. machines (42-in.and larger) to hold the machine in place while the push block dogs are retracted and moved to the next push block thrust holes. A remote control for the 72-in. machine sits on the operator stand of the machine but can be disengaged and used remotely by the operator to assist for critical alignments, or even out of the pit, if required.
Michael Byrne Mfg. is proud to have a nearly 40-year relationship with Pacific Boring, assisting with critical infrastructure projects throughout the Western United States. The MBM D72-1.5 Auger Bore machine ranks Pacific Boring among very few contractors in the Western United States with these capabilities.
Michael Byrne Mfg. machines are CE-compliant with Tier 4 EPA approved engines and provide the customer with the power, torque, thrust, safety and environmental requirements to provide the utility contractor equipment to get their bores done on-time, on-line and on budget.
