Caltrans Takes on $16.2M Interchange

Wed July 29, 2009
Erik Pisor

Typically, expanding a 0.2-mi. (0.3 km) stretch of highway from four lanes to six lanes and reconstructing four of the highway’s existing on/off ramps isn’t considered a large transportation project in San Luis Obispo County, Calif.

However, when the project also involves the demolition of two single span bridges which cross over the highway, and the construction of a new double span bridge, the project becomes notable, especially to a city with a population less than 30,000.

Located north of San Luis Obispo and south of Paso Robles, where Highway 101 meets Highway 41, the city of Atascadero is home to the $16.2 million Highway 101/41 Interchange project, which is aimed at increasing each highway’s capacity and improving access onto and off each highway.

“There is a lot of congestion on [Highway] 41, which is locally used. This [project] will help alleviate that,” said Colin Jones, public affairs for Caltrans District 5.

The project, which began in September 2007, has at times been challenging for Granite Construction, the general contractor, due to the staging/phasing of the project.

“In order to keep traffic moving along both Highway 101 and Highway 41, the project is broken up into four different stages with a total of 14 phases within the stages,” said Jeff Grimm, project manager and estimator for Granite, who was the lowest qualified bidder. “Careful planning has been required to ensure that all of the phases fit together.”

The major milestone during stage one was the construction of the middle portion of the new Highway 101 bridge.

Currently this portion of bridge is being used to detour traffic during stages two and three, which include demolishing the two existing single span, steel girder bridges and replacing them with a cast-in-place, box girder, double span bridge.

“The project is driven by the construction of the bridge,” Grimm said, explaining that for Highway 41 lane widening to occur underneath Highway 101, the two existing bridges first had to be demolished.

Following demolition of the two existing bridges, all the steel was salvaged and the bridge’s concrete was crushed onsite, into base, by a Kolberg Pioneer track mounted 4250 horizontal impactor portable crusher, which was cited as the only piece of specialty equipment utilized.

Other pieces of equipment used onsite have included: Cat 330 excavators; Cat 140H motorgraders; Cat 623 scrapers; Cat 966, 950, 928 loaders; John Deere 710 backhoes; Cat D6 and John Deere 550 dozers; Cat padfoot compactors, various paving equipment; Bidwell screeds; 100- and 14-ton (90-t and 12.7-t) truck mounted cranes; and a 70-ton (63 t) crawler crane.

Granite or its subcontractors own the majority of equipment used on the project.

As of mid-May the deck for the new northbound portion of the Highway 101 bridge had been completed and the new northbound on-ramp, which will carry two additional lanes compared to the previous on-ramp, was nearly finished, Grimm said, adding this portion of construction is part of stage two.

Widening work associated with Highway 41 and the reconstruction of the other three existing on/off ramps also has progressed following bridge demolition, as a crew of five to 15 employees has worked mainly in daytime, single shifts with very little double shifting.

Stage three of the project, which has yet to begin, focuses on constructing the new southbound portion of the Highway 101 bridge.

“Before, the bridges only accommodated two lanes in each direction. The new bridge will have the future capacity to handle three lanes,” Grimm said.

Prior to beginning each stage of bridge construction, the staging/phasing of the project required Granite to place 8 ft. (2.4 m) of dirt at the site where upcoming bridgework would occur and surcharge it.

A surcharge is a vertical load that is applied at the ground surface or above the bottom of a footing as a soil consolidation method.

Granite was required to surcharge each bridge construction site because of the poor subgrade conditions onsite and the fact that the project involves increasing the grade on Highway 101 by 3 ft. (0.9 m).

While Granite had to import some dirt for the surcharge requirement, 73,250 cu. yds. (56,000 cu m) of earth was moved onsite, stockpiled and reused, Grimm said.

Following the three stages of bridge construction, stage four involves finishing up all lane widening on Highway 41, completing all on and off ramp work, and constructing a bike lane adjacent to a portion of Highway 41.

Throughout, construction lanes on Highway 41 have been reduced from two to one lane in each direction, and periodic ramp and Highway 101 closures have occurred.

However “collaborative and forward thinking” by all parties involved has helped reduce the impact of these delays, and allowed Granite to remain on schedule.

“Everything is on track. We’re about 50 percent complete in terms of contract time,” he said.

Currently the project is set for a summer 2010 completion.

When the project reaches completion 16,100 cu. yds. (12,300 cu m) of class 2 aggregate base; 19,600 tons (17,780 t) of asphalt concrete; 2,000 linear ft. (610 m) of pipe, both RCP and CSP; 2,416 cu. yds. (1,850 cu m) of structural concrete; 8,700 linear ft. (2,650 m) of steel pipe piling and 484,000 lbs. (219,540 kg) of reinforcing steel will have been used.

Key subcontractors on the project have included: C.C. Myers, bridge construction; Lee Wilson Electric, signals and lighting; Statewide Safety and Sign, project signage; Coral Construction, overhead sign structures; and Proline Striping, striping. CEG

This story also appears on Construction Equipment Guide.