MNS Transportation Division, Construction Management Team: Spotlight Project

Hazardous Rock-slides on One of California’s Landmark Motorways

The Pitkins Curve and Rain Rocks Shed project, located between Monterey and Cambria on California State Route 1 (Highway 1) was a major undertaking aimed at making a dangerous section of the scenic state highway safer for motorists.

The Pitkins Curve area of Highway 1 is part of an active landslide­; rock slides are a fact of life here, rather than an unusual occurrence. Its geological composition is particularly unstable. Rock slides repeatedly closed the original road and presented a significant danger to motorists.

Foreseeing that Pitkins Curve would continue to be a major safety issue and an access impediment for the millions of tourists traveling through the area each year, not to mention a major maintenance and cost issue, the California Department of Transportation (Caltrans) developed an innovative solution to the problem.

Caltrans Finds an Innovative, Permanent Solution

Rather than continuing to repair Highway 1 at Pitkins Curve or attempting to stabilize a cliff face whose underlying geologic composition would not benefit from mitigating measures, Caltrans determined that bypassing the curve with a bridge would be an optimal solution.

Repeated rock slides at Pitkins Curve have hollowed the side of the cliff into a concave shape; connecting either side of the carved-out area with a bridge will allow the slides to continue without affecting motorists on the bridge. The bypassed portion of the old highway will be left intact, but inaccessible to traffic, so that it will catch debris from future rock slides.

Pairing the planned bridge with a protective rock shed structure over a nearby portion of the road that could not be bypassed, Caltrans developed the Pitkins Curve and Rain Rocks project as a permanent solution to a problem that has plagued the road since its opening in 1937. Maintaining that quick emergency solutions are inferior, Caltrans was diligent during the planning stages and held public meetings as early as 2006 to begin planning strategically for an optimal solution and assembling the best team for the construction project.

Innovative Design Solutions

The project involved the construction of a cast-in-place segmental bridge combined with a post-tensioned concrete rock shed. The complexity of this project led to many technical submittals that required approval through engineering analysis. This includes shoring and excavation, temporary trestles, on-site concrete batch plant, numerous working drawings, mass concrete placement, falsework, and post tensioning.

MNS Construction Management At Pitkins Curve and Rain Rocks

The Construction Inspector’s Role

Aaron Hilton, PE, was the sole on-site inspector; his role involved checking all work completed on site for compliance with engineering design plans and specifications. Because the Pitkins Curve bridge was the first cast-in-place segmental bridge in Caltrans District 5, both MNS and the Caltrans civil engineer who designed the bridge were required to adapt quickly to an entirely new construction method. MNS collaborated with the off-site Caltrans designer regularly to make sure the project was progressing as expected.

Our construction inspector was also responsible for documenting all labor performed on site and tracking all work and supply shipments involved in the project. A day at Pitkins Curve commonly involved documenting the work of 40 people and tracking five trades; as a result, the MNS construction inspector’s project management skills of the highest importance.

Support During Unforeseen Emergencies

Numerous storms over the course of project construction at Pitkins Curve and Rain Rocks caused problems; twice, the storms caused rock slides so severe that emergency repairs to Highway 1 were required immediately. Under the expert guidance of MNS Vice President and Principal Construction Manager Gregory Chelini, MNS was able to marshal resources necessary to deal with these emergency situations quickly and effectively.

Traffic Control

The project required painstaking traffic control strategies, planned far in advance but necessarily adaptable on the spur of the moment. The Caltrans traffic control plan, as mentioned above, had to keep Highway 1 open in order to avoid damaging regional commerce or cutting residents off from access to the outside world. A four-type traffic control plan was developed, with each type allowing traffic through to different degrees and with varying safety measures taken.

Reducing Visual Impact to Protect an Important Landmark

In order to preserve the natural beauty of a historic state highway and its appeal to sightseers, Caltrans held multiple public informational meetings and used feedback from multiple sources to arrive at the solution of using faux surface painting to help the rock shed blend into the local environment. Additionally, preservation of the natural scenery has neutralized any negative impact to this area’s appeal as a tourist destination. Arguably, the construction of Pitkins Curve and Rain Rocks has provided an increased economic benefit to local communities by increasing safety and showcasing a feat of modern engineering.

Ask us a question or just find out more about the MNS Transportation Division’s Construction Management Team by contacting us today.