Since May, Legacy Foundations has worked with general contractor OHL, owner County of Riverside Transportation Department, and construction manager Falcon Engineering on the $49.3 million Hamner Avenue Bridge Replacement project in Norco, California over the Santa Anna River. The new, 1200-foot-long bridge will have six lanes of traffic rather than two, easing congestion to the Silver Lakes event center as well as the cities of Norco and Eastvale and helping first responders travel between Eastvale, Norco, Corona, and Jurupa Valley.
Unique Drilling Method Increasing Efficiency
Although Legacy generally utilizes a single drilling method on a project, to increase efficiency in installing the large-diameter shafts, the team is using a unique blend of oscillator and crane drilling in tandem with conventional drill rig drilling through the rock socket from within the temporary drill casing. The team is drilling:
Overcoming Environmental and Geographical Challenges
Legacy Foundations has done many similar wet-shaft projects, giving the team a leg-up in overcoming the project’s challenges. Because Legacy is drilling within the flood plain of the Santa Ana River, a very environmentally sensitive area, they must adhere to stringent environmental requirements to minimize impact to surrounding ecosystems. All Legacy equipment has secondary containment, minimizing soil and river contamination, and remains within the tight work zone to not impact the surrounding wildlife.
Within the floodplain, the average existing ground water is 3 feet below working grade, meaning the heavy equipment needed to place the shafts on less-than-ideal ground conditions. To avoid sinking the equipment in the saturated sand, Legacy works from a safe, level crane mat working platform. The shallow groundwater also poses challenges as the team completes the top of the CIDH at the end of the concrete pour due to water “rushing” in and potentially washing out the top of the shaft. Legacy, OHL, and the owner’s representative engineered a solution involving overpouring the pile cutoff elevation above groundwater to prevent any quality control concerns and provide a dry work zone for OHL to erect the column.
Access Challenges
Another major challenge has been drilling within the tight work zones with limited accessibility because of the ESA restrictions of working within the flood plain. The tight work zone has created interesting logistical problems for site mobilization. For example, the team’s 3-meter casing oscillator could not be transported to the working grade below bridge via road access. Legacy closed the bridge at night and used the HS 8200 crane to lift and lower the 118,000-pound oscillator off the bridge to the work area below. This process was utilized again in reverse while demobilizing the drill rig from the work area up to the bridge structure.
Project Moving Forward
The project will be executed in two phases to allow traffic to remain open throughout construction. Phase one includes constructing half of the new bridge and swapping traffic from the existing bridge to the new structure. Phase two includes demolition of the existing structure and construction of the remaining bridge segments, tying in the two new structures.