This month, the California Department of Transportation (Caltrans) had a ribbon cutting for the opening of the new State Route 29 Napa River Bridge in Calistoga, California. The replacement bridge was deemed necessary by Caltrans, which inspects bridges throughout the state every two years. While the work of replacing the bridge was not excessively complex, outside factors made the project more unique than it otherwise would have been.
Calistoga, a small city and part of California's Napa Valley, is known for hot springs, mud baths, and wineries. American settlers came to the area in the 1840's after hearing that the hot springs had healing powers. The town continues to be a draw for tourists still visiting the hot springs and who are drawn to the natural beauty found in the area.
Because of Calistoga's history and dependence on tourism, construction in the area requires a gentle touch and sensitivity. Tony Tavares is the Caltrans District 4 Director and is responsible for oversight of all the projects and day-to-day activities within nine California counties including Napa County, home of Calistoga. He said, "When the project was first presented to the community, there were concerns about what to do about the bridge." Tavares credits the Project Manager, Kelly Hirschberg, who has been with Caltrans for over 27 years, and the Caltrans public affairs team for working with the community and easing their concerns.
Replacing the Bridge
Upon inspection in 2009, the bridge was found to have scour at its pier foundation and would need to be replaced. Caltrans placed the bridge on scour critical as they were concerned that the bridge could be undermined if there was a large flow. The bridge also needed to be brought up to current seismic standards.
After receiving environmental clearance, construction began in the spring of 2017. Replacing the bridge was a two-season project as the bridge was built one half at a time. This was done as part of Caltrans’ commitment to the community, which wanted to maintain two lanes of travel at all times whenever possible.
Tavares emphasized the tightness of the footprint. Because of this condition, the contractor, Valentine Corporation, retained the existing abutment and reinforced them with steel casings and soil nails to provide support.
The former bridge had a pier wall that was in the water, leaving it susceptible to the water and eventually, scour. The replacement bridge, a box girder bridge, is a single span with none of the bridge in the water. "It was done this way to remove it from potential scour issues down the road," said Tavares.
The decision to utilize a box girder design was also made with utilities in mind. The hollow section within the design houses the utilities that were stubbed in. Stubbing utility lines in the bridge makes them less prone to issues than if they were under the bridge and exposed to water.
The Effect of Community Input
In addition to the tight footprint, there were four business property owners surrounding the bridge. Caltrans took their concerns into consideration while planning and working on the project. Tavares praises the Valentine Corporation, "They were a true partner and worked closely with us to have minimal delays, communicate if something came up, and considered the needs of the community."
On a project like the replacement of the Napa River Bridge, an access road is typically created so the contractor could get equipment in place to demolish the previous bridge. However, in this case, the contractor utilized timber mats by the river bed. They lowered the equipment down to the river bed when it was dry thereby alleviating the need for an access road which would have meant more inconvenience for the surrounding property owners.
There were other benefits to using the timber mats primarily related to reducing environmental impacts. "With the timber mats, the contractor did not have moving tracks from the equipment," said Tavares. This led to less impact on the river bed.
Driving piles into the ground causes great amounts of vibration and noise. The townspeople of Calistoga were concerned about the vibration and its potential impact on the historical buildings in the area. To alleviate this concern, the contractor used a rotating machine rather than a pile driver. The rotating machinery placed piles down vertically and rotated them into place instead of driving them straight down.
While a rotating machinery ultimately does the same work as a pile driver, it's quieter and causes less vibration, but it's slower. Tavares again notes the contractor's flexibility in regards to this matter, "The contractor worked with us to not just utilize the cheapest method, but to find the best solution for the community, us, and him." The timber mats also helped to reduce vibration.
It was these types of considerate decisions that ultimately helped the project gain the full support of the town. “We worked with the town as much as possible, minimized delays and sought their input regarding features,” says Tavares. Those features include railings and sidewalks. Keeping these things in mind has pleased the town and ultimately, Tavares said, made them feel like “part of the team.”
The 82-foot-long Napa River Bridge, which stands 22 feet above the water, was built for just under $16 million. This includes the design of the bridge, construction, and right of way. Surrounding business owners were compensated for their concerns about the impact the construction would have upon their businesses. The project was completed on budget, which Tavares says is a tribute to the project manager who monitored support costs and construction costs.
It takes all parties involved communicating regularly, being proactive, and coordinating their activities to ensure a construction project is completed on time and on budget. When working in an historic area such as Calistoga, the need for communication and coordination increases. With the completion of the new Napa River Bridge, local residents and tourists will be able to safely traverse the area and enjoy all that Calistoga has to offer.
Photos courtesy of the California Department of Transportation
Our newsletter right to your inbox.
See stories from other regions.