Jensen Culvert Bridges LADWP Aqueduct Realignment

The Los Angeles Aqueduct is more than just important to the City of Angels.

It’s precious.

The 419 mile engineering marvel provides clean water to millions of people. Without it, modern Los Angeles would not have become the major metropolitan megalopolis it is today.

For the Los Angeles Department of Water and Power (LADWP), protecting the Los Angeles Aqueduct is more than just necessary.

It’s crucial.

Where the Sierra meets the Mojave, a bridge, a dam, and an aqueduct come together for better seismic protection.   

Earthquakes and Aqueducts Do Not Mix

To maintain and protect the aqueduct, LADWP conducts seismic investigations to determine how vulnerable key areas of the aqueduct are to potential major earthquakes.

One such investigation determined the North Haiwee Dam, which sits along the aqueduct 175 miles north of Los Angeles in Olancha, California, rests atop a fault line and could settle up to 9’ during a major earthquake.

That would be bad.

A failure of the North Haiwee Dam could be catastrophic for the inundation area around and downstream of the North Haiwee Dam and for Los Angeles’ water supply, according to LADWP.

So that’s why the agency baked up a three phase plan with the ultimate goal of building a second dam 800’ north of the existing dam to protect the reservoir in the case of a catastrophic earthquake.

To get to the final phase of the project – building the dam – LADWP brought in Jensen to help it complete phase two.

Jensen’s segmental box culvert sits in the middle of the diversion channel acting as a bridge for vehicles and a tunnel for water.

A Bridge Over Diverted Water

Phase two of this massive project has two steps. First, realign the Los Angeles Aqueduct. Next, create a diversion channel.

The aqueduct needs to be realigned to make way for the new dam, while the diversion channel is going to be used to fill the newfound basin created between the two dams with water, increasing the reservoir’s storage capacity.

However, adding a diversion channel now creates a challenge. How will construction crews cross the channel to complete the dam while still allowing water to flow freely into the basin?

With a Jensen segmental Type 2 box culvert.

“The box culvert is acting as a bridge over the diversion channel,” says Chris Franco, Project Engineer for Road and Highway Builders, the contractor on this project. “They are 18’W x 18’H culvert side by side with a 3” gap between them. The culvert structure is running right through our diversion channel and the structure will be used as a bridge for an access point building the dam.”

In other words, the culvert is a crucial cog in a colossal project.

The Precast Advantage

In the end, precast concrete won the day for three major reasons.

First, resistance to the elements. Since precast concrete is manufactured off site, it is not affected by the weather or site conditions, which were an issue on this project.

“One of the biggest concerns is the material out here,” Franco says. “It’s a very silty sand material. It takes a lot of water to get it to the correct moisture condition we need to for it to firm up and hold.”

Second, ease of installation. Precast concrete is ready to go right off the truck. Just slap some sealant on the connection points and you are good to go.

“We have six bases and six tops in U shapes, which are sealed with a butyl sealant and a water stop sealant,” Franco says. “It has three of those inside to make a correct seal. So when water passes through, there are no leaks or brakes outside of the joints.”

Third, a two day Installation turnaround. Time is money in construction. Precast concrete means contractors don’t have to sweat their timeline and can keep their projects running smoothly.

“The intention was we didn’t want to overload the staff by putting both sections of the box culvert in on the same day,” Franco explains. “So, we did the bottom sections of both culvert structures. I had 10  trucks come in, spaced at about 30 minutes. All of the pieces coming out of the Jensen Fontana facility.

“Then we also have the top sections, which all got delivered by 10 trucks, all within a 30 minute interval to give us enough spacing.”

Lastly, when you purchase a product from Jensen, customers are treated as partners, ensuring everything possible is considered to make customers happy.

“Having the team down in Fontana work with us and being very responsive with emails and correspondence whenever we needed to was helpful,” Franco says. “Being out here in the middle of nowhere in Olancha, it’s hard to get subs out and get everything planned out.

“Every job has its own different challenges and delays. The type of material we are using and kind of being behind schedule, Jensen was really good to work with. They were holding structures for us when we needed to and they are always a call away.”

Get a quote from Jensen for your next project now.