How are old and new freeway lanes joined?

With Jamzilla approaching this weekend on the 405 freeway, I thought this would be a good time to re-run a post from the I-405 Sepulveda Pass Improvement Project’s web page. The aim of the work this weekend is to pave a major segment of the new northbound HOV lane in the Sepulveda Pass. The work is considered key to meeting the project’s scheduled completion date of 2014.

Here’s the article by Ashley Meachem: 

Although it appears to be a flat gray ribbon uncurling toward the horizon, a freeway lane has tiny peaks and valleys, slopes and divots created by hundreds of thousands of automobiles and their tires or—in the case of the I-405 through the Sepulveda Pass—tens of millions of cars.

As workers add a new lane, as will happen along 10 miles of the I-405, matching the contour of the new lane with the veteran lane takes some finesse.  If the existing lane and new lane are not well married, the pavement will be subjected to high stress levels from the traffic that it serves. Tires will find ridges between the slabs, creating an uneven and rough surface that is sure to take a toll on your vehicle’s performance.

The roadway for the I-405 Sepulveda Pass Project has three layers. First is an aggregate base (AB) composed of crushed rocks in varying sizes from 3/4 inch to dust. Following that is lean concrete base (LCB) which provides a stable, ridged, and low eroding platform for the concrete slabs. LCB is a mixture of AB with a small amount of concrete to bind the aggregate tighter.


Although drivers roll over the jointed plain concrete pavement, that is only the top of three layers composing the I-405 roadway. This graphic shows how a new piece of freeway is held to existing pieces.

The final layer, which you are most familiar with, is composed of ridged pavement known as jointed plain concrete pavement (JPCP). JPCP is the common standard for California freeways as it is engineered to include longitudinal and transvers joints. These joints are created by using a saw cutter to create cracks at specific intervals in the concrete.

“To ensure that lanes are properly aligned, dowels are used to relieve the stress between concrete slabs,” Caltrans engineer Steven Zaw explains. These dowel bars are made of smooth epoxy coated steel and bonded into existing concrete sections to act as a guide when the new concrete is added. When the new concrete is poured, dowel bars are placed into the new concrete as well.

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Jamzilla 405 operation more complex than Carmageddon

The Presidents' Day northbound 405 paving operation will realign a portion of the freeway centerline to the west in the San Fernando Valley.

The Presidents’ Day northbound 405 paving operation will realign a portion of the freeway centerline to the west in the San Fernando Valley. Photo taken from project area on the southbound side of the 405.

The planned 80-hour “Jamzilla” paving operation now scheduled for Presidents’ Day Weekend, February 14-18 is more complex, requires new construction and is more time-consuming than the epic “Carmageddon” bridge demolitions of 2011 and 2012.

The I-405 Sepulveda Pass Improvements project contractor, Kiewit Infrastructure West, will not benefit from gravity in the frenzied destruction of an iconic freeway bridge. Instead, the contractor will take its time to pour a single layer of pavement at a time.  Each concrete layer takes its own time to cure.  The operation is similar to baking layers of a wedding cake.

“Operationally speaking, demolishing a bridge is a much simpler operation than paving and striping freeway lanes that must return to public use as quickly as possible,” said K.N. Murthy, Executive Director of Transit Project Delivery at Metro. “It’s the essential difference between destroying a structure and building a structure. Building something is much more difficult, and the paving methods we are using vary between each material type and have specific requirements that must be adhered to.”

A car drives on the No. 1 lane that will receive a final pave during Jamzilla lane closures.

A car drives on the unfinished No. 1 northbound lane that will receive a final pave during Jamzilla lane closures.

The operation officially begins Friday night, February 14.  After a full northbound freeway closure at 1 a.m., Kiewit will begin excavating and paving multiple areas within the 5.6-mile area of the northbound I-405 in the Sepulveda Pass simultaneously. In order to complete as much paving work as possible, the contractor will use new polyester pavement that cures and reaches specified strength within hours instead of days, and provides an extremely durable roadway surface for the hundreds of thousands of vehicles that drive on the northbound 405 every day.

But the operation depends on the weather.  The polyester paving requires favorable temperatures in order to cure properly and give strength. If temperatures are less than favorable or if it rains, it could complicate the operation, or at worse, cause it to be rescheduled over several consecutive 55-hour weekend operations.

Polyester concrete has quick-dry, high-strength properties and is very compact.

Polyester concrete has quick-dry, high-strength properties and is very compact.

The contractor will perform up to four separate paving operations during the 80-hour period on various portions of the northbound 405.  The contractor must grind, tack, pave and stripe the freeway in a carefully choreographed sequence. Because the paving areas abut one other, the contractor will operate in a very confined work zone.  Maneuvering construction vehicles within this area for all needed work will be a logistical challenge.

Adding to the complexity of the operation, the contractor must shift the freeway centerline 20 feet to the west for approximately 1,000 feet as the northbound I-405 winds its way down into the San Fernando Valley.  There was no room for the freeway to be widened to the east due to the existence of a multi-residential building adjacent to the northbound 405 in Sherman Oaks.

A 1,000 portion of the freeway centerline in Sherman Oaks must be shifted 20 feet to the west.

A 1,000 portion of the freeway centerline in Sherman Oaks must be shifted 20 feet to the west.

Also in this area, approximately 1,700 feet of freeway and shoulder lanes must be completely excavated to full depths and rebuilt in order to realign the freeway to the west.

The most complex work will occur where the northbound 405 meets the Sepulveda Boulevard undercrossing bridge just before the U.S. 101 connector ramps.  The contractor must demolish and then rebuild the approach slabs on both sides of the freeway bridge to upgrade the slabs for seismic safety and roadway durability.  This includes first building a seat to accommodate the new approach slab. The contractor must also reinforce the concrete with rebar for seismic safety and ensure the new approach slabs comply with state highway standards.

Three concrete pours will be required to rebuild the approach slabs.  Each of those pours requires its own 8-hour cure time.  The extensive work required to rebuild these slabs drives the critical path for the entire 80-hour operation.


The Sepulveda undercrossing approach slab has to be rebuilt. The new roadway surface will be much improved for motorists.

Finally, when all paving and approach slab work is completed, the contractor will restripe the freeway prior to reopening lanes by 6 a.m. Tuesday morning, February 18.

Compared to the flurry of activity of the Carmageddon bridge demolitions, this new paving operation will have little visual excitement.  There will be periods during the 80-hour operation when concrete is curing where nothing appears to be happening. However, the contractor will still be working from a meticulous schedule to complete all tasks within the 80-hour period.

A Caltrans engineer shows the different layers of paving needed for the 80-hour operation.

A Caltrans engineer shows a cross-section of freeway to indicate the multiple layers of needed paving during the 80-hour operation.

Motorists are reminded to fully cooperate with agency calls to stay off the freeway just as they did during the previous Carmageddon closures.  Motorists should eliminate unnecessary auto trips, avoid the area and/or divert to other freeways to avoid major traffic delays.

Jamzilla is coming: Unprecedented 80-hour paving operation planned for northbound 405 Presidents’ Day weekend


Northbound traffic on the 405 through the Sepulveda Pass will be greatly curtailed President’s Day weekend. Avoid the area if you can. Photo by Jonathan Poh, via Flickr creative commons.

Los Angeles transportation officials are alerting I-405 and regional freeway motorists of an unprecedented 80-hour northbound I-405 freeway lane closure operation in the Sepulveda Pass this Presidents’ Day weekend, February 14 to 18, 2014.

The Los Angeles Metropolitan Transportation Authority (Metro), in conjunction with California Department of Transportation (Caltrans), Los Angeles Department of Transportation (LADOT), and a host of law enforcement and emergency response agencies throughout L.A. County are giving the public advance notice that if they do not have a critical need to travel northbound through West Los Angeles and the Sepulveda Pass during the Presidents’ Day three-day weekend, they should eliminate unnecessary auto trips, avoid the area and/or divert to other freeways to avoid major traffic delays.

Traffic conditions on local streets and freeways within the region of Los Angeles County and beyond could become severe, with significant, hours-long delays if motorists do not cooperate with authorities and limit northbound freeway trips.

Motorists who must travel during this weekend are advised to prepare their itineraries in advance, monitor real-time traffic conditions prior to beginning their trips and follow alternate routes that are provided. Motorists will be continually informed of the closure in advance by Caltrans-operated freeway message signs.

The I-405 contractor will be paving a major segment of the future northbound I-405 High-Occupancy Vehicle (HOV) lane in the Sepulveda Pass. The work is considered key to meeting the project’s scheduled completion date of 2014.

Work over the Presidents’ Day weekend will eliminate the need for several consecutive 55-hour freeway closures from the project schedule. This closure operation will save significant time and minimize future closure impacts to the community and traveling public.

The closure operation consists of a partial day-time lane reduction and a full night-time directional freeway closure on the northbound I-405 between Getty Center Drive and Ventura Boulevard.  The closure area is approximately 5.6 miles long, or nearly two-thirds of the entire I-405 project area.

During daytime hours, two northbound lanes will remain open while the remaining three lanes will be closed.  During night-time hours, all five northbound freeway lanes in this area will be closed.

The southbound I-405 will remain fully open during the day, but some southbound lanes may be closed during night-time only paving operations.

Work is scheduled to begin Friday night, February 14 starting at 11 p.m. and will last until Tuesday, February 18 at 6 a.m.

Ramps within the project area will begin to close as early as 7 p.m. Traffic officers provided by LADOT will help guide motorists at each I-405 northbound on-ramp.

Full northbound night-time freeway closure times are as follows:

  • Friday night, February 14 – 1 a.m. to 6 a.m.
  • Saturday night, February 15 - 2 a.m. to 7 a.m.
  • Sunday night, February 16 – 12 a.m. to 5 a.m.
  • Monday night, February 17 – 12 a.m. to 5 a.m.

The designated alternative route for night-time full closures will be for motorists to take the Wilshire northbound to westbound off-ramp to northbound Sepulveda Boulevard, returning to northbound I-405 at the Greenleaf northbound on-ramp.

Sepulveda Boulevard also will be fully open with two lanes in each direction during the paving operation.  However, Sepulveda Boulevard will not have the capacity to accommodate all diverted northbound freeway traffic, and could become severely congested. Freeway motorists should instead divert to other freeway routes.

I-10 connectors to the northbound I-405 also will be closed. Motorists detouring from the closed I-10 connectors should use freeway detour routes rather than local streets.

The connector detour routes will be as follows:

  • For eastbound I-10 to northbound I-405 – use northbound I-110, northbound US 101, to northbound I-405.
  • For westbound I-10 to northbound I-405 – use northbound I-5, westbound SR 134, northbound US 101, to northbound I-405.

The construction schedule is subject to change, and paving work is dependent on favorable weather conditions. In the event of inclement weather during the 80-hour closure, the project will commence continuous 55-hour weekend closures of the northbound freeway starting the following weekend, February 21 for up to four weekends to complete the originally intended work.

The I-405 Sepulveda Pass Improvements project has now concluded most major freeway widening work between the I-10 and U.S. 101. The contractor is now building the future northbound HOV lane that will connect West Los Angeles with the San Fernando Valley.

The project will officially complete the last remaining gap in the entire I-405 lane network.  Additional project benefits include improved freeway safety through standardized lane and shoulder widths, greater ramp capacities at key locations, new sound and retaining walls, widened overpasses, widened and seismically updated bridges.

The project is a joint effort between Metro and Caltrans, and is being constructed by Kiewit Infrastructure West Co.

Carmageddon Revisited: Metro, Caltrans and Kiewit reopen iconic Mulholland Bridge

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The iconic Mulholland Bridge that spawned two unprecedented weekend closures of the nation’s busiest freeway and introduced the word “Carmageddon” into the American vernacular was fully reopened to traffic in Los Angeles at 6 a.m. Wednesday after nearly two-and-a-half years of intensive bridge reconstruction work.

The contractor, Kiewit Infrastructure West, implemented the final traffic switch, signal and lane striping work needed to reopen the new northern half of the bridge, returning all lanes to full capacity in time for the mid-week morning rush hour today. Approximately 20,000 vehicles travel over the bridge on a daily basis.

The return of the new bridge to full capacity is the latest milestone for the I-405 Sepulveda Pass Improvements Project, which is building a 10-mile carpool lane on the northbound I-405 between the 10 and 101 freeways.  As the administrator of the design-build project, Metro and its project partner Caltrans have committed to continue opening parts of the massive freeway widening project as soon as they are deemed safe and ready for public use.

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I-405 project is now 85 percent complete

405 Sign

The end is in sight for the 405 improvements project.

Good news from the I-405 Sepulveda Pass Improvements Project, which has successfully navigated through some considerable obstacles during construction of a 10-mile northbound HOV lane between the 10 and 101 freeways. Project managers now report that the project is officially 85 percent complete, with major milestones planned before the end of the year.

The project that brought the public the “Carmageddon I and II” mega-closures in 2011 and 2012, respectively, was originally scheduled to open in May of this year. However, retaining wall problems, utility relocations, legal challenges, problems with procuring needed rights-of-way and efforts to avoid a county storm drain, among others, have required extensive mitigation efforts. The project team continues to open parts of the project as soon as they are ready and safe for public use — but the entire project won’t be done until the middle of next year.

The Design-Build delivery method used to build the I-405 improvements has allowed design and construction to occur simultaneously, shaving up to seven years off the construction schedule compared to traditional Design-Bid-Build methods, but even still the unavoidable project delays and cost increases have taken a toll on public patience. U.S. Congressman Henry Waxman recently queried the U.S. Department of Transportation regarding the federally funded project and its delays, asking how the project could be completed as quickly as possible.

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Mulholland bridge a new congestion point on 405 project

Looking East, Mulholland Bridge reduced to one lane in each direction. Photo: Gary Leonard

The fun never ends with the 405 improvements project, where work crews are in the full thrust of construction virtually everywhere in the 10-mile project area.  Witness the latest public warning on potential congestion, this time on the Mulholland Drive Bridge in Los Angeles.  It now has one lane in each direction following last month’s demolition of the south side of the bridge during “Carmageddon” weekend.

The lane reduction on Mulholland Drive will further slow access in the area already impacted by reduced lanes on nearby Skirball Center Drive Bridge, which provides access to the 405.  Workers are busy rebuilding half of that bridge now.

It may take a few weeks for traffic to adjust to the new reductions, but the project team has observed a normalization of traffic (i.e., cars choosing other routes) at the  Sunset and Skirball bridges when their lanes were first reduced.  It is expected that Mulholland Bridge will also follow that pattern.

So, you commuters who intentionally bypass Sepulveda Boulevard and the 405 driving through the canyon passes and on Mulholland Drive to get to work, here’s a wake-up call:  Congestion ahead.  Let the locals use the road.  Plan ahead and pick another route.

Read the news release after the jump. Continue reading

One week later: Carmageddon revisited in photos

Partial demolition of the Mulholland Bridge stopped traffic on Carmageddon weekend. One week later, a school bus crosses on the remaining half of the Mulholland Bridge as traffic pours under the bridge at the start of rush hour on Friday, July 22. Photos by Gary Leonard

Here are a few images from photographer Gary Leonard’s pictorial on how the south half of the Mulholland Bridge came down the weekend of July 15 to 17. Above is a shot showing what the bridge looked like last Friday afternoon.


The demolition began the evening of Friday, July 15, when work crews began closing freeway on- and off-ramps.

Two very large light plants and some 12 regular light plants turn night into day in the area surrounding the Mulholland Bridge.

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