What's next for the Nalley Valley interchange? Two-plus years of delays, detours and closures

First, the good news.

When the next wave of Nalley Valley highway construction is finished, if all goes as planned, eastbound drivers on state Highway 16 will sail over the valley on a spacious new viaduct and merge onto Interstate 5 in either direction without touching their brakes.

Officials say the annoying backups and hair-raising merges that now characterize morning and evening rush hours at Pierce County’s busiest interchange will be gone, and once again drivers will be able to access the interstate from Sprague Avenue.

And now the bad news.

Getting there is going to mean 2½ more years of construction delays, single-lane detours, closed ramps and nighttime road closures for eastbound drivers.

Construction that officially started last week on the $115 million eastbound Nalley Valley project won’t be finished until spring 2014, and there’ll be some pain on the way there.

“The citizens of Pierce County are going to experience some inconveniences,” Kevin Dayton, the Transportation Department’s Olympic Region administrator, said Oct. 28 at a ceremonial ground breaking beneath the old viaduct.

“But when we’re done, they’ll see a significant improvement,” he said. “The light is coming on at the end of the tunnel.”

INEVITABLE DELAYS

Drivers on state Route 16 have been dealing with heavy construction since 2002, when work on the second Tacoma Narrows bridge began. That project took five years.

The first phase of the Nalley Valley project, a $184 million job that streamlined the westbound half of the interchange, took 2½ years and was completed in June.

The upcoming phase was designed to minimize disruption, but the complexity of the work will make some delays inevitable, said Neal Uhlmeyer, the Transportation Department’s project engineer on the eastbound portion.

The project will involve high-level destruction of the existing viaduct and simultaneous construction of the new viaduct, he said.

“During the girder-setting for the new viaduct we’re going to have to have complete nighttime closures of eastbound 16,” he said. “They’ll be setting almost 200 girders.”

That means up to 80 nights of closures, Uhlmeyer said.

Traffic will be diverted onto city streets on those nights, Uhlmeyer said.

During construction, two I-5 ramps – exit 133 on northbound I-5, which takes drivers to Tacoma’s city center, and the southbound I-5 exit 132 to South 38th Street and the Tacoma Mall – will be closed for as long as three months.

Current plans call for closing the northbound ramp early in 2012 and the southbound ramp about a year into construction.

Contracts spell out that the southbound ramp cannot be closed between Thanksgiving and New Year’s because of the likely effect to retailers during the heavy shopping season, said Kim Mueller, the project’s assistant project engineer.

VIADUCT DEMOLITION

The biggest engineering challenge in the eastbound project, Uhlmeyer said, will be tearing down what remains of the existing viaduct, which opened to traffic in 1971 and is supported by unusual concrete “tetrapod” piers. Mowat plans to demolish the old viaduct in two phases.

During the initial phase, eastbound traffic will be diverted onto the now unused westbound portion of the old viaduct while the eastbound portion is torn down and a temporary route built.

Drivers will use the temporary route while the other half is torn down and the new viaduct constructed.

The old viaduct will be demolished bit by bit, Ulhmeyer said, with machinery that breaks apart the concrete and steel reinforcement.

Mowat was awarded the eastbound Nalley Valley construction contract with a bid of $74.7 million, nearly $18 million less that state engineers estimated.

The Guy F. Atkinson Construction Co., which built the westbound Nalley Valley portion of the interchange for $120 million, bid unsuccessfully on the eastbound portion.

STOPLIGHTS

The Transportation Department promises that this phase of Nalley Valley construction will make sense of the Sprague Avenue interchange, which, in its partially completed state, has been a sore point with many Tacoma drivers.

During the first few weeks of the Sprague exit’s opening, some drivers misjudged their speed on a 90-degree left turn at the top of the ramp, causing several run-ins with concrete jersey barriers there.

Also during this phase of construction, ramps leading to I-5, both northbound and southbound, will be added to the Sprague overpass. Drivers leaving state Route 16 at Sprague will be controlled by a stoplight at the top of the exit ramp.

A second stoplight partway across the overpass will control access to a ramp heading for I-5 north.

Some have expressed concerns that a stoplight at the top of the Sprague exit ramp will back up traffic onto the mainline of state Route 16.

Not so, Uhlmeyer said.

“It won’t back up onto 16 because the intersection has been engineered to handle the volumes that are expected,” he said.

The project also includes several technological improvements, including traffic cameras, ramp meters, traffic data collectors and other hardware that the state says will improve its ability to manage traffic and communicate traffic conditions to the public.

THE FINAL PHASE

Finally, the project will include aspects that will be used in a third and final phase of Nalley Valley work – car pool access ramps between state Route 16 and I-5 HOV lanes and an HOV bridge between the eastbound and westbound viaduct structures.

That phase of the project, already funded for $213 million, will be built between 2020 and 2022, the state says. At the ground-breaking ceremony, State Sen. Steve Conway, D-Tacoma, noted the coincidence that this phase of construction, which Mowat says will provide about 215 jobs, is occurring just a short distance from Nalley’s, the company that gave its name to the valley.

Nalley’s closed this year, putting 139 people out of work.

“Infrastructure work like this is exactly what we should be doing in these bad times,” Conway said. “Infrastructure is our economic future.”

Rob Carson: 253-597-8693
rob.carson@thenewstribune.com