Mark Nothaft

Special for The Republic | azcentral.com

The "Deck Park Tunnel" is not really a tunnel, but a series of 19 underpasses arranged side-by-side

Voters defeated a plan for a raised highway in 1973 and then another plan like today's model

The plan for the "tunnel" finally passed in 1979 and construction started in 1983

Rand McNally and Google Maps must love the flat, square precision of our town.

Local vernacular is steeped in the north, south, east, west grid. Here's a text I recently sent my teenage daughter: Take the 101 north to the 202 east, go south on Greenfield and it's on the southeast corner at McKellips.

Doesn't everyone talk like this? Maybe not.

We need a tunnel?

Anyhow, excluding our local mountain preserves, Phoenix may be one of the flattest cities in the country. So why does downtown Phoenix have a tunnel? Don't those typically bore through mountains?

Yes. But first, let's be clear, the mile-long Interstate-10 “tunnel” that runs both east- and west-bound between North Third Street and North Third Avenue in Phoenix is actually called the Papago Freeway Tunnel, though most of us call it the Deck Park Tunnel because of the park above it.

Although it's Margaret T. Hance Park above the tunnel and not Deck Park, so not entirely sure where that comes from.

Maybe because I-10's Deck Park Tunnel is not really a tunnel, but a series of 19 underpasses or decks arranged side-by-side; the final leg of the 2,460-mile I-10 that spans from California to Florida that was completed in August 1990. But we can't exactly call it the 19 Underpasses Tunnel. Doesn't roll off the tongue.

Key commerce corridor

“The I-10 Deck Park Tunnel is more than simply a way to get through downtown Phoenix,” says Arizona Department of Transportation Director John Halikowski. “It is part of a key commerce corridor that is integral to the state’s continued economic growth and development, connecting Arizona to the world.”

So why build it at all? Couldn't the highway just bisect the city without the elaborate underpass?

That's where the story becomes more interesting. When the highway was first discussed in the 1960s, Phoenix was a fraction of its current size at about 440,000 people, but growing. The need for connecting the East and West Valley was apparent as was the uninterrupted continuation of the interstate highway.

Plans for a raised highway through downtown, one that wouldn't displace current roads or utilities, was struck down by voters in 1973.

Another plan two years later called for a series of decks to be built over the highway with a 30-acre park established on top — the current model — but that, too, was defeated by voters.

Final passage

The project faced voters again 1979 and was overwhelmingly passed three-to-one in favor of building the freeway, underpass and park. Construction of the $500 million thoroughfare finally began in 1983.

“The Deck Park Tunnel shows the potential for great solutions when the community and government work together,” Halikowski says. “The tunnel is a monument to that partnership — a fitting tribute for the final mile of I-10 constructed in the nation.”

Contact “Only in Arizona” columnist Mark Nothaft at marknothaft.onlyinaz@gmail.com. Send him the weird and fun facts and places found #OnlyInArizona.

About Papago Freeway Tunnel

• Better known as Deck Park Tunnel

• Interstate-10 between North Third Street and North Third Avenue

• Opened August 1990

• 2,887 feet long

• 260,000 vehicles use it daily

• 3,000 lightbulbs inside, changed three times each year Four ventilation fans inside tunnel in case of an emergency

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