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Riley Mahaffey


One of the spookiest construction projects underway at the Grand Canyon is a so-called "skybridge" that stretches out over the yawning gulf of the canyon. The see-through bridge hangs 4,000 feet above the canyon floor, off of property owned by the Hualapai Tribe of Arizona. The controversial project--some Grand Canyon devotees are bothered by the manmade structure's intrusion--was built by a company with ties to Boise. Lochsa Engineering, which opened up a Boise office three years ago (Riley Mahaffey and his partner Lee Harrison are the local principals), has designed numerous hotel projects in Las Vegas and is also working on the remodel of the Simplot mansion, as it becomes the Idaho Governor's mansion. Mahaffey, a structural engineer, has been involved in everything from the famous First Street Viaduct Bridge in Los Angeles to the Idaho Independent Bank building just down Broad Street from the BW offices. The University of Idaho graduate may be afraid of heights, but he does know how to walk on a girder suspended several stories above the ground.

BW: Tell me how this odd-looking skybridge came to be.

The Hualapai Tribe wanted a revenue-maker, but they wanted something to really stand out, to make a statement. So the architect and the tribe came up with this.

It's gone through various permutations. It started out as a diving board kind of look. But they wanted people to not end up where they started. They wanted more flow.

Was the see-through floor part of it from the beginning?

Yes, they wanted people to experience the power of the Grand Canyon. You're almost 4,000 feet up.

How do you get something like that to be see-through, but also strong enough to hold people?

It's a plexiglass material. It's six inches thick at a minimum, in multiple layers. It's in three or four different layers. They can take the upper layer off and replace it as it gets worn. But the base structure will always be there. It will hold an 'emergency exit'-type load, which is 100 pounds per square foot. It's designed to be full of people.

I presume the maximum occupancy will be posted very clearly?

Oh, yeah. It was also designed for the wind. They did a site-specific wind analysis for it. The winds off of that face are huge.

So what else holds this up?

There's steel that holds it up, six-foot beams, with two-inch walls. There's two of them, an outer ring and inner ring. They stem back to the land, and it's anchored into the earth, about 40 or 60 feet. We drilled in to the rock. It's built sitting [on the cliff] and then it's rolled out into place, on rollers. Then they'll weld it into place.

That better be one heckuva weld.

Well, it's steel to steel.

You've seen how much damage an earthquake can do; did that give you any pause about building this bridge?

The factor of safety that's put into this is above and beyond. One thing might fail but there are other things that support it. It would have to be a pretty major catastrophe.

What did you do when you started?

I started out doing public-works structures for the city of Los Angeles. City wastewater treatment plants, municipal-owned infrastructure. It was interesting, and I learned a lot, but I wanted to get into more interesting, bigger stuff. And I also wanted to get back to Idaho.

Are all engineers alike, that they want to build something big?

Not necessarily. My partner and I were driven, and we wanted more challenging work. We wanted to get into high rises. Currently we have two six-stories here in Boise. Idaho Independent Bank, right here, and the building next door to it.

Is that the one with the crooked roofline? What's going on there?

The roof slopes, for drainage. Once the skin is put on, you won't even see it. It's intentional.

Now that you've been in other cities, do you see Boise with a more jaundiced eye, architecturally?

The budgets here are tighter. They're not able to do the sort of things they might do in Vegas. But the architectural talent around here is pretty impressive.

So what about the Boise tower site? Are they going to have to go in and start over?

There'll be some replacement, but not all of it. It's got the potential to be a landmark. It's right in the perfect spot. I'd like to see it built.