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THV Extra at 6: The secret under Murray Lock & Dam | News

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THV Extra at 6: The secret under Murray Lock & Dam

LITTLE ROCK, Ark. (KTHV) -- Floating down one of the Mississippi's largest tributaries, the Arkansas River travels 1,450 miles. And along the river, you'll come across 18 lock and dams between Oklahoma and Arkansas. Little Rock's Murray Lock and Dam is one of the 13 in the Natural State.

You've probably seen this structure before, but it's what beneath the river that captures our attention. Resting more than 70 below the Arkansas River is a tunnel running 110 feet in length.

This tunnel is essential function to the day to day operations of Murray Lock and Dam. And since the general public isn't allowed down there, we're going to take you.

Murray Lock and Dam has probably seen more visitors than another lock and dam in the state thanks to the development of the Big Dam Bridge. Touted as the longest pedestrian bridge in the world, the Big Dam Bridge is a sight to see. But it's what's under this bridge that captures our attention.

"We're basically on the bottom of the lock chamber in the Arkansas river," says Eric Gillespie, Lock Leader at Murray Lock and Dam.

Construction on Murray Lock and Dam began in 1964. That includes -- a 110 foot tunnel running below the lock and dam.

"The water is around us. It's just a tunnel going right on the bottom of the Arkansas River. And you got water on both sides and you got your spillway on top of us," Gillespie adds.

Gillespie has worked at Murray Lock and Dam for seven years. Although this tunnel was completed more than 40 years ago, in 1969, Gillespie says it's still a solid structure.

"A boat could hit this concrete wall and we're not going to have to worry about anything. These things are over 40 years old and they're still, you can look at that concrete and it looks like it did you just poured it," he says.

Inside the tunnel, cracks in the walls and pumps, called uplift drains, keep the lock and dam working properly.

"And you'll see, as we go through here, you'll see stuff coming up out of them. This is basically to relieve pressure from the bottom. These dams and locks are designed to leak some. If they don't leak, you'll have too much pressure on them you end up having a failure," adds Gillespie.

Once a month, Gillespie and his team check on the tunnel.

"We have to come down here and basically do our preventive maintenance. Check our pumps make sure they're properly working, check the lighting, just look for cracks. Anything out of the abnormal," he says.

The tunnel is filled with all sorts of nature. Walls are slimy, ceiling has stalactites, and the ground has stalagmites.

Near the end of the tunnel, there are special pumps which serve as an important function for the lock and dam. Gillespie explains their purpose.

"The water level gets too high, that cable right there is a float and it'll hit that float when it raises it up and it'll kick the pumps on and it'll pump the water up so the water does not get too high. Right now with no flow in the river, they're probably [going to] run three maybe four times in a 24 hour period. And they'll only run for a 30 seconds to a minute then they'll shut themselves off."

Gillespie says even heavy rains and earthquakes haven't lessened effectiveness of the tunnel.

"Our dive teams go in and do annual inspections and we check all that stuff. And there's nothing there. Nothing. I've been at this lock and dam for seven years now and I've never had it flood."

In addition to Mother Nature's markings, there are ways for you find your way around the tunnel.

"That P stands for pier. That's letting you know that there's a pier on the other side of this wall... holding up the catwalk and stuff above the gates," Gillespie explains.

But you don't want to get caught down here without your flashlight.