Brian Turk, left, a civil engineering technician for the U.S. Corps of Engineers, and Kipp Walters, a park ranger with the corps at Clinton Lake, inspect tunnel walls inside the dam at Clinton. A comprehensive five-year inspection of the dam was done this week.

The small stream of water made a garden hose-like hiss as it forced its way under the steel gate and into the nearly 700-foot tunnel that is the closest thing Lawrence has to a massive cannon.

The constant spray provided an ominous hint of what lay on the other side.

Outside the tunnel, tattered fishing tackle – hundreds of lures, weights and jigs encased in tangled line – lie in a pile of ultimate fishing frustration. Inside, men with halogen lights shined sharp beams that illuminated water-worn concrete, crawdads and the occasional remains of an unlucky catfish that didn’t survive its trip down the tube.

But make no mistake. The steel gates are what everyone is here to see.

The two gates – 14 inches thick and requiring a 30 ton crane to lift – are Lawrence’s hidden infrastructure, a linchpin that lurks beneath the ground doing a job that thousands of Lawrence residents never think twice about.

This is the Clinton Lake outlet. The big 13-foot tube where water comes rushing out of the lake and into the Wakarusa River. Day after day, these two pieces of steel are what stand between Lawrence and the constantly pushing, ever forceful 7,000 acres of water in Clinton Lake.

Sure, boaters, fishermen, campers, swimmers and a whole host of other fun-seekers know about Clinton Lake. It is the big body of water west of Lawrence.

Yes, the water. It’s always the big body of water that gets all the attention and love. But somebody also has to pay attention to the big pile of dirt – the 9.4 million cubic yards of earth that make up the Clinton Dam.

“We do parks and we do recreation, but those are really secondary functions out here,” said Lew Ruona, the project manager who oversees all operations at Clinton Lake for the U.S. Army Corps of Engineers. “Our major function at the lake is the integrity of this dam. That is always my No. 1 concern.”

In a town that talks a lot about infrastructure – rough streets, cracked sidewalks, strained sewers – this massive piece of infrastructure largely stays out of the public conscience. But all it would take is one bad day at the dam to make everyone forget about the potholes on 19th Street.

“This dam, like all Corps of Engineers dams, is a high hazard dam,” said Doug Crum, the dam safety program manager for the Kansas City district of the Corps of Engineers. “That means there would be an expected loss of life if there was ever a breach.”

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The water temperature in the Wakarusa River is about 45 degrees. That also happens to be about the air temperature on this dreary day that is covered in low clouds flirting with the idea of dropping a cold rain.

Not the best of days to go for a swim.

But two men in wetsuits and two more in hip-waders are in the middle of the Wakarusa. A sandbag line has been formed, and at the end of the day they’ll have placed about a thousand of the 45-pound bags to build what’s called a cofferdam.

It’s all in preparation for the most visible sign of how serious the Corps takes dam safety. About a dozen engineers from the Corps – some from as far away as Portland, Ore., – arrived at the dam this week to inspect every aspect of the 31-year old structure.

But a lot of the fun happened before the engineers ever arrived on scene.

First, there’s the building of the sandbag dam. It’s constructed about 200 feet downstream of the tube – or the outlet – that releases water out of the lake.

Once the dam is built, two six-inch pumps are lowered by crane to the edge of the river. A crew works overnight to pump most of the water out of the area immediately in front of the tube. Next come the men with nets. They catch whatever fish still remain in the area and place them in a bucket attached to the crane, which then lowers them into the river a little farther downstream. This year, the catch was small – by crane standards anyway. Only about two to three dozen walleye.

Up next is an old-fashioned housecleaning exercise. All sorts of debris – some sucked through the tube, others tossed over the railing – is cleared from the area in front of the outlet.

Mainly, the debris is just lots and lots of rocks. This year it was about two dump-truck loads. Other times it is more exciting. Ruona tells of finding an ATM machine at one project, and Crum said it is not uncommon to find a handgun that probably has an interesting story to tell.

But most times, the finds are more innocuous, unless you’re a fisherman.

“One time we pulled out a shopping cart, and it was completely covered in lures that it had snagged,” said Dave Rhoades, the park manager at Clinton for the Corps.

This year, fisherman should have had less to cuss. Two computers – much more lure friendly – were the only odd finds.

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This inspection is just one of many the dam gets on a regular basis. Each day, a Corps employee does some sort of inspection on the dam – looking along the embankments for any signs of seepage or burrowing rodents.

Every quarter, employees do a series of tests inside the dam tower – the big concrete, beacon-like structure in the center of the dam – that houses the gates and the nearly two-foot in diameter hydraulic shafts that raise and lower them.

Once a year, another inspection occurs that includes more mechanical testing and checking of gauges and instruments that measure the pressure the water exerts upon the dam.

But this week’s inspection – it concluded on Tuesday – was the big one. It happens once every five years, and every aspect of the dam gets a review by a set of outside eyes. That includes the tower, the concrete joints of the tunnel, the rip-rap rock on the face of the dam, and – in a sense – even the city bike path that runs near the dam. That’s because the path runs through the dam’s spillway – which is just what it sounds like. It’s the area that the lake would spill into if it ever rose so high that it began testing the engineering limits of the dam. That hasn’t ever happened at Clinton, but has occurred at other Kansas lakes, including Milford and Tuttle Creek, Crum said.

But to the uninitiated, the gates are the big attraction. They can make a man standing in front of them ponder thoughts that often go unpondered – like the science of engineering and the soundness of giving work to the lowest bidder. Open these two gates just a few inches, and no man could run fast enough down this dark tunnel to save himself.

The gates also get a good look from inspectors. Crum said making sure the gates – there are three in total, two primary gates and one emergency gate – work properly is a major safety issue.

“It is important that the gates work when you need them,” Crum said. “If you can’t open them during a high water event, water could overtop the dam. If you can’t close them when you need to, there’s a risk you could lose the entire reservoir.”

In the future, Crum said, Corps inspections likely will include even more engineering analysis to make sure that the engineering assumptions used to build the dam are still valid. That’s already happened at Tuttle Creek Reservoir near Manhattan. There, engineers decided the dam needed to be strengthened to withstand a possible earthquake. A multimillion-dollar project is under way. Crum doesn’t expect such work will be needed at Clinton.

Thus far, the Clinton Dam has held up well. Ruona said inspectors found no major issues during this week’s inspection. Both Ruona and Crum said that the inspection programs should allow downstream residents to always rest assured.

But they also offer one other tidbit – one that almost any Corps man mentions if talked to long enough. No Corps of Engineer dam – and there are more than 400 in the country – has ever failed.

“And we’re not going to start now,” Ruona said.

Knock on wood. Or better yet, a steel gate.