The Martians

Chapter 17 Saving Noctis Dam

The Noctis Dam was not a good idea in any case, and then unfortunately they botched the engineering as well. They placed the dam in the mouth of the southernmost Noctis canyon, where the rim is a basalt cap resting on old sandstone. Naturally as soon as the reservoir filled the sandstone began to saturate, which weakened the dam foundations. Then the only emergency runoff as designed was a big glory hole that ran water down through a tunnel in the rock on the side, letting it out into the headwaters of the Ius River below. They lined the tunnel with concrete, of course, but it was sandstone behind that. Thus when the weather became more violent and we saw the first superstorms, the dam was not designed to handle such runoffs. The reservoir level would rise very fast. One of the very first times that happened I was there to see it, and it was a daunting thing to witness. We opened the glory hole the moment rain was forecast, but it seemed to make little difference. And this time the rock behind the concrete was so weakened by seepage that the cavitation ripped the concrete right out of there, apparently. All the instrument readings for the tunnel went dead, and then we saw the concrete being shot out of the hole at the bottom into the shallows of the headwaters; sometimes after a minute or two of complete blockage, so that house-sized chunks of concrete went flying hundreds of meters, as out of a cannon. A very disturbing sight for all of us.

Of course the water going down the tunnel would immediately begin to rip the sandstone out of the hole, and soon enough there would be no rim underneath us left to hold up the south side of the dam.

Thus we had no choice but to close the glory hole from the top; indeed we were happy that the option still existed. But after that we had no other way to release water from the reservoir. And it was still raining harder than we had ever seen, as if the clouds had been seeded; and Noctis Labyrinthus is an extremely big watershed, even just the southernmost quadrant of it, which was what drained into the reservoir.

So the reservoir level rose, two meters in an hour, then three. At that rate we had only a few more hours before it reached the top of the dam and started pouring over, and then inevitably the top would tear somewhere, and without further ado the entire dam, all 330 vertical meters of it, would peel down, probably in a single collapse. The rim walls just behind the dam were very likely to go as well. More importantly, the resulting flood would certainly sweep away all the canyon-floor settlements in Oudemans Crater and upper Marineris, perhaps all the way down to Melas Chasma.

For some time after we closed the glory hole we were at a loss concerning what next to do. Mary of course called emergency services in Cairo, and told them to warn the people down in Oudemans and in Ius Chasma to get out of the crater and canyon, or at least as high on their walls as they could, as there was no quick way for great numbers of people to get out of that deep crater and gorge. But beyond that it was not clear what we could do. We hastened back and forth between the command center and the dam, looking at the water rising, then walking back up to the command center to check the weather reports, all the while in a terrific downpour. The reports gave us reason to hope that the rain might soon stop—it already had upstream in the watershed, and farther west. And the last squall had consisted mostly of hail—hail the size of oranges, which drove us to the shelter of the center, but had the advantage of staying where it was on the ground upstream, at least until it melted. So that too gave us some hope.

Nevertheless, the upstream flow readings coming in to the center made it clear that the lake was going to rise higher than the dam, by what the AI said would be two or three meters. Some rough calculations led me to the conclusion that the overflow would probably be more than the lip of the dam could tolerate. I informed the others of this unhappy conclusion.

“Three meters!” Mary said at last, and expressed the wish that the dam were just four meters higher. Certainly that would have helped.

Without really considering it, I said, “Perhaps we can make it four meters higher.”

They said, “How is that?”

“Well,” I said, “the pressure up top will not be that bad. Even just a plywood barrier might do the trick.”

This they found amusing, nevertheless we got in the truck and drove wildly to Cairo Lumber over a road sheeted with big hail balls, and we bought their entire stock of plywood sheets. We were too nervous to tell them what we wanted it for.

Back at the dam we set up the plywood sheets against the railing, nail-gunning them to the plastic footing of the rail just to keep the wind from blowing them away before the water trapped them against the railing. It started to rain again while we did this. We worked at the highest speed we could manage, I assure you—never have I worked with such a sense of haste. Even so, by the time we finished our work, the water had lipped over the concrete, and we had to run back along the road on the top of the dam splashing ankle deep through the water—an awful experience.

Once off the dam and up the road toward the command center, we stopped to look back. If the plywood did not hold and the dam gave way, the rim there would very likely go too, and we would all be killed; nevertheless, we stopped to look back. We could not help it.

The last squall had passed while we labored, and the sky had gone wild over our heads: dark orange to the east, then both to north and south an intense turquoise, like no sky color we had ever seen. It was still black to the west, but the sun was peeping under a distant cloud, illuminating the scene in brassy horizontal light. Below us we saw that the lake was continuing to rise, up the sides of the plywood. Finally, as dusk fell, it was quite a bit more than halfway up the plywood sheets. When we couldn’t see it very well anymore—and I didn’t want to see it either, I confess, it looked so flimsy—we walked back to the command center.

Up there we waited. Very possibly the whole structure would go very quickly; we would see this on the instrumentation, then perhaps be taken along with it, swept down with the rim walls. So all night we watched the readouts on the computers. Meanwhile we told people over the phone what we had done. My throat stayed dry no matter how hard I swallowed. We occupied ourselves telling jokes—a specialty of mine, but never had people laughed so hard at my jokes before. After one Mary hugged me, and I felt she was shaking; and I saw my hands too were shaking.

In the morning the water was still flush against the plywood, but it did not seem so high. It seemed it was going to hold. It remained a frightening sight, however; the lake surface was simply too high, as in some optical illusion; yet undeniably there below us, spread vast and colorful in the morning light.

So the dam held. But our celebration, after pumps arrived and we slowly lowered the water level back below the top of the dam, was muted, almost stunned. We too were drained, so to speak. Looking at the wet curve of plywood sheets topping the dam, Mary said, “By God, Stephan, we did a Nadia on that dam!”

Later of course they took it out. I cannot say I regret it.